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The meteorological history of Hurricane Wilma, the most intense known tropical cyclone in the Western Hemisphere, began in the second week of October 2005. A large area of disturbed weather developed across much of the Caribbean Sea and gradually organized to the southeast of Jamaica. By late on October 15, the system was sufficiently organized for the National Hurricane Center to designate it as Tropical Depression Twenty-Four. The depression drifted southwestward, and under favorable conditions, it strengthened into Tropical Storm ''Wilma'' on October 17. Initially, development was slow due to its large size, though convection steadily organized. From October 18, and through the following day, Wilma underwent explosive deepening over the open waters of the Caribbean; in a 30-hour period, the system's central atmospheric pressure dropped from 982 mbar (29.00 inHg) to the record-low value of 882 mbar (26.05 inHg), while the winds increased to . At its peak intensity, the eye of Wilma was about in diameter, the smallest known eye in an Atlantic hurricane. After the inner eye dissipated due to an eyewall replacement cycle, Hurricane Wilma weakened to Category 4 status, and on October 21, it made landfall on Cozumel and on the Mexican mainland with winds of about . Wilma weakened over the Yucatán Peninsula, and reached the southern Gulf of Mexico before accelerating northeastward. Despite increasing amounts of vertical wind shear, the hurricane re-strengthened to hit Cape Romano, Florida, as a major hurricane. Wilma weakened as it quickly crossed the state, and entered the Atlantic Ocean near Jupiter, Florida. The hurricane again re-intensified before cold air and wind shear penetrated the inner core of convection. By October 26, it transitioned into an extratropical cyclone, and the next day, the remnants of Wilma were absorbed by another extratropical storm over Atlantic Canada. ==Formation== During the second week of October, an unusually large, monsoon-like lower-level circulation and a broad area of disturbed weather developed over much of the Caribbean Sea. The system was enhanced by diffluence from an upper-level low across the southwestern Atlantic. By October 13, a broad area of low pressure developed and persisted about southeast of Jamaica,〔 possibly aided by the passage of tropical waves through the area at the time.〔 Convection increased and became slightly better organized, though upper-level wind shear initially prevented development. The system drifted westward, and early on October 14 the convection became more concentrated and a little better organized as upper-level wind shear lessened slightly. Later on October 14, the system became much better defined, with increasingly organized shower and thunderstorm activity, as conditions in the upper levels of the atmosphere became significantly more favorable. It was then that the National Hurricane Center first indicated that it was possible for a tropical depression to develop in the area. Dvorak classifications were initiated on October 15.〔 The system continued to organize, with the National Hurricane Center remarking the system could ultimately become a hurricane. By late on October 15, the surface circulation became defined well enough, with sufficiently organized deep convection, for the National Hurricane Center to designate the system as Tropical Depression Twenty-Four while it was located about east-southeast of Grand Cayman.〔 The depression tracked slowly westward, a motion due to weak steering currents caused by a high pressure area to its north across the Gulf of Mexico. Initially, the center of circulation was broad without a defined inner core; forecaster Lixion Avila remarked, "The area of minimum pressure could (been ) anywhere within of its (advisory position )." Initially, the tropical depression was forecast to drift west-southwestward before turning to the north; within five days of the forecast's issuance, the system was predicted to be located about south of the Isle of Youth as a hurricane. However, the National Hurricane Center noted in the first advisory on the depression that there were "all indications that there could a dangerous hurricane in the northwestern Caribbean Sea in 3 to 5 days." This was due to the depression being located within an environment very conducive for development, specifically low amounts of wind shear and very warm water temperatures. As Tropical Depression Twenty-Four drifted southwestward, it steadily organized; by early on October 16, rainbands began to gradually consolidate with well-established outflow, and a large upper-level anticyclone developed over the depression. Although deep convection and banding features increased, mid-level dry air from the north prevented significant organization, and the convection was split into two primary areas. Surface buoy reports indicated that, due to its large size, the system failed to strengthen beyond tropical depression status, even though it received tropical storm strength Dvorak classifications from The National Hurricane Center's Tropical Analysis and Forecast Branch and the National Oceanic and Atmospheric Administration's Satellite Analysis Branch. Continued reconnaissance flights reported peak winds of about . 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「Meteorological history of Hurricane Wilma」の詳細全文を読む スポンサード リンク
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