An atmospheric system characterized by the rapid inward circulation of air masses about a low-pressure centre, usually accompanied by stormy, often destructive weather. A tropical cyclone is defined as sustaining gale force winds of at least 63 km per hour and if the sustained wind force is at least 118 km per hour it is defined as a severe tropical cyclone. The severity of a cyclone is described in terms of categories ranging from 1 to 5, related to the strength of maximum winds.
Cyclones rotate clockwise in the southern hemisphere and anti-clockwise in the northern hemisphere.
Image: Cyclone Larry, Australian Red Cross