ANTICYCLONE IS A term for a region of closed circulation of air in the troposphere (the lowest 6 mi. [10 km.] or so of Earths atmosphere) with descending air from aloft and high atmospheric pressure at the surface. Anti-cyclonic circulation is usually accompanied by relatively high atmospheric pressure at the surface, and so the term high is often used interchangeably with anticyclone.

Anticyclones, as the name suggests, are the opposite of cyclones, which are regions of low pressure and typically associated with clouds, precipitation, and storms. On a surface weather map, meteorologists often denote anticyclones with a capital letter “H,” and cyclones by a capital “L.” Unlike cyclones, anticyclones are not usually associated with weather fronts. Anticyclones are sometimes referred to as ridges of high pressure. ...