Tropical Storm Muifa formed over the Western North Pacific Ocean southeast of the Ryukyu Islands on Wednesday night. At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Muifa was located at latitude 17.2°N and longitude 132.6°E which put it about 730 miles (1175 km) south-southeast of Okinawa. Muifa was moving toward the west at 8 m.p.h. (13 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.

The circulation around a low pressure system southeast of the Ryukyu Islands exhibited more organization on Wednesday night and the Japan Meteorological Agency designated the system as Tropical Storm Muifa. The distribution of thunderstorms around Tropical Storm Muifa was asymmetrical. Most of the thunderstorms were occurring in bands in the western side of Muifa’s circulation. Bands in the eastern side of Muifa consisted primarily of showers and lower clouds. Storms west of the center of circulation generated upper level divergence that pumped mass away to the west of the tropical storm. Winds to tropical storm force extended out 100 miles (160 km) from the center of circulation.

Tropical Storm Muifa will move through an environment favorable for intensification during the next 24 hours. Muifa will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern part of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Muifa’s circulation. Those winds will cause some vertical wind shear, but the wind shear will not be strong enough to prevent intensification. Tropical Storm Muifa will intensify during the next 48 hours. Muifa could strengthen to a typhoon in 24 hours. Muifa could intensify to the equivalent of a major hurricane in 48 hours.

Tropical Storm Muifa will move around the southwestern part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Muifa toward the northwest during the next 48 hours. On its anticipated track Tropical Storm Muifa could approach the southern Ryukyu Islands in 72 hours. Muifa is likely to be a typhoon when it approaches the southern Ryukyu Islands.