High-Pressure Area

A high-pressure area, also called a high or an anticyclone, is a region near a planet surface where the atmospheric pressure is greater than in the surrounding area. The strongest highs form from cold air masses spreading out from polar regions, while weaker but more frequent ones form through subsidence, in which descending air warms and dries through compression. High-pressure systems typically bring clear skies, since the dry, sinking air suppresses cloud formation; this lets more solar radiation reach the ground and warm it by day, while the same lack of cloud cover lets heat escape freely at night, cooling temperatures. In temperate latitudes a high tends to bring warm, dry weather in summer and cold, dry weather in winter. Winds flow outward from the center of a high toward lower pressure but are deflected by the Coriolis effect, rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.