Tropical Storm Chaba formed over the South China Sea south of Hong Kong on Wednesday night. At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Chaba was located at latitude 15.7°N and longitude 115.1°E which put it about 440 miles (710 km) south of Hong Kong, China. Chaba was moving toward the northeast at 6 m.p.h. (10 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1000 mb.

The circulation around a low pressure system over the South China Sea south of Hong Kong strengthened on Wednesday night and the Japan Meteorological Agency designated the system as Tropical Storm Chaba. The distribution of thunderstorms around Tropical Storm Chaba was asymmetrical. The strongest thunderstorms were occurring in bands in the western half of Chaba’s circulation. Bands in the eastern half of the circulation consisted primarily of showers and lower clouds. Winds to tropical storm force extended out 115 miles (185 km) from the center of circulation.

An upper level ridge over southern China was producing northeasterly winds that were blowing toward the top of Tropical Storm Chaba. Those winds were causing moderate vertical wind shear. The wind shear was contributing to the asymmetrical distribution of thunderstorms.

Tropical Storm Chaba will move through an environment somewhat favorable for intensification during the 36 hours. Chaba will move over water where the Sea Surface Temperatures are near 29˚C. However, the upper level ridge over southern China will continue to cause vertical wind shear. The wind shear will inhibit intensification, but the shear will not be strong enough to prevent some intensification of Chaba. Tropical Storm Chaba is likely to intensify gradually during the next 36 hours.

Tropical Storm Chaba will move around the western end of a high pressure system over the Western North Pacific Ocean during the next 36 hours. The high will steer Chaba toward the north-northwest. On its anticipated track Tropical Storm Chaba could approach Hainan Island and the coast of southern China in 36 hours.