Tropical cyclone: Difference between revisions
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{{tropical cyclone}}{{Redirect4|Hurricane|Typhoon}} |
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A '''tropical cyclone''' is a meteorological term for a [[storm|storm system]] characterized by a [[low pressure]] center and [[thunderstorms]] |
A '''tropical cyclone''' is a meteorological term for a [[storm|storm system]] characterized by a [[low pressure]] center and [[thunderstorms]] that produces strong wind and flooding rain. A tropical cyclone feeds on the heat released when moist air rises and the water vapor it contains [[condensation|condenses]]. Because tropical cyclones are "warm core" storm systems, they are fueled by a different heat mechanism than other cyclonic windstorms such as [[nor'easter]]s, [[European windstorm]]s, and [[polar low]]s. |
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The adjective "tropical" refers to both the geographic origin of these systems, which form almost exclusively in [[tropics|tropical]] regions of the globe, and their formation in [[Air mass#Classification|Maritime Tropical air masses]]. The noun "cyclone" refers to such storms' [[cyclone|cyclonic]] nature, with [[Clockwise and counterclockwise|counterclockwise]] rotation in the [[Northern Hemisphere]] and clockwise rotation in the [[Southern Hemisphere]]. Depending on their location and strength, |
The adjective "tropical" refers to both the geographic origin of these systems, which form almost exclusively in [[tropics|tropical]] regions of the globe, and their formation in [[Air mass#Classification|Maritime Tropical air masses]]. The noun "cyclone" refers to such storms' [[cyclone|cyclonic]] nature, with [[Clockwise and counterclockwise|counterclockwise]] rotation in the [[Northern Hemisphere]] and clockwise rotation in the [[Southern Hemisphere]]. Depending on their location and strength, tropical cyclones are referred to by various other names, such as '''hurricane''', '''typhoon''', '''tropical storm''', '''cyclonic storm''', and '''tropical depression'''. |
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While tropical cyclones can produce extremely |
While tropical cyclones can produce extremely powerful winds and torrential [[rain]], they are also able to produce high waves and damaging [[storm surge]]. They develop over large bodies of warm water, and lose their strength if they move over land. This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from receiving strong winds. Heavy rains, however, can produce significant flooding inland, and storm surges can produce extensive coastal [[flood]]ing up to 25 [[mile|mi]] (40 [[kilometre|km]]) from the coastline. Although their effects on human populations can be devastating, tropical cyclones can also relieve [[drought]] conditions. They also carry heat and energy away from the tropics and transport it towards [[temperate]] [[latitudes]], which makes them an important part of the global [[atmospheric circulation]] mechanism. As a result, tropical cyclones help to maintain equilibrium in the Earth's [[troposphere]], and to maintain a relatively stable and warm temperature worldwide. |
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Many tropical cyclones [[tropical cyclogenesis|develop]] when the atmospheric conditions around a weak disturbance in the atmosphere are favorable. Others form when [[#Related cyclone types|other types of cyclones]] acquire tropical characteristics. Tropical systems are then moved by [[#Steering winds|steering winds]] in the [[troposphere]]; if the conditions remain favorable, the tropical disturbance intensifies, and can develop an [[eye (cyclone)|eye]]. On the other end of the spectrum, if the conditions around the system deteriorate |
Many tropical cyclones [[tropical cyclogenesis|develop]] when the atmospheric conditions around a weak disturbance in the atmosphere are favorable. Others form when [[#Related cyclone types|other types of cyclones]] acquire tropical characteristics. Tropical systems are then moved by [[#Steering winds|steering winds]] in the [[troposphere]]; if the conditions remain favorable, the tropical disturbance intensifies, and can even develop an [[eye (cyclone)|eye]]. On the other end of the spectrum, if the conditions around the system deteriorate or the tropical cyclone makes landfall, the system weakens and eventually dissipates. |
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==Physical structure== |
==Physical structure== |
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{{Seealso|Eye (cyclone)}} |
{{Seealso|Eye (cyclone)}} |
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[[Image:Hurricane structure graphic.jpg|thumb|250px|right|Structure of a tropical cyclone]] |
[[Image:Hurricane structure graphic.jpg|thumb|250px|right|Structure of a tropical cyclone]] |
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All tropical cyclones are areas of [[low pressure area|low]] [[atmospheric pressure]] near the Earth's surface. The pressures recorded at the centers of tropical cyclones are among the lowest that occur on Earth's surface at [[sea level]].<ref name="ABC pressures">{{cite news | author = Symonds, Steve |title = Highs and Lows | work = Wild Weather | publisher = [[Australian Broadcasting Corporation]] | date = [[November 17]], [[2003]] | accessdate = 2007-03-23 | url = http://www.abc.net.au/northcoast/stories/s989385.htm}}</ref> Tropical cyclones are characterized and driven by the release of large amounts of latent [[heat of condensation]] |
All tropical cyclones are areas of [[low pressure area|low]] [[atmospheric pressure]] near the Earth's surface. The pressures recorded at the centers of tropical cyclones are among the lowest that occur on Earth's surface at [[sea level]].<ref name="ABC pressures">{{cite news | author = Symonds, Steve |title = Highs and Lows | work = Wild Weather | publisher = [[Australian Broadcasting Corporation]] | date = [[November 17]], [[2003]] | accessdate = 2007-03-23 | url = http://www.abc.net.au/northcoast/stories/s989385.htm}}</ref> Tropical cyclones are characterized and driven by the release of large amounts of latent [[heat of condensation]], which occurs when moist air is carried upwards and its water vapor condenses. This heat is distributed vertically around the center of the storm. Thus, at any given altitude (except close to the surface, where water temperature dictates air temperature) the environment inside the cyclone is warmer than its outer surroundings.<ref name = "AOML FAQ A7">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an extra-tropical cyclone? | publisher = [[NOAA]] | accessdate = 2007-03-23 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html}}</ref> |
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[[Rainbands]] are bands of showers and thunderstorms that spiral cyclonically toward the storm center. High wind gusts and heavy downpours often occur in individual rainbands, with relatively calm weather between bands. Tornadoes often form in the rainbands of landfalling tropical cyclones.<ref name="JetStream structure">{{cite web | url = http://www.srh.noaa.gov/jetstream/tropics/tc_structure.htm | author = [[National Weather Service]] | publisher = [[National Oceanic & Atmospheric Administration]] | title = Tropical Cyclone Structure | accessdate = 2006-12-14 | work = JetStream - An Online School for Weather | date = [[October 19]], [[2005]]}}</ref> [[Annular hurricane|Intense annular tropical cyclones]] are distinctive for their lack of rainbands; instead, they possess a thick circular area of disturbed weather around their low pressure center.<ref name="KnaffJournal">{{cite journal | url = http://www.ssec.wisc.edu/~kossin/articles/annularhurr.pdf | title = Annular Hurricanes | accessdate = 2006-07-23 | last = Knaff | first = John A. | coauthors = James P. Kossin, and Mark DeMaria | year = 2003 | month = April | format = PDF | journal = Weather and Forecasting | publisher = American Meteorological Society | pages = 204–223 | volume = 18 | issue = 2}}</ref> While all surface low pressure areas require divergence aloft to continue deepening, the divergence over tropical cyclones is in all directions away from the center. The upper levels of a tropical cyclone feature winds directed away from the center of the storm with an [[anticyclonic]] rotation, due to the [[Coriolis effect]]. [[Wind]]s at the surface are strongly cyclonic, weaken with height, and eventually reverse themselves. Tropical cyclones owe this unique characteristic to requiring a relative lack of vertical [[wind shear]] to maintain the warm core at the center of the storm.<ref>{{citeweb|publisher=[[University of Illinois]]|url=http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/grow/home.rxml |title=Hurricanes|accessdate= 2006-10-21}}</ref><ref>{{citebook|title=Flood Geomorphology |author= R. Craig. Kochel, Victor R. Baker, Peter C. Patton|year= 1988|publisher=Wiley-Interscience|id=ISBN 0471625582|url= http://books.google.com/books?vid=ISBN0471625582&id=snLfvo2w-ngC&pg=PA18&lpg=PA18&ots=chABkSpKQ9&dq=%22Tropical+Cyclone%22+%22wind+shear%22&ie=ISO-8859-1&output=html&sig=av-CZCexGMtTR2KVVtbXryYzr68}}</ref> |
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⚫ | A strong tropical cyclone will harbor an area of sinking air at the center of circulation, |
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⚫ | A strong tropical cyclone will harbor an area of sinking air at the center of circulation. If this area is strong enough, it can develop into an [[eye (cyclone)|eye]]. Weather in the eye is normally calm and free of clouds, though the sea may be extremely violent.<ref name="JetStream structure"/> The eye is normally circular in shape, and may range in size from 3 to 370 km (2–230 miles) in diameter.<ref name="WilmaTCR">{{cite web|last=Pasch|first=Richard J.|coauthors=Eric S. Blake, Hugh D. Cobb III, and David P. Roberts | url=http://www.nhc.noaa.gov/pdf/TCR-AL252005_Wilma.pdf | format=PDF | title= Tropical Cyclone Report: Hurricane Wilma: 15-25 October 2005 | publisher=[[National Hurricane Center]] | date=[[September 28]], [[2006]]|accessdate=2006-12-14}}</ref><ref name="MWR Lander 1999">{{cite journal | author = Lander, Mark A. | title = A Tropical Cyclone with a Very Large Eye | url = http://ams.allenpress.com/archive/1520-0493/127/1/pdf/i1520-0493-127-1-137.pdf | format =PDF | journal = [[Monthly Weather Review]] | date = January 1999 | volume = 127 | issue = 1 | accessdate=2006-12-14}}</ref> Intense, mature hurricanes can sometimes exhibit an inward curving of the eyewall's top, making it resemble a football stadium; this phenomenon is thus sometimes referred to as the ''[[Eye_%28cyclone%29#Stadium_effect|stadium effect]]''.<ref name="MWR 1996 AHS summary">{{cite journal | author = Pasch, Richard J. and [[Lixion Avila|Lixion A. Avila]] | title = Atlantic Hurricane Season of 1996 | journal = [[Monthly Weather Review]] | pages = 581–610 | url = http://ams.allenpress.com/archive/1520-0493/127/5/pdf/i1520-0493-127-5-581.pdf | format = PDF | date = May 1999 | volume = 127 | issue = 5 | accessdate = 2006-12-14}}</ref> |
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⚫ | There are other features that either surround the eye, or cover it. The [[central dense overcast]] is the concentrated area of strong thunderstorm activity near the center of a tropical cyclone;<ref name="CDO AMS">{{cite web|author = [[American Meteorological Society]] | url = http://amsglossary.allenpress.com/glossary/browse?s=c&p=19 | title = AMS Glossary: C | work = Glossary of Meteorology | accessdate=2006-12-14 | publisher = [[Allen Press]]}}</ref> in weaker tropical cyclones, the CDO may cover the center completely.<ref name = "AOML FAQ A9">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is a "CDO"? | publisher = [[NOAA]] | accessdate = 2007-03-23 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A9.html}}</ref> The [[eyewall]] is a circle of strong thunderstorms |
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⚫ | There are other features that either surround the eye, or cover it. The [[central dense overcast]] is the concentrated area of strong thunderstorm activity near the center of a tropical cyclone;<ref name="CDO AMS">{{cite web|author = [[American Meteorological Society]] | url = http://amsglossary.allenpress.com/glossary/browse?s=c&p=19 | title = AMS Glossary: C | work = Glossary of Meteorology | accessdate=2006-12-14 | publisher = [[Allen Press]]}}</ref> in weaker tropical cyclones, the CDO may cover the center completely.<ref name = "AOML FAQ A9">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is a "CDO"? | publisher = [[NOAA]] | accessdate = 2007-03-23 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A9.html}}</ref> The [[eyewall]] is a circle of strong thunderstorms that surrounds the eye; here is where the greatest wind speeds are found, where clouds reach the highest, and precipitation is the heaviest. The heaviest wind damage occurs where a hurricane's eyewall passes over land.<ref name="JetStream structure"/> Associated with eyewalls are [[Eye (cyclone)#Eyewall replacement cycle|eyewall replacement cycles]], which occur naturally in intense tropical cyclones. When cyclones reach peak intensity they usually—but not always—have an eyewall and [[radius of maximum wind]]s that contract to a very small size, around 10–25 km (5 to 15 miles). At this point, some of the outer rainbands may organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and [[angular momentum]]. During this phase, the tropical cyclone weakens (i.e., the maximum winds die off somewhat and the central pressure goes up), but eventually the outer eyewall replaces the inner one completely. The storm can be of the same intensity as it was previously or, in some cases, it can be even stronger after the eyewall replacement cycle. Even if the cyclone is weaker at the end of the cycle, the storm may strengthen again as it builds a new outer ring for the next eyewall replacement.<ref name = "AOML FAQ D8">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What are "concentric eyewall cycles" (or "eyewall replacement cycles") and why do they cause a hurricane's maximum winds to weaken? | publisher = [[NOAA]] | accessdate = 2006-12-14 | url = http://www.aoml.noaa.gov/hrd/tcfaq/D8.html}}</ref> |
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⚫ | A tropical cyclone's primary [[energy]] source is the release of the [[heat of condensation]] from water vapor [[condensation|condensing]] at high altitudes, with [[solar heating]] being the initial source for evaporation. Therefore, a tropical cyclone can be visualized as a giant vertical [[heat engine]] supported by mechanics driven by physical forces such as the [[rotation]] and [[gravity]] of the [[Earth]].<ref name = "NOAA preparedness">{{cite web | author = [[National Weather Service]] | date = September 2006 | title = Hurricanes... Unleashing Nature's Fury: A Preparedness Guide | publisher = [[NOAA]] | accessdate = 2006-12-02 | format = PDF | url = http://www.weather.gov/os/hurricane/pdfs/Hurricane_unleashing06.pdf}}</ref> In another way, tropical cyclones could be viewed as a special type of [[Mesoscale Convective Complex|mesoscale convective complex]], which continues to develop over a vast source of relative warmth and moisture. Condensation leads to higher wind speeds, as a tiny fraction of the released energy is converted into mechanical energy;<ref name = "AOML FAQ C5c">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by nuking them? | publisher = [[NOAA]] | accessdate = 2006-07-25|url = http://www.aoml.noaa.gov/hrd/tcfaq/C5c.html}}</ref> the faster winds and lower pressure associated with them in turn cause increased surface evaporation and thus even more condensation. Much of the released energy drives [[vertical draft|updrafts]] that increase the height of the storm clouds, speeding up condensation.<ref name="NOAA Question of the Month">{{cite web | author = [[National Oceanic & Atmospheric Administration]] | url = http://www.noaa.gov/questions/question_082900.html | title = NOAA Question of the Month: How much energy does a hurricane release? | date = August 2000 | accessdate=2006-03-31 | publisher = [[NOAA]]}}</ref> This gives rise to factors that provide the system with enough energy to be self-sufficient, and cause a [[positive feedback loop]] that continues as long as the tropical cyclone can draw energy from a [[heat sink|thermal reservoir]]. In this case, the heat source is the warm water at the surface of the ocean. Factors such as a continued lack of equilibrium in air mass distribution would also give supporting energy to the cyclone. The rotation of the Earth causes the system to spin, an effect known as the [[Coriolis effect]], giving it a cyclonic characteristic and affecting the trajectory of the storm. |
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The factors to form a tropical cyclone include a pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds aloft. If the right conditions persist and allow it to create a feedback loop by maximizing the energy intake possible – for example, such as high winds to increase the rate of evaporation – they can combine to produce the violent winds, incredible waves, torrential rains, and floods associated with this phenomenon. |
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What primarily distinguishes tropical cyclones from other meteorological phenomena is deep [[convection#Atmospheric heat-driven convection|convection]] as a driving force.<ref name="BOM Question 6">{{cite web | author = [[Bureau of Meteorology]] | work = Frequently Asked Questions | title = How are tropical cyclones different to mid-latitude cyclones? | url = http://www.bom.gov.au/weather/wa/cyclone/about/faq/faq_def_6.shtml | accessdate = 2006-03-31}}</ref> Because convection is strongest in a [[tropical climate]], it defines the initial domain of the tropical cyclone. By contrast, [[mid-latitude cyclone]]s draw their energy mostly from pre-existing horizontal temperature [[gradient]]s in the atmosphere.<ref name="BOM Question 6"/> To continue to drive its heat engine, a tropical cyclone must remain over warm water, which provides the needed atmospheric moisture to maintain the positive feedback loop running. As a result, when a tropical cyclone passes over land, it is cut off from its heat source and its strength diminishes rapidly.<ref name = "AOML FAQ C2">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Doesn't the friction over land kill tropical cyclones?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C2.html}}</ref> |
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[[Image:GulfMexTemps 2005Hurricanes.gif|thumb|180px|Chart displaying the drop in surface temperature in the [[Gulf of Mexico]] as Hurricanes [[Hurricane Katrina|Katrina]] and [[Hurricane Rita|Rita]] passed over]] |
[[Image:GulfMexTemps 2005Hurricanes.gif|thumb|180px|Chart displaying the drop in surface temperature in the [[Gulf of Mexico]] as Hurricanes [[Hurricane Katrina|Katrina]] and [[Hurricane Rita|Rita]] passed over]] |
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The passage of a tropical cyclone over the ocean can cause the upper ocean to cool substantially, which can influence subsequent cyclone development. Cooling is primarily caused by upwelling of cold water from |
The passage of a tropical cyclone over the ocean can cause the upper layers of the ocean to cool substantially, which can influence subsequent cyclone development. Cooling is primarily caused by upwelling of cold water from deeper in the ocean due to the wind stresses the storm itself induces upon the sea surface. Additional cooling may come in the form of cold water from falling raindrops. Cloud cover may also play a role in cooling the ocean, by shielding the ocean surface from direct sunlight before and slightly after the storm passage. All these effects can combine to produce a dramatic drop in sea surface temperature over a large area in just a few days.<ref name="NASA Cooling">{{cite web | author = Earth Observatory | url = http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17164 | title = Passing of Hurricanes Cools Entire Gulf | year = 2005 | accessdate = 2006-04-26 | publisher = [[NASA|National Aeronautics and Space Administration]]}}</ref> |
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Scientists at the [[National Center for Atmospheric Research]] estimate that a tropical cyclone releases heat energy at the rate of 50 to 200 [[1000000000000 (number)|trillion]] [[joule]]s per day.<ref name="NOAA Question of the Month"/> For comparison, this rate of energy release is equivalent to exploding a 10-megaton [[nuclear bomb]] every 20 minutes<ref name="UCAR">[[University Corporation for Atmospheric Research]] [http://www.ucar.edu/news/features/hurricanes/index.jsp Hurricanes: Keeping an eye on weather's biggest bullies] accessed March 31, 2006</ref> |
Scientists at the [[National Center for Atmospheric Research]] estimate that a tropical cyclone releases heat energy at the rate of 50 to 200 [[1000000000000 (number)|trillion]] [[joule]]s per day.<ref name="NOAA Question of the Month"/> For comparison, this rate of energy release is equivalent to 200 times the world-wide electrical generating capacity per day,<ref name="NOAA Question of the Month"/> or to exploding a 10-[[megaton]] [[nuclear bomb]] every 20 minutes.<ref name="UCAR">[[University Corporation for Atmospheric Research]] [http://www.ucar.edu/news/features/hurricanes/index.jsp Hurricanes: Keeping an eye on weather's biggest bullies] accessed March 31, 2006</ref> |
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While the most obvious motion of clouds is toward the center, tropical cyclones also develop an upper-level (high-altitude) outward flow of clouds. These originate from air that has released its moisture and is expelled at high altitude through the "chimney" of the storm engine.<ref name = "NOAA preparedness"/> This outflow produces high, thin [[cirrus cloud]]s that spiral away from the center. |
While the most obvious motion of clouds is toward the center, tropical cyclones also develop an upper-level (high-altitude) outward flow of clouds. These originate from air that has released its moisture and is expelled at high altitude through the "chimney" of the storm engine.<ref name = "NOAA preparedness"/> This outflow produces high, thin [[cirrus cloud]]s that spiral away from the center. These high cirrus clouds may be the first signs of an approaching tropical cyclone when seen from dry land.<ref name = "AOML FAQ H5">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What's it like to go through a hurricane on the ground? What are the early warning signs of an approaching tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-26 | url = http://www.aoml.noaa.gov/hrd/tcfaq/H5.html}}</ref> |
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==Major basins and related warning centers== |
==Major basins and related warning centers== |
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⚫ | There are six [[Regional Specialised Meteorological Centre]]s (RSMCs) worldwide. These organizations are designated by the [[World Meteorological Organization]] and are responsible for tracking and issuing bulletins, warnings, and advisories about tropical cyclones in their designated areas of responsibility. Additionally, there are five [[Tropical Cyclone Warning Centre]]s (TCWCs) that provide information to smaller regions.<ref name="WMO RSMC list">{{cite web | author = [[World Meteorological Organization]] | title = RSMCs | date = [[April 25]], [[2006]] | accessdate = 2006-11-05 | work = Tropical Cyclone Programme (TCP) | url = http://www.wmo.ch/web/www/TCP/rsmcs.html}}</ref> The RSMCs and TCWCs, however, are not the only organizations that provide information about tropical cyclones to the public. The [[Joint Typhoon Warning Center]] (JTWC) issues informal advisories in all basins except the Northern Atlantic and Northeastern Pacific. The [[Philippine Atmospheric, Geophysical and Astronomical Services Administration]] (PAGASA) issues informal advisories and names for tropical cyclones that approach the [[Philippines]] in the Northwestern Pacific. The [[Canadian Hurricane Centre]] (CHC) issues advisories on hurricanes and their remnants when they affect Canada. |
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=== Warning centers === |
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⚫ | There are six [[Regional Specialised Meteorological Centre]]s (RSMCs) worldwide. These organizations are designated by the [[World Meteorological Organization]] and are responsible for tracking and issuing bulletins, warnings, and advisories about tropical cyclones in their designated areas of responsibility. Additionally, there are five [[Tropical Cyclone Warning Centre]]s (TCWCs) that provide information to smaller regions.<ref name="WMO RSMC list">{{cite web | author = [[World Meteorological Organization]] | title = RSMCs | date = [[April 25]], [[2006]] | accessdate = 2006-11-05 | work = Tropical Cyclone Programme (TCP) | url = http://www.wmo.ch/web/www/TCP/rsmcs.html}}</ref> The RSMCs and TCWCs, however, are not the only organizations that provide information about tropical cyclones to the public. The [[Joint Typhoon Warning Center]] (JTWC) issues informal advisories in all basins except the Northern Atlantic and Northeastern Pacific. The [[Philippine Atmospheric, Geophysical and Astronomical Services Administration]] (PAGASA) issues informal advisories |
