A tropical cyclone is a cyclone of tropical origin of small diameter (some hundreds of kilometres) with a minimum surface pressure in some cases of less than 900 hPa, very violent winds and torrential rain; sometimes accompanied by thunderstorms. It usually contains a central region, known as the ‘eye’ of the storm, with a diameter of the order of some tens of kilometres, and with light winds and a more or less lightly clouded sky (WMO, 2017).

A tropical storm is a rapid rotating storm originating over tropical oceans. It has a low pressure centre and clouds spiralling towards the eyewall surrounding the ‘eye’. Its diameter is typically around 200 to 500 km, but can reach 1000 km. The related hazards are very violent winds, torrential rain, high waves, storm surges and in some cases tornadoes, causing direct effects such as flash floods, flooding, coastal inundation, and indirect effects such as landslides and mudslides.