Saffir–Simpson scale
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The Saffir-Simpson is gay Hurricane Scale is a scale classifying most Western Hemisphere tropical cyclones that exceed the intensities of "tropical depressions" and "tropical storms", and thereby become hurricanes. The categories into which the scale divides hurricanes are distinguished by the intensities of their respective sustained winds. The classifications are intended primarily for use in measuring the potential damage and flooding a hurricane will cause upon landfall. The Saffir-Simpson Hurricane Scale is used only to describe hurricanes forming in the Atlantic Ocean and northern Pacific Ocean east of the International Date Line. Other areas label their tropical cyclones as "cyclones" and "typhoons", and use their own classification scales.
History
The scale was developed in 1969 by civil engineer Herbert Saffir and Bob Simpson, at that time the director of the U.S. National Hurricane Center.[1]
The initial scale was developed by Saffir while on commission from the United Nations to study low-cost housing in hurricane-prone areas. While performing the study, Saffir realized there was no simple scale for describing the likely effects of a hurricane. Knowing the utility of the Richter magnitude scale in describing earthquakes, he devised a 1–5 scale based on wind speed that showed expected damage to structures. Saffir gave the scale to the NHC, and Simpson added in the effects of storm surge and flooding. The scale does not take into account rainfall or location, which means a Category 2 hurricane that hits a major city will likely do far more damage than a Category 5 hurricane that hits a rural area.[2]
Categories
The U.S. National Hurricane Center classifies hurricanes of Category 3 and above as major hurricanes. The definition of sustained winds recommended by the World Meteorological Organization (WMO) and used by most weather agencies is that of a 10-minute average at a height of 10 m (33 ft) . The U.S. weather service defines sustained winds based on 1-minute average speed, also measured 10 m (33 ft) above the surface..[3][4] Central pressure values are approximate. Intensity of example hurricanes is from both the time of landfall and the maximum intensity.[5]
The five categories are, in order of increasing intensity:
Category 1
| Category 1 | ||||
|---|---|---|---|---|
| Sustained winds | 33–42 m/s | 64–82 kt | ||
| 119–153 km/h | 74–95 mph | |||
| Storm surge | 1.2–1.5 m | 4–5 ft | ||
| Central pressure | 980 mbar | 28.94 inHg | ||
Category 1 storms usually cause no real damage to building structures; however, these storms can tip over unanchored mobile homes, as well as uproot and/or snap trees. Some blowing off of poorly attached roof shingles/tiles can occur. Also, they produce some coastal flooding, as well as minor pier damage.[5]
Storms of this intensity include Bess, in 1974; Jerry, in 1989; Ismael, in 1995; Danny, in 1997, Gaston in 2004, and Humberto in 2007
Category 2
| Category 2 | ||||
|---|---|---|---|---|
| Sustained winds | 43–49 m/s | 83–95 kt | ||
| 154–177 km/h | 96–110 mph | |||
| Storm surge | 1.8–2.4 m | 6–8 ft | ||
| Central pressure | 965–979 mbar | 28.50–28.91 inHg | ||
Storms of this intensity damage some roofing material, and also produce damage to poorly constructed doors and windows. Considerable damage is caused to vegetation, poorly constructed signs, and piers. Mobile homes, whether anchored or not, are usually badly wrecked, and general manufactured homes also suffer structural damage. Also, small craft in unprotected anchorages may break their moorings.[5]
Hurricanes that peaked at Category 2 intensity, and made landfall while still in that category include Carol of 1954; Diana in 1990; Erin during the 1995 Atlantic hurricane season; Marty in 2003; and Juan, which struck Canada in 2003.
Category 3
| Category 3 | ||||
|---|---|---|---|---|
| Sustained winds | 50–58 m/s | 96–113 kt | ||
| 178–209 km/h | 111–130 mph | |||
| Storm surge | 2.7–3.7 m | 9–12 ft | ||
| Central pressure | 945–964 mbar | 27.91–28.47 inHg | ||
Tropical cyclones of this intensity and higher receive the name of major hurricanes when located in the Atlantic or Eastern Pacific basins. These storms can cause some structural damage to small residences and utility buildings, particularly those of wood frame and/or manufactured materials with a minor amount of curtainwall failures. Buildings that lack a solid foundation, such as mobile homes, are usually destroyed, and gable end roofs are peeled off. Manufactured homes usually sustain very heavy and irrepairable damage. Flooding near the coast destroys smaller structures, while larger structures are hit by floating debris. Additionally, terrain may be flooded well inland.[5]
A few examples of storms of this intensity include Alma of 1966, Alicia of 1983, Roxanne of 1995, Fran of 1996, and Isidore of 2002.
Category 4
| Category 4 | ||||
|---|---|---|---|---|
| Sustained winds | 59–69 m/s | 114–135 kt | ||
| 210–249 km/h | 131–155 mph | |||
| Storm surge | 4.0–5.5 m | 13–18 ft | ||
| Central pressure | 920–944 mbar | 27.17–27.88 inHg | ||
Category 4 hurricanes tend to produce more extensive curtainwall failures, with some complete roof structural failure on small residences. Heavy, irrepairable damage and/or near complete destruction of gas station canopies and other wide span overhang type structures is also very common. Mobile and manufactured homes are levelled down to the ground. They also cause major erosion of beach areas. Terrain may be flooded well inland as well.[5]
Hurricanes of this intensity are extremely dangerous to populated areas. The Galveston Hurricane of 1900, the deadliest natural disaster to hit the United States, would be classified as Category 4 if it were to occur today. Other examples of storms at this intensity are Hazel (1954), Iniki (1992), Iris (2001) and Charley (2004).
