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A surface weather analysis is a special type of weather map which provides a view of weather elements over a geographical area at a specified time.^[1] Weather maps are created by plotting or tracing the values of relevant quantities such as sea level pressure, temperature, cloud cover onto a geographical map to help find synoptic scale features such as weather fronts.

The first weather maps in the 19th century were drawn well after the fact to help devise a theory on storm systems.^[2] After the advent of the telegraph, simultaneous observations of weather became possible for the first time, and beginning in the late 1840s, the Smithsonian Institution became the first organization to draw real-time surface analyses. Use of surface analyses began first in the United States, spreading worldwide during the 1870s. Use of the Norwegian cyclone model for frontal analysis began in the late 1910s across Europe, with its use finally spreading to the United States during World War II.

Surface weather analyses have special symbols which show frontal systems, cloud cover, precipitation, or other important information. For example, an H may represent high pressure, implying good and fair weather. An L on the other hand may represent low pressure, which frequently accompanies precipitation. Various symbols are used not just for frontal zones and other surface boundaries on weather maps, but also to depict the present weather at various locations on the weather map. Areas of precipitation help determine the frontal type and location.

History of surface analysis

The use of weather charts in a modern sense began in the middle portion of the 19th century. Weather map pioneers include William Redfield, William Reid, Elias Loomis,^[2] and Sir Francis Galton, who created the first weather maps in order to devise a theory on storm systems.^[3] The invention of the telegraph in 1845 made it possible to gather weather information from multiple distant locations quickly enough to preserve its value for real-time applications. The Smithsonian Institution developed its network of observers over much of the central and eastern United States between the 1840s and 1860s once Joseph Henry took the helm.^[4] Beginning in 1849, the Smithsonian started producing surface analyses on a daily basis using the 150 stations in their network.^[5] The U.S. Army Signal Corps, which evolved into the modern National Weather Service, inherited this network between 1870 and 1874 by an act of Congress, and expanded it to the west coast soon afterwards. Three times daily, all stations would telegraph in their observations to the central office which would then plot the information on a map upon which isobars, or lines of equal pressure, would be drawn which would identify centers of high and low pressure, as well as squall lines.^[6] At first, all the data on the map was not taken at exactly the same time in the early days of these analyses because of a lack of time standardization. The first attempts at time standardization may have taken hold in the Great Britain by 1855, but in the United States standard time did not come to pass until 1883, when time zones started to come into use across America for railroad use. The entire United States did not finally come under the influence of time zones until 1905, when Detroit finally fell into line.^[7]

Internationally, other countries followed the lead of the United States, in regards to taking simultaneous weather observations, starting in 1873.^[8] Other countries then began preparing surface analyses. In Australia, the first weather map showed up in print media in 1877.^[9] Japan's Tokyo Meteorological Observatory, the forerunner of the Japan Meteorological Agency, began constructing surface weather maps in 1883.^[10] The use of frontal zones on weather maps did not appear until the introduction of the Norwegian cyclone model in the late 1910s, despite Loomis' earlier attempt at a similar notion in 1841.^[11] The use of the term "front" to describe a weather line on a map or the interface between air masses that the line symbolizes came from the line's resemblance to the military fronts of World War I.^[12]

File:Weather symbolsNEW2.gif

Present weather symbols used on weather maps

The earliest surface analyses from the United States featured only a map of the continental U.S. with the day's air temperature, barometric pressure, wind velocity and direction, and a general indication of the weather for various cities around the country plotted directly on the map. Within a short time the Signal Corps added a table showing the amount of change in barometric pressure during the most recent 8 hours, the temperature change within the most recent 24 hours, relative humidity, and total precipitation within the most recent 24 hours. The Signal Office also added a general discussion of synoptic weather features and forecast, and then isobars and isotherms, on the maps. By the end of 1872 the maps had established the format it would use until the introduction of frontal analysis.^[13]

