Editing Surface weather analysis (section)

=== Pressure centers ===
[[Image:Wind barbs.gif|thumb|upright|Wind barb interpretation]]

Centers of surface high- and low-pressure areas that are found within closed isobars on a surface weather analysis are 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,<ref>Weather Doctor. [http://www.islandnet.com/~see/weather/elements/high.htm Weather's Highs and Lows: Part 1 The High.]</ref> while Spanish-speaking countries will depict their highs as As and lows as Bs.<ref>Agencia Estatal de Meteorología. [http://www.aemet.es/en/divulgacion/aeronautica/detalles/Meteorologia_del_aeropuerto_de_La_Palma Meteorología del aeropuerto de La Palma.].</ref>

==== Low pressure ====
Low-pressure systems, also known as [[cyclone]]s, are located in minima in the pressure field.  Rotation is inward at the surface 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 low]]s can form over relatively mild ocean waters when cold air sweeps in from the ice cap. The relatively warmer water leads to upward convection, causing a low to form, and precipitation usually in the form of snow. Tropical cyclones and winter storms are intense varieties of low pressure. Over land, [[thermal low]]s are indicative of hot weather during the summer.<ref>BBC Weather. [http://www.bbc.co.uk/weather/features/basics_lowpressure.shtml Weather Basics - Low Pressure.] Retrieved on 2007-05-05.</ref>

==== High pressure ====
High-pressure systems, also known as [[anticyclone]]s, rotate outward at the surface and clockwise in the northern hemisphere as opposed to outward and counterclockwise in the southern hemisphere. Under surface highs, sinking of the atmosphere slightly warms the air by compression, leading to clearer skies, winds that are lighter, and a reduced chance of precipitation.<ref>BBC Weather. [http://www.bbc.co.uk/weather/features/understanding/highpressure.shtml High Pressure.] Retrieved on 2007-05-05.</ref> The descending air is dry, hence less energy is required to raise its temperature. 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.<ref>United Kingdom School System. [http://atschool.eduweb.co.uk/radgeog/metlink/ppt/highs/Press-System.ppt Pressure, Wind and Weather Systems.] {{webarchive|url=https://web.archive.org/web/20070927190000/http://atschool.eduweb.co.uk/radgeog/metlink/ppt/highs/Press-System.ppt |date=2007-09-27 }} Retrieved on 2007-05-05.</ref>