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NOTE: We've guessed that you're not using a client that supports colored tables and have tried to compensate. Low graphics mode looks much better on clients that do... we recommend switching to Netscape 3.0 or Microsoft Internet Explorer.
Low Pressure Centers
also known as cyclones

A surface low pressure center is where the pressure has been measured to be the lowest relative to its surroundings. That means, moving any horizontal direction away from the Low will result in increasing pressure. Low pressure centers often represent the centers of midlatitude cyclones.

A low pressure center is represented on a weather map by a red L. Winds flow counterclockwise around the low in the northern hemisphere. The opposite is true in the southern hemisphere, where winds flow clockwise around an area of low pressure. The counterclockwise winds associated with northern hemisphere midlatitude cyclones play a significant role in the movement air masses, typically transporting warm moist air northward ahead of a low while dragging colder and drier air southward behind it.

[Image: low pressure animation (53K)]
** Press "Reload" to restart the animation **

Rising air in the vicinity of a low pressure center favors the development of clouds and precipitation, which is why cloudy weather (and likely precipitation) are commonly associated with an area of low pressure. Cyclones are easily identifiable on certain types of weather maps by remembering some key signatures. For example, a cyclone can be found on a map of surface observations by recognizing a counterclockwise rotation of the wind barbs for a group of stations, while on satellite images, cyclones are identifiable by the trademark comma shaped configuration of cloud bands.

Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.