A tropical depression formed over the Western North Pacific Ocean southeast of Yap on Sunday morning. At 10:00 a.m. EST on Sunday the center of Tropical Depression 17W was located at latitude 7.2°N and longitude 139.9°E which put it about 205 miles (320 km) southeast of Yap. The tropical depression was moving toward the west-northwest at 11 m.p.h. (17 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1003 mb.
More thunderstorms formed in a low pressure system over the Western North Pacific Ocean southeast of Yap on Sunday morning and both the Japan Meteorological Agency and the U.S. Joint Typhoon Warning Center designated the system as a tropical depression. The distribution of thunderstorms in Tropical Depression 17W was asymmetrical. Thunderstorms were occurring in bands in the western half of the tropical depression. Bands in the eastern side of Tropical Depression 17W consisted primarily of showers and lower clouds.
Tropical Depression 17W was moving under the southern part of an upper level ridge over the Western North Pacific Ocean. The upper level ridge was producing easterly wind that were blowing toward the top of the tropical depression’s circulation. Those winds were causing moderate vertical wind shear. The moderate vertical wind shear was causing the asymmetrical distribution of thunderstorms.
Tropical Depression 17W will move through an environment somewhat favorable for intensification during the next 48 hours. The tropical depression will move over water where the Sea Surface Temperatures are near 29°C. However, the upper level ridge over the Western North Pacific will continue to cause moderate vertical wind shear. The wind shear will inhibit intensification, but the shear probably will not be strong enough to prevent some strengthening. Tropical Depression 17W is likely to gradually intensify to a tropical storm during the next 48 hours.
Tropical Depression 17W will move south of an upper high pressure system over the Western North Pacific Ocean. The high pressure system will steer the tropical depression toward the west during the next 48 hours. On its anticipated track, Tropical Depression 17W will move south of Yap.