South Pacific tropical cyclone

A South Pacific 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 the South Pacific Ocean. Within the Southern Hemisphere there are officially three areas where tropical cyclones develop on a regular basis, these areas are 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 South Pacific basin between 160°E and 120°W is officially monitored by the Fiji Meteorological Service and New Zealand's MetService, while others like the Australian Bureau of Meteorology and the United States National Oceanic and Atmospheric Administration also monitor the basin. Each tropical cyclone year within this basin starts on July 1 and runs throughout the year, encompassing the tropical cyclone season which runs from November 1 and lasts until April 30 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 more than 65 km/h (35 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).

During June 1995, the Fiji Meteorological Service's Nadi — Tropical Cyclone Centre, was designated as a Regional Specialized Meteorological Center by the World Meteorological Organization.

During the 1980s there were three major Southern Oscillation episodes; two El Niño's (1982–83 and 1986/87) when the Southern Oscillation Index (SOI) was negative and one La Nina when the SOI was positive.

During the 2000s, activity was generally below the long term average, with 60 tropical cyclones developing out of 160 tropical disturbances and tropical depressions. However activity during the 2002–03, 2004–05 and 2009–10 seasons all experienced activity, near the long term average of about 8 - 9 tropical cyclones.

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