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On [[March 26]], [[2004]], [[Cyclone Catarina]] became the first recorded [[South Atlantic tropical cyclone|South Atlantic cyclone]] and subsequently struck southern [[Brazil]] as the equivalence of a Category 2 hurricane on the [[Saffir-Simpson Hurricane Scale]]. As the cyclone formed outside of the authority of another warning center, Brazilian meteorologists initially treated the system as an [[extratropical cyclone]], though subsequently classified it as tropical.<ref name="Emerson Marcelino">{{cite web | author = Marcelino, Emerson Vieira; Isabela Pena Viana de Oliveira Marcelino; Frederico de Moraes Rudorff | title = Cyclone Catarina: Damage and Vulnerability Assessment | url = http://www.dsr.inpe.br/geu/Rel_projetos/Relatorio_IAI_Emerson_Marcelino.pdf | format = PDF | date = 2004 | accessdate = 2006-12-24 | publisher = Santa Catarina Federal University}}</ref> |
On [[March 26]], [[2004]], [[Cyclone Catarina]] became the first recorded [[South Atlantic tropical cyclone|South Atlantic cyclone]] and subsequently struck southern [[Brazil]] as the equivalence of a Category 2 hurricane on the [[Saffir-Simpson Hurricane Scale]]. As the cyclone formed outside of the authority of another warning center, Brazilian meteorologists initially treated the system as an [[extratropical cyclone]], though subsequently classified it as tropical.<ref name="Emerson Marcelino">{{cite web | author = Marcelino, Emerson Vieira; Isabela Pena Viana de Oliveira Marcelino; Frederico de Moraes Rudorff | title = Cyclone Catarina: Damage and Vulnerability Assessment | url = http://www.dsr.inpe.br/geu/Rel_projetos/Relatorio_IAI_Emerson_Marcelino.pdf | format = PDF | date = 2004 | accessdate = 2006-12-24 | publisher = Santa Catarina Federal University}}</ref> |
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== Formation== |
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⚫ | Worldwide, tropical cyclone activity peaks in late [[summer]] when the difference between temperatures aloft and sea surface temperatures |
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===Times=== |
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⚫ | Worldwide, tropical cyclone activity peaks in late [[summer]], when the difference between temperatures aloft and sea surface temperatures is the greatest. However, each particular basin has its own seasonal patterns. On a worldwide scale, May is the least active month, while September is the most active.<ref name = "AOML FAQ G1">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: When is hurricane season?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/G1.html}}</ref> |
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In the North [[Atlantic Ocean|Atlantic]], a distinct hurricane season occurs from [[June 1]] to [[November 30]], sharply peaking from late August through September. The statistical peak of the North Atlantic hurricane season is [[September 10]]. The Northeast Pacific has a broader period of activity, but in a similar time frame to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November.<ref name = "AOML FAQ G1"/> |
In the North [[Atlantic Ocean|Atlantic]], a distinct hurricane season occurs from [[June 1]] to [[November 30]], sharply peaking from late August through September.<ref name = "AOML FAQ G1"/> The statistical peak of the North Atlantic hurricane season is [[September 10]]. The Northeast Pacific has a broader period of activity, but in a similar time frame to the Atlantic.<ref name="NHC Atl climatology">{{cite web | author = McAdie, Colin | publisher = [[National Hurricane Center]] | title = Tropical Cyclone Climatology | url = http://www.nhc.noaa.gov/pastprofile.shtml | date = [[May 10]], [[2007]] | accessdate = 2007-06-09}}</ref> The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November.<ref name = "AOML FAQ G1"/> |
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In the [[Southern Hemisphere]], tropical cyclone activity begins in late October and ends in May. Southern Hemisphere activity peaks in mid-February to early March.<ref name = "AOML FAQ G1"/> |
In the [[Southern Hemisphere]], tropical cyclone activity begins in late October and ends in May. Southern Hemisphere activity peaks in mid-February to early March.<ref name = "AOML FAQ G1"/> |
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{|class="wikitable" style="font-size: 92%;" |
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! colspan=6 style="background: #ccf;" | Season |
! colspan=6 style="background: #ccf;" | Season lengths and seasonal averages<ref name = "AOML FAQ G1"/><ref name = "AOML FAQ E10">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What are the average, most, and least tropical cyclones occurring in each basin? | publisher = [[NOAA]] | accessdate = 2006-11-30 | url = http://www.aoml.noaa.gov/hrd/tcfaq/E10.html}}</ref> |
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! Basin !! Season |
! Basin !! Season start !! Season end !! Tropical Storms<br />(>34 knots) !! Tropical Cyclones<br />(>63 knots)!! Category 3+ TCs<br />(>95 knots) |
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| Northwest Pacific || April || January || 26.7 || 16.9 || 8.5 |
| Northwest Pacific || April || January || 26.7 || 16.9 || 8.5 |
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== |
===Factors=== |
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===Factors in formation=== |
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[[Image:Atlantic hurricane graphic.gif|thumb|180px|right|Waves in the trade winds in the Atlantic Ocean—areas of converging winds that move along the same track as the prevailing wind—create instabilities in the atmosphere that may lead to the formation of hurricanes.]] |
[[Image:Atlantic hurricane graphic.gif|thumb|180px|right|Waves in the trade winds in the Atlantic Ocean—areas of converging winds that move along the same track as the prevailing wind—create instabilities in the atmosphere that may lead to the formation of hurricanes.]] |
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The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood. |
The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood. While six factors appear to be generally necessary, tropical cyclones may occasionally form without meeting all of the following conditions. In most situations, [[Sea surface temperature|water temperatures]] of at least 26.5 °C (80 °F) are needed<ref name = "AOML FAQ A15">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: How do tropical cyclones form? | publisher = [[NOAA]] | accessdate = 2006-07-26 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A15.html}}</ref> down to a depth of at least 50 m (150 feet). Waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms.<ref name = "AOML FAQ A16">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why do tropical cyclones require 80 °F (26.5 °C) ocean temperatures to form?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A16.html}}</ref> Another factor is rapid cooling with height. This allows the release of [[latent heat]], which is the source of energy in a tropical cyclone.<ref name = "AOML FAQ A15"/> High humidity is needed, especially in the lower-to-mid [[troposphere]]; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop.<ref name = "AOML FAQ A15"/> Low amounts of [[wind shear]] are needed, as when shear is high, the convection in a cyclone or disturbance will be disrupted, preventing formation of the feedback loop.<ref name = "AOML FAQ A15"/> Tropical cyclones generally need to form more than 500 km (310 miles) or 5 degrees of [[latitude]] away from the [[equator]]. This allows the [[Coriolis effect]] to deflect winds blowing towards the low pressure center, causing a circulation.<ref name = "AOML FAQ A15"/> Lastly, a formative tropical cyclone needs a pre-existing system of disturbed weather. The system must have some sort of circulation as well as a low pressure center.<ref name = "AOML FAQ A15"/> |
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===Locations |
===Locations=== |
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Most tropical cyclones form in a worldwide band of thunderstorm activity called by several names: the Intertropical Discontinuity (ITD), the [[Intertropical Convergence Zone]] (ITCZ), or the [[monsoon trough]]. Another important source of atmospheric instability is found in [[tropical wave]]s, which cause about 85% of intense tropical cyclones in the Atlantic ocean,<ref name="MWR Avila 1995">{{cite journal | last = [[Lixion Avila|Avila, Lixion]] | coauthors = Richard Pasch | year = 1995 | month = March | title = Atlantic tropical systems of 1993 | journal = [[Monthly Weather Review]] | volume = 123 | issue = 3 | pages = 887-896 | url = http://ams.allenpress.com/perlserv/?request=res-loc&uri=urn%3Aap%3Apdf%3Adoi%3A10.1175%2F1520-0493%281995%29123%3C0887%3AATSO%3E2.0.CO%3B2 | format = PDF | accessdate = 2006-07-25 }}</ref> and |
Most tropical cyclones form in a worldwide band of thunderstorm activity called by several names: the Intertropical Discontinuity (ITD), the [[Intertropical Convergence Zone]] (ITCZ), or the [[monsoon trough]]. Another important source of atmospheric instability is found in [[tropical wave]]s, which cause about 85% of intense tropical cyclones in the Atlantic ocean,<ref name="MWR Avila 1995">{{cite journal | last = [[Lixion Avila|Avila, Lixion]] | coauthors = Richard Pasch | year = 1995 | month = March | title = Atlantic tropical systems of 1993 | journal = [[Monthly Weather Review]] | volume = 123 | issue = 3 | pages = 887-896 | url = http://ams.allenpress.com/perlserv/?request=res-loc&uri=urn%3Aap%3Apdf%3Adoi%3A10.1175%2F1520-0493%281995%29123%3C0887%3AATSO%3E2.0.CO%3B2 | format = PDF | accessdate = 2006-07-25 }}</ref> and become most of the tropical cyclones in the Eastern Pacific basin.<ref name = "AOML FAQ A4">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an easterly wave? | publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A4.html}}</ref><ref name="Landsea 1993">{{cite journal | author = [[Chris Landsea|Landsea, Chris]] | url = http://ams.allenpress.com/perlserv/?request=res-loc&uri=urn%3Aap%3Apdf%3Adoi%3A10.1175%2F1520-0493%281993%29121%3C1703%3AACOIMA%3E2.0.CO%3B2 | format = PDF | title = A Climatology of Intense (or Major) Atlantic Hurricanes | journal = [[Monthly Weather Review]] | volume = 121 | issue = 6 | year = 1993 | month = June | accessdate = 2006-03-25 | pages = 1703-1713}}</ref> |
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Tropical cyclones |
Tropical cyclones originate on the eastern side of oceans, but move west, intensifying as they move. Most of these systems form between 10 and 30 degrees away of the [[equator]], and 87% form no farther away than 20 degrees of latitude, north or south. Because the [[Coriolis effect]] initiates and maintains tropical cyclone rotation, tropical cyclones rarely form or move within about 5 degrees of the equator, where the Coriolis effect is weakest.<ref name=BOMmap>{{cite web | publisher = [[Bureau of Meteorology]] | url = http://www.bom.gov.au/bmrc/pubs/tcguide/ch1/figures_ch1/figure1.9.htm | title = Worldwide Tropical Cyclone Tracks 1979-88 | author = Neumann, Charles J. | work = Global Guide to Tropical Cyclone Forecasting | accessdate = 2006-12-12}}</ref> However, it is possible for tropical cyclones to form within this boundary as did [[Typhoon Vamei]] in 2001 and [[Cyclone Agni]] in 2004. |
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==Movement and track== |
==Movement and track== |
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Although tropical cyclones are large systems generating enormous energy, their movements over the Earth's surface are controlled by large-scale winds—the streams in the Earth's atmosphere. The path of motion is referred to as a tropical cyclone's ''track'' and has been analogized by Dr. Neil Frank, former director of the [[National Hurricane Center]], to "leaves carried along by a stream."<ref name = "AOML FAQ G6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What determines the movement of tropical cyclones?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/G6.html}}</ref> |
Although tropical cyclones are large systems generating enormous energy, their movements over the Earth's surface are controlled by large-scale winds—the streams in the Earth's atmosphere. The path of motion is referred to as a tropical cyclone's ''track'' and has been analogized by Dr. Neil Frank, former director of the [[National Hurricane Center]], to "leaves carried along by a stream."<ref name = "AOML FAQ G6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What determines the movement of tropical cyclones?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/G6.html}}</ref> |
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Tropical systems, while generally located [[equator]]ward of the |
Tropical systems, while generally located [[equator]]ward of the 20<sup>th</sup> parallel, are steered primarily westward by the east-to-west winds on the equatorward side of the [[subtropical ridge]]—a persistent high pressure area over the world's oceans.<ref name = "AOML FAQ G6"/> In the tropical North Atlantic and Northeast Pacific oceans, [[trade winds]]—another name for the westward-moving wind currents—steer [[tropical waves]] westward from the [[Africa]]n coast and towards the Caribbean Sea, North America, and ultimately into the central Pacific ocean before the waves dampen out.<ref name = "AOML FAQ A4">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an easterly wave? | publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A4.html}}</ref> These waves are the precursors to many tropical cyclones within this region.<ref name="MWR Avila 1995">{{cite journal | last = [[Lixion Avila|Avila, Lixion]] | coauthors = Richard Pasch | year = 1995 | month = March | title = Atlantic tropical systems of 1993 |journal = [[Monthly Weather Review]] | volume = 123 | issue = 3 | pages = 887-896 | url = http://ams.allenpress.com/pdfserv/10.1175%2F1520-0493(1995)123%3C0887:ATSO%3E2.0.CO%3B2 | format = PDF | accessdate = 2006-07-25 }}</ref> In the Indian Ocean and Western Pacific (both north and south of the equator), tropical cyclogenesis is strongly influenced by the seasonal movement of the [[Intertropical Convergence Zone]] and the [[monsoon trough]], rather than by easterly waves.<ref name="MILLER7">{{cite web | author = DeCaria, Alex | publisher = [[Millersville University of Pennsylvania|Millersville University]] | url = http://www.atmos.millersville.edu/~adecaria/ESCI344/esci344_lesson08_TC_climatology.html | title = Lesson 7 – Tropical Cyclones: Climatology. | work = ESCI 344 – Tropical Meteorology | year = 2005 | accessdate = 2006-11-26}}</ref> |
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===Coriolis effect=== |
===Coriolis effect=== |
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[[Image:Cyclone Monica.gif|thumb|180px|right|Infrared image of [[Cyclone Monica]] near peak intensity, showing [[clockwise]] rotation due to the [[Coriolis effect]].]] |
[[Image:Cyclone Monica.gif|thumb|180px|right|Infrared image of [[Cyclone Monica]] near peak intensity, showing [[clockwise]] rotation due to the [[Coriolis effect]].]] |
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The Earth's rotation imparts an acceleration known as the ''Coriolis Acceleration'' or '' |
The Earth's rotation imparts an acceleration known as the ''[[Coriolis Effect]]'', ''Coriolis Acceleration'', or colloquially, ''Coriolis Force''. This acceleration causes cyclonic systems to turn towards the poles in the absence of strong steering currents.<ref name="Paleoglossary Cn-Cz">{{cite web | author = Baum, Steven K. | url = http://stommel.tamu.edu/~baum/paleo/paleogloss/node10.html | title = The Glossary: Cn-Cz. | work = Glossary of Oceanography and the Related Geosciences with References | publisher = [[Texas A&M University]] | date = [[January 20]], [[1997]] | accessdate = 2006-11-29}}</ref> The poleward portion of a tropical cyclone contains easterly winds, and the Coriolis effect pulls them slightly more poleward. The westerly winds on the equatorward portion of the cyclone pull slightly towards the equator, but, because the Coriolis effect weakens toward the equator, the net drag on the cyclone is poleward. Thus, tropical cyclones in the [[Northern Hemisphere]] usually turn north (before being blown east), and tropical cyclones in the [[Southern Hemisphere]] usually turn south (before being blown east) when no other effects counteract the Coriolis effect. |
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The Coriolis |
The Coriolis effect also initiates cyclonic rotation, but it is not the driving force that brings this rotation to high speeds. These speeds instead result from [[conservation of angular momentum]]. This means that air is drawn in from an area much larger than the cyclone such that the tiny rotational speed (originally imparted by the Coriolis effect) is magnified greatly as the air is drawn into the low pressure center.<ref name="Angular Momentum">{{cite web | publisher = [[University of Tennessee]] | url = http://csep10.phys.utk.edu/astr161/lect/solarsys/angmom.html | title = Conservation of Angular Momentum | work = Astronomy 161 Lectures | accessdate = 2006-11-29}}</ref> |
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===Interaction with the mid-latitude westerlies=== |
===Interaction with the mid-latitude westerlies=== |
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[[Image:Ioke 2006 track.png|thumb|right|Strom track of [[Hurricane Ioke|Typhoon Ioke]], showing recurvature off the [[Japan]]ese coast in [[2006 Pacific hurricane season|2006]]]] |
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When a tropical cyclone crosses the [[subtropical ridge]] axis, its general track around the high-pressure area is deflected significantly by winds moving towards the general low-pressure area to its north. When the cyclone track becomes strongly poleward with an easterly component, the cyclone has begun ''recurvature.''<ref>U. S. Navy. [http://www.nrlmry.navy.mil/~chu/chap4/se200.htm SECTION 2: TROPICAL CYCLONE MOTION TERMINOLOGY.] Retrieved on [[2007-04-10]].</ref> A typhoon moving through the Pacific Ocean towards [[Asia]], for example, will recurve to the north and then |
When a tropical cyclone crosses the [[subtropical ridge]] axis, its general track around the high-pressure area is deflected significantly by winds moving towards the general low-pressure area to its north. When the cyclone track becomes strongly poleward with an easterly component, the cyclone has begun ''recurvature.''<ref>U. S. Navy. [http://www.nrlmry.navy.mil/~chu/chap4/se200.htm SECTION 2: TROPICAL CYCLONE MOTION TERMINOLOGY.] Retrieved on [[2007-04-10]].</ref> A typhoon moving through the Pacific Ocean towards [[Asia]], for example, will recurve offshore of [[Japan]] to the north, and then to the northeast, if the typhoon encounters winds blowing northeastward toward a low-pressure system passing over [[China]] or [[Siberia]]. Many tropical cyclones are eventually forced toward the northeast by [[extratropical cyclone]]s, which move from west to east to the north of the subtropical ridge. An example of a tropical cyclone in recurvature was [[Hurricane Ioke|Typhoon Ioke]] in 2006, which took a similar trajectory.<ref name="CPHC Ioke">{{cite web | url = http://www.prh.noaa.gov/cphc/summaries/2006.php#ioke | title = Hurricane Ioke: 20-27 August 2006 | date = May 2007 | accessdate = 2007-06-09 | author = Powell, Jeff, et al. | work = 2006 Tropical Cyclones Central North Pacific | publisher = [[Central Pacific Hurricane Center]]}}</ref> |
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===Landfall=== |
===Landfall=== |
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{{see also|List of notable tropical cyclones|Tropical cyclogenesis#Unusual areas of formation|l2=Unusual areas of tropical cyclone formation}} |
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Officially, |
Officially, ''[[landfall (meteorology)|landfall]]'' is when a storm's center (the center of its circulation, not its edge) crosses the coastline.<ref name="NHC glossary"/> Storm conditions may be experienced on the coast and inland hours before landfall; in fact, a tropical cyclone can launch its strongest winds over land, yet not make landfall; if this occurs, then it is said that the storm made a ''direct hit'' on the coast.<ref name="NHC glossary"/> Due to this definition, the landfall area experiences half of a land-bound storm by the time the actual landfall occurs. For emergency preparedness, actions should be timed from when a certain wind speed or intensity of rainfall will reach land, not from when landfall will occur.<ref name="NHC glossary">{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/aboutgloss.shtml | year = 2005 | title = Glossary of NHC/TPC Terms | accessdate= 2006-11-29 | publisher = [[National Oceanic and Atmospheric Administration]]}}</ref> |
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==Dissipation== |
==Dissipation== |
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=== Factors === |
=== Factors === |
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[[Image:TropicalStormFranklin05.jpg|thumb|right|180px|[[Tropical Storm Franklin (2005)|Tropical Storm Franklin]], an example of a strongly [[windshear|sheared]] tropical cyclone in the [[Atlantic hurricane|Atlantic Basin]] during [[2005 Atlantic hurricane season|2005]]]] |
[[Image:TropicalStormFranklin05.jpg|thumb|right|180px|[[Tropical Storm Franklin (2005)|Tropical Storm Franklin]], an example of a strongly [[windshear|sheared]] tropical cyclone in the [[Atlantic hurricane|Atlantic Basin]] during [[2005 Atlantic hurricane season|2005]]]] |
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A tropical cyclone can cease to have tropical characteristics |
A tropical cyclone can cease to have tropical characteristics through several different ways. One such way is if it moves over land, thus depriving it of the warm water it needs to power itself, quickly losing strength. Most strong storms lose their strength very rapidly after landfall and become disorganized areas of low pressure within a day or two, or evolve into [[extratropical cyclone]]s. While there is a chance a tropical cyclone could regenerate it managed to get back over open warm water, if it remains over mountains for even a short time, it can rapidly lose its structure. Many storm fatalities occur in mountainous terrain, as the dying storm unleashes torrential rainfall, leading to deadly [[flood]]s and [[mudslide]]s, similar to those that happened with [[Hurricane Mitch]] in 1998. Additionally, dissipation can occur if a storm remains in the same area of ocean for too long, mixing the upper 30 meters (100 feet) of water. This occurs because the cyclone draws up colder water from deeper in the sea through [[upwelling]], and causes the water surface to become too cool to support the storm. Without warm surface water, the storm cannot survive.<ref name="Shays et al 1989">{{cite journal | url = http://ams.allenpress.com/archive/1520-0485/19/5/pdf/i1520-0485-19-5-649.pdf | author = Shay, Lynn K., Russell L. Elsberry and Peter G. Black | title = Vertical Structure of the Ocean Current Response to a Hurricane | month = May | year = 1989 | accessdate = 2006-12-12 | format = PDF | journal = Journal of Physical Oceanography | volume = 19 | issue = 5}}</ref> |
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A tropical cyclone can dissipate when it moves over waters significantly below 26 °C. This will cause the storm to lose its tropical characteristics (i.e. thunderstorms near the center and warm core) and become a remnant low pressure area, which can persist for several days. This is the main dissipation mechanism in the Northeast Pacific ocean.<ref name="Edwards genesis">{{cite web | author = Edwards, Jonathan | url = http://www.hurricanezone.net/articles/tropical-cyclone-formation.html | title = Tropical Cyclone Formation | accessdate = 2006-11-30 | publisher = HurricaneZone.net}}</ref> Weakening or dissipation can occur if it experiences vertical [[wind shear]], causing the convection and heat engine to move away from the center |