Despite the introduction of the Norwegian cyclone model just after World War I, the United States did not formally analyze fronts on surface analyses until late 1942, when the WBAN Analysis Center opened in downtown Washington, D.C..^[14] The effort to automate map plotting began in the United States in 1969,^[15] with the process complete in the 1970s. Hong Kong completed their process of automated surface plotting by 1987.^[16] By 1999, computer systems and software had finally become sophisticated enough to allow for the ability to underlay on the same workstation satellite imagery, radar imagery, and model-derived fields such as atmospheric thickness and frontogenesis in combination with surface observations to make for the best possible surface analysis. In the United States, this development was achieved when Intergraph workstations were replaced by n-AWIPS workstations.^[17] By 2001, the various surface analyses done within the National Weather Service were combined into the Unified Surface Analysis, which is issued every six hours and combines the analyses of four different centers.^[18] Recent advances in both the fields of meteorology and geographic information systems have made it possible to devise finely tailored products that take us from the traditional weather map into an entirely new realm. Weather information can quickly be matched to relevant geographical detail. For instance, icing conditions can be mapped onto the road network. This will likely continue to lead to changes in the way surface analyses are created and displayed over the next several years.^[19]

Station model used on weather maps

When analyzing a weather map, a station model is plotted at each point of observation. Within the station model, the temperature, dewpoint, wind, sea level pressure, pressure tendency, and ongoing weather are plotted.^[20] The circle in the middle represents cloud cover. If completely filled in, it is overcast. If conditions are completely clear, the circle is empty. If conditions are partly cloudy, the circle is partially filled in.^[21] Outside the United States, temperature and dewpoint are plotted in degrees Celsius. Each full flag on the wind barb represents 10 knots of wind, each half flag represents 5 knots. When winds reach 50 knots, a filled in triangle is used for each 50 knots of wind.^[22] In the United States, rainfall plotted in the corner of the station model are in imperial units, such as inches. Internationally, the standard rainfall measurment unit is the millimeter. Once a map has a field of station models plotted, the analyzing isobars (lines of equal pressure), isallobars (lines of equal pressure change), isotherms (lines of equal temperature), and isotachs (lines of equal wind speed) can be easily accomplished.^[23] Symbols for weather are not straightforward, and were devised to take up the least room possible on weather maps.

Synoptic scale features

A synoptic scale feature is one whose dimensions are large in scale, more than several hundred kilometers in length.^[24] Migratory pressure systems and frontal zones exist on this scale.

Pressure centers

Centers of surface high and low pressure areas are found within closed isobars on a surface weather analysis where there the absolute maxima and minima in the pressure field, and can tell a user in a glace what the general weather is in their vicinity. Weather maps in English-speaking countries will depict their highs as Hs and lows as Ls,^[25] while Spanish-speaking countries will depict their highs as As and lows as Bs.^[26]

Low pressure

Low pressure systems are located in minima in the pressure field. Rotation is inward and counterclockwise in the northern hemisphere as opposed to inward and clockwise in the southern hemisphere due to the coriolis force. Weather is normally unsettled in the vicinity of a cyclone, with increased cloudiness, increased winds, increased temperatures, and upward motion in the atmosphere which leads to an increased chance of precipitation. Polar lows can form over relatively mild ocean waters when cold air sweeps in from the ice cap, leading to upward motion and convection, usually in the form of snow. Tropical cyclones and winter storms are intense varieties of low pressure. Over land, thermal lows are indicative of hot weather during the summer. ^[27]

High pressure

High pressure systems rotate outward and clockwise in the northern hemisphere as opposed to outward and counterclockwise in the southern hemisphere. Under surface highs, sinking motion leads to skies that are clearer, winds that are lighter, and there is a reduced chance of precipitation.^[28] There is normally a greater range between high and low temperature due to the drier airmass present. If high pressure persists, air pollution will build up due to pollutants trapped near the surface caused by the subsiding motion associated with the high.^[29]

Fronts

File:Occludedcyclone.gif

Occluded cyclone example. The triple point is the intesection of the cold, warm, and occluded fronts.

Fronts in meteorology are the leading edges of air masses with different density (e.g., air temperature and/or humidity). When a front passes over an area, it is marked by changes in temperature, moisture, wind speed and direction, atmospheric pressure, and often a change in the precipitation pattern. Cold fronts are often closely associated with low pressure systems, normally lying at the leading edge of high pressure systems and, in the case of the polar front, at approximately the equatorward edge of the high-level polar jet. Fronts are generally guided by winds aloft, but they normally move at lesser speeds. In the northern hemisphere, they usually travel from some west to east direction (even though they can move in a more north-south direction as well). Movement is largely due to the pressure gradient force (due to horizontal differences in atmospheric pressure) and the Coriolis effect, caused by the earth spinning about its axis. Frontal zones can be contorted by geographic features like mountains and large bodies of water.^[18]

