Tropical Storm Rai strengthened east of Palau on Monday night. At 10:00 p.m. EST on Monday the center of Tropical Storm Rai was located at latitude 7.7°N and longitude 136.3°E which put it about 170 miles (275 km) east of Koror, Palau. Rai was moving toward the west-northwest at 21 m.p.h. (33 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 990 mb.

Tropical Storm Rai strengthened steadily over the Western North Pacific Ocean on Monday. Although Rai intensified, the distribution of thunderstorms was asymmetrical. The strongest thunderstorms were occurring in bands in the western half of Tropical Storm Rai’s circulation. The inner end of a rainband wrapped around the western and southern side of the center of Rai’s circulation. Bands in the eastern half of the tropical storm consisted primarily of showers and lower clouds. Storms near the center of circulation generated upper level divergence that pumped mass away to the west and north of the tropical storm. Winds to tropical storm force extended out 200 miles (320 km) from the center of Rai.

Tropical Storm Rai will move through an environment favorable for intensification during the next 48 hours. 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 and the shear is already contributing to the current asymmetrical distribution of thunderstorms. The upper level winds are forecast to weaken, and the vertical wind shear will be too small to prevent intensification. Tropical Storm Rai will intensify and it likely to strengthen to a typhoon during the next 24 hours. Rai 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 north of Palau during the next 12 hours. Rai could bring gusty winds and locally heavy rain to Palau. Tropical Storm Rai could approach the Philippines in 60 hours. Rai is likely to be a typhoon when it reaches the Philippines.