A tropical cyclone can dissipate when it moves over waters significantly below 26.5 °C. This will cause the storm to lose its tropical characteristics (i.e. thunderstorms near the center and warm core) and become a remnant low pressure area, which can persist for several days. This is the main dissipation mechanism in the Northeast Pacific ocean.<ref name="Edwards genesis">{{cite web | author = Edwards, Jonathan | url = http://www.hurricanezone.net/articles/tropical-cyclone-formation.html | title = Tropical Cyclone Formation | accessdate = 2006-11-30 | publisher = HurricaneZone.net}}</ref> Weakening or dissipation can occur if it experiences vertical [[wind shear]], causing the convection and heat engine to move away from the center; this normally ceases development of a tropical cyclone.<ref name="EAM">{{citebook|title=East Asian Monsoon |author= Chih-Pei Chang|year= 2004|publisher=World Scientific|id=ISBN 9812387692 |url=http://books.google.com/books?vid=ISBN9812387692&id=N8QYOdqGdgkC&pg=PA484&lpg=PA484&ots=jH3lLnS6LHie=ISO-8859-1&output=html&sig=Dxv5vz1f9RSR-VHJPygruiitADo}}</ref> Additionally, its interaction with the main belt of the Westerlies, by means of merging with a nearby frontal zone, can cause tropical cyclones to evolve into [[extratropical cyclones]]. This transition can take 1–3 days.<ref name = "JWTC intensity">{{cite web | url = http://www.nrlmry.navy.mil/~chu/chap6/se300.htm | author = [[United States Naval Research Laboratory]] | work = Tropical Cyclone Forecasters' Reference Guide| title = Tropical Cyclone Intensity Terminology | accessdate = 2006-11-30 | date = [[September 23]], [[1999]]}}</ref> Even after a tropical cyclone is said to be extratropical or dissipated, it can still have tropical storm force (or occasionally hurricane force) winds and drop several inches of rainfall. In the [[Pacific ocean]] and [[Atlantic ocean]], such tropical-derived cyclones of higher latitudes can be violent and may occasionally remain at hurricane-force wind speeds when they reach the west coast of [[North America]]. These phenomena can also affect Europe, where they are known as ''[[European windstorm]]s''; [[Hurricane Iris (1995)|Hurricane Iris]]'s extratropical remnants became one in 1995.<ref name="IrisTCR">{{cite web| author = Rappaport, Edward N. | url= http://www.nhc.noaa.gov/1995iris.html | title=Preliminary Report: Hurricane Iris: 22 August-4 September 1995 | publisher=[[National Hurricane Center]] | date=[[November 2]], [[2000]]|accessdate=2006-11-29}}</ref> Additionally, a cyclone can merge with another area of low pressure, becoming a larger area of low pressure. This can strengthen the resultant system, although it may no longer be a tropical cyclone.<ref name="EAM"/> |
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===Artificial dissipation=== |
===Artificial dissipation=== |
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In the 1960s and 1970s, the United States government attempted to weaken hurricanes |
In the 1960s and 1970s, the [[United States government]] attempted to weaken hurricanes through [[Project Stormfury]] by [[cloud seeding|seeding]] selected storms with [[silver iodide]]. It was thought that the seeding would cause [[supercooled water]] in the outer rainbands to freeze, causing the inner eyewall to collapse and thus reducing the winds. The winds of [[1969 Atlantic hurricane season#Hurricane Debbie|Hurricane Debbie]]—a hurricane seeded in Project Stormfury—dropped as much as 30%, but Debby regained its strength after each of two seeding forays. In an earlier episode in 1947, disaster struck when a hurricane east of [[Jacksonville, Florida]] promptly changed its course after being seeded, and smashed into [[Savannah, Georgia]].<ref name="Whipple 151">{{cite book | author = Whipple, Addison | year = 1982 | title = Storm | pages = 151 | location = [[Alexandria, Virginia|Alexandria, VA]] | publisher = [[Time Life|Time Life Books]] | id = ISBN 0-8094-4312-0}}</ref> Because there was so much uncertainty about the behavior of these storms, the federal government would not approve seeding operations unless the hurricane had a less than 10% chance of making landfall within 48 hours, greatly reducing the number of possible test storms. The project was dropped after it was discovered that [[eye (cyclone)#eyewall replacement cycles|eyewall replacement cycles]] occur naturally in strong hurricanes, casting doubt on the result of the earlier attempts. Today, it is known that silver iodide seeding is not likely to have an effect because the amount of supercooled water in the rainbands of a tropical cyclone is too low.<ref name = "AOML FAQ C5a">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by seeding them with silver iodide?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C5a.html}}</ref> |
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Other approaches have been suggested over time, including cooling the water under a tropical cyclone by towing [[iceberg]]s into the tropical oceans, dropping large quantities of ice into the eye at very early stages so that latent heat is absorbed by ice |
Other approaches have been suggested over time, including cooling the water under a tropical cyclone by towing [[iceberg]]s into the tropical oceans.<ref name = "AOML FAQ C5e"/> Other ideas range from covering the ocean in a substance that inhibits evaporation,<ref name = "AOML FAQ C5b">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by placing a substance on the ocean surface? |publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C5b.html}}</ref> dropping large quantities of ice into the eye at very early stages of development (so that the [[heat of condensation|latent heat]] is absorbed by the ice, instead of being converted to kinetic energy that would feed the positive feedback loop),<ref name = "AOML FAQ C5e">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by cooling the surface waters with icebergs or deep ocean water? |publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C5e.html}}</ref> or blasting the cyclone apart with nuclear weapons.<ref name = "AOML FAQ C5c">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by nuking them? |publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C5c.html}}</ref> Project Cirrus even involved throwing dry ice on a cyclone.<ref name="Sudden Sea">{{cite book | author = Scotti, R. A. | title = Sudden Sea: the Great Hurricane of 1938 | year = 2003 | pages=47 | edition = 1st ed. | publisher = Little, Brown, and Company | id = ISBN 0-316-73911-1}}</ref> These approaches all suffer from the same flaw: tropical cyclones are simply too large for any of them to be practical.<ref name = "AOML FAQ C5f">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why do not we try to destroy tropical cyclones by (fill in the blank)?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C5f.html}}</ref> |
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==Effects== |
==Effects== |
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[[Image:Hurricane katrina damage gulfport mississippi.jpg|thumb|180px|right|The aftermath of [[Hurricane Katrina]] in [[Gulfport, Mississippi]]. Katrina was the costliest tropical cyclone in [[United States]] history.]] |
[[Image:Hurricane katrina damage gulfport mississippi.jpg|thumb|180px|right|The aftermath of [[Hurricane Katrina]] in [[Gulfport, Mississippi]]. Katrina was the costliest tropical cyclone in [[United States]] history.]] |
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{{ |
{{main|Effects of tropical cyclones}} |
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Tropical cyclones out at sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks.<ref name="18cva">{{cite web|author=David Roth and Hugh Cobb|year=2001|title=Eighteenth Century Virginia Hurricanes|publisher=NOAA|accessdate=2007-02-24|url=http://www.hpc.ncep.noaa.gov/research/roth/va18hur.htm}}</ref> Tropical cyclones stir up water, leaving a cool wake behind them,<ref name="NASA Cooling"/> which causes the region to be less favourable for subsequent tropical cyclones. |
Tropical cyclones out at sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks.<ref name="18cva">{{cite web|author=David Roth and Hugh Cobb|year=2001|title=Eighteenth Century Virginia Hurricanes|publisher=NOAA|accessdate=2007-02-24|url=http://www.hpc.ncep.noaa.gov/research/roth/va18hur.htm}}</ref> Tropical cyclones stir up water, leaving a cool wake behind them,<ref name="NASA Cooling"/> which causes the region to be less favourable for subsequent tropical cyclones. On land, strong [[wind]]s can damage or destroy vehicles, buildings, bridges, and other outside objects, turning loose debris into deadly flying projectiles. The [[storm surge]], or the increase in sea level due to the cyclone, is typically the worst effect from landfalling tropical cyclones, historically resulting in 90% of tropical cyclone deaths.<ref name="oxfo">{{cite web|author=James M. Shultz, Jill Russell and Zelde Espinel|year=2005|title=Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development|publisher=Oxford Journal|accessdate=2007-02-24|url=http://epirev.oxfordjournals.org/cgi/content/full/27/1/21}}</ref> |
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The broad rotation of a landfalling tropical cyclone, and vertical wind shear at its periphery, spawns [[History of tropical cyclone-spawned tornadoes|tornadoes]]. Tornadoes can also be spawned |
The broad rotation of a landfalling tropical cyclone, and vertical wind shear at its periphery, spawns [[History of tropical cyclone-spawned tornadoes|tornadoes]]. Tornadoes can also be spawned |
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as a result of [[Eye (cyclone)#Eyewall mesovortices|eyewall mesovortices]], which persist until landfall.<ref name = "AOML FAQ L6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Are TC tornadoes weaker than midlatitude tornadoes?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/L6.html}}</ref> Within the last two centuries, tropical cyclones have been responsible for the deaths of about 1.9 million persons worldwide. Large areas of standing water caused by flooding lead to infection, as well as contributing to mosquito-borne illnesses. Crowded evacuees in [[shelter]]s increase the risk of disease propagation.<ref name="Shultz Epid Reviews 2005"/> Tropical cyclones sigificantly interrupt infrastructure, leading to power outages, bridge destruction, and hamper reconstruction efforts.<ref name="Power failures">{{cite news|author=Staff Writer|date=2005-08-30|title=Hurricane Katrina Situation Report #11|publisher=Office of Electricity Delivery and Energy Reliability (OE) [[United States Department of Energy]]|accessdate=2007-02-24|url=http://www.oe.netl.doe.gov/docs/katrina/katrina_083005_1600.pdf | format = PDF}}</ref> |
as a result of [[Eye (cyclone)#Eyewall mesovortices|eyewall mesovortices]], which persist until landfall.<ref name = "AOML FAQ L6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Are TC tornadoes weaker than midlatitude tornadoes?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/L6.html}}</ref> Within the last two centuries, tropical cyclones have been responsible for the deaths of about 1.9 million persons worldwide. Large areas of standing water caused by flooding lead to infection, as well as contributing to mosquito-borne illnesses. Crowded evacuees in [[shelter]]s increase the risk of disease propagation.<ref name="Shultz Epid Reviews 2005"/> Tropical cyclones sigificantly interrupt infrastructure, leading to power outages, bridge destruction, and hamper reconstruction efforts.<ref name="Shultz Epid Reviews 2005"/><ref name="Power failures">{{cite news|author=Staff Writer|date=2005-08-30|title=Hurricane Katrina Situation Report #11|publisher=Office of Electricity Delivery and Energy Reliability (OE) [[United States Department of Energy]]|accessdate=2007-02-24|url=http://www.oe.netl.doe.gov/docs/katrina/katrina_083005_1600.pdf | format = PDF}}</ref> |
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Although cyclones take an enormous toll in lives and personal property, they may be important factors in the [[precipitation (meteorology)|precipitation]] regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions.<ref name="2005 EPac outlook">[[National Oceanic and Atmospheric Administration]] [http://www.cpc.ncep.noaa.gov/products/Epac_hurr/Epac_hurricane.html 2005 Tropical Eastern North Pacific Hurricane Outlook] accessed May 2, 2006</ref> Tropical cyclones also help maintain the global heat balance by moving warm, moist tropical air to the [[middle latitudes]] and polar regions.<ref name="Zurich">{{cite web | publisher = Zurich Financial Services | url = http://www.zurich.com/main/productsandsolutions/industryinsight/2005/july2005/industryinsight20050711_004.htm | title = Living With an Annual Disaster | date = July/August 2005 | accessdate = 2006-11-29}}</ref> The storm surge and winds of hurricanes may be destructive to human-made structures, but they also stir up the waters of coastal [[estuary|estuaries]], which are typically important fish breeding locales. Tropical cyclone destruction spurs redevelopment, greatly increasing local property values.<ref name="Christopherson">{{cite book | author = Christopherson, Robert W. | date = 1992 | title = Geosystems: An Introduction to Physical Geography | pages = 222–224 | publisher = Macmillan Publishing Company | location = [[New York City|New York]] | id = ISBN 0-02-322443-6}}</ref> |
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==Observation and forecasting== |
==Observation and forecasting== |
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{{main|Tropical cyclone observation}} |
{{main|Tropical cyclone observation}} |
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[[Image:Isidore091902-p3sunset.jpg|right|thumb|180px|Sunset view of [[Hurricane Isidore]]'s rainbands photographed at 7,000 feet.]] |
[[Image:Isidore091902-p3sunset.jpg|right|thumb|180px|Sunset view of [[Hurricane Isidore]]'s rainbands photographed at 7,000 feet.]] |
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Intense tropical cyclones pose a particular observation challenge. As they are a dangerous oceanic phenomenon and are relatively small, [[weather station]]s are rarely available on the site of the storm itself. Surface observations are generally available only if the storm is passing over an island or a coastal area, or if there is a nearby ship. Usually, real-time measurements are taken in the periphery of the cyclone, where conditions are less catastrophic and its true strength |
Intense tropical cyclones pose a particular observation challenge. As they are a dangerous oceanic phenomenon and are relatively small, [[weather station]]s are rarely available on the site of the storm itself. Surface observations are generally available only if the storm is passing over an island or a coastal area, or if there is a nearby ship. Usually, real-time measurements are taken in the periphery of the cyclone, where conditions are less catastrophic and its true strength cannot be evaluated. For this reason, there are teams of meteorologists that move into the path of tropical cyclones to help evaluate their strength at the point of landfall. |
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Tropical cyclones far from land are tracked by [[weather satellite]]s capturing [[visible light|visible]] and [[infrared]] images from space, usually at half-hour to quarter-hour intervals. As a storm approaches land, it can be observed by land-based [[Doppler radar]]. Radar plays a crucial role around landfall because it shows a storm's location and intensity minute by minute. |
Tropical cyclones far from land are tracked by [[weather satellite]]s capturing [[visible light|visible]] and [[infrared]] images from space, usually at half-hour to quarter-hour intervals. As a storm approaches land, it can be observed by land-based [[Doppler radar]]. Radar plays a crucial role around landfall because it shows a storm's location and intensity minute by minute. |
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[[In-situ]] measurements, in real-time, can be taken by sending specially equipped reconnaissance flights into the cyclone. In the Atlantic basin, these flights are regularly flown by United States government [[hurricane hunters]].<ref name="Hurricane Hunters">{{cite web | author = 403rd Wing | url = http://www.hurricanehunters.com | title = The Hurricane Hunters | publisher = [[Hurricane Hunters|53rd Weather Reconnaissance Squadron]] | accessdate = 2006-03-30}}</ref> The aircraft used are [[WC-130]] Hercules and [[WP-3D]] Orions, both four-engine [[turboprop]] cargo aircraft. These aircraft fly directly into the cyclone and take direct and remote-sensing measurements. The aircraft also launch [[GPS dropsonde]]s inside the cyclone. These sondes measure temperature, humidity, pressure, and especially winds between flight level and the ocean's surface. |
[[In-situ]] measurements, in real-time, can be taken by sending specially equipped reconnaissance flights into the cyclone. In the Atlantic basin, these flights are regularly flown by United States government [[hurricane hunters]].<ref name="Hurricane Hunters">{{cite web | author = 403rd Wing | url = http://www.hurricanehunters.com | title = The Hurricane Hunters | publisher = [[Hurricane Hunters|53rd Weather Reconnaissance Squadron]] | accessdate = 2006-03-30}}</ref> The aircraft used are [[WC-130]] Hercules and [[WP-3D]] Orions, both four-engine [[turboprop]] cargo aircraft. These aircraft fly directly into the cyclone and take direct and remote-sensing measurements. The aircraft also launch [[GPS dropsonde]]s inside the cyclone. These sondes measure temperature, humidity, pressure, and especially winds between flight level and the ocean's surface. A new era in hurricane observation began when a remotely piloted [[Aerosonde]], a small drone aircraft, was flown through Tropical Storm Ophelia as it passed Virginia's Eastern Shore during the 2005 hurricane season. A similar mission was also completed successfully in the western Pacific ocean. This demonstrated a new way to probe the storms at low altitudes that human pilots seldom dare.<ref name="SunHerald">{{cite news | author = Bowman, Lee | title = Drones defy heart of storm | url = http://www.sunherald.com/mld/sunherald/12699210.htm | publisher = [[The Sun Herald]] | accessdate = 2006-03-30}}</ref> |
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A new era in hurricane observation began when a remotely piloted [[Aerosonde]], a small drone aircraft, was flown through Tropical Storm Ophelia as it passed Virginia's Eastern Shore during the 2005 hurricane season. A similar mission was also completed successfully in the western Pacific ocean. This demonstrated a new way to probe the storms at low altitudes that human pilots seldom dare.<ref name="SunHerald">{{cite news | author = Bowman, Lee | title = Drones defy heart of storm | url = http://www.sunherald.com/mld/sunherald/12699210.htm | publisher = [[The Sun Herald]] | accessdate = 2006-03-30}}</ref> |
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[[Image:NHC Atlantic Forecast Error Trends.gif|thumb|right|180px|A general decrease in error trends in tropical cyclone path prediction is evident since the 1970s]] |
[[Image:NHC Atlantic Forecast Error Trends.gif|thumb|right|180px|A general decrease in error trends in tropical cyclone path prediction is evident since the 1970s]] |
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===Forecasting=== |
===Forecasting=== |
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{{seealso|Tropical cyclone forecasting|Tropical cyclone prediction model|Tropical cyclone rainfall forecasting}} |
{{seealso|Tropical cyclone forecasting|Tropical cyclone prediction model|Tropical cyclone rainfall forecasting}} |
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Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high- and low-pressure areas, and predicting how those areas will change during the life of a tropical system. The deep layer mean flow is considered to be the best tool in determining track direction and speed. If storms are significantly sheared, use of a lower |
Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high- and low-pressure areas, and predicting how those areas will change during the life of a tropical system. The deep layer mean flow is considered to be the best tool in determining track direction and speed. If storms are significantly sheared, use of wind speed measurements at a lower altitude, such as at the 700 [[mbar|hpa]] pressure surface (3000 meters or 10000 feet above sea level) will produce better predictions. Tropical forecasters also consider smoothing out short-term wobbles of the storm center in order a best practice, as it allows them to determine a more accurate trajectory.<ref>{{cite web | author = [[United States Navy]] | url = http://www.nrlmry.navy.mil/~chu/chap4/se100.htm | title = Influences on Tropical Cyclone Motion | accessdate = 2007-04-10}}</ref> High-speed computers and sophisticated simulation software allow forecasters to produce [[tropical cyclone prediction model|computer models]] that predict tropical cyclone tracks based on the future position and strength of high- and low-pressure systems. Combining forecast models with increased understanding of the forces that act on tropical cyclones, as well as with a wealth of data from Earth-orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades.<ref name="NHC forecast verifications models">{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/verification/verify6.shtml?#FIG1 | work = National Hurricane Center Forecast Verification | title = Annual average model track errors for Atlantic basin tropical cyclones for the period 1994-2005, for a homogeneous selection of "early" models | accessdate = 2006-11-30 | publisher = [[National Oceanic and Atmospheric Administration]] | date = [[May 22]], [[2006]]}}</ref> However, scientists say they are less skillful at predicting the intensity of tropical cyclones.<ref name="NHC forecast verifications Atlantic">{{cite web | author = [[National Hurricane Center]] | work = National Hurricane Center Forecast Verification | url = http://www.nhc.noaa.gov/verification/verify5.shtml? | title = Annual average official track errors for Atlantic basin tropical cyclones for the period 1989-2005, with least-squares trend lines superimposed | accessdate = 2006-11-30 | publisher = [[National Oceanic and Atmospheric Administration]] | date = [[May 22]], [[2006]]}}</ref> They attribute the lack of improvement in intensity forecasting to the complexity of tropical systems and an incomplete understanding of factors that affect their development. |
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==Classifications, terminology, and naming== |
==Classifications, terminology, and naming== |
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===Intensity classifications=== |
===Intensity classifications=== |
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{{main|Tropical cyclone scales}} |
{{main|Tropical cyclone scales}} |
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[[Image:Typhoon saomai 060807.jpg|thumb|right|180px|Three tropical cyclones at different stages of development. The weakest |
[[Image:Typhoon saomai 060807.jpg|thumb|right|180px|Three tropical cyclones at different stages of development. The weakest (left), demonstrates only the most basic circular shape. A stronger storm (top right) demonstrates [[rainbands|spiral banding]] and increased centralization, while the the strongest (lower right) has developed an [[eye (cyclone)|eye]].]] |
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Tropical cyclones are classified into three main groups, based on intensity: tropical depressions, tropical storms, and a third group of more intense storms, whose name depends on the region. For example, if a [[#Tropical Storm|tropical storm]] in the Northwestern Pacific reaches hurricane-strength winds on the [[Beaufort scale]], it is referred to as a ''typhoon''; if a tropical storm passes the same benchmark in the [[Pacific hurricane| |
Tropical cyclones are classified into three main groups, based on intensity: tropical depressions, tropical storms, and a third group of more intense storms, whose name depends on the region. For example, if a [[#Tropical Storm|tropical storm]] in the Northwestern Pacific reaches hurricane-strength winds on the [[Beaufort scale]], it is referred to as a ''typhoon''; if a tropical storm passes the same benchmark in the [[Pacific hurricane|Northeast Pacific Ocean]], or in [[Atlantic hurricane|the Atlantic]], it is called a ''hurricane''.<ref name="NHC glossary"/> Neither "hurricane" nor "typhoon" is used in the South Pacific. |
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Additionally, as indicated in the table below, each basin uses a separate [[Tropical cyclone scales|system of terminology]], making comparisons between different basins difficult. In the Pacific Ocean, hurricanes from the Central North Pacific sometimes cross the [[International Date Line]] into the Northwest Pacific, becoming typhoons (such as [[Hurricane Ioke|Hurricane/Typhoon Ioke]] in 2006); on rare occasions, the reverse will occur.<ref name="CPHC John TCR">{{cite web | author=[[Central Pacific Hurricane Center]] | title=Hurricane John Preliminary Report | publisher=[[National Oceanic and Atmospheric Administration]] | url=http://www.prh.noaa.gov/cphc/summaries/1994.php#John | year= 2004 | accessdate=2007-03-23}}</ref> It should also be noted that typhoons with sustained winds greater than 130 [[knot (speed)|knots]] (240 [[kilometres per hour|km/h]] or 150 [[miles per hour|mph]]) are called ''Super Typhoons'' by the Joint Typhoon Warning Center.<ref name="SUPERDUPER">{{cite web | author = Bouchard, R. H. | url = http://metocph.nmci.navy.mil/jtwc/pubref/References/where_have_all_the_super_typhoons_gone.ppt | title = A Climatology of Very Intense Typhoons: Or Where Have All the Super Typhoons Gone? | format = [[Microsoft PowerPoint|PPT]] | accessdate = 2006-12-05 | date = April 1990}}</ref> |