Cold front

A cold front's location is at the leading edge of the temperature drop off, which in an isotherm analysis would show up as the leading edge of the isotherm gradient, and it normally lies within a sharp surface trough. Cold fronts can move up to twice as fast and produce sharper changes in weather than warm fronts, since cold air is denser than warm air it rapidly replaces the warm air preceding the boundary. Cold fronts are typically accompanied by a narrow band of showers and thunderstorms. On weather maps, the surface position of the cold front is marked with the symbol of a blue line of triangles/spikes (pips) pointing in the direction of travel, and it is placed at the leading edge of the cooler airmass.^[18]

Warm front

Warm fronts are at the leading edge of the temperature drop off, which is located on the equatorward edge of the gradient in isotherms, and lie within broader troughs of low pressure than cold fronts. Warm fronts move more slowly than the cold front which usually follows due to the fact that cold air is more dense, and harder to remove from the earth's surface. This also forces temperature differences across warm fronts to be broader in scale. Clouds ahead of the warm front are mostly stratiform and rainfall gradually increases as the front approaches. Fog can also occur preceding a warm frontal passage. Clearing and warming is usually rapid after frontal passage. If the warm air mass is unstable, thunderstorms may be embedded among the stratiform clouds ahead of the front, and after frontal passage, thundershowers may continue. These may become organized ahead of the following cold front as a squall line. On weather maps, the surface location of a warm front is marked with a red line of half circles pointing in the direction of travel.^[18]

Occluded front

An occluded front is formed during the process of cyclogenesis when a cold front overtakes a warm front.^[30] The cold and warm fronts curve up naturally into the point of occlusion, which is known as a triple point in meteorology.^[31] It lies within a sharp trough, but the airmass behind the boundary can be either warm or cold. In a cold occlusion, the air mass overtaking the warm front is cooler than the cool air ahead of the warm front, and plows under both air masses. In a warm occlusion, the air mass overtaking the warm front is not as cool as the cold air ahead of the warm front, and rides over the colder air mass while lifting the warm air. A wide variety of weather can be found along an occluded front, with thunderstorms possible, but usually their passage is associated with a drying of the airmass. Occluded fronts are indicated on a weather map by a purple line with alternating half-circles and triangles pointing in direction of travel.^[18] Occluded fronts usually form around mature low pressure areas.

Stationary fronts and shearlines

A stationary front is a non-moving boundary between two different air masses, neither of which is strong enough to replace the other. They tend to remain essentially in the same area for extended periods of time, usually moving in waves.^[32] There is normally a broad temperature gradient behind the boundary with more widely spaced isotherm packing. A wide variety of weather can be found along a stationary front, but usually clouds and prolonged precipitation are found there. Stationary fronts will either dissipate after several days or devolve into shear lines, but can change into a cold or warm front if conditions aloft change. Stationary fronts are marked on weather maps with alternating red half-circles and blue spikes pointing in opposite directions, indicating no significant movement.

When stationary fronts become smaller in scale, degenerating to a narrow zone where wind direction changes significantly over a relatively short distance, they become known as shear lines.^[33] If the shear line becomes active with thunderstorms, it may support formation of a tropical storm or a regeneration of the feature back into a stationary front. A shear line is depicted as a line of red dots and dashes.^[18]

Mesoscale features

Mesoscale features are smaller than synoptic scale systems like fronts, but larger than storm-scale systems like thunderstorms. Horizontal dimensions generally range from around 50 miles to several hundred miles.^[34]

Dry line

The dry line is the boundary between air masses with significant moisture differences, depicted at the leading edge of the most significant contrast in moisture, or dew point gradient. During daylight hours, drier air from mixes down to the surface due to daytime heating, wedges under the warm moist airmass to its east like a cold front and progresses eastward. At night, the boundary reverts back to the west as daytime.^[35] If moisture pools along with boundary during the warm season, it can be the focus of diurnal thunderstorms.^[36] A dry line is depicted on NWS surface analyses as a brown line with scallops facing into the moist sector. Dry lines are one of the few surface fronts where the pips indicated do not necessarily reflect the direction of motion.^[37]

