Tropical Cyclones are described by the Bureau of Meteorology as low pressure systems that form over warm tropical waters and have gale force winds (sustained winds of 63 km/h or greater and gusts in excess of 90 km/h) near the centre. Tropical cyclones are like giant whirlwinds where the air moves in a large spiral around the centre of very low air pressure Tropical cyclones generally occur in the northern parts of Australia and often cause widespread damage and destruction.
