Former Tropical Storm Choi-wan strengthened to a typhoon over the Western North Pacific Ocean west of the Northern Marianas on Friday. At 11:00 a.m. EDT on Friday the center of Typhoon Choi-wan was located at latitude 18.0°N and longitude 144.7°E which put the center about 80 miles (130 km) west of Alamagan. Choi-wan was moving toward the north at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h). The minimum surface pressure was 981 mb.
A Typhoon Warning is in effect for Agrihan and Pagan.
A Tropical Storm Warning is in effect for Tinian, Saipan, and Alamagan.
A Typhoon Watch is in effect for Alamagan.
Former Tropical Storm Choi-wan strengthened to a typhoon on Friday. The inner end of a rainband wrapped around the center of Typhoon Choi-wan. Other bands of showers and thunderstorms were revolving around the center of Choi-wan’s circulation. Storms near the center of Choi-wan generated upper level divergence that pumped mass away from the typhoon. The removal of mass caused the surface pressure to decrease.
The distribution of wind speeds in Typhoon Choi-wan was asymmetrical. Winds to typhoon force extended out 110 miles (175 km) in the southern half of Choi-wan’s circulation. Winds to tropical storm force extended out 50 miles (80 km) in the northern half of Typhoon Choi-wan. Winds to tropical storm force extended out 250 miles (400 km) in the southern side of Typhoon Choi-wan. Winds to tropical storm force extended out 175 miles (280 km) in the northern side of Choi-wan’s circulation.
Typhoon Choi-wan will move through an environment that will be favorable for intensification during the next 24 hours. Choi-wan Choi-wan will move over water where the Sea Surface Temperatures are near 29°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Choi-wan will intensify during the next 24 hours. Choi-wan is likely to strengthen to the equivalent of a major hurricane during the weekend.
Tropical Storm Choi-wan will move around the western end of a high pressure system that is over the Western North Pacific Ocean. The high pressure system will steer Choi-wan toward the north during the next 24 hours. On its anticipated track, Tropical Storm Choi-wan will move away from the Northern Marianas during the weekend.
Tropical Storm Choi-wan will bring strong winds and heavy rain to Alamagan, Agrihan, Pagan, and Anataham. Heavy rain could cause floods in some locations. Choi-wan could also bring gusty winds and heavy rain to Tinian and Saipan. Bands in the southern periphery of Typhoon Choi-wan could drop heavy rain over Guam and Rota.
Flood Watches are in effect for Guam, Rota, Tinian, and Saipan.