Additionally, as indicated in the table below, each basin uses a separate [[Tropical cyclone scales|system of terminology]], making comparisons between different basins difficult. In the Pacific Ocean, hurricanes from the Central North Pacific sometimes cross the [[International Date Line]] into the Northwest Pacific, becoming typhoons (such as [[Hurricane Ioke|Hurricane/Typhoon Ioke]] in 2006); on rare occasions, the reverse will occur.<ref name="CPHC John TCR">{{cite web | author=[[Central Pacific Hurricane Center]] | title=Hurricane John Preliminary Report | publisher=[[National Oceanic and Atmospheric Administration]] | url=http://www.prh.noaa.gov/cphc/summaries/1994.php#John | year= 2004 | accessdate=2007-03-23}}</ref> It should also be noted that typhoons with sustained winds greater than 130 [[knot (speed)|knots]] (240 [[kilometres per hour|km/h]] or 150 [[miles per hour|mph]]) are called ''Super Typhoons'' by the Joint Typhoon Warning Center.<ref name="SUPERDUPER">{{cite web | author = Bouchard, R. H. | url = http://metocph.nmci.navy.mil/jtwc/pubref/References/where_have_all_the_super_typhoons_gone.ppt | title = A Climatology of Very Intense Typhoons: Or Where Have All the Super Typhoons Gone? | format = [[Microsoft PowerPoint|PPT]] | accessdate = 2006-12-05 | date = April 1990}}</ref> |
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! NE Pacific &<br />N Atlantic<br />[[National Hurricane Center|NHC]] & [[Central Pacific Hurricane Center|CPHC]] |
! NE Pacific &<br />N Atlantic<br />[[National Hurricane Center|NHC]] & [[Central Pacific Hurricane Center|CPHC]] |
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|- |
|- |
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| 0–6 |
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| <28 |
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| Depression |
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| |
| Trop. Disturbance |
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|rowspan="3" |
|rowspan="3" | Tropical Low |
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|rowspan="3" |
|rowspan="3" | Tropical Depression |
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|rowspan="3" |
|rowspan="3" | Tropical Depression |
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|rowspan="2" |
|rowspan="2" | Tropical Depression |
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|rowspan="2" |
|rowspan="2" | Tropical Depression |
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|- |
|- |
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|rowspan="2" |
|rowspan="2" | 7 |
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| 28-29 |
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|rowspan="2" |
|rowspan="2" | Deep Depression |
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|rowspan="2" |
|rowspan="2" | Depression |
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|- |
|- |
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| 30-33 |
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|rowspan="3" |
|rowspan="3" | Tropical Storm |
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|rowspan="3" |
|rowspan="3" | Tropical Storm |
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|- |
|- |
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| 8–9 |
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| 34–47 |
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| Cyclonic Storm |
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| Moderate Tropical Storm |
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| Trop. Cyclone (1) |
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|rowspan="11" |
|rowspan="11" | Tropical Cyclone |
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| Tropical Storm |
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|- |
|- |
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| 10 |
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| 48–55 |
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|rowspan="2" |
|rowspan="2" | Severe Cyclonic Storm |
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|rowspan="2" |
|rowspan="2" | Severe Tropical Storm |
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|rowspan="2" |
|rowspan="2" | Tropical Cyclone (2) |
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|rowspan="2" |
|rowspan="2" | Severe Tropical Storm |
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|- |
|- |
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| 11 |
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| 56–63 |
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|rowspan="7" |
|rowspan="7" | Typhoon |
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|rowspan="2" |
|rowspan="2" | Hurricane (1) |
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|- |
|- |
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|rowspan="8" |
|rowspan="8" | 12 |
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| 64–72 |
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|rowspan="7" |
|rowspan="7" | Very Severe Cyclonic Storm |
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|rowspan="3" |
|rowspan="3" | Tropical Cyclone |
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|rowspan="2" |
|rowspan="2" | Severe Tropical Cyclone (3) |
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|rowspan="8" |
|rowspan="8" | Typhoon |
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|- |
|- |
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| 73–85 |
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| Hurricane (2) |
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|- |
|- |
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| 86–89 |
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|rowspan="3" |
|rowspan="3" | Severe Tropical Cyclone (4) |
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|rowspan="2" |
|rowspan="2" | Major Hurricane (3) |
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|- |
|- |
||
| 90–99 |
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|rowspan="3" |
|rowspan="3" | Intense Tropical Cyclone |
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|- |
|- |
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| 100–106 |
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|rowspan="3" |
|rowspan="3" | Major Hurricane (4) |
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|- |
|- |
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| 107-114 |
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|rowspan="3" |
|rowspan="3" | Severe Tropical Cyclone (5) |
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|- |
|- |
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| 115–119 |
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|rowspan="2" |
|rowspan="2" | Very Intense Tropical Cyclone |
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|rowspan="2" |
|rowspan="2" | Super Typhoon |
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|- |
|- |
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| >120 |
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| Super Cyclonic Storm |
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| Major Hurricane (5) |
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|} |
|} |
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==Notable tropical cyclones== |
==Notable tropical cyclones== |
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{{main|List of notable tropical cyclones|List of notable Atlantic hurricanes|List of notable Pacific hurricanes}} |
{{main|List of notable tropical cyclones|List of notable Atlantic hurricanes|List of notable Pacific hurricanes}} |
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Tropical cyclones that cause extreme destruction are rare, though when they occur, |
Tropical cyclones that cause extreme destruction are rare, though when they occur, they can cause great amounts of damage or thousands of fatalities. |
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The [[1970 Bhola cyclone]] is the deadliest tropical cyclone on record, killing over 300,000 people<ref name="faqe9">{{cite web|author=Chris Landsea|year=1993|title=Which tropical cyclones have caused the most deaths and most damage?|publisher=Hurricane Research Division|accessdate=2007-02-23|url=http://www.aoml.noaa.gov/hrd/tcfaq/E9.html}}</ref> and potentially as many as 1 million<ref name="1970death">{{cite news|author=Lawson|year=1999|title=South Asia: A history of destruction|publisher=[[BBC|British Broadcasting Corporation]]|accessdate=2007-02-23|url=http://news.bbc.co.uk/1/hi/world/south_asia/503139.stm}}</ref> after striking the densely population [[Ganges Delta]] region of [[Bangladesh]] on [[November 13]], [[1970]]. Its powerful |
The [[1970 Bhola cyclone]] is the deadliest tropical cyclone on record, killing over 300,000 people<ref name="faqe9">{{cite web|author=Chris Landsea|year=1993|title=Which tropical cyclones have caused the most deaths and most damage?|publisher=Hurricane Research Division|accessdate=2007-02-23|url=http://www.aoml.noaa.gov/hrd/tcfaq/E9.html}}</ref> and potentially as many as 1 million<ref name="1970death">{{cite news|author=Lawson|year=1999|title=South Asia: A history of destruction|publisher=[[BBC|British Broadcasting Corporation]]|accessdate=2007-02-23|url=http://news.bbc.co.uk/1/hi/world/south_asia/503139.stm}}</ref> after striking the densely population [[Ganges Delta]] region of [[Bangladesh]] on [[November 13]], [[1970]]. Its powerful storm surge was responsible for the high death toll.<ref name="faqe9"/> The [[List of North Indian Ocean cyclone seasons|North Indian cyclone basin]] has historically been the deadliest basin, with several cyclones since 1900 killing over 100,000 people, all in Bangladesh.<ref name="Shultz Epid Reviews 2005">{{cite journal | author = Shultz, James M., Jill Russell and Zelde Espinel | title = Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development | journal = Epidemiologic Reviews | volume = 27 | issue = 1 | pages = 21–25 | url = http://epirev.oxfordjournals.org/cgi/content/full/27/1/21 | date = July 2005 | accessdate=2006-12-14}}</ref><ref name="Deadliest cyclone">{{cite journal | author = Frank, Neil L. and S. A. Husain | title = The Deadliest Tropical Cyclone in History | date = June 1971 | url = http://ams.allenpress.com/archive/1520-0477/52/6/pdf/i1520-0477-52-6-438.pdf | format = PDF | journal = Bulletin of the American Meteorological Society | volume = 52 | issue = 6 | pages = 438–445 | accessdate = 2006-12-14}}</ref> Elsewhere, [[Typhoon Nina (1975)|Typhoon Nina]] killed 29,000 in [[China]] due to [[100-year flood|2000-year flooding]] which caused 62 dams along the [[Banqiao Dam]] to fail; another 145,000 were killed during the subsequent famine and epidemic.<ref name="nina75">{{cite web|author=Hydrology Department of Henan Province|year=2006|title=Flood and drought disaster|language=Chinese|accessdate=2007-02-23|url=http://www.hnsl.gov.cn/look0/article.php?L_Type=1&id=297}}</ref> The [[Great Hurricane of 1780]] is the deadliest [[Atlantic hurricane]] on record, killing about 22,000 people in the [[Lesser Antilles]].<ref name=NHCPastDeadly>{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/pastdeadlyapp1.shtml? | title = The Deadliest Atlantic Tropical Cyclones, 1492-1996 | accessdate = 2006-03-31 | date = [[April 22]], [[1997]] | publisher = [[National Oceanic and Atmospheric Administration]]}}</ref> A tropical cyclone does need not be particularly strong to cause memorable damage, primarily if the deaths are from rainfall or mudslides. [[Tropical Storm Thelma]] in November 1991 killed thousands in the [[Philippines]],<ref name="JTWCThelma">{{cite web | url = https://metocph.nmci.navy.mil/jtwc/atcr/1991atcr/pdf/wnp/27w.pdf | title = Typhoon Thelma (27W) | accessdate = 2006-03-31 | author = [[Joint Typhoon Warning Center]] | work = 1991 Annual Tropical Cyclone Report | format = PDF}}</ref> while in 1982, the unnamed tropical depression that eventually became [[Hurricane Paul (1982)|Hurricane Paul]] killed around 1,000 people in [[Central America]].<ref name="MWR Paul 1982">{{cite journal | author = Gunther, E. B., R.L. Cross, and R.A. Wagoner | title = Eastern North Pacific Tropical Cyclones of 1982 | url = http://ams.allenpress.com/archive/1520-0493/111/5/pdf/i1520-0493-111-5-1080.pdf | month = May | year = 1983 | journal = [[Monthly Weather Review]] | format = PDF | volume = 111 | issue = 5 | accessdate = 2006-03-31}}</ref> |
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[[Hurricane Katrina]] is estimated as the costliest tropical cyclone worldwide,<ref name="epi">{{cite web|author=Earth Policy Institute|year=2006|title=Hurricane Damages Sour to New Levels|publisher=United States Department of Commerce|accessdate=2007-02-23|url=http://www.earth-policy.org/Updates/2006/Update58_data.htm}}</ref> causing $81.2 billion in property damage (2005 USD)<ref name="KatrinaTCR">{{cite web|author = Knabb, Richard D., Jamie R. Rhome and Daniel P. Brown | url=http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf | format=PDF | title=Tropical Cyclone Report: Hurricane Katrina: 23-30 August 2005 | publisher=[[National Hurricane Center]] | date=[[December 20]], [[2005]] | accessdate=2006-05-30}}</ref> with overall damage estimates exceeding $100 billion (2005 USD).<ref name="epi"/> Katrina is considered the worst natural disaster caused by a hurricane in [[History of the United States|United States history]],<ref name="NHC Atlantic Monthly Report for August 2005">{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/archive/2005/tws/MIATWSAT_aug.shtml? | title = Monthly Tropical Weather Summary for the North Altantic, Caribbean Sea and the Gulf of Mexico | accessdate = 2006-03-31 | publisher = [[National Oceanic and Atmospheric Administration]] | date = August 2005}}</ref> killing at least 1,836 after striking [[Louisiana]] and [[Mississippi]] as a [[tropical cyclone scales|major hurricane]] in August 2005. [[Hurricane Iniki]] in 1992 was the most powerful storm to strike [[Hawaii]] in recorded history, hitting [[Kauai]] as a Category 4 hurricane, killing six people, and causing U.S. $3 billion in damage.<ref name="InikiTCR">{{cite web|publisher = [[National Oceanic and Atmospheric Administration]] | url= http://www.prh.noaa.gov/cphc/summaries/1992.php#Iniki | title=Hurricane Iniki Natural Disaster Survey Report |author=[[Central Pacific Hurricane Center]]| accessdate=2006-03-31}}</ref> Other destructive Eastern [[Pacific hurricane]]s include [[Hurricane Pauline|Pauline]] and [[Hurricane Kenna|Kenna]], both causing severe damage after striking [[Mexico]] as a major hurricane.<ref name="PaulineTCR">{{cite web | last=Lawrence | first=Miles B. | url=http://www.nhc.noaa.gov/1997pauline.html | title=Preliminary Report: Hurricane Pauline: 5-10 October 1997 | publisher=[[National Hurricane Center]] | date=[[November 7]], [[1997]] | accessdate=2006-03-31}}</ref><ref name="KennaTCR">{{cite web | author = [[James Franklin (meteorologist)|Franklin, James L]]. | url=http://www.nhc.noaa.gov/2002kenna.shtml | title=Tropical Cyclone Report: Hurricane Kenna: 22-26 October 2002 | publisher=[[National Hurricane Center]] | date=[[December 26]], [[2002]] | accessdate=2006-03-31}}</ref> In March 2004, [[Cyclone Gafilo]] struck northeastern [[Madagascar]] as a powerful cyclone, killing 74, affecting more than 200,000, and becoming the worst cyclone to affect the nation for over 20 years.<ref name="gafilo">{{cite web|author=World Food Programme|year=2004|title=WFP Assists Cyclone And Flood Victims in Madagascar|accessdate=2007-02-24|url=http://www.sidsnet.org/archives/other-newswire/2004/msg00182.html}}</ref> |
[[Hurricane Katrina]] is estimated as the costliest tropical cyclone worldwide,<ref name="epi">{{cite web|author=Earth Policy Institute|year=2006|title=Hurricane Damages Sour to New Levels|publisher=United States Department of Commerce|accessdate=2007-02-23|url=http://www.earth-policy.org/Updates/2006/Update58_data.htm}}</ref> causing $81.2 billion in property damage (2005 USD)<ref name="KatrinaTCR">{{cite web|author = Knabb, Richard D., Jamie R. Rhome and Daniel P. Brown | url=http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf | format=PDF | title=Tropical Cyclone Report: Hurricane Katrina: 23-30 August 2005 | publisher=[[National Hurricane Center]] | date=[[December 20]], [[2005]] | accessdate=2006-05-30}}</ref> with overall damage estimates exceeding $100 billion (2005 USD).<ref name="epi"/> Katrina is considered the worst natural disaster caused by a hurricane in [[History of the United States|United States history]],<ref name="NHC Atlantic Monthly Report for August 2005">{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/archive/2005/tws/MIATWSAT_aug.shtml? | title = Monthly Tropical Weather Summary for the North Altantic, Caribbean Sea and the Gulf of Mexico | accessdate = 2006-03-31 | publisher = [[National Oceanic and Atmospheric Administration]] | date = August 2005}}</ref> killing at least 1,836 after striking [[Louisiana]] and [[Mississippi]] as a [[tropical cyclone scales|major hurricane]] in August 2005.<ref name="KatrinaTCR"/> [[Hurricane Iniki]] in 1992 was the most powerful storm to strike [[Hawaii]] in recorded history, hitting [[Kauai]] as a Category 4 hurricane, killing six people, and causing U.S. $3 billion in damage.<ref name="InikiTCR">{{cite web|publisher = [[National Oceanic and Atmospheric Administration]] | url= http://www.prh.noaa.gov/cphc/summaries/1992.php#Iniki | title=Hurricane Iniki Natural Disaster Survey Report |author=[[Central Pacific Hurricane Center]]| accessdate=2006-03-31}}</ref> Other destructive Eastern [[Pacific hurricane]]s include [[Hurricane Pauline|Pauline]] and [[Hurricane Kenna|Kenna]], both causing severe damage after striking [[Mexico]] as a major hurricane.<ref name="PaulineTCR">{{cite web | last=Lawrence | first=Miles B. | url=http://www.nhc.noaa.gov/1997pauline.html | title=Preliminary Report: Hurricane Pauline: 5-10 October 1997 | publisher=[[National Hurricane Center]] | date=[[November 7]], [[1997]] | accessdate=2006-03-31}}</ref><ref name="KennaTCR">{{cite web | author = [[James Franklin (meteorologist)|Franklin, James L]]. | url=http://www.nhc.noaa.gov/2002kenna.shtml | title=Tropical Cyclone Report: Hurricane Kenna: 22-26 October 2002 | publisher=[[National Hurricane Center]] | date=[[December 26]], [[2002]] | accessdate=2006-03-31}}</ref> In March 2004, [[Cyclone Gafilo]] struck northeastern [[Madagascar]] as a powerful cyclone, killing 74, affecting more than 200,000, and becoming the worst cyclone to affect the nation for over 20 years.<ref name="gafilo">{{cite web|author=World Food Programme|year=2004|title=WFP Assists Cyclone And Flood Victims in Madagascar|accessdate=2007-02-24|url=http://www.sidsnet.org/archives/other-newswire/2004/msg00182.html}}</ref> |
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[[Image:Typhoonsizes.jpg|right|frame|The relative sizes of [[Typhoon Tip]], [[Cyclone Tracy]], and the United States.]] |
[[Image:Typhoonsizes.jpg|right|frame|The relative sizes of [[Typhoon Tip]], [[Cyclone Tracy]], and the United States.]] |
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The most intense storm on record was [[Typhoon Tip]] in the northwestern Pacific Ocean in 1979, which reached a minimum pressure of 870 |
The most intense storm on record was [[Typhoon Tip]] in the northwestern Pacific Ocean in 1979, which reached a minimum pressure of 870 [[millibar|mbar]] (25.69 [[inHg]]) and maximum sustained wind speeds of 165 knots (190 mph, 305 km/h).<ref name="jtwc">{{cite web | author=George M. Dunnavan & John W. Dierks | year=1980 | title=An Analysis of Super Typhoon Tip (October 1979) | publisher=Joint Typhoon Warning Center | accessdate=2007-01-24| format = PDF | url=http://ams.allenpress.com/archive/1520-0493/108/11/pdf/i1520-0493-108-11-1915.pdf}}</ref> Tip, however, does not solely hold the record for fastest sustained winds in a cyclone. [[1997 Pacific typhoon season#Typhoon Keith|Typhoon Keith]] in the Pacific and Hurricanes [[Hurricane Camille|Camille]] and [[Hurricane Allen|Allen]] in the North Atlantic currently share this record with Tip.<ref name="Weathermatrix Mitch">{{cite web | author = Ferrell, Jesse | publisher = Weathermatrix.net | url = http://www.weathermatrix.net/tropical/1998/13/mitch.html | title = Hurricane Mitch | accessdate = 2006-03-30 | date = [[October 26]], [[1998]]}}</ref> Camille was the only storm to actually strike land while at that intensity, making it, with 165 knots (190 mph, 305 km/h) sustained winds and 210 mph (335 km/h) gusts, the strongest tropical cyclone on record at landfall.<ref name="hurdat">{{cite web|author=NHC Hurricane Research Division|date=2006-02-17|title=Atlantic hurricane best track ("HURDAT")|publisher=NOAA|accessdate=2007-02-22|url=http://www.aoml.noaa.gov/hrd/hurdat/easyhurdat_5105.html#0_0}}</ref> [[Typhoon Nancy (1961)|Typhoon Nancy]] in 1961 had recorded wind speeds of 185 knots (215 mph, 345 km/h), but recent research indicates that wind speeds from the 1940s to the 1960s were gauged too high, and this is no longer considered the fastest storm on record.<ref name = "AOML FAQ E1">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Which is the most intense tropical cyclone on record? | publisher = [[NOAA]] | accessdate = 2006-07-25|url = http://www.aoml.noaa.gov/hrd/tcfaq/E1.html}}</ref> Similarly, a surface-level gust caused by [[Typhoon Paka]] on [[Guam]] was recorded at 205 knots (235 mph, 380 km/h). Had it been confirmed, it would be the strongest non-[[tornado|tornadic]] wind ever recorded on the [[Earth]]'s surface, but the reading had to be discarded since the [[anemometer]] was damaged by the storm.<ref name="NWSPaka">{{cite web | author = Houston, Sam, Greg Forbes and Arthur Chiu | publisher = [[National Weather Service]] | date = [[17 August]], [[1998]] | url = http://www.aoml.noaa.gov/hrd/project98/sh_proj1.html | title = Super Typhoon Paka's (1997) Surface Winds Over Guam | accessdate = 2006-03-30}}</ref> |
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In addition to being the most intense tropical cyclone on record, Tip was the largest cyclone on record, with tropical storm-force winds 2,170 km (1,350 miles) in diameter. The smallest storm on record, [[Cyclone Tracy]], was roughly 100 km (60 miles) wide before striking [[Darwin, Northern Territory|Darwin]], [[Australia]] in 1974.<ref name = "AOML FAQ E5">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Which are the largest and smallest tropical cyclones on record?|publisher = [[NOAA]] | accessdate= 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/E5.html}}</ref> |
In addition to being the most intense tropical cyclone on record, Tip was the largest cyclone on record, with tropical storm-force winds 2,170 km (1,350 miles) in diameter. The smallest storm on record, [[Cyclone Tracy]], was roughly 100 km (60 miles) wide before striking [[Darwin, Northern Territory|Darwin]], [[Australia]] in 1974.<ref name = "AOML FAQ E5">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Which are the largest and smallest tropical cyclones on record?|publisher = [[NOAA]] | accessdate= 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/E5.html}}</ref> |
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[[Hurricane John (1994)|Hurricane John]] is the longest-lasting tropical cyclone on record, lasting 31 days in [[1994 Pacific hurricane season|1994]]. Prior to the advent of satellite imagery in 1961, however, many tropical cyclones were underestimated in their durations.<ref name="john94">{{cite web|author=Neal Dorst|year=2006|title=Which tropical cyclone lasted the longest?|publisher=Hurricane Research Division|accessdate=2007-02-23|url=http://www.aoml.noaa.gov/hrd/tcfaq/E6.html}}</ref> John is the second longest-tracked tropical cyclone in the Northern Hemisphere on record, behind [[1960 Pacific typhoon season#Typhoon Ophelia|Typhoon Ophelia]] of 1960 which had a path of |
[[Hurricane John (1994)|Hurricane John]] is the longest-lasting tropical cyclone on record, lasting 31 days in [[1994 Pacific hurricane season|1994]]. Prior to the advent of satellite imagery in 1961, however, many tropical cyclones were underestimated in their durations.<ref name="john94">{{cite web|author=Neal Dorst|year=2006|title=Which tropical cyclone lasted the longest?|publisher=Hurricane Research Division|accessdate=2007-02-23|url=http://www.aoml.noaa.gov/hrd/tcfaq/E6.html}}</ref> John is the second longest-tracked tropical cyclone in the Northern Hemisphere on record, behind [[1960 Pacific typhoon season#Typhoon Ophelia|Typhoon Ophelia]] of 1960 which had a path of 8,500 miles (12,500 km). Reliable data for Southern Hemisphere cyclones is unavailable.<ref name="faqe7">{{cite web|author=Neal Dorst|year=2006|url=http://www.aoml.noaa.gov/hrd/tcfaq/E7.html|accessdate=2007-02-23|title=What is the farthest a tropical cyclone has traveled ?|publisher=Hurricane Research Division}}</ref> |
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== Long term trends |
== Long term activity trends == |
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[[Image:NOAA ACE index 1950-2004 RGB.svg|thumb|right|250px|Atlantic Multidecadal Cycle since 1950, using accumulated cyclone energy (ACE)]] |
