Photographed by Jeff Schmaltz, LANCE MODIS Rapid Pesponse; also Adam Voiland with information from Patrick Minnis, NASA Langley; Joanna Joiner, NASA Goddard; Steve Lang; NASA Goddard; and Heather Hyre, NASA Goddard.  In general, winds blow outward and away from high pressure areas, pulling air downward.  As air sinks, it warms, increasing evaporation and making it difficult for the air to sustain clouds.  In contrast, areas of low pressure pull air upward, generating clouds and stormy weather.  While low-pressure systems often produce circular cyclonic storms and clouds, high-pressure systems (sometimes called anticyclones) can yield large circular areas of clear skies — an anti-storm.
photo source: Wired  Or try a larger size.