Typhoon Ketsana

Typhoon Ketsana (International designation: 0916, JTWC designation: 17W, PAGASA name: Ondoy) formed early on September 23, 2009, about 860 km (535 mi) to the northwest of Palau. The depression remained weak and was downgraded to a low pressure area later that day by the Japan Meteorological Agency. The low pressure area then reintensified early the next day and was named as Tropical Depression Ondoy by the Philippine Atmospheric, Geophysical and Astronomical Services Administration as the Joint Typhoon Warning Center issued a Tropical Cyclone Formation Alert on the depression. It was then reupgraded to a tropical depression by the JMA later that morning before the JTWC followed suit early on September 25, designating the depression as 17W.

The intensification of Ondoy was hampered throughout September 25 by the system moving into an area of moderate vertical windshear and an upper level trough of pressure which was moving over the system. It was then upgraded to a Tropical Storm and named as Ketsana before passing over the island of Luzon in the Philippines. As it moved into the South China sea later that day the system dramatically deepened and expanded whilst moving towards the west which lead to the JMA upgrading it to a Severe Tropical Storm.

Ketsana brought the worst rainfall to Metro Manila among recorded typhoons since the start of rainfall record keeping according by PAGASA, producing only moderate winds but hours of extremely heavy rain. 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 20 feet high in rural areas. As of October 24, 2009, at least 464 deaths were officially reported from the typhoon in the Philippines.

Reference : Wikipedia.org