Tropical Storms Sinlaku and Hagupit formed over the Western North Pacific Ocean on Saturday. At 11:00 a.m. EDT on Saturday the center of Tropical Storm Sinlaku was located at latitude 19.4°N and longitude 107.1°E which put it about 90 miles (145 km) southeast of Nam Dinh, Vietnam. Sinlaku was moving toward the northwest at 12 m.p.h. (19 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 993 mb.
The circulation around a low pressure system near Vietnam exhibited greater organization on Saturday and the Japan Meteorological Agency designated the system as Tropical Storm Sinlaku. Bands of showers and thunderstorms were revolving around the center of Sinlaku. There were more thunderstorms in the bands on the western side of the circulation. Winds to tropical storm force extended out 110 miles (185 km) from the center of circulation.
Tropical Storm Sinlaku has about 12 hours to strengthen before it makes landfall in northern Vietnam. Sinlaku will move over water where the Sea Surface Temperature is near 30°. It will move under the southeast part of an upper level ridge over Asia. The ridge will produce easterly winds which will blow toward the top of Sinlaku. Those winds will cause moderate vertical wind shear and the shear will limit intensification. Tropical Storm Sinlaku will bring gusty winds and rain to northern Vietnam on Sunday.
The circulation around a second low pressure system east of Taiwan also exhibited more organization on Saturday and the Japan Meteorological Agency designated that system as Tropical Storm Hagupit. At 11:00 a.m. EDT on Saturday the center of Tropical Storm Hagupit was located at latitude 21.8°N and longitude 126.5°W which put it about 220 miles (350 km) southeast of Ishigaki, Japan. Hagupit was moving toward the northwest at 13 m.p.h. (20 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 1003 mb.
The circulation around Tropical Storm Hagupit was still organizing on Saturday. Thunderstorms were developing in bands in the eastern half of Hagupit. Bands in the western side of the circulation consisted primarily of showers and lower clouds. Storms near the center of Hagupit were generating upper level divergence which was pumping mass away to the east of the tropical storm.
Tropical Storm Hagupit will move through an environment favorable for intensification. Hagupit will move over water where the Sea Surface Temperature is near 30°C. Hagupit will move into a region where the upper level winds are weaker and there will not be a lot of vertical wind shear. Tropical Storm Hagupit is likely to intensify during the next 24 to 36 hours.
Tropical Storm Hagupit will move around the western end of a high pressure system over the Western North Pacific Ocean. The high will steer Hagupit toward the northwest during the next several days. On its anticipated track the center of Tropical Storm Hagupit will pass near Ishigaki, Japan in about 24 hours. Hagupit will approach the coast of China south of Shanghai in about 48 hours.