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Cyclone Ofa
Severe Tropical Cyclone Ofa was considered to be the worst tropical cyclone to affect Polynesia since Cyclone Bebe. The system was first noted on January 27 near Tuvalu, as a shallow tropical depression that had developed within the South Pacific Convergence Zone. The cloud pattern slowly organized, and on January 31, while located east of Tuvalu, Ofa attained cyclone intensity. Moving slowly southeast, Ofa developed storm-force winds. It attained hurricane-force winds on February 2. Cyclone Ofa reached peak intensity on February 4. Shortly after, its peak Ofa began to weaken over a less favourable environment. Ofa was declared an extratropical cyclone on February 8, though the system was still tracked by meteorologists until February 10.
Ofa produced gales or high winds or gales on many islands, resulting in widespread damage due to a combination of storm surge and high seas. In all, eight people were killed and damage totaled to . The worst effects were recorded in Samoa, where seven people were killed. Roughly 200 people were evacuated, and 10 to 20 others were injured through the islands. Extreme damage to crops and trees was also recorded. Elsewhere, Ofa was blamed for the lowest ever recorded pressure on the island of Niue, along with considerable damage.
==Meteorological history==
Towards the end of January 1990, a surge in the Northern Hemisphere's trade winds and the Southern Hemispheres monsoon, led to the South Pacific Convergence Zone (SPCZ) and the Australian monsoon trough becoming active after a prolonged period of dormancy. As a result, two shallow tropical depressions were spawned; one over the Coral Sea that went on to become Cyclone Nancy, while the other was first noted within the SPCZ over Tuvalu on January 27.〔 Over the next two days the system developed little and remained slow moving, near the Tuvaluan atoll of Funafuti.〔 During January 30, the depression moved towards the north-east and started to organize, as pressures near the systems center rapidly falling.〔 During the next day the system subsequently started to curve south-eastwards and away from Tuvalu, before the United States Naval Western Oceanography Center (NWOC) initiated advisories on the system and designated it as Tropical Cyclone 13P during January 31. At 19:17 UTC on January 31, Fiji Meteorological Service's Nadi Tropical Cyclone Warning Center named the system Ofa, after it had developed into a category 1 tropical cyclone on the Australian tropical cyclone intensity scale.〔 As it was named the system was located about to the east of Tuvalu and had started to curve more towards the south-southeast. During February 1, as Ofa started to affect Western Samoa, the NWOC reported that Ofa had become equivalent to a category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale (SSHWS).
TCWC Nadi subsequently reported during the next day that the system had become a category 3 severe tropical cyclone.〔 Ofa passed about to the west of the Western Samoan Island of Savai'i between 10:00 and 18:00 UTC during February 3.〔 Early the next day as the system started to accelerate towards the south-southeast towards the island nation of Niue, the NWOC estimated that Ofa had peaked with 1-minute sustained wind speeds of 215 km/h (130 mph), which made it equivalent to a category 4 hurricane on the SSHWS.〔 Later that day TCWC Nadi also estimated that the system had peaked as a category 4 severe tropical cyclone, with 10-minute sustained wind speeds of 185 km/h (115 mph).〔 Early on February 5, Ofa started to show signs that it had started to weaken, as it passed about to the west of Niue.〔 Over the next day the system slowly weakened as it moved southwards, before late on February 6, TCWC Nadi passed the primary warning responsibility for Ofa to the New Zealand Meteorological Service, after the system had moved below 25°S.〔 The system subsequently weakened very quickly and started to transition into an extratropical cyclone, as it encountered strong upper level winds and cooler waters.〔 The system completed this transition during February 8, before the remnants were last noted during February 10 after they had performed a small clockwise loop.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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