Tropical Storm Jangmi formed south of the Ryukyu Islands on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Jangmi was located at latitude 22.4°N and longitude 126.3°E which put it about 375 miles (605 km) south-southwest of Okinawa.  Jangmi was moving toward the north at 21 m.p.h. (34 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 998 mb.

A low pressure system east of Taiwan and south of the Ryukyu Islands strengthened on Saturday and the Japan Meteorological Agency designated the system as Tropical Storm Jangmi.  The distribution of  thunderstorms around Jangmi was asymmetrical.  Thunderstorms were occurring in bands in the eastern half of the tropical storm.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 200 miles (325 km) on the eastern side of Tropical Storm Jangmi.

Tropical Storm Jangmi will move through an environment somewhat favorable for intensification during the next 24 hours.  Jangmi will move over water where the Sea Surface Temperature is near 29°C.  It will move under the western side of an upper level ridge northeast of the Philippines.  The ridge will produce southerly winds which will blow toward the top of the tropical storm.  Those winds will cause moderate vertical wind shear which will inhibit intensification.  Tropical Storm Jangmi could strengthen on Sunday despite the vertical wind shear.

Tropical Storm Jangmi will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean.  The high will steer Jangmi toward the north during the next 36 hours.  On its anticipated tack the center of Tropical Storm Jangmi will pass west of Okinawa in 12 to 18 hours.  Jangmi will bring gusty winds and locally heavy rain to Okinawa.  Tropical Storm Jangmi could approach South Korea in 36 hours.