Usagi Strengthens to a Typhoon East of Southern Vietnam

Former Tropical Storm Usagi strengthened into a typhoon east of southern Vietnam on Friday night.  At 10:00 p.m. EST on Friday the center of Typhoon Usagi was located at latitude 9.6°N and longitude 109.2°E which put it about 205 miles (335 km) east-southeast of Ho Chi Minh City, Vietnam.  Usagi was moving toward the west-southwest at 10 m.p.h. (16 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.

A small circular eye was visible at the center of Typhoon Usagi on both conventional and microwave satellite imagery.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Usagi.  The strongest rain bands were in the western half of the typhoon.  Storms near the core of Usagi were generating upper level divergence which was pumping mass away from the typhoon.  Winds to typhoon force extended out about 30 miles (50 km) from the center of circulation.  Winds to tropical storm force extended out about 125 miles (200 km) from the center.

Typhoon Usagi will move through an environment favorable for intensification during the next 24 hours.  Usagi will move over water where the Sea Surface Temperature is near 29°C.  It will move south of an upper level ridge.  The ridge will produce easterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, which will reduce the rate of intensification.  Typhoon Usagi will strengthen on Saturday.

The ridge north of Typhoon Usagi will steer the typhoon a little to the south of due west.  On its anticipated track the center of Typhoon Usagi will approach the Mouths of the Mekong River in about 24 hours.  Usagi will bring strong winds and drop heavy rain on southern Vietnam.  Winds to tropical storm force could affect Ho Chi Minh City.  There could be a storm surge of 6 to 9 feet (2 to 3 meters) along the coast.  Locally heavy rain could cause floods over portions of southern Vietnam and Cambodia.

Elsewhere over the Western North Pacific Typhoon Man-yi started to weaken southeast of Okinawa.  At 10:00 p.m. EST on Friday the center of Typhoon Man-yi was located at latitude 18.1°N and longitude 135.4°E which put it about 760 miles (1230 km) southeast of Okinawa.  Man-yi was moving toward the north at 5 m.p.h. (8 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.