Tropical Storm Sanba dropped heavy rain on parts of southern China on Thursday. At 5:00 p.m. EDT on Thursday the center of Tropical Storm Sanba was located at latitude 21.3°N and longitude 109.2°E which put it about 25 miles (40 km) southeast of Beihai China. Sanba was moving toward the north-northeast at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 1001 mb.

Tropical Storm Sanba dropped heavy rain on parts of Guangxi and Guangdong in southern China on Thursday. The center of Sanba’s circulation was still over the northeastern Gulf of Tonkin. Much of the northern half of Tropical Storm Sanba was over southern China. Part of the eastern side of Sanba’s circulation was over Hainan. Winds to tropical storm force extended out 60 miles (95 km) from the center of Tropical Storm Sanba.

An upper level trough over eastern Asia and an upper level ridge centered north of the Philippines were interacting to produce southwesterly winds that were blowing toward the top of Sanba’s circulation. Those winds were causing moderate vertical wind shear and they were also causing the distribution of thunderstorms to be asymmetrical. Thunderstorms were occurring in bands in the northern and eastern parts of Tropical Storm Sanba. Bands in the southern and western parts of Sanba’s circulation consisted primarily of showers and lower clouds.

Tropical Storm Sanba will be in an environment that is mostly unfavorable for intensification during the next 24 hours. Sanba will move over water where the Sea Surface Temperatures are near 28°C. The upper level trough over eastern Asia and the upper level ridge north of the Philippines will continue to cause moderate vertical wind shear. Almost half of Sanba’s circulation will be over land and increased friction will slow the wind in those areas. Tropical Storm Sanba is likely to weaken during the next 24 hours even if the center of circulation does not move over southern China.

The movement of Tropical Storm Sanba during the next 24 hours will depend on how strong the vertical wind shear is. If the wind shear is moderate and the upper and lower parts of Sanba’s circulation remain connected, then southwesterly winds will steer Tropical Storm Sanba toward the north-northeast. If Sanba moves north-northeast it will move inland over southern China. If the vertical wind shear gets stronger, then the upper level winds will push the top part of Sanba’s circulation toward the north-northeast. If the wind shear rips the top off of Tropical Storm Sanba, then the lower part of the circulation could meander over the northeastern Gulf of Tonkin during the next 24 hours.

Tropical Storm Sanba will continue to drop heavy rain over southern China during the next 24 hours. Heavy rain will fall on parts of Guangxi and Guangdong. Prolonged heavy rain will cause floods in some locations.