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A surface weather analysis is a special type of , Temperature , and 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.Eric R. Miller. American Pioneers in Meteorology. Retrieved on 2007-04-18 . 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 See Also: History of surface weather analysis on March 12, 1888 at 10 pm]] The use of weather charts in a modern sense began in the middle portion of the 19th century in order to devise a theory on storm systems.Human Intelligence. Francis Galton. Retrieved on . The U.S. Army Signal Corps inherited this network between 1870 and 1874 by an act of Congress, and expanded it to the west coast soon afterwards. 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 took hold in the Great Britain by 1855. The entire United States did not finally come under the influence of time zones until 1905, when . Despite the introduction of the Norwegian . 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. Hydrometeorological Prediction Center . [http://www.hpc.ncep.noaa.gov/html/Accomplish99/Accomplish99.html Hydrometeorological Prediction Center 1999 Accomplishment Report.] Retrieved on . STATION MODEL USED ON WEATHER MAPS See Also: Station model 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.National Weather Service. Station Model Example. Retrieved on . The abstract present weather symbols used on surface weather analyses for obstructions to visibility, precipitation, and thunderstorms were devised to take up the least room possible on weather maps. SYNOPTIC SCALE FEATURES See Also: Synoptic scale A synoptic scale feature is one whose dimensions are large in scale, more than several hundred kilometers in length.Glossary of meteorology. Synoptic scale. Retrieved on 2007-05-10 . 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 glance what the general weather is in their vicinity. Weather maps in English-speaking countries will depict their highs as Hs and lows as Ls,Weather Doctor. Weather's Highs and Lows: Part 1 The High. while Spanish-speaking countries will depict their highs as As and lows as Bs.Instituto Nacional de Meteorologia. Meteorologia del Aeropuerto de la Palma. Retrieved on 2007-05-05 . Low pressure Low pressure systems, also known as . High pressure High pressure systems, also known as . Fronts See Also: Weather fronts Fronts in meteorology are the leading edges of Air Mass es 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 Front s 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. Cold front See Also: 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 air mass. Warm front See Also: Warm front Warm Front s 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. 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. Occluded front See Also: Occluded front |
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