Outflow boundaries and squall lines

File:Shelfcloudspc.jpg

A shelf cloud such as this one can be a sign that a squall is imminent

Organized areas of thunderstorm activity not only reinforce pre-existing frontal zones, but they can outrun cold fronts in a pattern where the upper level jet splits into two streams, with the resultant mesoscale convective system (MCS) forming at the point of the upper level split in the wind pattern running southeast into the warm sector parallel to low-level thickness lines. When the convection is strong and linear or curved, the MCS is called a squall line, with the feature placed at the leading edge of the significant wind shift and pressure rise.^[38] Even weaker and less organized areas of thunderstorms will lead to locally cooler air and higher pressures, and outflow boundaries exist ahead of this type of activity, which can act as foci for additional thunderstorm activity later in the day.^[39] These features will commonly be depicted in the warm season across the United States on surface analyses, and they lie within surface troughs. If outflow boundaries or squall lines form over arid regions, a duststorm known as a haboob may result due to the high winds in their wake picking up dust from the desert floor.^[40] Squall lines are depicted on NWS surface analyses as an alternating pattern of two red dots and a dash labelled SQLN or SQUALL LINE, while outflow boundaries are depicted as troughs with a label of OUTFLOW BNDRY.

File:LAKE BREEZE.gif

Idealized circulation pattern associated with a sea breeze

Sea, lake, river, and land breeze fronts

Sea/lake/river breeze fronts occur mainly on sunny days when the landmass warms up above the water temperature. Since the specific heat of water is so significant compared to most other substances, there is little diurnal change in ocean/lakes/bays even on the sunniest days...usually limited to one degree Celsius, or one to two degrees Fahrenheit. During the afternoon, sea breezes move inland when relatively cooler/milder air from the water body moves inland to fill in the gap left by lowered pressures caused by the relatively warm air over the landmass. This process reverses at night, leading to a land breeze and wind acceleration offshore. If enough moisture exists, thunderstorms can form along sea/lake/river/land breeze fronts which then can send out their outflow boundaries, which can lead to chaotic wind/pressure regimes if winds are light and variable with height. Like all other surface features, sea/lake/river/land breeze fronts also lie inside troughs, but if surface data is not dense enough, this trough may not be readily apparent. ^[41]

