User:Jason Rees/SPac

A South Pacific tropical cyclone is a tropical cyclone that occurs within the South Pacific Ocean, between the Australian East Coast and South America. Within the region that tropical cyclones form in, they are primarily monitored by the Australian Bureau of Meteorology, Papua New Guinea's National Weather Service, Fiji Meteorological Service and the Meteorological Service of New Zealand as well as various other warning centers such as Meteo France.

Origins
Within the Southern Pacific tropical cyclones generally have their origins, within the South Pacific Convergence Zone or within the Northern Australian monsoon trough, which are both considered to be dominant features of the season.

General areas of Formation
The South Pacific Basin can be broken down into 3 general areas in which tropical cyclones form, which are the Coral Sea and the Australian region, the Fiji-Samoa-Tonga region and Polynesia.

The Coral Sea and the Australian region
Tropical Cyclones can form within the Gulf of Carpentaria or the Australian part of the Coral Sea and move into the basin by crossing 160°E. Tropical Cyclones in this region generally either move towards Australia or towards Fiji, however some have been known to move erratically around this region. Island countries affected can include any of the following: Australia, Papua New Guinea, the Solomon Islands, Vanautu, New Caledonia, New Zealand and or Fiji.

Activity within the Fiji-Samoa-Tonga region
Interannual variability of tropical cyclone activity specifically for the Fiji, Samoa and Tonga (FST) region is examined by Chand and Walsh (2009). During El Niño events, the highest tropical cyclone density is centred over the northern part of Fiji and tropical cyclone genesis occurs mainly between 6° and 18°S, 170°E and 170°W. Tropical cyclones that form during the El Niño phase take three characteristic paths. 1) Tropical cyclones forming poleward of 10°S west of the dateline are frequently steered southeastward into the northern part of the Fiji and Tonga region; 2) Tropical cyclones forming east of the dateline are usually steered north of the Samoa region; 3) Tropical cyclones that, on average, are generated in the mean northeasterly flow regime between 5° and 10°S, 170°E and 180° recurve west-southwest of Fiji. In the La Niña phase, fewer tropical cyclones are observed in the FST region compared to the El Niño phase. The genesis locations are displaced southwestward relative to their El Niño counterparts, with the maximum density centred near 15°S, 170°E. Tropical cyclones that form during La Niña are often steered over Fiji and Tonga with relatively little or no threat to the Samoa region. During the neutral phase, maximum genesis occurs immediately north of Fiji with enhanced genesis south of Samoa. TC tracks during the neutral phase are very similar to those in the El Niño phase except for slight poleward displacement. This accounts for enhanced activity south of Fiji and Samoa (Chand & Walsh, 2009).

Polynesia
Tropical Cyclone formation within the Polynesian region is rare

Monitoring centres
In addition to the Fiji Meteorological Service and the New Zealand Meteorological Service who are the official warning centres for the basin, there are several other centres who monitor tropical cyclones that develop within this basin. These include the United States Military, United States NOAA and the Australian BoM.

Fiji Meteorological Service
In 1970 after Britain had granted Fiji its independence the Fiji Department of Meteorology gradually assumed the responsibility, for naming and issuing warnings about tropical cyclones from 160°E to 120°W. In 1975 the Fiji Department of Meteorology was renamed and became the Fiji Meteorological Service, before in 1985 the World Meteorological Organization (WMO) created the RA V Tropical Cyclone Committee for the South Pacific and South-East Indian Ocean. At the first committee session in 1986, the Nadi Tropical Cyclone centre became the regional tropical cyclone warning centre and given "enhanced international recognition." In 1995, after the FMS had fulfilled various technical criteria, the WMO made it an Regional Specialized Meteorological Centre with activity specialization in tropical cyclones.

United States Military
On October 1, 1980 the United States Militaries Naval Western Oceanography Center (NWOC) and Joint Typhoon Warning Centre's (JTWC) areas of responsibility were expanded to include warning on tropical cyclones within the Southern Hemisphere between the eastern coast of Africa and the western coast of South America. Initially the JTWC warned on tropical cyclones located in the area from the eastern coast of Africa to 180° while the NWOC warned on the area between 180° and the western coast of South America. In 1994, the Naval Western Oceanography Center was renamed the Naval Pacific Meteorological and Oceanographic Center, before in 1995 the Base Realignment and Closure Commission, ordered the JTWC to relocate to Hawaii and merge with the NPMOC by 2001. The merger was subsequently completed during November and December 1998.

Other meteorological services
The Australian Bureau of Meteorology's Tropical cyclone Warning Centre in Brisbane Australia monitors the basin and issues As tropical cyclones move towards 160°E both the Australian Bureau of Meteorology and the National Weather Service of Papua New Guinea monitor

Both the Australian Bureau of Meteorology and the National Weather Service of Papua New Guinea monitor the coral sea area in cas