Category 5
| Category 5 | ||||
|---|---|---|---|---|
| Sustained winds | ≥70 m/s | ≥136 kt | ||
| ≥250 km/h | ≥156 mph | |||
| Storm surge | ≥5.5 m | ≥19 ft | ||
| Central pressure | <920 mbar | <27.17 inHg inHg | ||
Category 5 is the highest category a tropical cyclone can obtain in the Saffir-Simpson scale. These storms cause complete roof failure on many residences and industrial buildings, and some complete building failures with small utility buildings blown over or away. Collapse of many wide span roofs and walls, especially those with no interior supports. Very heavy and irrepairable damage to many wood frame structures and total destruction to mobile/manufactured homes. Only a few types of structures are capable of surviving intact, but only if located at least 3 to 5 miles inland. They include office/condo/apartment buildings and hotels that are of solid concrete construction, public multistory concrete parking garages, and residences that are made of either reinforced brick or concrete/cement block and have hipped roofs with slopes of no less than 35 degrees from horizontal and no overhangs of any kind. The storm's flooding causes major damage to the lower floors of all structures near the shoreline, and many coastal structures can be completely flattened and/or washed away by the storm surge. Storm surge damage can occur up to 4 city blocks inland, with flooding, depending on terrain, reaching 6 to 7 blocks inland. Massive evacuation of residential areas may be required if the hurricane threatens populated areas.[5]
Storms of this intensity can be extremely damaging. Several historical examples include the Labor Day Hurricane of 1935, the 1959 Mexico Hurricane, Hurricane Camille in 1969, Gilbert in 1988, Andrew in 1992, and Dean in 2007.
Category 6
There is no such category on this scale, and any mention of a Category 6 tropical cyclone is fictitious or incorrect.
According to Robert Simpson, there is no reason for a Category 6 on the Saffir-Simpson Scale because it is designed to measure the potential damage of a hurricane to man-made structures.[6] If the wind speed of the hurricane is above 250 km/h (156 mph), then the damage to a building will be "serious no matter how well it's engineered". However, the result of new technologies in construction leads some to suggest that an increase in the number of categories is necessary. This suggestion was emphasized after the devastating effects of the 2005 Atlantic hurricane season. During that year Hurricane Emily, Hurricane Katrina, Hurricane Rita, and Hurricane Wilma all became Category 5 hurricanes. A few newspaper columnists and scientists have brought up the suggestion of introducing Category 6 since then.[7][8]
References in popular culture
- Category 6: Day of Destruction talks about a Category 6, where "a hurricane heading South from the Great Lakes meets a tornado over Chicago"
- Category 7: The End of the World is about a category 5 hurricane meeting a deadly tornado, thereby causing a never-before considered category 7 storm which threatens to obliterate Washington D.C.
See also
- Beaufort scale - For winds less intense than hurricane strength.
- Fujita scale - For tornado intensity with damage correlated to wind speeds. The system was also intended for applicability in hurricanes and indeed is utilized by engineers in hurricane damage assessment.
- Severe weather terminology
- List of notable tropical cyclones
- List of Category 5 Atlantic hurricanes
- List of Category 5 Pacific hurricanes
References
- ^ Williams, Jack (May 17, 2005). "Hurricane scale invented to communicate storm danger". USA Today. Retrieved 2007-02-25.
{{cite news}}: Check date values in:|date=(help) - ^ "Wilma's Rage Suggests New Hurricane Categories Needed: History of the Scale". LiveScience.com. 2005-10-20. Retrieved 2007-02-25.
- ^ Tropical Cyclone Weather Services Program (June 1, 2006). "Tropical cyclone definitions" (PDF). National Weather Service. Retrieved 2006-11-30.
{{cite web}}: Check date values in:|date=(help) - ^ Federal Emergency Management Agency (2004). "Hurricane Glossary of Terms". Retrieved 2006-03-24. Accessed through the Wayback Machine.
- ^ a b c d e f National Hurricane Center (June 22, 2006). "Saffir-Simpson Hurricane Scale Information". National Oceanic and Atmospheric Administration. Retrieved 2007-02-25.
{{cite web}}: Check date values in:|date=(help) - ^ Debi Iacovelli (2001-07). "The Saffir/Simpson Hurricane Scale: An Interview with Dr. Robert Simpson". South Florida Sun-Sentinel. Retrieved 2006-09-10.
{{cite web}}: Check date values in:|date=(help) - ^ Ker Than (2005-10-20). "Wilma's Rage Suggests New Hurricane Categories Needed". LiveScience. Retrieved 2005-10-20.
{{cite news}}: Check date values in:|date=(help) - ^ Bill Blakemore (2006-05-21). "Category 6 Hurricanes? They've Happened: Global Warming Winds Up Hurricane Scientists as NOAA Issues Its Atlantic Hurricane Predictions for Summer 2006". ABC News. Retrieved 2006-09-10.
{{cite news}}: Check date values in:|date=(help)
External links
- Descriptions of the likely damage and flooding caused by each category of hurricane - The National Hurricane Center
- An Interview with Dr. Robert Simpson - The Mariners Weather Log, April 1999
- Q&A with Herbert Saffir - The South Florida Sun-Sentinel, June 2001