A tropical depression formed just to the south of Hainan Island on Friday night. At 11:00 p.m. EDT on Friday the center of Tropical Depression 05W was located at latitude 18.3°N and longitude 109.5°E which put it about 35 miles (55 km) south of Sanya, China. The depression was moving toward the west at 16 m.p.h. (26 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 1000 mb.

Thunderstorms developed closer to the center of a low pressure system south of Hainan Island on Friday night and both the Japan Meteorological Agency and the Joint Typhoon Warning Center designated the system as a tropical depression. The distribution of thunderstorms around Tropical Depression 05W was asymmetrical. The strongest thunderstorms were occurring in bands southwest of the center of the tropical depression. Bands in the other parts of the circulation consisted primarily of showers and lower clouds. An upper level ridge centered over southern China was producing moderate northeasterly winds that were blowing toward the top of the depression. Those winds were causing moderate vertical wind shear and they were also causing the asymmetrical distribution of thunderstorms.

The center of Tropical Depression 05W will move near Hainan Island during the next few hours. The northern half of the circulation around the tropical depression will be over Hainan Island, which will inhibit intensification. Tropical Depression 05W will move into an environment favorable for intensification when it moves west of Hainan Island. The tropical depression will move over an area where the Sea Surface Temperatures are near 30°C. The upper level ridge over southern China will continue to produce moderate vertical wind shear. Even with the moderate wind shear, Tropical Depression 05W is likely to intensify to a tropical storm during the next 24 hours.

Tropical Depression 05W will move around the southern part of a subtropical high pressure system over the Western North Pacific Ocean during the next 36 hours. The high pressure system will steer the tropical depression toward the west-northwest. On its anticipated track the center of Tropical Depression 05W will pass near the southern part of Hainan Island. Since the strongest thunderstorms are in the southwestern part of the circulation, the tropical depression will cause mainly gustier winds over Hainan Island. Tropical Depression 05W could approach northern Vietnam in 24 hours. It could bring gusty winds and locally heavy rain to parts of northern Vietnam. Heavy rain could cause flash floods in some locations.