Any large system of winds that circulates about a centre of low atmospheric pressure in a counterclockwise direction north of the Equator and in a clockwise direction south of it. Cyclones that occur in the mid- and high latitudes are known as extratropical cyclones; they are frequently preceded by thickening and lowering clouds, followed by precipitation. Cyclones that form in the lower latitudes are known as tropical cyclones; smaller than extratropical cyclones, they tend to be more violent and can cause considerable damage (see tropical cyclone). Wind systems that circulate around a high-pressure centre in directions opposite to that of cyclones are known as anticyclones.

This entry comes from Encyclopædia Britannica Concise.
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