Typhoon Sendong

Severe Tropical Storm Washi (Sendong)

Severe tropical storm (JMA scale)
Tropical storm (Saffir–Simpson scale)
Severe Tropical Storm Washi approaching Mindanao on December 16
Formed	December 13, 2011
Dissipated	December 19, 2011
Highest winds	10-minute sustained: 95 km/h (60 mph) 1-minute sustained: 95 km/h (60 mph)
Lowest pressure	992 hPa (mbar); 29.29 inHg
Fatalities	2,546 total
Damage	$97.8 million (2011 USD)
Areas affected	Micronesia, Palau, Philippines
Part of the 2011 Pacific typhoon season

Severe Tropical Storm Washi, known in the Philippines as Tropical Storm Sendong, was a late-season tropical cyclone that caused catastrophic damage in the Philippines in late 2011. Washi, which means Aquila in Japanese, made landfall over Mindanao, a major island in the Philippines, on December 16. Washi weakened slightly after passing Mindanao, but regained strength in the Sulu Sea, and made landfall again over Palawan on December 17.

On December 12, the Joint Typhoon Warning Center (JTWC) noted that a developing area of low pressure had persisted about 945 km (585 mi) south-southeast of Guam. Situated along the southern edge of a subtropical ridge, the system tracked steadily westward towards the Philippines. Located within a region of good diffluence and moderate wind shear, deep convection was able to maintain itself over the circulation. Development of banding features and improvement of outflow indicated strengthening was likely. Further development over the following day prompted the JTWC to issue a Tropical Cyclone Formation Alert early on December 13. Less than six hours later, both the JTWC and the Japan Meteorological Agency (JMA) classified the system as a tropical depression, with the former assigning the identifier 27W. Maintaining a westward track, the depression was forecast to intensify slowly over the following three days. For much of December 13, a slight increase in shear displaced thunderstorm activity from the center of the depression, delaying intensification. By December 14, convection redeveloped over the low and the JTWC subsequently assessed the system to have attained tropical storm status.