References

^ Air Apparent: How Meteorologists Learned to Map, Predict, and Dramatize Weather. University of Chicago Press. Chicago: 1999.
^ ^a ^b Eric R. Miller. American Pioneers in Meteorology. Retrieved on 2007-04-18.
^ Human Intelligence.Francis Galton. Retrieved on 2007-04-18.
^ Frank Rives Millikan. Smithsonian Institution. Joseph Henry: Father of the Weather Service. Retrieved on 2006-10-22.
^ National Oceanic and Atmospheric Administration. Evolution of the National Weather Service. Retrieved on 2006-10-22.
^ NOAA> General Myer: Establishing a Legacy of Weather Service. Retrieved on 2007-05-05.
^ WebExhibits. Daylight Savings Time. Retrieved on 2007-04-20.
^ NOAA. An Expanding Presence. Retrieved on 2007-05-05.
^ Bureau of Meteorology. Australia's First Weathermen. Retrieved on 2006-10-22.
^ Japan Meteorological Agency. History. Retrieved on 2006-10-22.
^ John D. Reid. Weather Prediction in the 19th and Early 20th Centuries: A Canadian Perspective. Retrieved on 2006-10-22.
^ Bureau of Meteorology. Air Masses and Weather Maps. Retrieved on 2006-10-22.
^ NOAA Central Library. U.S. Daily Weather Maps Project. Retrieved on 2007-05-10.
^ Hydrometeorological Prediction Center. A Brief History of the Hydrometeorological Prediction Center. Retrieved on 2007-05-05.
^ ESSA. Prospectus for an NMC Digital Facsimile Incoder Mapping Program. Retrieved on 2007-05-05.
^ Hong Kong Observatory. The Hong Kong Observatory Computer System and Its Applications. Retrieved on 2007-05-05.
^ Hydrometeorological Prediction Center. [http://www.hpc.ncep.noaa.gov/html/Accomplish99/Accomplish99.html Hydrometeorological Prediction Center 1999 Accomplishment Report.] Retrieved on 2007-05-05.
^ ^a ^b ^c ^d ^e ^f David Roth. Hydrometeorological Prediction Center. Unified Surface Analysis Manual. Retrieved on 2006-10-22.
^ Saseendran S. A., Harenduprakash L., Rathore L. S. and Singh S. V. A GIS application for weather analysis and forecasting. Retrieved on 2007-05-05.
^ National Weather Service. Station Model Example. Retrieved on 2007-04-29.
^ Dr Elizabeth R. Tuttle. Weather Maps. Retrieved on 2007-05-10.
^ American Meteorological Society. Selected DataStreme Atmosphere Weather Map Symbols. Retrieved on 2007-05-10.
^ CoCoRAHS. INTRODUCTION TO DRAWING ISOPLETHS. Retrieved on 2007-04-29.
^ Glossary of meteorology. Synoptic scale. Retrieved on 2007-05-10.
^ Weather Doctor. Weather's Highs and Lows: Part 1 The High.
^ Instituto Nacional de Meteorologia. Meteorologia del Aeropuerto de la Palma. Retrieved on 2007-05-05.
^ BBC Weather. Weather Basics - Low Pressure. Retrieved on 2007-05-05.
^ BBC Weather. High Pressure. Retrieved on 2007-05-05.
^ United Kingdom School System. Pressure, Wind and Weather Systems. Retrieved on 2007-05-05.
^ University of Illinois. Occluded Front. Retrieved on 2006-10-22.
^ National Weather Service Office, Norman, Oklahoma. Triple Point. Retrieved on 2006-10-22.
^ University of Illinois. Stationary Front. Retrieved on 2006-10-22.
^ Glossary of Meteorology. Shear Line. Retrieved on 2006-10-22.
^ Fujita, T. T., 1986. Mesoscale classifications: their history and their application to forecasting. Mesoscale Meteorology and Forecasting. American Meteorological Society, Boston, p. 18-35.
^ Lewis D. Grasso. A Numerical Simulation of Dryline Sensitivity to Soil Moisture. Retrieved on 2007-05-10.
^ Glossary of Meteorology. Lee Trough. Retrieved on 2006-10-22.
^ University of Illinois. Dry Line: A Moisture Boundary. Retrieved on 2006-10-22.
^ Office of the Federal Coordinator for Meteorology. Chapter 2: Definitions. Retrieved on 2006-10-22.
^ Michael Branick. National Weather Service Office, Norman, Oklahoma. A Comprehensive Glossary of Weather. Retrieved on 2006-10-22.
^ Western Region Climate Center. H. Retrieved on 2006-10-22.
^ Glossary of Meteorology. Sea Breeze. Retrieved on 2006-10-22.

External links

Template:Met vars

[1] Air Apparent: How Meteorologists Learned to Map, Predict, and Dramatize Weather. University of Chicago Press. Chicago: 1999.

[MILLER-2] Eric R. Miller. American Pioneers in Meteorology. Retrieved on 2007-04-18.

[3] Human Intelligence.Francis Galton. Retrieved on 2007-04-18.

[4] Frank Rives Millikan. Smithsonian Institution. Joseph Henry: Father of the Weather Service. Retrieved on 2006-10-22.

[5] National Oceanic and Atmospheric Administration. Evolution of the National Weather Service. Retrieved on 2006-10-22.

[6] NOAA> General Myer: Establishing a Legacy of Weather Service. Retrieved on 2007-05-05.

[7] WebExhibits. Daylight Savings Time. Retrieved on 2007-04-20.

[8] NOAA. An Expanding Presence. Retrieved on 2007-05-05.

[9] Bureau of Meteorology. Australia's First Weathermen. Retrieved on 2006-10-22.

[10] Japan Meteorological Agency. History. Retrieved on 2006-10-22.

[11] John D. Reid. Weather Prediction in the 19th and Early 20th Centuries: A Canadian Perspective. Retrieved on 2006-10-22.

[12] Bureau of Meteorology. Air Masses and Weather Maps. Retrieved on 2006-10-22.

[13] NOAA Central Library. U.S. Daily Weather Maps Project. Retrieved on 2007-05-10.

[14] Hydrometeorological Prediction Center. A Brief History of the Hydrometeorological Prediction Center. Retrieved on 2007-05-05.

[15] ESSA. Prospectus for an NMC Digital Facsimile Incoder Mapping Program. Retrieved on 2007-05-05.

