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Typhoon Oliwa was one of a record eleven super typhoons in the 1997 Pacific typhoon season. It formed in the central Pacific Ocean on September 2 to the southwest of Hawaii, but it became a typhoon in the western Pacific. Oliwa explosively deepened on September 8, increasing its winds from 85 mph to 160 mph in a 24‑hour period. Afterward, it slowly weakened, and after passing east of Okinawa, Oliwa turned northeast and struck Japan with winds of 85 mph (140 km/h). There, it affected 30,000 people and killed 13; thousands of houses were flooded, and some were destroyed.〔Benjamin C. Hablutzel, (),"National Weather Service",04/12/2012〕 Offshore South Korea, the winds and waves wrecked 28 boats, while one boat went missing with a crew of 10 people. Typhoon Oliwa dissipated on September 19 in northern Pacific Ocean near the International Date Line. ==Meteorological history== The origins of Typhoon Oliwa were from an unusually eastward extension of the monsoon trough in late August 1997. The tropical disturbance organized southwest of Hawaii, and slowly organized. On September 2, the Central Pacific Hurricane Center (CPHC) initiated advisories on Tropical Depression Two-C about 590 miles (950 km) southwest of Johnston Island, slightly east of the International Date Line. The depression quickly attained tropical storm status, and the CPHC gave it the name "Oliwa", meaning "Oliver" in the Hawaiian language.〔 A moderately powerful ridge persisted north of Tropical Storm Oliwa, which caused a slow west to west-northwest track. Water temperatures were slightly warmer than usual, and there was a favorable upper-level environment for strengthening. Initially, however, Oliwa was somewhat disorganized on satellite imagery, and on September 4, as it crossed the International Date Line, there may have been multiple circulations. Upon entering the western Pacific Ocean, the Joint Typhoon Warning Center (JTWC) and the Japan Meteorological Agency (JMA) began issuing advisories on the system (9719). Despite the favorable conditions, further intensification was slow, and it reached typhoon status - winds of at least 75 mph (120 km/h) - on September 8. Prior to that time, Oliwa co-existed with a weak tropical cyclone that formed in a similar location in the south Pacific.〔 About twelve hours after reaching typhoon status, Oliwa began to undergo unexpected explosive deepening. In a 24‑hour period, the JTWC assessed the typhoon as nearly doubling in intensity, from 85 to 160 mph (140 to 260 km/h 1-min winds), while the pressure dropped 69 mbar to a minimum of 898 mbar; based on the estimated intensity, the JTWC classified Oliwa as a super typhoon.〔 The JMA, which is the official agency of the western Pacific, assessed Oliwa as reaching a peak of 115 mph (185 km/h 10-min winds), with a pressure of 915 mbar.〔 Around that time, satellite imagery indicated a possible eyewall mesovorticy, which is a small scale rotational feature found in the eyewall of an intense tropical cyclone. Additionally, concentric eyewalls developed in the center of Oliwa, which typically occur in strong typhoons.〔 After maintaining peak intensity for 36 hours, Oliwa gradually weakened as it continued to the west-northwest, during which it passed through the Northern Marianas Islands. On September 14, the typhoon slowed to the north of Okinawa, and it turned to the northeast toward Japan.〔 As a weakened typhoon, Oliwa moved ashore on Makurazaki, Kagoshima, Kyushu with winds of 85 mph (140 km/h) late on September 15. It weakened to tropical storm strength while crossing Japan, and deteriorated further to tropical depression status on September 16.〔 On September 17, the JTWC issued the final advisory on Oliwa while it was in the eastern portion of the Sea of Japan.〔 The JMA maintained advisories as the storm crossed northern Japan, and it accelerated over the open Pacific Ocean. On September 19, Oliwa dissipated near the International Date Line to the south of the Aleutian Islands.〔 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「Typhoon Oliwa」の詳細全文を読む スポンサード リンク
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