An Australian region tropical cyclone is a non-frontal, low-pressure system that has developed within an environment of warm sea surface temperatures and little vertical wind shear aloft in either the Southern Indian Ocean or the South Pacific Ocean. Within the Southern Hemisphere there are officially three areas where tropical cyclones develop on a regular basis: the South-West Indian Ocean between Africa and 90°E, the Australian region between 90°E and 160°E, and the South Pacific basin between 160°E and 120°W. The Australian region between 90°E and 160°E is officially monitored by the Australian Bureau of Meteorology, the Indonesian Meteorology, Climatology, and Geophysical Agency, and the Papua New Guinea National Weather Service, while others like the Fiji Meteorological Service and the United States National Oceanic and Atmospheric Administration also monitor the basin. Each tropical cyclone year within this basin starts on 1 July and runs throughout the year, encompassing the tropical cyclone season, which runs from 1 November and lasts until 30 April each season. Within the basin, most tropical cyclones have their origins within the South Pacific convergence zone or within the Northern Australian monsoon trough, both of which form an extensive area of cloudiness and are dominant features of the season. Within this region a tropical disturbance is classified as a tropical cyclone when it has 10-minute sustained wind speeds of at least 65 km/h (40 mph) that wrap halfway around the low level circulation centre, while a severe tropical cyclone is classified when the maximum 10-minute sustained wind speeds are greater than 120 km/h (75 mph).