[[Image:NOAA ACE index 1950-2004 RGB.svg|thumb|right|250px|Atlantic Multidecadal Cycle since 1950, using accumulated cyclone energy (ACE)]] |
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:{{seealso|Atlantic hurricane reanalysis}} |
:{{seealso|Atlantic hurricane reanalysis}} |
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While the number of storms in the Atlantic has increased since 1995, there is no obvious global trend; the annual |
While the number of storms in the Atlantic has increased since 1995, there is no obvious global trend; the annual number of tropical cyclones worldwide remains about 87 ± 10. However, the ability of climatologists to make long-term data analysis in certain basins is limited by the lack of reliable historical data in some basins, primarily in the Southern Hemisphere.<ref name="Landsea Trends">{{cite journal | author = [[Chris Landsea|Landsea, Chris]], et al. | title = Can We Detect Trends in Extreme Tropical Cyclones? | url = http://www.aoml.noaa.gov/hrd/Landsea/landseaetal-science06.pdf | journal = [[Science (journal)|Science]] | format = PDF| volume = 313 | pages = 452-4 | date = [[July 28]], [[2006]] | accessdate = 2007-06-09}}</ref> In spite of that, there is some evidence that the intensity of hurricanes is increasing. [[Kerry Emanuel]] stated, "Records of hurricane activity worldwide show an upswing of both the maximum wind speed in and the duration of hurricanes. The energy released by the average hurricane (again considering all hurricanes worldwide) seems to have increased by around 70% in the past 30 years or so, corresponding to about a 15% increase in the maximum wind speed and a 60% increase in storm lifetime."<ref name="EmanuelHomepage">{{cite web | url = http://wind.mit.edu/~emanuel/anthro2.htm | author = [[Kerry Emanuel|Emanuel, Kerry]] | title = Anthropogenic Effects on Tropical Cyclone Activity | accessdate = 2006-03-30 | date = January 2006}}</ref> |
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Atlantic storms are becoming more destructive financially, since five of the ten most expensive storms in [[United States]] history have occurred since 1990. This can be attributed to the increased intensity and duration of hurricanes striking North America,<ref name="EmanuelHomepage"/> and to a greater degree, the number of people living in susceptible coastal |
Atlantic storms are becoming more destructive financially, since five of the ten most expensive storms in [[United States]] history have occurred since 1990. This can be attributed to the increased intensity and duration of hurricanes striking North America,<ref name="EmanuelHomepage"/> and to a greater degree, the number of people living in susceptible coastal areas, following increased development in the region since the last surge in Atlantic hurricane activity in the 1960s. |
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Often in part because of the threat of hurricanes, many coastal regions had sparse population between major ports until the advent of automobile tourism; therefore, the most severe portions of hurricanes striking the coast may have gone unmeasured in some instances. The combined effects of ship destruction and remote landfall severely limit the number of intense hurricanes in the official record before the era of hurricane reconnaissance aircraft and satellite meteorology. Although the record shows a distinct increase in the number and strength of intense hurricanes, therefore, experts regard the early data as suspect.<ref name="BOM TC Guide 1.3">{{cite web | publisher = [[Bureau of Meteorology]] | url = http://www.bom.gov.au/bmrc/pubs/tcguide/ch1/ch1_3.htm | title = 1.3: A Global Climatology | author = Neumann, Charles J. | work = Global Guide to Tropical Cyclone Forecasting | accessdate = 2006-11-30}}</ref> |
Often in part because of the threat of hurricanes, many coastal regions had sparse population between major ports until the advent of automobile tourism; therefore, the most severe portions of hurricanes striking the coast may have gone unmeasured in some instances. The combined effects of ship destruction and remote landfall severely limit the number of intense hurricanes in the official record before the era of hurricane reconnaissance aircraft and satellite meteorology. Although the record shows a distinct increase in the number and strength of intense hurricanes, therefore, experts regard the early data as suspect.<ref name="BOM TC Guide 1.3">{{cite web | publisher = [[Bureau of Meteorology]] | url = http://www.bom.gov.au/bmrc/pubs/tcguide/ch1/ch1_3.htm | title = 1.3: A Global Climatology | author = Neumann, Charles J. | work = Global Guide to Tropical Cyclone Forecasting | accessdate = 2006-11-30}}</ref> |
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The number and strength of Atlantic hurricanes may undergo a 50-70 year cycle, also known as |
The number and strength of Atlantic hurricanes may undergo a 50-70 year cycle, also known as the [[Atlantic Multidecadal Oscillation]]. Although more common since 1995, few above-normal hurricane seasons occurred during 1970-1994.<ref name="RMS activity">{{cite web | author = [[Risk Management Solutions]] | url = http://www.rms.com/Publications/60HUActivityRates_whitepaper.pdf | format = PDF | title = U.S. and Caribbean Hurricane Activity Rates. | date = March 2006 | accessdate = 2006-11-30}}</ref> Destructive hurricanes struck frequently from 1926-60, including many major New England hurricanes. A record 21 Atlantic tropical storms formed in [[1933 Atlantic hurricane season|1933]], a record only recently exceeded in [[2005 Atlantic hurricane season|2005]], which saw 28 storms. Tropical hurricanes occurred infrequently during the seasons of 1900-1925; however, many intense storms formed 1870-1899. During the 1887 season, 19 tropical storms formed, of which a record 4 occurred after [[1 November]] and 11 strengthened into hurricanes. Few hurricanes occurred in the 1840s to 1860s; however, many struck in the early 1800s, including an 1821 storm that made a direct hit on [[New York City]]. Some historical weather experts say these storms may have been as high as [[Saffir-Simpson Hurricane Scale|Category 4]] in strength.<ref name="Columbia CCSR">{{cite web | author = Center for Climate Systems Research | title = Hurricanes, Sea Level Rise, and New York City | url = http://www.ccsr.columbia.edu/information/hurricanes/ | publisher = [[Columbia University]] | accessdate = 2006-11-29}}</ref> |
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These active hurricane seasons predated satellite coverage of the Atlantic basin. Before the satellite era began in 1960, tropical storms or hurricanes went undetected unless a ship reported a voyage through the storm or a storm hit land in a populated area.<ref name="BOM TC Guide 1.3"/> The official record, therefore, could miss storms in which no ship experienced gale-force winds, recognized it as a tropical storm (as opposed to a high-latitude extra-tropical cyclone, a tropical wave, or a brief squall), returned to port, and reported the experience. |
These active hurricane seasons predated satellite coverage of the Atlantic basin. Before the satellite era began in 1960, tropical storms or hurricanes went undetected unless a ship reported a voyage through the storm or a storm hit land in a populated area.<ref name="BOM TC Guide 1.3"/> The official record, therefore, could miss storms in which no ship experienced gale-force winds, recognized it as a tropical storm (as opposed to a high-latitude extra-tropical cyclone, a tropical wave, or a brief squall), returned to port, and reported the experience. |
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==Global warming== |
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The [[United States|U.S.]] [[National Oceanic and Atmospheric Administration]] [[Geophysical Fluid Dynamics Laboratory]] performed a simulation to determine if there is a [[statistics|statistical]] [[trend]] in the frequency or strength of cyclones. The simulation concluded "the strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century as the earth's climate is warmed by increasing levels of greenhouse gases in the atmosphere."<ref name="GFDL warming">{{cite web | author = [[Geophysical Fluid Dynamics Laboratory]] | url = http://www.oar.noaa.gov/spotlite/archive/spot_gfdl.html | title = Global Warming and Hurricanes | accessdate = 2006-11-29 | publisher = [[National Oceanic and Atmospheric Administration]]}}</ref> In an article in ''[[Nature (journal)|Nature]]'', [[Kerry Emanuel]] stated that potential hurricane destructiveness, a measure combining hurricane strength, duration, and frequency, "is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multidecadal oscillations in the North Atlantic and North Pacific, and global warming." Emanuel predicted "a substantial increase in hurricane-related losses in the twenty-first century."<ref name="Nature Emanuel 2005">{{cite journal | url = ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf | format = PDF | author = [[Kerry Emanuel|Emanuel, Kerry]] | journal =[[Nature (journal)|Nature]] | volume = 436 | issue = 7051 | pages = 686–688 | accessdate = 2006-03-20 | title = Increasing destructiveness of tropical cyclones over the past 30 years}}</ref> |
The [[United States|U.S.]] [[National Oceanic and Atmospheric Administration]] [[Geophysical Fluid Dynamics Laboratory]] performed a simulation to determine if there is a [[statistics|statistical]] [[trend]] in the frequency or strength of cyclones over time. The simulation concluded "the strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century as the earth's climate is warmed by increasing levels of greenhouse gases in the atmosphere."<ref name="GFDL warming">{{cite web | author = [[Geophysical Fluid Dynamics Laboratory]] | url = http://www.oar.noaa.gov/spotlite/archive/spot_gfdl.html | title = Global Warming and Hurricanes | accessdate = 2006-11-29 | publisher = [[National Oceanic and Atmospheric Administration]]}}</ref> In an article in ''[[Nature (journal)|Nature]]'', [[Kerry Emanuel]] stated that potential hurricane destructiveness, a measure combining hurricane strength, duration, and frequency, "is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multidecadal oscillations in the North Atlantic and North Pacific, and global warming." Emanuel predicted "a substantial increase in hurricane-related losses in the twenty-first century."<ref name="Nature Emanuel 2005">{{cite journal | url = ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf | format = PDF | author = [[Kerry Emanuel|Emanuel, Kerry]] | journal =[[Nature (journal)|Nature]] | volume = 436 | issue = 7051 | pages = 686–688 | accessdate = 2006-03-20 | title = Increasing destructiveness of tropical cyclones over the past 30 years}}</ref> |
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Similarly, P.J. Webster and others published an article in ''[[Science (journal)|Science]]'' examining the "changes in tropical cyclone number, duration, and intensity" over the last 35 years, the period when satellite data has been available. The main finding was although the number of cyclones decreased throughout the planet excluding the north [[Atlantic Ocean]], there was a great increase in the number and proportion of very strong cyclones.<ref name="Webster et al. 2005">{{cite journal | author = Webster, P. J., G. J. Holland, J. A. Curry and H.-R. Chang | url = http://www.sciencemag.org/cgi/reprint/309/5742/1844.pdf | title = Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment | format = PDF | journal = [[Science (journal)|Science]] | date = [[September 16]], [[2005]] | volume = 309 | issue = 5742 | pages = 1844-1846 | accessdate = 2006-03-20}}</ref> Both Emanuel and Webster et al. consider [[sea surface temperatures]] to be vital in the development of cyclones. The increase in temperatures is believed to be due to global warming and the hypothesized [[Atlantic Multidecadal Oscillation]] (AMO), a possible 50–70 year pattern of temperature variability. However, Emanuel observed the recent temperature increase as outside the range of previous sea surface temperature peaks. Thus, both global warming and a natural variation such as the AMO could have contributed to the warming of the tropical Atlantic over the past decades, though an exact attribution has not been defined.<ref name=realclimate/> |
Similarly, P.J. Webster and others published an article in ''[[Science (journal)|Science]]'' examining the "changes in tropical cyclone number, duration, and intensity" over the last 35 years, the period when satellite data has been available. The main finding was although the number of cyclones decreased throughout the planet excluding the north [[Atlantic Ocean]], there was a great increase in the number and proportion of very strong cyclones.<ref name="Webster et al. 2005">{{cite journal | author = Webster, P. J., G. J. Holland, J. A. Curry and H.-R. Chang | url = http://www.sciencemag.org/cgi/reprint/309/5742/1844.pdf | title = Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment | format = PDF | journal = [[Science (journal)|Science]] | date = [[September 16]], [[2005]] | volume = 309 | issue = 5742 | pages = 1844-1846 | accessdate = 2006-03-20}}</ref> Both Emanuel and Webster et al. consider [[sea surface temperatures]] to be vital in the development of cyclones. The increase in temperatures is believed to be due to global warming and the hypothesized [[Atlantic Multidecadal Oscillation]] (AMO), a possible 50–70 year pattern of temperature variability. However, Emanuel observed the recent temperature increase as outside the range of previous sea surface temperature peaks. Thus, both global warming and a natural variation such as the AMO could have contributed to the warming of the tropical Atlantic over the past decades, though an exact attribution has not been defined.<ref name=realclimate/> |
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In February 2007, the [[United Nations]] [[Intergovernmental Panel on Climate Change]] released its [[IPCC Fourth Assessment Report|fourth assessment report]] on [[climate change]]. The report noted many observed changes in the climate including atmospheric composition, global average temperatures, ocean conditions, |
In February 2007, the [[United Nations]] [[Intergovernmental Panel on Climate Change]] released its [[IPCC Fourth Assessment Report|fourth assessment report]] on [[climate change]]. The report noted many observed changes in the climate, including atmospheric composition, global average temperatures, ocean conditions, among others. The report concluded the observed increase in tropicaly intensity is larger than climate models predict. Additionally, the report considered that it is likely that storm intensity will continue to increase through the 21st century, and declared it more likely than not that there has been some human contribution to the increases in tropical cyclone intensity.<ref name="ipcc">{{cite web|author=Richard Alley, et. al|year=2007|title=Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change|publisher=United Nations|accessdate=2007-02-23|url=http://www.ipcc.ch/SPM2feb07.pdf|format=PDF}}</ref> However, there is no universal agreement about the magnitude of the effects anthropogenic global warming has on tropical cyclone formation, track, and intensity. For example, critics such as [[Chris Landsea]] assert that man-made effects would be "quite tiny compared to the observed large natural hurricane variability."<ref name = "AOML FAQ G3">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What may happen with tropical cyclone activity due to global warming? | publisher = [[NOAA]] | accessdate = 2007-06-02 | url = http://www.aoml.noaa.gov/hrd/tcfaq/G3.html}}</ref> A statement by the [[American Meteorological Society]] on [[February 1]], [[2007]] stated that trends in tropical cyclone records offer "evidence both for and against the existence of a detectable anthropogenic signal" in [[tropical cyclogenesis]].<ref name="AMS climate change">{{cite journal | title= Climate Change: An Information Statement of the American Meteorological Society | author = [[American Meteorological Society]] | date = 2007-02-01 | journal = Bulletin of the American Meteorological Society | pages = 5 | url = http://www.ametsoc.org/POLICY/2007climatechange.pdf | format = PDF | volume = 88 | accessdate = 2007-06-03}}</ref> Albeit many aspects of a link between tropical cyclones and global warming are still being "hotly debated",<ref name="IWTC-VI"/> a point of agreement is that no individual tropical cyclone or season can be attributed to global warming.<ref name="IWTC-VI">{{cite web|author = [[World Meteorological Organization]] | title = Statement on Tropical Cyclones and Climate Change | pages = 6 | url = http://www.wmo.ch/pages/themes/wmoprod/documents/iwtc_statement.pdf | format = PDF | date = [[December 11]], [[2006]] | accessdate = 2007-06-02}}</ref><ref name="realclimate">{{cite web | author = [[Stefan Rahmstorf|Rahmstorf, Stefan]], [[Michael Mann]], Rasmus Benestad, [[Gavin Schmidt]] and [[William Connolley]] | url = http://www.realclimate.org/index.php?p=181 | title = Hurricanes and Global Warming - Is There a Connection? | publisher = [[RealClimate]] | date = [[September 2]], [[2005]] | accessdate = 2006-03-20}}</ref> |
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==Related cyclone types== |
==Related cyclone types== |
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An ''extratropical cyclone'' is a storm that derives energy from horizontal temperature differences, which are typical in higher latitudes. A tropical cyclone can become extratropical as it moves toward higher latitudes if its energy source changes from heat released by condensation to differences in temperature between air masses;<ref name = "AOML FAQ A7">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an extra-tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html}}</ref> additionally, although not as frequently, an extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone. From space, extratropical storms have a characteristic "[[comma (punctuation)|comma]]-shaped" cloud pattern. Extratropical cyclones can also be dangerous when their low-pressure centers cause powerful winds and very high seas. |
An ''extratropical cyclone'' is a storm that derives energy from horizontal temperature differences, which are typical in higher latitudes. A tropical cyclone can become extratropical as it moves toward higher latitudes if its energy source changes from heat released by condensation to differences in temperature between air masses;<ref name = "AOML FAQ A7">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an extra-tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html}}</ref> additionally, although not as frequently, an extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone. From space, extratropical storms have a characteristic "[[comma (punctuation)|comma]]-shaped" cloud pattern. Extratropical cyclones can also be dangerous when their low-pressure centers cause powerful winds and very high seas. |
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A ''subtropical cyclone'' is a [[weather]] system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. They can form in a wide band of [[latitude]], from the [[equator]] to 50°. Although subtropical storms rarely have hurricane-force winds, they may become tropical in nature as their cores warm.<ref name = "AOML FAQ A6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is a sub-tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A6.html}}</ref> From an operational standpoint, a tropical cyclone is usually not considered to become subtropical during its extratropical transition.<ref name=PadgetDecember2000>{{cite web | author = Padgett, Gary | url = http://australiasevereweather.com/cyclones/2001/summ0012.txt | title = Monthly Global Tropical Cyclone Summary for December 2000 | year = 2001 | accessdate = 2006-03-31}}</ref> |
A ''subtropical cyclone'' is a [[weather]] system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. They can form in a wide band of [[latitude]]s, from the [[equator]] to 50°. Although subtropical storms rarely have hurricane-force winds, they may become tropical in nature as their cores warm.<ref name = "AOML FAQ A6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is a sub-tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A6.html}}</ref> From an operational standpoint, a tropical cyclone is usually not considered to become subtropical during its extratropical transition.<ref name=PadgetDecember2000>{{cite web | author = Padgett, Gary | url = http://australiasevereweather.com/cyclones/2001/summ0012.txt | title = Monthly Global Tropical Cyclone Summary for December 2000 | year = 2001 | accessdate = 2006-03-31}}</ref> |
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==Tropical cyclones in popular culture== |
==Tropical cyclones in popular culture== |
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==See also== |
==See also== |
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;Current seasons |
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* [[2007 Atlantic hurricane season]] |
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* [[2007 North Indian Ocean cyclone season]] |
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* [[2007 Pacific hurricane season]] |
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* [[2007 Pacific typhoon season]] |
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* [[2006-07 Southern Hemisphere tropical cyclone season]] |
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;Annual seasons |
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* [[List of Atlantic hurricane seasons]] |
* [[List of Atlantic hurricane seasons]] ([[2007 Atlantic hurricane season|current]]) |
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* [[List of Pacific hurricane seasons]] |
* [[List of Pacific hurricane seasons]] ([[2007 Pacific hurricane season|current]]) |
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* [[List of Pacific typhoon seasons]] |
* [[List of Pacific typhoon seasons]] ([[2007 Pacific typhoon season|current]]) |
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* [[List of North Indian Ocean cyclone seasons]] |
* [[List of North Indian Ocean cyclone seasons]] ([[2007 North Indian Ocean cyclone season|current]]) |
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* [[List of Southern Hemisphere tropical cyclone seasons]] |
* [[List of Southern Hemisphere tropical cyclone seasons]] ([[2006-07 Southern Hemisphere tropical cyclone season|current]]) |
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{{col-2}} |
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;Meteorology |
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*[[Lists of tropical cyclone names]] |
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*[[Mesoscale Convective Complex]] |
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*[[Tropical cyclogenesis]] |
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;Forecasting and preparation |
;Forecasting and preparation |
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* [[Catastrophe modeling]] |
* [[Catastrophe modeling]] |
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* [[Effects of tropical cyclones]] |
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* [[Hong Kong Tropical Cyclone Warning Signals]] |
* [[Hong Kong Tropical Cyclone Warning Signals]] |
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* [[Hurricane preparedness]] |
* [[Hurricane preparedness]] |
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* [[Hurricane proof building]] |
* [[Hurricane proof building]] |
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* [[Tropical cyclone forecasting]] |
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* [[Tropical cyclone watches and warnings]] |
* [[Tropical cyclone watches and warnings]] |
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{{col-end}} |
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;Categories |
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* [[:Category:Lists of tropical cyclones]] |
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* [[:Category:Tropical cyclones by basin]] |
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* [[:Category:Tropical cyclones by region]] |
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* [[:Category:Tropical cyclones by season]] |
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* [[:Category:Tropical cyclones by strength]] |
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{{Cyclones}} |
{{Cyclones}} |
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[[Category:Types of cyclone]] |
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Revision as of 05:35, 9 June 2007
Template:Tropical cycloneTemplate:Redirect4
A tropical cyclone is a meteorological term for a storm system characterized by a low pressure center and thunderstorms that produces strong wind and flooding rain. A tropical cyclone feeds on the heat released when moist air rises and the water vapor it contains condenses. Because tropical cyclones are "warm core" storm systems, they are fueled by a different heat mechanism than other cyclonic windstorms such as nor'easters, European windstorms, and polar lows.
