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Severe Tropical Cyclone Olivia was a powerful Category 4 cyclone during April 1996 that produced the highest non-tornadic winds on record, 408 km/h (253 mph). ==Meteorological history== Severe Tropical Cyclone Olivia was first identified by the Bureau of Meteorology as a low to mid-level area of low pressure over Indonesia north of Darwin, Australia on 2 April 1996. The system slowly became better organized despite strong wind shear as it sharply turned south. Early on 5 April, the Joint Typhoon Warning Center (JTWC) classified the system as Tropical Depression 25S as it resumed its westward track. Shortly thereafter, the Bureau of Meteorology upgraded the system to a Category 1 cyclone, designating the storm as Tropical Cyclone Olivia.〔 The westward turn occurred in response to a mid-level ridge to the south of Olivia strengthened.〔 Shortly after being upgraded by the Bureau of Meteorology, the JTWC followed suit and classified the system as a tropical storm.〔 Over the following several days, persistent wind shear prevented convection from developing around the center of circulation. However, by 8 April, an upper-level trough passed to the south of the developing cyclone, leading to lower shear.〔 Following this, the system had developed sufficiently for the JTWC to upgrade it to a Category 1 equivalent on the Saffir–Simpson Hurricane Scale (SSHS), with winds estimated at 120 km/h (75 mph 1-minute sustained) around the center of the storm.〔 Around the same time, the Bureau of Meteorology upgraded Olivia to a severe tropical cyclone, having similar wind speeds.〔〔 After reaching this intensity, the mid-level ridge south of the cyclone began to weaken, leading to Olivia turning towards the southwest. By 9 April, the system attained Category 4 intensity as it continued to strengthen.〔 During the afternoon of 9 April, Olivia attained its lowest barometric pressure of 925 hPa (mbar) and sustained winds were estimated at 195 km/h (120 mph 10-minute sustained) by the Bureau of Meteorology.〔〔 Several hours later, the JTWC assessed the cyclone to have attained Category 4 status on the SSHS with winds of 230 km/h (145 mph 1-minute sustained).〔 By this time, another trough bypassed the cyclone, this time causing Olivia to turn southward before rapidly tracking southeast. Early on 10 April, data from a nearby weather radar at the Learmonth Airport near Exmouth, Western Australia, showed that the storm had developed a 65 km (40 mi) wide eye.〔 Late on 10 April, the center of Olivia passed near Barrow Island at peak intensity. Shortly thereafter, the storm passed near Varanus Island as a high-end Category 4 or low-end Category 5 cyclone.〔 Within several hours of passing by Varanus Island, Olivia made landfall near Mardie at peak intensity.〔 Shortly thereafter, the storm began to weaken overland. Accelerating to the southeast, the storm became disorganized and winds decreased below hurricane-force.〔 During the afternoon of 11 April, Olivia weakened to a tropical low over southern Australia before moving over the Great Australian Bight and losing its identity as a gale-force low.〔 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 Olivia」の詳細全文を読む スポンサード リンク
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