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​​Tropical cyclones are low pressure systems that form over warm tropical waters. Tropical cyclones are dangerous because they produce destructive winds, heavy rainfall with flooding and damaging storm surges that can cause inundation of low-lying coastal areas.

Tropical cyclones derive their energy from the warm tropical oceans and do not form unless the sea-surface temperature is above 26.5°C, although once formed, they can persist over lower sea-surface temperatures. Tropical cyclones can persist for many days and may follow quite erratic paths. They usually dissipate over land or colder oceans Winds in a cyclone travel in a clockwise direction around the centre. Cyclones have wind gusts in excess of 90 km/h around their centres and, in the most severe cyclones, gusts can exceed 280 km/h.

The severity of a tropical cyclone is described in terms of categories ranging from 1 to 5 related to the zone of maximum winds. More information is available at

For more information regarding warnings, preparation for and response to tropical cyclones please refer to