The adjective "tropical" refers to both the geographic origin of these systems, which form almost exclusively in tropical regions of the globe, and their formation in Maritime Tropical air masses. The noun "cyclone" refers to such storms' cyclonic nature, with counterclockwise rotation in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere. Depending on their location and strength, tropical cyclones are referred to by various other names, such as hurricane, typhoon, tropical storm, cyclonic storm, and tropical depression.
While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and damaging storm surge. They develop over large bodies of warm water, and lose their strength if they move over land. This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from receiving strong winds. Heavy rains, however, can produce significant flooding inland, and storm surges can produce extensive coastal flooding up to 25 mi (40 km) from the coastline. Although their effects on human populations can be devastating, tropical cyclones can also relieve drought conditions. They also carry heat and energy away from the tropics and transport it towards temperate latitudes, which makes them an important part of the global atmospheric circulation mechanism. As a result, tropical cyclones help to maintain equilibrium in the Earth's troposphere, and to maintain a relatively stable and warm temperature worldwide.
Many tropical cyclones develop when the atmospheric conditions around a weak disturbance in the atmosphere are favorable. Others form when other types of cyclones acquire tropical characteristics. Tropical systems are then moved by steering winds in the troposphere; if the conditions remain favorable, the tropical disturbance intensifies, and can even develop an eye. On the other end of the spectrum, if the conditions around the system deteriorate or the tropical cyclone makes landfall, the system weakens and eventually dissipates.
Physical structure
![](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Hurricane_structure_graphic.jpg/250px-Hurricane_structure_graphic.jpg)
All tropical cyclones are areas of low atmospheric pressure near the Earth's surface. The pressures recorded at the centers of tropical cyclones are among the lowest that occur on Earth's surface at sea level.[1] Tropical cyclones are characterized and driven by the release of large amounts of latent heat of condensation, which occurs when moist air is carried upwards and its water vapor condenses. This heat is distributed vertically around the center of the storm. Thus, at any given altitude (except close to the surface, where water temperature dictates air temperature) the environment inside the cyclone is warmer than its outer surroundings.[2]
Rainbands are bands of showers and thunderstorms that spiral cyclonically toward the storm center. High wind gusts and heavy downpours often occur in individual rainbands, with relatively calm weather between bands. Tornadoes often form in the rainbands of landfalling tropical cyclones.[3] Intense annular tropical cyclones are distinctive for their lack of rainbands; instead, they possess a thick circular area of disturbed weather around their low pressure center.[4] While all surface low pressure areas require divergence aloft to continue deepening, the divergence over tropical cyclones is in all directions away from the center. The upper levels of a tropical cyclone feature winds directed away from the center of the storm with an anticyclonic rotation, due to the Coriolis effect. Winds at the surface are strongly cyclonic, weaken with height, and eventually reverse themselves. Tropical cyclones owe this unique characteristic to requiring a relative lack of vertical wind shear to maintain the warm core at the center of the storm.[5][6]
A strong tropical cyclone will harbor an area of sinking air at the center of circulation. If this area is strong enough, it can develop into an eye. Weather in the eye is normally calm and free of clouds, though the sea may be extremely violent.[3] The eye is normally circular in shape, and may range in size from 3 to 370 km (2–230 miles) in diameter.[7][8] Intense, mature hurricanes can sometimes exhibit an inward curving of the eyewall's top, making it resemble a football stadium; this phenomenon is thus sometimes referred to as the stadium effect.[9]
There are other features that either surround the eye, or cover it. The central dense overcast is the concentrated area of strong thunderstorm activity near the center of a tropical cyclone;[10] in weaker tropical cyclones, the CDO may cover the center completely.[11] The eyewall is a circle of strong thunderstorms that surrounds the eye; here is where the greatest wind speeds are found, where clouds reach the highest, and precipitation is the heaviest. The heaviest wind damage occurs where a hurricane's eyewall passes over land.[3] Associated with eyewalls are eyewall replacement cycles, which occur naturally in intense tropical cyclones. When cyclones reach peak intensity they usually—but not always—have an eyewall and radius of maximum winds that contract to a very small size, around 10–25 km (5 to 15 miles). At this point, some of the outer rainbands may organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and angular momentum. During this phase, the tropical cyclone weakens (i.e., the maximum winds die off somewhat and the central pressure goes up), but eventually the outer eyewall replaces the inner one completely. The storm can be of the same intensity as it was previously or, in some cases, it can be even stronger after the eyewall replacement cycle. Even if the cyclone is weaker at the end of the cycle, the storm may strengthen again as it builds a new outer ring for the next eyewall replacement.[12]
Mechanics
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/Hurricane_profile.svg/250px-Hurricane_profile.svg.png)
A tropical cyclone's primary energy source is the release of the heat of condensation from water vapor condensing at high altitudes, with solar heating being the initial source for evaporation. Therefore, a tropical cyclone can be visualized as a giant vertical heat engine supported by mechanics driven by physical forces such as the rotation and gravity of the Earth.[13] In another way, tropical cyclones could be viewed as a special type of mesoscale convective complex, which continues to develop over a vast source of relative warmth and moisture. Condensation leads to higher wind speeds, as a tiny fraction of the released energy is converted into mechanical energy;[14] the faster winds and lower pressure associated with them in turn cause increased surface evaporation and thus even more condensation. Much of the released energy drives updrafts that increase the height of the storm clouds, speeding up condensation.[15] This gives rise to factors that provide the system with enough energy to be self-sufficient, and cause a positive feedback loop that continues as long as the tropical cyclone can draw energy from a thermal reservoir. In this case, the heat source is the warm water at the surface of the ocean. Factors such as a continued lack of equilibrium in air mass distribution would also give supporting energy to the cyclone. The rotation of the Earth causes the system to spin, an effect known as the Coriolis effect, giving it a cyclonic characteristic and affecting the trajectory of the storm.
What primarily distinguishes tropical cyclones from other meteorological phenomena is deep convection as a driving force.[16] Because convection is strongest in a tropical climate, it defines the initial domain of the tropical cyclone. By contrast, mid-latitude cyclones draw their energy mostly from pre-existing horizontal temperature gradients in the atmosphere.[16] To continue to drive its heat engine, a tropical cyclone must remain over warm water, which provides the needed atmospheric moisture to maintain the positive feedback loop running. As a result, when a tropical cyclone passes over land, it is cut off from its heat source and its strength diminishes rapidly.[17]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/GulfMexTemps_2005Hurricanes.gif/180px-GulfMexTemps_2005Hurricanes.gif)
The passage of a tropical cyclone over the ocean can cause the upper layers of the ocean to cool substantially, which can influence subsequent cyclone development. Cooling is primarily caused by upwelling of cold water from deeper in the ocean due to the wind stresses the storm itself induces upon the sea surface. Additional cooling may come in the form of cold water from falling raindrops. Cloud cover may also play a role in cooling the ocean, by shielding the ocean surface from direct sunlight before and slightly after the storm passage. All these effects can combine to produce a dramatic drop in sea surface temperature over a large area in just a few days.[18]
Scientists at the National Center for Atmospheric Research estimate that a tropical cyclone releases heat energy at the rate of 50 to 200 trillion joules per day.[15] For comparison, this rate of energy release is equivalent to 200 times the world-wide electrical generating capacity per day,[15] or to exploding a 10-megaton nuclear bomb every 20 minutes.[19]
While the most obvious motion of clouds is toward the center, tropical cyclones also develop an upper-level (high-altitude) outward flow of clouds. These originate from air that has released its moisture and is expelled at high altitude through the "chimney" of the storm engine.[13] This outflow produces high, thin cirrus clouds that spiral away from the center. These high cirrus clouds may be the first signs of an approaching tropical cyclone when seen from dry land.[20]
Major basins and related warning centers
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There are six Regional Specialised Meteorological Centres (RSMCs) worldwide. These organizations are designated by the World Meteorological Organization and are responsible for tracking and issuing bulletins, warnings, and advisories about tropical cyclones in their designated areas of responsibility. Additionally, there are five Tropical Cyclone Warning Centres (TCWCs) that provide information to smaller regions.[22] The RSMCs and TCWCs, however, are not the only organizations that provide information about tropical cyclones to the public. The Joint Typhoon Warning Center (JTWC) issues informal advisories in all basins except the Northern Atlantic and Northeastern Pacific. The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) issues informal advisories and names for tropical cyclones that approach the Philippines in the Northwestern Pacific. The Canadian Hurricane Centre (CHC) issues advisories on hurricanes and their remnants when they affect Canada.
On March 26, 2004, Cyclone Catarina became the first recorded South Atlantic cyclone and subsequently struck southern Brazil as the equivalence of a Category 2 hurricane on the Saffir-Simpson Hurricane Scale. As the cyclone formed outside of the authority of another warning center, Brazilian meteorologists initially treated the system as an extratropical cyclone, though subsequently classified it as tropical.[23]
Formation
Times
Worldwide, tropical cyclone activity peaks in late summer, when the difference between temperatures aloft and sea surface temperatures is the greatest. However, each particular basin has its own seasonal patterns. On a worldwide scale, May is the least active month, while September is the most active.[24]
In the North Atlantic, a distinct hurricane season occurs from June 1 to November 30, sharply peaking from late August through September.[24] The statistical peak of the North Atlantic hurricane season is September 10. The Northeast Pacific has a broader period of activity, but in a similar time frame to the Atlantic.[25] The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November.[24]
In the Southern Hemisphere, tropical cyclone activity begins in late October and ends in May. Southern Hemisphere activity peaks in mid-February to early March.[24]
Season lengths and seasonal averages[24][26] | |||||
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Basin | Season start | Season end | Tropical Storms (>34 knots) |
Tropical Cyclones (>63 knots) |
Category 3+ TCs (>95 knots) |
Northwest Pacific | April | January | 26.7 | 16.9 | 8.5 |
South Indian | October | May | 20.6 | 10.3 | 4.3 |
Northeast Pacific | May | November | 16.3 | 9.0 | 4.1 |
North Atlantic | June | November | 10.6 | 5.9 | 2.0 |
Australia Southwest Pacific | October | May | 10.6 | 4.8 | 1.9 |
North Indian | April | December | 5.4 | 2.2 | 0.4 |
Factors
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Atlantic_hurricane_graphic.png/180px-Atlantic_hurricane_graphic.png)
The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood. While six factors appear to be generally necessary, tropical cyclones may occasionally form without meeting all of the following conditions. In most situations, water temperatures of at least 26.5 °C (80 °F) are needed[27] down to a depth of at least 50 m (150 feet). Waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms.[28] Another factor is rapid cooling with height. This allows the release of latent heat, which is the source of energy in a tropical cyclone.[27] High humidity is needed, especially in the lower-to-mid troposphere; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop.[27] Low amounts of wind shear are needed, as when shear is high, the convection in a cyclone or disturbance will be disrupted, preventing formation of the feedback loop.[27] Tropical cyclones generally need to form more than 500 km (310 miles) or 5 degrees of latitude away from the equator. This allows the Coriolis effect to deflect winds blowing towards the low pressure center, causing a circulation.[27] Lastly, a formative tropical cyclone needs a pre-existing system of disturbed weather. The system must have some sort of circulation as well as a low pressure center.[27]
Locations
Most tropical cyclones form in a worldwide band of thunderstorm activity called by several names: the Intertropical Discontinuity (ITD), the Intertropical Convergence Zone (ITCZ), or the monsoon trough. Another important source of atmospheric instability is found in tropical waves, which cause about 85% of intense tropical cyclones in the Atlantic ocean,[29] and become most of the tropical cyclones in the Eastern Pacific basin.[30][31]
Tropical cyclones originate on the eastern side of oceans, but move west, intensifying as they move. Most of these systems form between 10 and 30 degrees away of the equator, and 87% form no farther away than 20 degrees of latitude, north or south. Because the Coriolis effect initiates and maintains tropical cyclone rotation, tropical cyclones rarely form or move within about 5 degrees of the equator, where the Coriolis effect is weakest.[32] However, it is possible for tropical cyclones to form within this boundary as did Typhoon Vamei in 2001 and Cyclone Agni in 2004.
Movement and track
Steering winds
Although tropical cyclones are large systems generating enormous energy, their movements over the Earth's surface are controlled by large-scale winds—the streams in the Earth's atmosphere. The path of motion is referred to as a tropical cyclone's track and has been analogized by Dr. Neil Frank, former director of the National Hurricane Center, to "leaves carried along by a stream."[33]
Tropical systems, while generally located equatorward of the 20th parallel, are steered primarily westward by the east-to-west winds on the equatorward side of the subtropical ridge—a persistent high pressure area over the world's oceans.[33] In the tropical North Atlantic and Northeast Pacific oceans, trade winds—another name for the westward-moving wind currents—steer tropical waves westward from the African coast and towards the Caribbean Sea, North America, and ultimately into the central Pacific ocean before the waves dampen out.[30] These waves are the precursors to many tropical cyclones within this region.[29] In the Indian Ocean and Western Pacific (both north and south of the equator), tropical cyclogenesis is strongly influenced by the seasonal movement of the Intertropical Convergence Zone and the monsoon trough, rather than by easterly waves.[34]
Coriolis effect
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Cyclone_Monica.png/180px-Cyclone_Monica.png)
The Earth's rotation imparts an acceleration known as the Coriolis Effect, Coriolis Acceleration, or colloquially, Coriolis Force. This acceleration causes cyclonic systems to turn towards the poles in the absence of strong steering currents.[35] The poleward portion of a tropical cyclone contains easterly winds, and the Coriolis effect pulls them slightly more poleward. The westerly winds on the equatorward portion of the cyclone pull slightly towards the equator, but, because the Coriolis effect weakens toward the equator, the net drag on the cyclone is poleward. Thus, tropical cyclones in the Northern Hemisphere usually turn north (before being blown east), and tropical cyclones in the Southern Hemisphere usually turn south (before being blown east) when no other effects counteract the Coriolis effect.
The Coriolis effect also initiates cyclonic rotation, but it is not the driving force that brings this rotation to high speeds. These speeds instead result from conservation of angular momentum. This means that air is drawn in from an area much larger than the cyclone such that the tiny rotational speed (originally imparted by the Coriolis effect) is magnified greatly as the air is drawn into the low pressure center.[36]
Interaction with the mid-latitude westerlies
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/95/Ioke_2006_track.png/220px-Ioke_2006_track.png)
When a tropical cyclone crosses the subtropical ridge axis, its general track around the high-pressure area is deflected significantly by winds moving towards the general low-pressure area to its north. When the cyclone track becomes strongly poleward with an easterly component, the cyclone has begun recurvature.[37] A typhoon moving through the Pacific Ocean towards Asia, for example, will recurve offshore of Japan to the north, and then to the northeast, if the typhoon encounters winds blowing northeastward toward a low-pressure system passing over China or Siberia. Many tropical cyclones are eventually forced toward the northeast by extratropical cyclones, which move from west to east to the north of the subtropical ridge. An example of a tropical cyclone in recurvature was Typhoon Ioke in 2006, which took a similar trajectory.[38]
Landfall
Officially, landfall is when a storm's center (the center of its circulation, not its edge) crosses the coastline.[39] Storm conditions may be experienced on the coast and inland hours before landfall; in fact, a tropical cyclone can launch its strongest winds over land, yet not make landfall; if this occurs, then it is said that the storm made a direct hit on the coast.[39] Due to this definition, the landfall area experiences half of a land-bound storm by the time the actual landfall occurs. For emergency preparedness, actions should be timed from when a certain wind speed or intensity of rainfall will reach land, not from when landfall will occur.[39]
Dissipation
Factors
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/TropicalStormFranklin05.jpg/180px-TropicalStormFranklin05.jpg)
A tropical cyclone can cease to have tropical characteristics through several different ways. One such way is if it moves over land, thus depriving it of the warm water it needs to power itself, quickly losing strength. Most strong storms lose their strength very rapidly after landfall and become disorganized areas of low pressure within a day or two, or evolve into extratropical cyclones. While there is a chance a tropical cyclone could regenerate it managed to get back over open warm water, if it remains over mountains for even a short time, it can rapidly lose its structure. Many storm fatalities occur in mountainous terrain, as the dying storm unleashes torrential rainfall, leading to deadly floods and mudslides, similar to those that happened with Hurricane Mitch in 1998. Additionally, dissipation can occur if a storm remains in the same area of ocean for too long, mixing the upper 30 meters (100 feet) of water. This occurs because the cyclone draws up colder water from deeper in the sea through upwelling, and causes the water surface to become too cool to support the storm. Without warm surface water, the storm cannot survive.[40]
A tropical cyclone can dissipate when it moves over waters significantly below 26.5 °C. This will cause the storm to lose its tropical characteristics (i.e. thunderstorms near the center and warm core) and become a remnant low pressure area, which can persist for several days. This is the main dissipation mechanism in the Northeast Pacific ocean.[41] Weakening or dissipation can occur if it experiences vertical wind shear, causing the convection and heat engine to move away from the center; this normally ceases development of a tropical cyclone.[42] Additionally, its interaction with the main belt of the Westerlies, by means of merging with a nearby frontal zone, can cause tropical cyclones to evolve into extratropical cyclones. This transition can take 1–3 days.[43] Even after a tropical cyclone is said to be extratropical or dissipated, it can still have tropical storm force (or occasionally hurricane force) winds and drop several inches of rainfall. In the Pacific ocean and Atlantic ocean, such tropical-derived cyclones of higher latitudes can be violent and may occasionally remain at hurricane-force wind speeds when they reach the west coast of North America. These phenomena can also affect Europe, where they are known as European windstorms; Hurricane Iris's extratropical remnants became one in 1995.[44] Additionally, a cyclone can merge with another area of low pressure, becoming a larger area of low pressure. This can strengthen the resultant system, although it may no longer be a tropical cyclone.[42]
Artificial dissipation
In the 1960s and 1970s, the United States government attempted to weaken hurricanes through Project Stormfury by seeding selected storms with silver iodide. It was thought that the seeding would cause supercooled water in the outer rainbands to freeze, causing the inner eyewall to collapse and thus reducing the winds. The winds of Hurricane Debbie—a hurricane seeded in Project Stormfury—dropped as much as 30%, but Debby regained its strength after each of two seeding forays. In an earlier episode in 1947, disaster struck when a hurricane east of Jacksonville, Florida promptly changed its course after being seeded, and smashed into Savannah, Georgia.[45] Because there was so much uncertainty about the behavior of these storms, the federal government would not approve seeding operations unless the hurricane had a less than 10% chance of making landfall within 48 hours, greatly reducing the number of possible test storms. The project was dropped after it was discovered that eyewall replacement cycles occur naturally in strong hurricanes, casting doubt on the result of the earlier attempts. Today, it is known that silver iodide seeding is not likely to have an effect because the amount of supercooled water in the rainbands of a tropical cyclone is too low.[46]
Other approaches have been suggested over time, including cooling the water under a tropical cyclone by towing icebergs into the tropical oceans.[47] Other ideas range from covering the ocean in a substance that inhibits evaporation,[48] dropping large quantities of ice into the eye at very early stages of development (so that the latent heat is absorbed by the ice, instead of being converted to kinetic energy that would feed the positive feedback loop),[47] or blasting the cyclone apart with nuclear weapons.[14] Project Cirrus even involved throwing dry ice on a cyclone.[49] These approaches all suffer from the same flaw: tropical cyclones are simply too large for any of them to be practical.[50]
Effects
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/42/Hurricane_katrina_damage_gulfport_mississippi.jpg/180px-Hurricane_katrina_damage_gulfport_mississippi.jpg)
Tropical cyclones out at sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks.[51] Tropical cyclones stir up water, leaving a cool wake behind them,[18] which causes the region to be less favourable for subsequent tropical cyclones. On land, strong winds can damage or destroy vehicles, buildings, bridges, and other outside objects, turning loose debris into deadly flying projectiles. The storm surge, or the increase in sea level due to the cyclone, is typically the worst effect from landfalling tropical cyclones, historically resulting in 90% of tropical cyclone deaths.[52] The broad rotation of a landfalling tropical cyclone, and vertical wind shear at its periphery, spawns tornadoes. Tornadoes can also be spawned as a result of eyewall mesovortices, which persist until landfall.[53] Within the last two centuries, tropical cyclones have been responsible for the deaths of about 1.9 million persons worldwide. Large areas of standing water caused by flooding lead to infection, as well as contributing to mosquito-borne illnesses. Crowded evacuees in shelters increase the risk of disease propagation.[54] Tropical cyclones sigificantly interrupt infrastructure, leading to power outages, bridge destruction, and hamper reconstruction efforts.[54][55]
Although cyclones take an enormous toll in lives and personal property, they may be important factors in the precipitation regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions.[56] Tropical cyclones also help maintain the global heat balance by moving warm, moist tropical air to the middle latitudes and polar regions.[57] The storm surge and winds of hurricanes may be destructive to human-made structures, but they also stir up the waters of coastal estuaries, which are typically important fish breeding locales. Tropical cyclone destruction spurs redevelopment, greatly increasing local property values.[58]
Observation and forecasting
Observation
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/95/Isidore091902-p3sunset.jpg/180px-Isidore091902-p3sunset.jpg)
Intense tropical cyclones pose a particular observation challenge. As they are a dangerous oceanic phenomenon and are relatively small, weather stations are rarely available on the site of the storm itself. Surface observations are generally available only if the storm is passing over an island or a coastal area, or if there is a nearby ship. Usually, real-time measurements are taken in the periphery of the cyclone, where conditions are less catastrophic and its true strength cannot be evaluated. For this reason, there are teams of meteorologists that move into the path of tropical cyclones to help evaluate their strength at the point of landfall.
