Former Typhoon Rai rapidly weakened to a tropical storm south-southwest of Hong Kong on Monday. At 4:00 p.m. EST on Monday the center of Tropical Storm Rai was located at latitude 20.1°N and longitude 113.5°E which put it about 190 miles (305 km) south-southwest of Hong Kong. Rai was moving toward the northeast at 13 m.p.h. (20 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 997 mb.

A surface high pressure system over eastern Asia produced northeasterly winds that transported drier air which was pulled into the circulation of former Typhoon Rai. The drier air caused the thunderstorms in Rai’s circulation to dissipate and the circulation weakened. Bands revolving around the center of Tropical Storm Rai consisted almost entirely of showers and lower clouds. Winds to tropical storm force extended out 65 miles (105 km) from the center of circulation.

Since Tropical Storm Rai consists of a shallow circulation, it will be steered by the winds in the lower levels of he atmosphere. Rai will move around the northwestern part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Tropical Storm Rai toward the east-northeast during the next 24 hours. On its anticipated track Tropical Storm Rai could be southwest of Taiwan in 24 hours.

Tropical Storm Rai will move through an environment unfavorable for a tropical cyclone. Rai will move over water where the Sea Surface Temperatures are near 27˚C. However, Rai will continue to be surrounded by drier air, which will prevent the formation of new thunderstorms. In addition, an upper level trough over eastern Asia will produce southwesterly winds that will blow across the top of Rai’s circulation. Those winds will cause strong vertical wind shear and the shear will also be unfavorable for intensification. Tropical Storm Rai will continue to weaken during the next 24 hours.