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Typhoon Ivan, known in the Philippines as Typhoon Narsing, was an intense tropical cyclone that existed simultaneously with another storm of the same intensity in October 1997. Forming out of an area of disturbed weather on October 13, Ivan gradually intensified into a typhoon as it tracked steadily to the west-northwest. On October 15, the storm underwent rapid intensification and reached an intensity corresponding to Category 5 status on the Saffir–Simpson Hurricane Scale. Late on October 17, Ivan reached its peak strength with winds of 295 km/h (185 mph) and a barometric pressure of 905 hPa (mbar). Shortly thereafter, the typhoon began to weaken as it approached the Philippines. Ivan eventually made landfall in northern Luzon with winds of 220 km/h (140 mph) on October 20 before weakening to a tropical storm the next day. The storm then curved northeastward and became extratropical on October 25 and dissipating the following day. Although Ivan was a powerful storm at landfall, its effects were relatively minor compared to the storms' intensity; however, 14 people were killed during the storm and two others were listed as missing. Agricultural industries sustained the most severe damage, as thousands of animals drowned in the storm. Total damage was estimated at $9.6 million (1997 USD; $13.1 million 2009 USD). A total of 1,779 homes were destroyed, 13,771 others were damaged and 4,600 hectares of farmland were flooded by the storm. ==Meteorological history== Typhoon Ivan originated from an area of disturbed weather near the equator during the first week of October 1997. Two equatorial troughs, one in the Northern Hemisphere and one in the Southern Hemisphere developed from this system. Three resultant areas of low pressure formed; one in the Southern Hemisphere developed into Tropical Cyclone Lusi on October 8, and two north of the equator steadily tracked westward. The eastern low developed into Typhoon Joan, while the western cyclone became the system that would intensify into Typhoon Ivan. Situated in an environment without significant convective activity, this system initially struggled to become organized.〔 However, the disturbance began to mature, and by October 11, the Joint Typhoon Warning Center (JTWC) discovered a low-level circulation center, prompting the issuance of a Tropical Cyclone Formation Alert the following day.〔 The system quickly tracked toward the west-northwest at a forward speed of 33 km/h (21 mph). The JTWC issued their first advisory on the storm early on October 13, designating it Tropical Depression 27W. Around this time, the Japan Meteorological Agency (JMA) also classified the cyclone as a tropical depression. Convective banding features developed late on October 13. The JTWC upgraded the depression to a tropical storm and gave it the name Ivan.〔 Early the next day, the JMA also upgraded Ivan to a tropical storm.〔 Later on October 14, Ivan passed roughly 100 km (65 mi) south of Guam and subsequently intensified.〔 Several hours afterwards, the JMA upgraded Ivan to a typhoon.〔 During a 24-hour span, Ivan's winds increased from 120 km/h (75 mph) to 270 km/h (165 mph), making it a Category 5 super typhoon, the eighth of the season. Late on October 17, Ivan attained its peak intensity with winds of 295 km/h (185 mph) and an official barometric pressure of 905 hPa (mbar).〔〔 However, the JTWC reported an unofficial pressure of 872 hPa (mbar), which would tie Ivan for the second strongest tropical cyclone worldwide with Typhoons Gay, Angela, Joan and Keith.〔 Due to the storm's proximity to Typhoon Joan, forecast models anticipated Ivan to re-curve before reaching the Philippines; however, the storm maintained its track and did not take the northward turn until impacting the country. The typhoon began to slow and weaken, and on October 20, its center made landfall in extreme northern Luzon with winds of 220 km/h (140 mph). After emerging into the Luzon Strait, Ivan turned to the north-northeast and weakened to a tropical storm. On October 22, the storm briefly re-attained typhoon status before accelerating in forward speed. The system steadily weakened and the JTWC issued their final advisory on the storm on October 24.〔 The JMA continued to monitor Ivan as a tropical cyclone for another day before classifying it as extratropical. The remnants of the powerful typhoon eventually dissipated on October 26.〔 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 Ivan」の詳細全文を読む スポンサード リンク
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