Tropical cyclones far from land are tracked by weather satellites capturing visible and infrared images from space, usually at half-hour to quarter-hour intervals. As a storm approaches land, it can be observed by land-based Doppler radar. Radar plays a crucial role around landfall because it shows a storm's location and intensity minute by minute.
In-situ measurements, in real-time, can be taken by sending specially equipped reconnaissance flights into the cyclone. In the Atlantic basin, these flights are regularly flown by United States government hurricane hunters.[59] The aircraft used are WC-130 Hercules and WP-3D Orions, both four-engine turboprop cargo aircraft. These aircraft fly directly into the cyclone and take direct and remote-sensing measurements. The aircraft also launch GPS dropsondes inside the cyclone. These sondes measure temperature, humidity, pressure, and especially winds between flight level and the ocean's surface. A new era in hurricane observation began when a remotely piloted Aerosonde, a small drone aircraft, was flown through Tropical Storm Ophelia as it passed Virginia's Eastern Shore during the 2005 hurricane season. A similar mission was also completed successfully in the western Pacific ocean. This demonstrated a new way to probe the storms at low altitudes that human pilots seldom dare.[60]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/NHC_Atlantic_Forecast_Error_Trends.png/180px-NHC_Atlantic_Forecast_Error_Trends.png)
Forecasting
Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high- and low-pressure areas, and predicting how those areas will change during the life of a tropical system. The deep layer mean flow is considered to be the best tool in determining track direction and speed. If storms are significantly sheared, use of wind speed measurements at a lower altitude, such as at the 700 hpa pressure surface (3000 meters or 10000 feet above sea level) will produce better predictions. Tropical forecasters also consider smoothing out short-term wobbles of the storm center in order a best practice, as it allows them to determine a more accurate trajectory.[61] High-speed computers and sophisticated simulation software allow forecasters to produce computer models that predict tropical cyclone tracks based on the future position and strength of high- and low-pressure systems. Combining forecast models with increased understanding of the forces that act on tropical cyclones, as well as with a wealth of data from Earth-orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades.[62] However, scientists say they are less skillful at predicting the intensity of tropical cyclones.[63] They attribute the lack of improvement in intensity forecasting to the complexity of tropical systems and an incomplete understanding of factors that affect their development.
Classifications, terminology, and naming
Intensity classifications
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/07/Maria%2C_Bopha_and_Saomai_2006-08-07_0435Z.jpg/180px-Maria%2C_Bopha_and_Saomai_2006-08-07_0435Z.jpg)
Tropical cyclones are classified into three main groups, based on intensity: tropical depressions, tropical storms, and a third group of more intense storms, whose name depends on the region. For example, if a tropical storm in the Northwestern Pacific reaches hurricane-strength winds on the Beaufort scale, it is referred to as a typhoon; if a tropical storm passes the same benchmark in the Northeast Pacific Ocean, or in the Atlantic, it is called a hurricane.[39] Neither "hurricane" nor "typhoon" is used in the South Pacific.
Additionally, as indicated in the table below, each basin uses a separate system of terminology, making comparisons between different basins difficult. In the Pacific Ocean, hurricanes from the Central North Pacific sometimes cross the International Date Line into the Northwest Pacific, becoming typhoons (such as Hurricane/Typhoon Ioke in 2006); on rare occasions, the reverse will occur.[64] It should also be noted that typhoons with sustained winds greater than 130 knots (240 km/h or 150 mph) are called Super Typhoons by the Joint Typhoon Warning Center.[65]
A tropical depression is an organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds of less than 17 m/s (33 kt, 38 mph, or 62 km/h). It has no eye and does not typically have the organization or the spiral shape of more powerful storms. However, it is already a low-pressure system, hence the name "depression."[13] The practice of the Philippines is to name tropical depressions from their own naming convention when the depressions are within the Philippines' area of responsibility.[66]
A tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 17 and 32 m/s (34–63 kt, 39–73 mph, or 62–117 km/h). At this point, the distinctive cyclonic shape starts to develop, although an eye is not usually present. Government weather services, other than the Philippines, first assign names to systems that reach this intensity (thus the term named storm).[13]
A hurricane or typhoon (sometimes simply referred to as a tropical cyclone, as opposed to a depression or storm) is a system with sustained winds of at least 33 m/s (64 kt, 74 mph, or 118 km/h).[13] A cyclone of this intensity tends to develop an eye, an area of relative calm (and lowest atmospheric pressure) at the center of circulation. The eye is often visible in satellite images as a small, circular, cloud-free spot. Surrounding the eye is the eyewall, an area about 16–80 km (10–50 mi) wide in which the strongest thunderstorms and winds circulate around the storm's center. Maximum sustained winds in the strongest tropical cyclones have been estimated at about 85 m/s (165 kt, 190 mph, 305 km/h).[67]
Tropical Cyclone Classifications (all winds are 10-minute averages) | ||||||||
---|---|---|---|---|---|---|---|---|
Beaufort scale | 10-minute sustained winds (knots) | N Indian Ocean IMD |
SW Indian Ocean MF |
Australia BOM |
SW Pacific FMS |
NW Pacific JMA |
NW Pacific JTWC |
NE Pacific & N Atlantic NHC & CPHC |
0–6 | <28 | Depression | Trop. Disturbance | Tropical Low | Tropical Depression | Tropical Depression | Tropical Depression | Tropical Depression |
7 | 28-29 | Deep Depression | Depression | |||||
30-33 | Tropical Storm | Tropical Storm | ||||||
8–9 | 34–47 | Cyclonic Storm | Moderate Tropical Storm | Trop. Cyclone (1) | Tropical Cyclone | Tropical Storm | ||
10 | 48–55 | Severe Cyclonic Storm | Severe Tropical Storm | Tropical Cyclone (2) | Severe Tropical Storm | |||
11 | 56–63 | Typhoon | Hurricane (1) | |||||
12 | 64–72 | Very Severe Cyclonic Storm | Tropical Cyclone | Severe Tropical Cyclone (3) | Typhoon | |||
73–85 | Hurricane (2) | |||||||
86–89 | Severe Tropical Cyclone (4) | Major Hurricane (3) | ||||||
90–99 | Intense Tropical Cyclone | |||||||
100–106 | Major Hurricane (4) | |||||||
107-114 | Severe Tropical Cyclone (5) | |||||||
115–119 | Very Intense Tropical Cyclone | Super Typhoon | ||||||
>120 | Super Cyclonic Storm | Major Hurricane (5) |
Origin of storm terms
The word typhoon, used today in the Northwest Pacific, has two possible and equally plausible origins. The first is from the Chinese 大風 (Cantonese: daaih fūng; Mandarin: dà fēng) which means "great wind."[68] (The Chinese term as 颱風 or 台风 táifēng, and 台風 taifū in Japanese, has an independent origin traceable variously to 風颱, 風篩 or 風癡 hongthai, going back to Song 宋 (960-1278) and Yuan 元(1260-1341) dynasties. The first record of the character 颱 appeared in 1685's edition of Summary of Taiwan 臺灣記略).[69] Alternatively, the word may be derived from Urdu, Persian and Arabic ţūfān[69] (طوفان), which in turn originates from Greek tuphōn (Τυφών), a monster in Greek mythology responsible for hot winds.[70] The related Portuguese word tufão, used in Portuguese for any tropical cyclone, is also derived from Greek tuphōn.
The word hurricane, used in the North Atlantic and Northeast Pacific, is derived from the name of a native Caribbean Amerindian storm god, Huracan, via Spanish huracán.[71] (Huracan is also the source of the word Orcan, another word for the European windstorm. These events should not be confused.)
Naming
Storms reaching tropical storm strength were initially given names to eliminate confusion when there are multiple systems in any individual basin at the same time which assists in warning people of the coming storm.[72] In most cases, a tropical cyclone retains its name throughout its life; however, under special circumstances, tropical cyclones may be renamed while active. These names are taken from lists which vary from region to region and are drafted a few years ahead of time. The lists are decided upon, depending on the regions, either by committees of the World Meteorological Organization (called primarily to discuss many other issues), or by national weather offices involved in the forecasting of the storms. Each year, the names of particularly destructive storms (if there are any) are "retired" and new names are chosen to take their place.
Notable tropical cyclones
Tropical cyclones that cause extreme destruction are rare, though when they occur, they can cause great amounts of damage or thousands of fatalities.
The 1970 Bhola cyclone is the deadliest tropical cyclone on record, killing over 300,000 people[73] and potentially as many as 1 million[74] after striking the densely population Ganges Delta region of Bangladesh on November 13, 1970. Its powerful storm surge was responsible for the high death toll.[73] The North Indian cyclone basin has historically been the deadliest basin, with several cyclones since 1900 killing over 100,000 people, all in Bangladesh.[54][75] Elsewhere, Typhoon Nina killed 29,000 in China due to 2000-year flooding which caused 62 dams along the Banqiao Dam to fail; another 145,000 were killed during the subsequent famine and epidemic.[76] The Great Hurricane of 1780 is the deadliest Atlantic hurricane on record, killing about 22,000 people in the Lesser Antilles.[77] A tropical cyclone does need not be particularly strong to cause memorable damage, primarily if the deaths are from rainfall or mudslides. Tropical Storm Thelma in November 1991 killed thousands in the Philippines,[78] while in 1982, the unnamed tropical depression that eventually became Hurricane Paul killed around 1,000 people in Central America.[79]
Hurricane Katrina is estimated as the costliest tropical cyclone worldwide,[80] causing $81.2 billion in property damage (2005 USD)[81] with overall damage estimates exceeding $100 billion (2005 USD).[80] Katrina is considered the worst natural disaster caused by a hurricane in United States history,[82] killing at least 1,836 after striking Louisiana and Mississippi as a major hurricane in August 2005.[81] Hurricane Iniki in 1992 was the most powerful storm to strike Hawaii in recorded history, hitting Kauai as a Category 4 hurricane, killing six people, and causing U.S. $3 billion in damage.[83] Other destructive Eastern Pacific hurricanes include Pauline and Kenna, both causing severe damage after striking Mexico as a major hurricane.[84][85] In March 2004, Cyclone Gafilo struck northeastern Madagascar as a powerful cyclone, killing 74, affecting more than 200,000, and becoming the worst cyclone to affect the nation for over 20 years.[86]
![](http://upload.wikimedia.org/wikipedia/commons/4/4e/Typhoonsizes.jpg)
The most intense storm on record was Typhoon Tip in the northwestern Pacific Ocean in 1979, which reached a minimum pressure of 870 mbar (25.69 inHg) and maximum sustained wind speeds of 165 knots (190 mph, 305 km/h).[87] Tip, however, does not solely hold the record for fastest sustained winds in a cyclone. Typhoon Keith in the Pacific and Hurricanes Camille and Allen in the North Atlantic currently share this record with Tip.[88] Camille was the only storm to actually strike land while at that intensity, making it, with 165 knots (190 mph, 305 km/h) sustained winds and 210 mph (335 km/h) gusts, the strongest tropical cyclone on record at landfall.[89] Typhoon Nancy in 1961 had recorded wind speeds of 185 knots (215 mph, 345 km/h), but recent research indicates that wind speeds from the 1940s to the 1960s were gauged too high, and this is no longer considered the fastest storm on record.[67] Similarly, a surface-level gust caused by Typhoon Paka on Guam was recorded at 205 knots (235 mph, 380 km/h). Had it been confirmed, it would be the strongest non-tornadic wind ever recorded on the Earth's surface, but the reading had to be discarded since the anemometer was damaged by the storm.[90]
In addition to being the most intense tropical cyclone on record, Tip was the largest cyclone on record, with tropical storm-force winds 2,170 km (1,350 miles) in diameter. The smallest storm on record, Cyclone Tracy, was roughly 100 km (60 miles) wide before striking Darwin, Australia in 1974.[91]
Hurricane John is the longest-lasting tropical cyclone on record, lasting 31 days in 1994. Prior to the advent of satellite imagery in 1961, however, many tropical cyclones were underestimated in their durations.[92] John is the second longest-tracked tropical cyclone in the Northern Hemisphere on record, behind Typhoon Ophelia of 1960 which had a path of 8,500 miles (12,500 km). Reliable data for Southern Hemisphere cyclones is unavailable.[93]
Long term activity trends
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/27/NOAA_ACE_index_1950-2004_RGB.svg/250px-NOAA_ACE_index_1950-2004_RGB.svg.png)
While the number of storms in the Atlantic has increased since 1995, there is no obvious global trend; the annual number of tropical cyclones worldwide remains about 87 ± 10. However, the ability of climatologists to make long-term data analysis in certain basins is limited by the lack of reliable historical data in some basins, primarily in the Southern Hemisphere.[94] In spite of that, there is some evidence that the intensity of hurricanes is increasing. Kerry Emanuel stated, "Records of hurricane activity worldwide show an upswing of both the maximum wind speed in and the duration of hurricanes. The energy released by the average hurricane (again considering all hurricanes worldwide) seems to have increased by around 70% in the past 30 years or so, corresponding to about a 15% increase in the maximum wind speed and a 60% increase in storm lifetime."[95]
Atlantic storms are becoming more destructive financially, since five of the ten most expensive storms in United States history have occurred since 1990. This can be attributed to the increased intensity and duration of hurricanes striking North America,[95] and to a greater degree, the number of people living in susceptible coastal areas, following increased development in the region since the last surge in Atlantic hurricane activity in the 1960s.
Often in part because of the threat of hurricanes, many coastal regions had sparse population between major ports until the advent of automobile tourism; therefore, the most severe portions of hurricanes striking the coast may have gone unmeasured in some instances. The combined effects of ship destruction and remote landfall severely limit the number of intense hurricanes in the official record before the era of hurricane reconnaissance aircraft and satellite meteorology. Although the record shows a distinct increase in the number and strength of intense hurricanes, therefore, experts regard the early data as suspect.[96]
The number and strength of Atlantic hurricanes may undergo a 50-70 year cycle, also known as the Atlantic Multidecadal Oscillation. Although more common since 1995, few above-normal hurricane seasons occurred during 1970-1994.[97] Destructive hurricanes struck frequently from 1926-60, including many major New England hurricanes. A record 21 Atlantic tropical storms formed in 1933, a record only recently exceeded in 2005, which saw 28 storms. Tropical hurricanes occurred infrequently during the seasons of 1900-1925; however, many intense storms formed 1870-1899. During the 1887 season, 19 tropical storms formed, of which a record 4 occurred after 1 November and 11 strengthened into hurricanes. Few hurricanes occurred in the 1840s to 1860s; however, many struck in the early 1800s, including an 1821 storm that made a direct hit on New York City. Some historical weather experts say these storms may have been as high as Category 4 in strength.[98]
These active hurricane seasons predated satellite coverage of the Atlantic basin. Before the satellite era began in 1960, tropical storms or hurricanes went undetected unless a ship reported a voyage through the storm or a storm hit land in a populated area.[96] The official record, therefore, could miss storms in which no ship experienced gale-force winds, recognized it as a tropical storm (as opposed to a high-latitude extra-tropical cyclone, a tropical wave, or a brief squall), returned to port, and reported the experience.
Global warming
The U.S. National Oceanic and Atmospheric Administration Geophysical Fluid Dynamics Laboratory performed a simulation to determine if there is a statistical trend in the frequency or strength of cyclones over time. The simulation concluded "the strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century as the earth's climate is warmed by increasing levels of greenhouse gases in the atmosphere."[99] In an article in Nature, Kerry Emanuel stated that potential hurricane destructiveness, a measure combining hurricane strength, duration, and frequency, "is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multidecadal oscillations in the North Atlantic and North Pacific, and global warming." Emanuel predicted "a substantial increase in hurricane-related losses in the twenty-first century."[100]
Similarly, P.J. Webster and others published an article in Science examining the "changes in tropical cyclone number, duration, and intensity" over the last 35 years, the period when satellite data has been available. The main finding was although the number of cyclones decreased throughout the planet excluding the north Atlantic Ocean, there was a great increase in the number and proportion of very strong cyclones.[101] Both Emanuel and Webster et al. consider sea surface temperatures to be vital in the development of cyclones. The increase in temperatures is believed to be due to global warming and the hypothesized Atlantic Multidecadal Oscillation (AMO), a possible 50–70 year pattern of temperature variability. However, Emanuel observed the recent temperature increase as outside the range of previous sea surface temperature peaks. Thus, both global warming and a natural variation such as the AMO could have contributed to the warming of the tropical Atlantic over the past decades, though an exact attribution has not been defined.[102]
In February 2007, the United Nations Intergovernmental Panel on Climate Change released its fourth assessment report on climate change. The report noted many observed changes in the climate, including atmospheric composition, global average temperatures, ocean conditions, among others. The report concluded the observed increase in tropicaly intensity is larger than climate models predict. Additionally, the report considered that it is likely that storm intensity will continue to increase through the 21st century, and declared it more likely than not that there has been some human contribution to the increases in tropical cyclone intensity.[103] However, there is no universal agreement about the magnitude of the effects anthropogenic global warming has on tropical cyclone formation, track, and intensity. For example, critics such as Chris Landsea assert that man-made effects would be "quite tiny compared to the observed large natural hurricane variability."[104] A statement by the American Meteorological Society on February 1, 2007 stated that trends in tropical cyclone records offer "evidence both for and against the existence of a detectable anthropogenic signal" in tropical cyclogenesis.[105] Albeit many aspects of a link between tropical cyclones and global warming are still being "hotly debated",[106] a point of agreement is that no individual tropical cyclone or season can be attributed to global warming.[106][102]
Related cyclone types
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/fe/Gustav_09_sep_2002_1805Z.jpg/180px-Gustav_09_sep_2002_1805Z.jpg)
In addition to tropical cyclones, there are two other classes of cyclones within the spectrum of cyclone types. These kinds of cyclones, known as extratropical cyclones and subtropical cyclones, can be stages a tropical cyclone passes through during its formation or dissipation.[107]
An extratropical cyclone is a storm that derives energy from horizontal temperature differences, which are typical in higher latitudes. A tropical cyclone can become extratropical as it moves toward higher latitudes if its energy source changes from heat released by condensation to differences in temperature between air masses;[2] additionally, although not as frequently, an extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone. From space, extratropical storms have a characteristic "comma-shaped" cloud pattern. Extratropical cyclones can also be dangerous when their low-pressure centers cause powerful winds and very high seas.
A subtropical cyclone is a weather system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. They can form in a wide band of latitudes, from the equator to 50°. Although subtropical storms rarely have hurricane-force winds, they may become tropical in nature as their cores warm.[108] From an operational standpoint, a tropical cyclone is usually not considered to become subtropical during its extratropical transition.[109]
Tropical cyclones in popular culture
In popular culture, tropical cyclones have made appearances in different types of media, including films, books, television, music, and electronic games. The media can have tropical cyclones that are entirely fictional, or can be based on real events.[110] For example, George Rippey Stewart's Storm, a best-seller published in 1941, is thought to have influenced meteorologists into giving female names to Pacific tropical cyclones.[111] Another example is the hurricane in The Perfect Storm, which describes the sinking of the Andrea Gail by the 1991 Halloween Nor'easter.[112] Also, hypothetical hurricanes have also been featured in parts of the plots of series such as The Simpsons, Invasion, Family Guy, Seinfeld, CSI Miami, and Dawson's Creek.
