Tropical Storm Rai formed over the Western North Pacific Ocean southeast of Yap on Monday morning. At 4:00 a.m. EST on Monday the center of Tropical Storm Rai was located at latitude 5.5°N and longitude 140.5°E which put it about 355 miles (575 km) southeast of Yap. Rai was moving toward the west-northwest at 11 m.p.h. (17 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 998 mb.

The circulation around a low pressure system strengthened on Monday morning and the Japan Meteorological Agency designated the system as Tropical Storm Rai. Thunderstorms formed near the center of Tropical Storm Rai. More thunderstorms also developed in bands revolving around the center of Rai. Storms near the center of circulation generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 150 miles (240 km) from the center of Tropical Storm Rai.

Tropical Storm Rai will move through an environment favorable for intensification during the next several days. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Tropical Storm Rai’s circulation. Those winds will cause some vertical wind shear, but the shear will be too small to prevent intensification. Tropical Storm Rai will intensify during the next several days. Rai could strengthen to a typhoon within 36 hours. It could strengthen more rapidly once an inner core with an eye and an eyewall forms.

Tropical Storm Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next several days. On its anticipated track the center of Tropical Storm Rai will south of Yap during the next 24 hours. Rai could bring gusty winds and locally heavy rain to Yap. Tropical Storm Rai could affect Palau within 36 hours. Rai could approach the Philippines within 72 hours. Rai is likely to be a typhoon when it reaches the Philippines.