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Low Pressure Center
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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 an increase in pressure. Low pressure centers also represent the centers of cyclones.

A low pressure center is represented on a weather map by a red L and winds flow counterclockwise around a 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, transporting warm moist air northward ahead of a low while dragging colder, 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.