<P> Within the Southern Hemisphere tropical cyclones generally form on a regular basis between the African coast and the middle of the South Pacific . Tropical and Subtropical Cyclones have also been noted occurring in the Southern Atlantic Ocean at times . For various reasons including where tropical cyclones form, there are several different ways to split the area between the American and African coasts . For instance the World Meteorological Organization define three different basins for the tracking and warning of tropical cyclones . These are the South - West Indian Ocean between the African Coast and 90 ° E, the Australian region between 90 ° E and 160 ° E and the South Pacific between 160 ° E and 120 ° W . The United States Joint Typhoon Warning Center also monitors the whole region, but splits it at 135 ° E into the South Pacific and the Southern Indian Ocean . </P> <P> The South - West Indian Ocean is located within the Southern Hemisphere between the Africa's east coast and 90 ° E and is primarily monitored by the Meteo France's La Reunion RSMC, while the Mauritian, Australian Indonesian, and Malagasy weather services also monitor parts of it . Until the start of the 1985--86 tropical cyclone season the basin only extended to 80 ° E, with the 10 degrees between 80 and 90E considered to be a part of the Australian region . On average about 9 cyclones per develop into tropical storms, while 5 of those go on to become tropical cyclones that are equivalent to a hurricane or a typhoon . The tropical cyclones that form in this area can affect some of the various Indian Ocean island nations and or various countries along Africa's east coast . </P> <P> Through the middle of 1985, this basin extended westward to 80E . Since then, its western boundary has been 90E . Tropical activity in this region affects Australia and Indonesia . According to the Australian Bureau of Meteorology, the most frequently hit portion of Australia is between Exmouth and Broome in Western Australia . The basin sees an average of about seven cyclones each year, although more can form or come in from other basins, such as the South Pacific . The tropical cyclone Cyclone Vance in 1999 produced the highest recorded speed winds in an Australian town or city at around 267 km / h (166 mph). </P> <P> The South Pacific Ocean basin runs between 160 ° E and 120 ° W, with tropical cyclones developing in it officially monitored by the Fiji Meteorological Service and New Zealand's MetService . Tropical Cyclones that develop within this basin generally affect countries to the west of the dateline, though during El Niños cyclones have been known to develop to the east of the dateline near French Polynesia . On average the basin sees nine tropical cyclones annually with about half of them becoming severe tropical cyclones . </P>

Regions and seasons of greatest frequency of trs