Tropical Depression 04W formed west of Luzon on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Depression 04W was located at latitude 16.6°N and longitude 116.8°E which put it about 430 miles (690 km) south-southeast of Hong Kong.  The depression was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1006 mb.

An area of thunderstorms moved west-northwestward across the Philippines and a circulation slowly consolidated around a distinct center.  The center of circulation became well enough defined on Saturday to cause the system to be classified as Tropical Depression 04W.  The inner core of the depression is still organizing.  A band of thunderstorms wrapped around the western and southern sides of the center of circulation.  Additional bands of showers and thunderstorms developed in other parts of the depression.  The area of showers and thunderstorms southwest of the center began to generate upper level divergence which pumped mass away from the depression.

Tropical Depression 04W will be moving through an environment that is favorable for intensification.  The depression will move over water where the Sea Surface Temperature is near 30°C.  The depression is moving under the eastern end of an upper level ridge.  The ridge is producing northerly winds which are blowing toward the top of the circulation.  The vertical wind shear may be part of the reason why there are more thunderstorms south of the center of circulation, but the shear is not strong enough to prevent intensification.  Tropical Depression 04W is expected to intensify into a tropical storm during the next 24 hours.

Tropical Depression 04W is moving around the western end of a subtropical ridge which is steering it toward the northwest.  A general northwesterly motion is expected for another 36 to 48 hours.  A turn toward the east will occur after that time.  On its anticipated track Tropical Depression 04W could be near Hong Kong in about 36 hours.  Tropical Depression 04W will have strengthened into a tropical storm by that time and there is a chance it could intensify into a typhoon by the time it nears the coast of China.