[16] Hong Kong Observatory. The Hong Kong Observatory Computer System and Its Applications. Retrieved on 2007-05-05.

[17] Hydrometeorological Prediction Center. [http://www.hpc.ncep.noaa.gov/html/Accomplish99/Accomplish99.html Hydrometeorological Prediction Center 1999 Accomplishment Report.] Retrieved on 2007-05-05.

[DR-18] ^ ^a ^b ^c ^d ^e ^f David Roth. Hydrometeorological Prediction Center. Unified Surface Analysis Manual. Retrieved on 2006-10-22.

[19] Saseendran S. A., Harenduprakash L., Rathore L. S. and Singh S. V. A GIS application for weather analysis and forecasting. Retrieved on 2007-05-05.

[20] National Weather Service. Station Model Example. Retrieved on 2007-04-29.

[21] Dr Elizabeth R. Tuttle. Weather Maps. Retrieved on 2007-05-10.

[22] American Meteorological Society. Selected DataStreme Atmosphere Weather Map Symbols. Retrieved on 2007-05-10.

[23] CoCoRAHS. INTRODUCTION TO DRAWING ISOPLETHS. Retrieved on 2007-04-29.

[24] Glossary of meteorology. Synoptic scale. Retrieved on 2007-05-10.

[25] Weather Doctor. Weather's Highs and Lows: Part 1 The High.

[26] Instituto Nacional de Meteorologia. Meteorologia del Aeropuerto de la Palma. Retrieved on 2007-05-05.

[27] BBC Weather. Weather Basics - Low Pressure. Retrieved on 2007-05-05.

[28] BBC Weather. High Pressure. Retrieved on 2007-05-05.

[29] United Kingdom School System. Pressure, Wind and Weather Systems. Retrieved on 2007-05-05.

[30] University of Illinois. Occluded Front. Retrieved on 2006-10-22.

[31] National Weather Service Office, Norman, Oklahoma. Triple Point. Retrieved on 2006-10-22.

[32] University of Illinois. Stationary Front. Retrieved on 2006-10-22.

[33] Glossary of Meteorology. Shear Line. Retrieved on 2006-10-22.

[34] Fujita, T. T., 1986. Mesoscale classifications: their history and their application to forecasting. Mesoscale Meteorology and Forecasting. American Meteorological Society, Boston, p. 18-35.

[35] Lewis D. Grasso. A Numerical Simulation of Dryline Sensitivity to Soil Moisture. Retrieved on 2007-05-10.

[36] Glossary of Meteorology. Lee Trough. Retrieved on 2006-10-22.

[37] University of Illinois. Dry Line: A Moisture Boundary. Retrieved on 2006-10-22.

[38] Office of the Federal Coordinator for Meteorology. Chapter 2: Definitions. Retrieved on 2006-10-22.

[39] Michael Branick. National Weather Service Office, Norman, Oklahoma. A Comprehensive Glossary of Weather. Retrieved on 2006-10-22.

[40] Western Region Climate Center. H. Retrieved on 2006-10-22.

[41] Glossary of Meteorology. Sea Breeze. Retrieved on 2006-10-22.