See also
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Notes
- ^ Symonds, Steve (November 17, 2003). "Highs and Lows". Wild Weather. Australian Broadcasting Corporation. Retrieved 2007-03-23.
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: Check date values in:|date=
(help) - ^ a b Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What is an extra-tropical cyclone?". NOAA. Retrieved 2007-03-23. Cite error: The named reference "AOML FAQ A7" was defined multiple times with different content (see the help page).
- ^ a b c National Weather Service (October 19, 2005). "Tropical Cyclone Structure". JetStream - An Online School for Weather. National Oceanic & Atmospheric Administration. Retrieved 2006-12-14.
{{cite web}}
: Check date values in:|date=
(help) - ^ Knaff, John A. (2003). "Annular Hurricanes" (PDF). Weather and Forecasting. 18 (2). American Meteorological Society: 204–223. Retrieved 2006-07-23.
{{cite journal}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help); Unknown parameter|month=
ignored (help) - ^ "Hurricanes". University of Illinois. Retrieved 2006-10-21.
- ^ R. Craig. Kochel, Victor R. Baker, Peter C. Patton (1988). Flood Geomorphology. Wiley-Interscience. ISBN 0471625582.
{{cite book}}
: CS1 maint: multiple names: authors list (link) - ^ Pasch, Richard J. (September 28, 2006). "Tropical Cyclone Report: Hurricane Wilma: 15-25 October 2005" (PDF). National Hurricane Center. Retrieved 2006-12-14.
{{cite web}}
: Check date values in:|date=
(help); Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - ^ Lander, Mark A. (January 1999). "A Tropical Cyclone with a Very Large Eye" (PDF). Monthly Weather Review. 127 (1). Retrieved 2006-12-14.
- ^ Pasch, Richard J. and Lixion A. Avila (May 1999). "Atlantic Hurricane Season of 1996" (PDF). Monthly Weather Review. 127 (5): 581–610. Retrieved 2006-12-14.
- ^ American Meteorological Society. "AMS Glossary: C". Glossary of Meteorology. Allen Press. Retrieved 2006-12-14.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What is a "CDO"?". NOAA. Retrieved 2007-03-23.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What are "concentric eyewall cycles" (or "eyewall replacement cycles") and why do they cause a hurricane's maximum winds to weaken?". NOAA. Retrieved 2006-12-14.
- ^ a b c d e National Weather Service (September 2006). "Hurricanes... Unleashing Nature's Fury: A Preparedness Guide" (PDF). NOAA. Retrieved 2006-12-02.
- ^ a b Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Why don't we try to destroy tropical cyclones by nuking them?". NOAA. Retrieved 2006-07-25. Cite error: The named reference "AOML FAQ C5c" was defined multiple times with different content (see the help page).
- ^ a b c National Oceanic & Atmospheric Administration (August 2000). "NOAA Question of the Month: How much energy does a hurricane release?". NOAA. Retrieved 2006-03-31.
- ^ a b Bureau of Meteorology. "How are tropical cyclones different to mid-latitude cyclones?". Frequently Asked Questions. Retrieved 2006-03-31.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Doesn't the friction over land kill tropical cyclones?". NOAA. Retrieved 2006-07-25.
- ^ a b Earth Observatory (2005). "Passing of Hurricanes Cools Entire Gulf". National Aeronautics and Space Administration. Retrieved 2006-04-26.
- ^ University Corporation for Atmospheric Research Hurricanes: Keeping an eye on weather's biggest bullies accessed March 31, 2006
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What's it like to go through a hurricane on the ground? What are the early warning signs of an approaching tropical cyclone?". NOAA. Retrieved 2006-07-26.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What regions around the globe have tropical cyclones and who is responsible for forecasting there?". NOAA. Retrieved 2006-07-25.
- ^ World Meteorological Organization (April 25, 2006). "RSMCs". Tropical Cyclone Programme (TCP). Retrieved 2006-11-05.
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: Check date values in:|date=
(help) - ^ Marcelino, Emerson Vieira; Isabela Pena Viana de Oliveira Marcelino; Frederico de Moraes Rudorff (2004). "Cyclone Catarina: Damage and Vulnerability Assessment" (PDF). Santa Catarina Federal University. Retrieved 2006-12-24.
{{cite web}}
: CS1 maint: multiple names: authors list (link) - ^ a b c d e Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: When is hurricane season?". NOAA. Retrieved 2006-07-25.
- ^ McAdie, Colin (May 10, 2007). "Tropical Cyclone Climatology". National Hurricane Center. Retrieved 2007-06-09.
{{cite web}}
: Check date values in:|date=
(help) - ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What are the average, most, and least tropical cyclones occurring in each basin?". NOAA. Retrieved 2006-11-30.
- ^ a b c d e f Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: How do tropical cyclones form?". NOAA. Retrieved 2006-07-26.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Why do tropical cyclones require 80 °F (26.5 °C) ocean temperatures to form?". NOAA. Retrieved 2006-07-25.
- ^ a b Avila, Lixion (1995). "Atlantic tropical systems of 1993" (PDF). Monthly Weather Review. 123 (3): 887–896. Retrieved 2006-07-25.
{{cite journal}}
: Unknown parameter|coauthors=
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suggested) (help); Unknown parameter|month=
ignored (help) Cite error: The named reference "MWR Avila 1995" was defined multiple times with different content (see the help page). - ^ a b Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What is an easterly wave?". NOAA. Retrieved 2006-07-25.
- ^ Landsea, Chris (1993). "A Climatology of Intense (or Major) Atlantic Hurricanes" (PDF). Monthly Weather Review. 121 (6): 1703–1713. Retrieved 2006-03-25.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - ^ Neumann, Charles J. "Worldwide Tropical Cyclone Tracks 1979-88". Global Guide to Tropical Cyclone Forecasting. Bureau of Meteorology. Retrieved 2006-12-12.
- ^ a b Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What determines the movement of tropical cyclones?". NOAA. Retrieved 2006-07-25.
- ^ DeCaria, Alex (2005). "Lesson 7 – Tropical Cyclones: Climatology". ESCI 344 – Tropical Meteorology. Millersville University. Retrieved 2006-11-26.
- ^ Baum, Steven K. (January 20, 1997). "The Glossary: Cn-Cz". Glossary of Oceanography and the Related Geosciences with References. Texas A&M University. Retrieved 2006-11-29.
{{cite web}}
: Check date values in:|date=
(help) - ^ "Conservation of Angular Momentum". Astronomy 161 Lectures. University of Tennessee. Retrieved 2006-11-29.
- ^ U. S. Navy. SECTION 2: TROPICAL CYCLONE MOTION TERMINOLOGY. Retrieved on 2007-04-10.
- ^ Powell, Jeff; et al. (May 2007). "Hurricane Ioke: 20-27 August 2006". 2006 Tropical Cyclones Central North Pacific. Central Pacific Hurricane Center. Retrieved 2007-06-09.
{{cite web}}
: Explicit use of et al. in:|author=
(help) - ^ a b c d National Hurricane Center (2005). "Glossary of NHC/TPC Terms". National Oceanic and Atmospheric Administration. Retrieved 2006-11-29.
- ^ Shay, Lynn K., Russell L. Elsberry and Peter G. Black (1989). "Vertical Structure of the Ocean Current Response to a Hurricane" (PDF). Journal of Physical Oceanography. 19 (5). Retrieved 2006-12-12.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Edwards, Jonathan. "Tropical Cyclone Formation". HurricaneZone.net. Retrieved 2006-11-30.
- ^ a b Chih-Pei Chang (2004). East Asian Monsoon. World Scientific. ISBN 9812387692.
- ^ United States Naval Research Laboratory (September 23, 1999). "Tropical Cyclone Intensity Terminology". Tropical Cyclone Forecasters' Reference Guide. Retrieved 2006-11-30.
{{cite web}}
: Check date values in:|date=
(help) - ^ Rappaport, Edward N. (November 2, 2000). "Preliminary Report: Hurricane Iris: 22 August-4 September 1995". National Hurricane Center. Retrieved 2006-11-29.
{{cite web}}
: Check date values in:|date=
(help) - ^ Whipple, Addison (1982). Storm. Alexandria, VA: Time Life Books. p. 151. ISBN 0-8094-4312-0.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Why don't we try to destroy tropical cyclones by seeding them with silver iodide?". NOAA. Retrieved 2006-07-25.
- ^ a b Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Why don't we try to destroy tropical cyclones by cooling the surface waters with icebergs or deep ocean water?". NOAA. Retrieved 2006-07-25.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Why don't we try to destroy tropical cyclones by placing a substance on the ocean surface?". NOAA. Retrieved 2006-07-25.
- ^ Scotti, R. A. (2003). Sudden Sea: the Great Hurricane of 1938 (1st ed. ed.). Little, Brown, and Company. p. 47. ISBN 0-316-73911-1.
{{cite book}}
:|edition=
has extra text (help) - ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Why do not we try to destroy tropical cyclones by (fill in the blank)?". NOAA. Retrieved 2006-07-25.
- ^ David Roth and Hugh Cobb (2001). "Eighteenth Century Virginia Hurricanes". NOAA. Retrieved 2007-02-24.
- ^ James M. Shultz, Jill Russell and Zelde Espinel (2005). "Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development". Oxford Journal. Retrieved 2007-02-24.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Are TC tornadoes weaker than midlatitude tornadoes?". NOAA. Retrieved 2006-07-25.
- ^ a b c Shultz, James M., Jill Russell and Zelde Espinel (July 2005). "Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development". Epidemiologic Reviews. 27 (1): 21–25. Retrieved 2006-12-14.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Staff Writer (2005-08-30). "Hurricane Katrina Situation Report #11" (PDF). Office of Electricity Delivery and Energy Reliability (OE) United States Department of Energy. Retrieved 2007-02-24.
- ^ National Oceanic and Atmospheric Administration 2005 Tropical Eastern North Pacific Hurricane Outlook accessed May 2, 2006
- ^ "Living With an Annual Disaster". Zurich Financial Services. July/August 2005. Retrieved 2006-11-29.
{{cite web}}
: Check date values in:|date=
(help) - ^ Christopherson, Robert W. (1992). Geosystems: An Introduction to Physical Geography. New York: Macmillan Publishing Company. pp. 222–224. ISBN 0-02-322443-6.
- ^ 403rd Wing. "The Hurricane Hunters". 53rd Weather Reconnaissance Squadron. Retrieved 2006-03-30.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - ^ Bowman, Lee. "Drones defy heart of storm". The Sun Herald. Retrieved 2006-03-30.
- ^ United States Navy. "Influences on Tropical Cyclone Motion". Retrieved 2007-04-10.
- ^ National Hurricane Center (May 22, 2006). "Annual average model track errors for Atlantic basin tropical cyclones for the period 1994-2005, for a homogeneous selection of "early" models". National Hurricane Center Forecast Verification. National Oceanic and Atmospheric Administration. Retrieved 2006-11-30.
{{cite web}}
: Check date values in:|date=
(help) - ^ National Hurricane Center (May 22, 2006). "Annual average official track errors for Atlantic basin tropical cyclones for the period 1989-2005, with least-squares trend lines superimposed". National Hurricane Center Forecast Verification. National Oceanic and Atmospheric Administration. Retrieved 2006-11-30.
{{cite web}}
: Check date values in:|date=
(help) - ^ Central Pacific Hurricane Center (2004). "Hurricane John Preliminary Report". National Oceanic and Atmospheric Administration. Retrieved 2007-03-23.
- ^ Bouchard, R. H. (April 1990). "A Climatology of Very Intense Typhoons: Or Where Have All the Super Typhoons Gone?" (PPT). Retrieved 2006-12-05.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What are the upcoming tropical cyclone names?". NOAA. Retrieved 2006-12-11.
- ^ a b Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Which is the most intense tropical cyclone on record?". NOAA. Retrieved 2006-07-25.
- ^ Earth Observatory. "Hurricanes: The Greatest Storms on Earth". National Aeronautics and Space Administration. Retrieved 2006-07-19.
- ^ a b Taiwan Ministry of Communications/Central Weather Bureau (2002-12-10). "臺灣百年來之颱風" (in Template:Zh icon). Government of the Republic of China. Retrieved 2006-12-13.
{{cite web}}
: Check date values in:|date=
(help)CS1 maint: unrecognized language (link) - ^ "Typhoon". The American Heritage Dictionary of the English Language (4th ed. ed.). Dictionary.com. 2004. Retrieved 2006-12-14.
{{cite encyclopedia}}
:|edition=
has extra text (help) - ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What is the origin of the word "hurricane"?". NOAA. Retrieved 2006-07-25.
- ^ National Hurricane Center. Worldwide Tropical Cyclone Names. Retrieved on 2006-12-28.
- ^ a b Chris Landsea (1993). "Which tropical cyclones have caused the most deaths and most damage?". Hurricane Research Division. Retrieved 2007-02-23.
- ^ Lawson (1999). "South Asia: A history of destruction". British Broadcasting Corporation. Retrieved 2007-02-23.
- ^ Frank, Neil L. and S. A. Husain (June 1971). "The Deadliest Tropical Cyclone in History" (PDF). Bulletin of the American Meteorological Society. 52 (6): 438–445. Retrieved 2006-12-14.
- ^ Hydrology Department of Henan Province (2006). "Flood and drought disaster" (in Chinese). Retrieved 2007-02-23.
- ^ National Hurricane Center (April 22, 1997). "The Deadliest Atlantic Tropical Cyclones, 1492-1996". National Oceanic and Atmospheric Administration. Retrieved 2006-03-31.
{{cite web}}
: Check date values in:|date=
(help) - ^ Joint Typhoon Warning Center. "Typhoon Thelma (27W)" (PDF). 1991 Annual Tropical Cyclone Report. Retrieved 2006-03-31.
- ^ Gunther, E. B., R.L. Cross, and R.A. Wagoner (1983). "Eastern North Pacific Tropical Cyclones of 1982" (PDF). Monthly Weather Review. 111 (5). Retrieved 2006-03-31.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ a b Earth Policy Institute (2006). "Hurricane Damages Sour to New Levels". United States Department of Commerce. Retrieved 2007-02-23.
{{cite web}}
:|author=
has generic name (help) - ^ a b Knabb, Richard D., Jamie R. Rhome and Daniel P. Brown (December 20, 2005). "Tropical Cyclone Report: Hurricane Katrina: 23-30 August 2005" (PDF). National Hurricane Center. Retrieved 2006-05-30.
{{cite web}}
: Check date values in:|date=
(help)CS1 maint: multiple names: authors list (link) - ^ National Hurricane Center (August 2005). "Monthly Tropical Weather Summary for the North Altantic, Caribbean Sea and the Gulf of Mexico". National Oceanic and Atmospheric Administration. Retrieved 2006-03-31.
- ^ Central Pacific Hurricane Center. "Hurricane Iniki Natural Disaster Survey Report". National Oceanic and Atmospheric Administration. Retrieved 2006-03-31.
- ^ Lawrence, Miles B. (November 7, 1997). "Preliminary Report: Hurricane Pauline: 5-10 October 1997". National Hurricane Center. Retrieved 2006-03-31.
{{cite web}}
: Check date values in:|date=
(help) - ^ Franklin, James L. (December 26, 2002). "Tropical Cyclone Report: Hurricane Kenna: 22-26 October 2002". National Hurricane Center. Retrieved 2006-03-31.
{{cite web}}
: Check date values in:|date=
(help) - ^ World Food Programme (2004). "WFP Assists Cyclone And Flood Victims in Madagascar". Retrieved 2007-02-24.
- ^ George M. Dunnavan & John W. Dierks (1980). "An Analysis of Super Typhoon Tip (October 1979)" (PDF). Joint Typhoon Warning Center. Retrieved 2007-01-24.
- ^ Ferrell, Jesse (October 26, 1998). "Hurricane Mitch". Weathermatrix.net. Retrieved 2006-03-30.
{{cite web}}
: Check date values in:|date=
(help) - ^ NHC Hurricane Research Division (2006-02-17). "Atlantic hurricane best track ("HURDAT")". NOAA. Retrieved 2007-02-22.
- ^ Houston, Sam, Greg Forbes and Arthur Chiu (17 August, 1998). "Super Typhoon Paka's (1997) Surface Winds Over Guam". National Weather Service. Retrieved 2006-03-30.
{{cite web}}
: Check date values in:|date=
(help)CS1 maint: multiple names: authors list (link) - ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: Which are the largest and smallest tropical cyclones on record?". NOAA. Retrieved 2006-07-25.
- ^ Neal Dorst (2006). "Which tropical cyclone lasted the longest?". Hurricane Research Division. Retrieved 2007-02-23.
- ^ Neal Dorst (2006). "What is the farthest a tropical cyclone has traveled ?". Hurricane Research Division. Retrieved 2007-02-23.
- ^ Landsea, Chris; et al. (July 28, 2006). "Can We Detect Trends in Extreme Tropical Cyclones?" (PDF). Science. 313: 452–4. Retrieved 2007-06-09.
{{cite journal}}
: Check date values in:|date=
(help); Explicit use of et al. in:|author=
(help) - ^ a b Emanuel, Kerry (January 2006). "Anthropogenic Effects on Tropical Cyclone Activity". Retrieved 2006-03-30.
- ^ a b Neumann, Charles J. "1.3: A Global Climatology". Global Guide to Tropical Cyclone Forecasting. Bureau of Meteorology. Retrieved 2006-11-30.
- ^ Risk Management Solutions (March 2006). "U.S. and Caribbean Hurricane Activity Rates" (PDF). Retrieved 2006-11-30.
- ^ Center for Climate Systems Research. "Hurricanes, Sea Level Rise, and New York City". Columbia University. Retrieved 2006-11-29.
- ^ Geophysical Fluid Dynamics Laboratory. "Global Warming and Hurricanes". National Oceanic and Atmospheric Administration. Retrieved 2006-11-29.
- ^ Emanuel, Kerry. "Increasing destructiveness of tropical cyclones over the past 30 years" (PDF). Nature. 436 (7051): 686–688. Retrieved 2006-03-20.
- ^ Webster, P. J., G. J. Holland, J. A. Curry and H.-R. Chang (September 16, 2005). "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment" (PDF). Science. 309 (5742): 1844–1846. Retrieved 2006-03-20.
{{cite journal}}
: Check date values in:|date=
(help)CS1 maint: multiple names: authors list (link) - ^ a b Rahmstorf, Stefan, Michael Mann, Rasmus Benestad, Gavin Schmidt and William Connolley (September 2, 2005). "Hurricanes and Global Warming - Is There a Connection?". RealClimate. Retrieved 2006-03-20.
{{cite web}}
: Check date values in:|date=
(help)CS1 maint: multiple names: authors list (link) - ^ Richard Alley; et al. (2007). "Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change" (PDF). United Nations. Retrieved 2007-02-23.
{{cite web}}
: Explicit use of et al. in:|author=
(help) - ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What may happen with tropical cyclone activity due to global warming?". NOAA. Retrieved 2007-06-02.
- ^ American Meteorological Society (2007-02-01). "Climate Change: An Information Statement of the American Meteorological Society" (PDF). Bulletin of the American Meteorological Society. 88: 5. Retrieved 2007-06-03.
- ^ a b World Meteorological Organization (December 11, 2006). "Statement on Tropical Cyclones and Climate Change" (PDF). p. 6. Retrieved 2007-06-02.
{{cite web}}
: Check date values in:|date=
(help) - ^ Mark A. Lander, N. Davidson, H. Rosendal, J. Knaff, and R. Edson, J. Evans, R. Hart. FIFTH INTERNATIONAL WORKSHOP on TROPICAL CYCLONES. Retrieved on 2006-12-14.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What is a sub-tropical cyclone?". NOAA. Retrieved 2006-07-25.
- ^ Padgett, Gary (2001). "Monthly Global Tropical Cyclone Summary for December 2000". Retrieved 2006-03-31.
- ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: What fictional books, plays, and movies have been written involving tropical cyclones?". NOAA. Retrieved 2006-07-25.
- ^ Heidorn, Keith C. "George Stewart's Storm: Remembering A Classic". The Weather Doctor. Retrieved 2006-12-10.
- ^ McCown, Sean (December 13, 2004). "Unnamed Hurricane 1991". Satellite Events Art Gallery: Hurricanes. National Climatic Data Center. Retrieved 2007-02-04.
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: Check date values in:|date=
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External links
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/40px-Wiktionary-logo-en-v2.svg.png)
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- Learning resources
- WMO guide on cyclone terminology
- Summary of cyclone terminology from NOAA FAQ
- NOVA scienceNOW: Hurricanes
- Template:PDF
- World Meteorological Organization Severe Weather Information Center - Shows all current tropical systems worldwide and their tracks
- Tropical Storms Worldwide - by Hawaii University
- FEMA for Kids: Hurricanes
- Regional specialised meteorological centers
- US National Hurricane Center - North Atlantic, Eastern Pacific
- Central Pacific Hurricane Center - Central Pacific
- Japan Meteorological Agency - NW Pacific
- India Meteorological Department - Bay of Bengal and the Arabian Sea
- Météo-France - La Reunion - South Indian Ocean from Africa to 90° E
- Fiji Meteorological Service - South Pacific east of 160°, north of 25° S
- Past storms
- Global climatology of tropical cyclones
- Tropical cyclone images and movies, from the United Kingdom Met Office
- Unisys historical and contemporary hurricane track data
- United States Tropical Cyclone Rainfall Climatology - Nearly 30 years of tropical cyclone histories with an emphasis on storm total rainfall, in color, up to present. Broken up by year, region, by point of landfall, and North American countries impacted
- Global ISCCP B1 Browse System Satellite Archive
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