<P> 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 . </P> <P> 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 . </P> <P> Early on December 15, the system crossed west of 135 ° E and entered the Philippine Atmospheric, Geophysical and Astronomical Services Administration's (PAGASA) area of responsibility . Upon doing so, PAGASA began issuing advisories and assigned the cyclone with the local name Sendong . Shortly thereafter, the storm passed close to or over Palau . By 0600 UTC, the JMA upgraded the system to tropical storm status, at which time they assigned it with the name Washi . Maintaining a rapid westward track, Washi slowly became more organized, with low - level inflow improving during the latter part of December 15 . On December 16, Washi reached its peak strength as a severe tropical storm and made its first landfall along the east coast of Mindanao . </P> <P> After passing Mindanao, Washi weakened due to land interaction, but the storm quickly regained its strength, in the Sulu Sea . Late on December 17, Washi crossed Palawan and arrived in the South China Sea, and the system moved out of the PAR on December 18 . Washi weakened to a tropical depression and dissipated on December 19, because of cool, dry air, in association with the Northeast Monsoon . </P>

When did sendong enter the philippine area of responsibility