Former Tropical Storm Yagi strengthened to a typhoon southeast of Hong Kong on Tuesday evening.  At 11:00 p.m. EDT on Tuesday the center of Typhoon Yagi was located at latitude 19.1°N and longitude 117.5°E which put the center about 315 miles (510 km) southeast of Hong Kong.  Yagi was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 977 mb.

Former Tropical Storm Yagi intensified rapidly to a typhoon after it moved over the South China Sea.  A circular eye formed at the center of Yagi’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Yagi.  Storms near the core generated upper level divergence that pumped mass away from the typhoon.  The removal of mass caused the surface pressure to decrease.

The circulation around Typhoon Yagi was symmetrical.  Winds to typhoon force extended out 35 miles (55 km) from the center of Yagi’s circulation.  Winds to tropical storm force extended out 110 miles (185 km) from the center of Typhoon Yagi.

Typhoon Yagi will move through an environment that will be very favorable for intensification during the next 24 hours.  Yagi will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the middle of an upper level ridge over the South China Sea. The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear.  Typhoon Yagi will intensify during then next 24 hours.  Yagi could intensify rapidly to the equivalent of a major hurricane.

Typhoon Yagi will move around the southern part of a high pressure system over China.  The high pressure system will steer Yagi toward the west-northwest during the next 24 hours.  On its anticipated track, the center of Typhoon Yagi will be south of Hong Kong in 36 hours.  Yagi will approach Hainan and the coast of southern China in 48 hours.  Typhoon Yagi could be the equivalent of a major hurricane when it approaches Hainan and the coast of southern China.