Tropical Storm Usagi formed over the South China Sea east of Vietnam on Thursday. At 10:00 a.m. EST on Thursday the center of Tropical Storm Usagi was located at latitude 11.2°N and longitude 113.7°E which put it about 350 miles (565 km) east of Lien Huong, Vietnam. Usagi was moving toward the west at 18 m.p.h. (29 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1001 mb.
More thunderstorms developed near the center of former Tropical Depression 33W and the Japan Meteorological Agency designated the system as Tropical Storm Usagi. Satellite imagery indicated that the inner end of a rainband was wrapping around the center of circulation. Several other bands of showers and thunderstorms were in the western half of Tropical Storm Usagi. Bands in the eastern half of the circulation consisted primarily of showers and low clouds. An upper level ridge north Usagi was producing southeasterly winds which were blowing toward the top of the circulation. Those winds were causing moderate vertical wind shear and they were the reason why the stronger thunderstorms were developing west of the center of circulation. Storms near the center were producing upper level divergence which was pumping mass away to the west of the tropical storm.
Tropical Storm Usagi will move through an environment favorable for intensification during the next 24 to 36 hours. Usagi will move over water where the Sea Surface Temperature is near 29°C. It will continue to move south of an upper level ridge and moderate vertical wind shear will continue to affect Tropical Storm Usagi. The wind shear will slow intensification, but Usagi will strengthen during the next day or so. It could intensify into a typhoon during the next 36 hours.
The ridge north of Tropical Storm Usagi will steer the tropical storm on a track a little to the south of due west. On its anticipated track the center of Tropical Storm Usagi will approach the coast of southern Vietnam in about 36 hours. Usagi could make landfall on the portion of the coast between Cam Ranh and Vung Tau. Tropical Storm Usagi will bring gusty winds and it could drop locally heavy rain over southern Vietnam and Cambodia. Heavy rain could cause flash foods in some locations.
Elsewhere over the Western North Pacific, Typhoon Man-yi was moving away from the Marianas after causing power outages in southern Guam. At 10:00 a.m. EST on Thursday the center of Typhoon Man-yi was located at latitude 13.5°N and longitude 137.8°E which put it about 1155 miles (1860 km) southeast of Okinawa. Man-yi was moving toward the northwest at 21 m.p.h. (34 km/h). The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h). The minimum surface pressure was 969 mb.