Tropical Storm Chanthu spun between Japan and China on Wednesday. At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Chanthu was located at latitude 30.5°N and longitude 125.2°E which put it about 360 miles (585 km) west-southwest of Kagoshima, Japan. Chanthu was moving toward the northwest at 4 m.p.h. (6 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 991 mb.
Tropical Storm Chanthu remained nearly stationary on Wednesday as it spun over the East China Sea between Japan and China. The atmospheric environment around Chanthu became more favorable for intensification when an upper level ridge moved over the tropical storm. Chanthu strengthened when the upper level ridge enhanced the upper level divergence that pumped more mass away from the tropical storm. The enhanced upper level divergence also contributed to the formation of more thunderstorms in the bands revolving around the center of Tropical Storm Chanthu. A rainband wrapped most of the way around the center of Chanthu and a new eye appeared to be forming at the center of the tropical storm. Winds to tropical storm force extended out 190 miles (305 km) on the northern side of Chanthu. Winds to tropical storm force extended out 90 miles (145 km) in the southern half of the circulation.
Tropical Storm Chanthu will move through an environment somewhat favorable for intensification during the next 24 hours. Chanthu will move over water where the Sea Surface Temperature is near 27˚C. Chanthu could mix cooler water to the surface while it remains nearly stationary, which could inhibit intensification. The upper level ridge will continue to enhance divergence, which will be favorable for intensification. Tropical Storm Chanthu is likely to intensify during the next 24 hours and it could strengthen back to a typhoon.
The steering winds are weak in the middle of the upper level ridge and Tropical Storm Chanthu may not move much during the next 12 to 18 hours. An upper level trough over eastern Asia will move eastward on Thursday. The upper level trough will start to steer Chanthu toward the west in 12 to 18 hours. On its anticipated track Tropical Storm Chanthu could approach Kyushu in 30 hours. Chanthu could be a typhoon when it reaches Kyushu. It will bring strong, gusty winds and locally heavy rain. Heavy rain could cause flash floods in some locations.