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Typhoon Ketsana, known in the Philippines as Tropical Storm Ondoy, was the second most devastating tropical cyclone in the 2009 Pacific typhoon season with a damage of $1.09 billion and 747 fatalities, only behind Morakot earlier in the season, which caused 789 deaths and damages worth $6.2 billion. The storm was the sixteenth tropical storm, eighth typhoon and the second major typhoon in the season. It was the most devastating typhoon to hit Manila, surpassing Typhoon Patsy (Yoling) in 1970. Ketsana formed early about 860 km (535 mi) to the northwest of Palau on September 23, 2009. The depression remained weak and was downgraded to a low pressure area later that day by the Japan Meteorological Agency and after drifting through extremely favorable conditions, it intensified the next day and was categorized as Tropical Depression by the Philippine Atmospheric, Geophysical and Astronomical Services Administration and was given the name Ondoy after entering the Philippine Area of Responsibility. The Joint Typhoon Warning Center issued a Tropical Cyclone Formation Alert on the depression. It was then upgraded to a tropical depression by the JMA later that morning before the JTWC followed suit early on September 25, designating the depression as 17W. Soon, Ketsana was upgraded to a Tropical Storm before passing over the Philippines. As it moved into the South China Sea the storm intensified while moving toward the west, and was categorized as a Severe Tropical Storm by the JMA. Philippine President Gloria Arroyo declared a "state of calamity" encompassing most of Luzon after at least 86 people were initially reported dead in landslides and other incidents. Flood water levels reached a record in rural areas. As of October 24, 2009, at least 464 deaths in the Philippines were officially reported from the typhoon.〔〔〔 ==Meteorological history== On September 23, 2009, the Japan Meteorological Agency (JMA), reported that a seasonal tropical depression had formed about 860 km (535 mi) to the northwest of Palau. The Joint Typhoon Warning Center (JTWC) then reported later that day that the depression had a developing low-level circulation center and was in a favorable environment with low vertical wind shear. The JMA then reported that the depression had weakened into an area of low pressure. However, early the next day, as deep convection started to consolidate around the low-level circulation center, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) reported that the low pressure area had become a Tropical Depression and assigned it a local name of Ondoy. Later that morning, the JTWC issued a Tropical Cyclone Formation Alert as central convection had continued to organize around a consolidating elongated but exposed low-level circulation center. The JMA then re-upgraded Ondoy to a tropical depression later that morning before the JTWC followed suit early on September 25, designating it as Tropical Depression 17W when it was located about 400 nm east of Manila in the Philippines. At this stage, the system was moving along the southern side of the subtropical ridge and had good poleward outflow into a tropical upper tropospheric trough (TUTT) cell.〔 Throughout September 25 the intensification of Ondoy was hampered by the system moving into an area of moderate vertical wind shear and by an upper-level trough of pressure that was moving over the system. But later that day the JTWC upgraded it to a Tropical Storm despite its low level circulation center being partially exposed. The JMA followed suit early the next day, assigning the international name of Ketsana and the international designation of 0916 to the storm. PAGASA then reported that Ketsana had made landfall on Northern Luzon near the boundary of the Philippine provinces of Aurora and Quezon. As a result of making landfall, its low-level circulation center had become fully exposed, but as the storm moved into the South China Sea, it dramatically deepened and expanded while moving west and was upgraded to a Severe Tropical Storm by the JMA early on September 27. During September 27, Ketsana gradually developed further and was upgraded to a Typhoon by the JTWC and the JMA early the next day, as multiple convective bands were continuing to consolidate more tightly around the low-level circulation center, leading to the formation of a disorganized eye. Typhoon Ketsena then intensified quickly under favorable conditions, reaching peak windspeeds later that day of 165 km/h, (105 mph) (1-min winds) and 140 km/h (85 mph) (10-min winds) which made it a Category 2 typhoon on the Saffir–Simpson hurricane scale. Ketsana then made a second landfall on Quảng Nam in Vietnam, at 0600 UTC on September 29 at its peak intensity. It then rapidly weakened into a Severe Tropical Storm, with the JTWC issuing its last advisory later that day; however, the JMA continued to monitor Ketsana as a Severe Tropical Storm until later that day, when it downgraded it to a Tropical Storm before further downgrading it to a Tropical Depression early the next day when the center of the depression was located over Laos. The JMA monitored the storm as a weak tropical depression until late on September 30, when it released its final advisory. 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 Ketsana」の詳細全文を読む スポンサード リンク
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