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@@ Line 12: / Line 12: @@
 Internationally, other countries followed the lead of the United States, in regards to taking simultaneous weather observations, starting in [[1873]].<ref>NOAA. [http://celebrating200years.noaa.gov/foundations/weather/#expand An Expanding Presence.] Retrieved on [[2007-05-05]].</ref>  Other countries then began preparing surface analyses.  In [[Australia]], the first weather map showed up in print media in [[1877]].<ref>Bureau of Meteorology. [http://www.bom.gov.au/lam/climate/levelthree/analclim/earlym.htm Australia's First Weathermen.] Retrieved on [[2006-10-22]].</ref>  [[Japan]]'s Tokyo Meteorological Observatory, the forerunner of the [[Japan Meteorological Agency]], began constructing surface weather maps in 1883.<ref>Japan Meteorological Agency. [http://www.jma.go.jp/jma/en/History/indexe_his.htm History.] Retrieved on [[2006-10-22]].</ref>  The use of frontal zones on weather maps did not appear until the introduction of the Norwegian cyclone model in the late [[1910s]], despite Loomis' earlier attempt at a similar notion in [[1841]].<ref>John D. Reid. [http://www.magma.ca/~jdreid/ Weather Prediction in the 19th and Early 20th Centuries:  A Canadian Perspective.] Retrieved on [[2006-10-22]].</ref>  The use of the term "front" to describe a weather line on a map or the interface between air masses that the line symbolizes came from the line's resemblance to the military fronts of World War I.<ref>Bureau of Meteorology. [http://www.bom.gov.au/info/ftweather/page_6.shtml Air Masses and Weather Maps.] Retrieved on [[2006-10-22]].</ref>
 [[Image:Weather symbolsNEW2.gif|thumb|right|250px|Present weather symbols used on weather maps]]
+The earliest surface analyses from the United States featured only a map of the continental U.S. with the day's air temperature, barometric pressure, wind velocity and direction, and a general indication of the weather for various cities around the country plotted directly on the map.  Within a short time the Signal Corps added a table showing the amount of change in barometric pressure during the most recent 8 hours, the temperature change within the most recent 24 hours, relative humidity, and total precipitation within the most recent 24 hours. The Signal Office also added a general discussion of synoptic weather features and forecast, and then isobars and isotherms, on the maps. By the end of 1872 the maps had established the format it would use until the introduction of frontal analysis.<ref>NOAA Central Library. [http://docs.lib.noaa.gov/rescue/dwm/data_rescue_daily_weather_maps_bak.html U.S. Daily Weather Maps Project.] Retrieved on [[2007-05-10]].</ref>
 Despite the introduction of the Norwegian [[cyclone]] model just after World War I, the United States did not formally analyze fronts on surface analyses until late [[1942]], when the WBAN Analysis Center opened in downtown [[Washington, D.C.]].<ref>[[Hydrometeorological Prediction Center]]. [http://www.hpc.ncep.noaa.gov/html/historyNMC.shtml A Brief History of the Hydrometeorological Prediction Center.] Retrieved on [[2007-05-05]].</ref>  The effort to automate map plotting began in the United States in [[1969]],<ref>ESSA. [http://www.ncep.noaa.gov/officenotes/NOAA-NPM-NCEPON-0001/013FD50A.pdf Prospectus for an NMC Digital Facsimile Incoder Mapping Program.] Retrieved on [[2007-05-05]].</ref> with the process complete in the [[1970s]].  [[Hong Kong]] completed their process of automated surface plotting by [[1987]].<ref>Hong Kong Observatory. [http://www.weather.gov.hk/wservice/tsheet/computer.htm The Hong Kong Observatory Computer System and Its Applications.] Retrieved on [[2007-05-05]].</ref>  By [[1999]], computer systems and software had finally become sophisticated enough to allow for the ability to underlay  on the same workstation satellite imagery, radar imagery, and model-derived fields such as atmospheric thickness and frontogenesis in combination with surface observations to make for the best possible surface analysis.  In the United States, this development was achieved when Intergraph workstations were replaced by n-[[Advanced Weather Interactive Processing System|AWIPS]] workstations.<ref>[[Hydrometeorological Prediction Center]]. [http://www.hpc.ncep.noaa.gov/html/Accomplish99/Accomplish99.html Hydrometeorological Prediction Center
 Accomplishment Report.] Retrieved on [[2007-05-05]].</ref>  By [[2001]], the various surface analyses done within the National Weather Service were combined into the Unified Surface Analysis, which is issued every six hours and combines the analyses of four different centers.<ref name="DR">David Roth. Hydrometeorological Prediction Center. [http://www.hpc.ncep.noaa.gov/sfc/UASfcManualVersion1.pdf Unified Surface Analysis Manual.] Retrieved on [[2006-10-22]].</ref>  Recent advances in both the fields of [[meteorology]] and [[Geographic information system|geographic information systems]] have made it possible to devise finely tailored products that take us from the traditional weather map into an entirely new realm.  Weather information can quickly be matched to relevant geographical detail.  For instance, icing conditions can be mapped onto the road network.  This will likely continue to lead to changes in the way surface analyses are created and displayed over the next several years.<ref>Saseendran S. A., Harenduprakash L., Rathore L. S. and Singh S. V.  [http://www.gisdevelopment.net/application/environment/conservation/envm0004.htm A GIS application for weather analysis and forecasting.] Retrieved on [[2007-05-05]].</ref>