Tropical Storm Jangmi formed over the Western North Pacific Ocean west of Yap on Tuesday night. At 5:00 a.m. EDT on Wednesday the center of Tropical Storm Jangmi was located at latitude 9.9°N and longitude 137.3°E which put the center about 40 miles (65 km) west of Yap. Jangmi was moving toward the north-northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1000 mb.
A low pressure system over the Western North Pacific Ocean west of Yap strengthened on Tuesday night and the Japan Meteorological Agency designated the system as Tropical Storm Jangmi.
The circulation around Tropical Storm Jangmi was large. Thunderstorms were occurring in bands in the western side of Jangmi’s circulation. Thunderstorms were also occurring in a band in the eastern periphery of Tropical Storm Jangmi. Other bands in the eastern side of Jangmi’s circulation consisted primarily of showers and lower clouds. Storms near the center of Jangmi generated upper level divergence that pumped mass away from the tropical storm. The removal of mass caused the surface pressure to decrease.
The circulation around Tropical Storm Jangmi was large. Winds to tropical storm force extended out 150 miles (240 km) from the center of Jangmi’s circulation.
Tropical Storm Jangmi will move through an environment favorable for intensification during the next 24 hours. Jangmi will move over water where the Sea Surface Temperatures are near 29°C. It will move under the middle of an upper level ridge that is east of the Philippines. The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear. Tropical Storm Jangmi will intensify during the next 24 hours. The large circulation around Jangmi could cause it to intensify slowly at first. Jangmi could strengthen to a typhoon by the weekend.
Tropical Storm Jangmi will move around the western end of a high pressure system that is over the Western North Pacific Ocean. The high pressure system will steer Jangmi toward the north-northwest during the next 24 hours. On its anticipated track, Tropical Storm Jangmi will move slowly away from Yap. Jangmi could approach the Ryukyu Islands in a few days.
Tropical Storm Jangmi will continue to bring gusty winds and heavy rain to Yap until it moves farther away later this week. Heavy rain could cause flash floods in some locations.
