A center of circulation developed within an area of thunderstorms east of Guam on Tuesday and the Japan Meteorological Agency designated the system as Tropical Storm Chaba. At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Chaba was located at latitude 14.2°N and longitude 147.7°E which put it about 225 miles (360 km) east of Guam. Chaba was moving toward the west at 17 m.p.h. (27 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.
The circulation of Tropical Storm Chaba is still organizing. The distribution of thunderstorms is asymmetrical. There are more thunderstorms east of the center of circulation. Additional thunderstorms are forming west of the center of circulation and some rainbands are developing. The thunderstorms near the center of Tropical Storm Chaba are generating upper level divergence which is pumping mass out in all directions.
Tropical Storm Chaba is moving through an environment that is favorable for intensification. It is moving over water where the Sea Surface Temperature is near 30°C. The upper level winds are light and there is not significant vertical wind shear. Tropical Storm Chaba is likely to continue to intensify as the circulation gets better organized. Chaba could become a typhoon later this week.
A subtropical ridge to the north of Chaba is steering the tropical storm toward the west and that general motion is expected to continue for another 24 to 36 hours. When Tropical Storm Chaba moves farther west, it will get closer to the western end of the subtropical ridge and Chaba is likely to turn more toward the west-northwest. On its anticipated track Tropical Storm Chaba will move through the Marianas between Guam and Saipan and Tinian on Wednesday. Chaba could be approaching Okinawa in about five days.