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Severe Tropical Cyclone Jasmine (RSMC Nadi designation: 12F, JTWC designation: 10P) was a long-lived annular tropical cyclone that affected several countries, particularly Vanuatu and Tonga, over a 19-day span in February 2012. The system was the second cyclone and the only severe tropical cyclone of the relatively quiet 2011–12 South Pacific cyclone season. Cyclone Jasmine developed from an area of disturbed weather on 1 February in the Gulf of Carpentaria. Initially, the storm moved towards the east and across the Cape York Peninsula. As it moved across the South Pacific, earlier existing wind shear conditions lessened, and Jasmine began to strengthen at a faster rate. Steadily intensifying, Jasmine reached peak intensity on 8 February as a Category 4 equivalent on the Saffir–Simpson Hurricane Scale, while beginning to show annular characteristics. The next day Jasmine entered an area of vertical wind shear, which consequently weakened the cyclone and caused its eye to expand. A high pressure area south of Jasmine later steered the weakening cyclone to the northeast on 12 February. Although it entered an area of warmer sea surface temperatures, Jasmine subsequently entered extratropical transition and later degenerated into an extratropical cyclone on 16 February, and later dissipated completely on 19 February. Cyclone Jasmine affected five countries during its existence. The predecessor to Jasmine brought heavy rainfall to areas of extreme northern Queensland. Jasmine also brought rainfall to areas of the Solomon Islands. As a result, pest infestations occurred across the region. In Vanuatu, heavy rains and wind from Jasmine destroy numerous crops. Banana trees in particular are affected by the cyclone. Jasmine inundated areas of Tonga that had already been affected by Cyclone Cyril just a week prior. Nuku'alofa recorded half of its average monthly rainfall in a 24–hour span due to rains associated with the cyclone. After the season, the name ''Jasmine'' was retired from the Australian list of tropical cyclone names. ==Meteorological history== During 31 January the Australian Bureau of Meteorology started to monitor a tropical low, that had developed within the monsoon trough over the western Cape York Peninsula. Over the next day the system moved into the southeastern part of the Gulf of Carpentaria, before it moved back over the Cape York Peninsula during 2 February.〔 The system subsequently emerged into the Coral Sea to the north of Cairns later that day, where a strong northwest monsoon flow with gales developed to the north of the low.〔 The system subsequently moved eastwards and intensified into a category 1 tropical cyclone on the Australian tropical cyclone intensity scale. On 1 February, the Australian Bureau of Meteorology's Brisbane tropical cyclone warning centre (TCWC Brisbane) and the United States Joint Typhoon Warning Center (JTWC) began to monitor a tropical low that had developed within a monsoon trough about to the north of Mornington Island. Over the next two days the low moved eastwards and passed over the Cape York Peninsula before it emerged into the Coral Sea to the north of Cairns. After emerging into the Coral Sea the low continued to develop, and on 4 February, the JTWC and TCWC Brisbane reported that the system had become a tropical cyclone with the latter naming it as ''Jasmine'' while it was located about to the east of Cairns.〔 Tracking eastward, Jasmine entered a flow of dry air, which prevented the storm from strengthening quickly at the time. On 5 February, the low–level atmospheric circulation center of Jasmine became exposed due to the presence of strong vertical wind shear. However, the cyclone was able to maintain its intensity due to the existence of an area of moisture over Australia. Throughout the rest of the day, the wind shear subdued, and the system began to organize as convective banding wrapped around the center. As a result, Cyclone Jasmine intensified into the equivalent of a Category 2 on the Australian tropical cyclone intensity scale, with winds of 95 km/h (60 mph), sustained for 10 minutes. The next day, Cyclone Jasmine began to track to the east–southeast in response to a strengthening subtropical ridge. The cyclone continued to steadily intensify as convection continued to wrap tightly around the center of Jasmine.〔 At the same time, the storm moved out of the BOM's area of responsibility and into the area of responsibility of the Fiji Meteorological Service's (FMS) tropical cyclone warning center at Nadi, Fiji (RSMC Nadi). Late on 7 February, while still tracking to the east–southeast, Jasmine rapidly intensified, with wind speeds increasing to 185 km/h (115 mph), sustained for one minute. The cyclone developed a ragged eye stretching 40 km (25 mi) across. Later that day, Jasmine reached its peak intensity as it passed 280 km (175 mi) to the north–northeast of New Caledonia, with wind speeds of 215 km/h (135 mph), equivalent to a Category 4 cyclone on both the Australian and Saffir-Simpson hurricane scales (SSHS). Throughout 8 February, Jasmine began to show characteristics of an annular hurricane, maintaining a large, asymmetric eye and rather shallow convective features. In addition, multiple eyewall mesovorticies developed within the eye. However, Jasmine did not maintain its peak intensity for an extended period of time. By 9 February, the cloud tops surrounding Jasmine began to warm, and thus weakened. In addition, the cyclone began to enter cooler SSTs. Although Jasmine's convective bands continued to thin out, the cyclone maintained a gradually expanding eyewall and remained a compact system. By 10 February, the eyewall of Cyclone Jasmine measured 95 km (60 mi) in diameter. The next day, the subtropical ridge that had been forcing Jasmine toward the southeast had weakened, and as a result the cyclone began to track east–northeast, toward a weakness in the ridge. The storm continued to disorganize, with its eye later becoming cloud–filled. By the end of 11 February, Jasmine had already weakened to a cyclone with wind speeds of just 85 km/h (50 mph), sustained for one minute, due to the presence of strong vertical wind shear. The low–level circulation center of Jasmine became partly exposed for a period of time on 12 February, before convection redeveloped over the center. As a weakening cyclone, Jasmine only maintained an area of weak convection displaced to its east as it approached Tonga.〔 On 13 February, convection re-developed and later strengthened over Jasmine's center of circulation due to the presence of the South Pacific convergence zone and warm SSTs. Cyclone Jasmine was able to attain a secondary peak intensity of 85 km/h (50 mph), sustained for one minute, as the system's banding features became better defined. Due to Jasmine's position between two anticyclones, the cyclone erratically moved in a loop in the vicinity of Tonga from 14 to 15 February, before moving to the southeast. The system later exited the favorable conditions and moved into an area of strong wind shear once again. Convection became sheared apart and Jasmine's center of circulation once again became ill–defined and exposed. Late on 15 February, the JTWC issued their last advisory on the system, and on the next day, RSMC Nadi reported that Cyclone Jasmine had degenerated into an extratropical cyclone. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cyclone Jasmine」の詳細全文を読む スポンサード リンク
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