Tag Archives: Anatahan

Tropical Storm Choi-wan Forms East of Northern Marianas

Tropical Storm Choi-wan formed over the Western North Pacific Ocean east of the Northern Marianas on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Choi-wan was located at latitude 16.3°N and longitude 149.5°E which put the center about 150 miles (240 km) east of Alamagan.  Choi-wan was moving toward the west-northwest at 9 m.p.h. (15 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.

A low pressure system over the Western North Pacific Ocean east of the Northern Marianas strengthened on Wednesday and the Japan Meteorological Agency designated the system as Tropical Storm Choi-wan.

The distribution of thunderstorms in Tropical Storm Choi-wan was asymmetrical.  Thunderstorms were occurring in bands in the western side of Choi-wan’s circulation.  Bands in the eastern side of Tropical Storm Choi-wan consisted primarily of showers and lower clouds.  Storms near the center of Choi-wan generated upper level divergence that pumped mass away to the west of the tropical storm.  The removal of mass caused the surface pressure to decrease.

The strongest winds in Tropical Storm Choi-wan were occurring in the bands of thunderstorms in the western side of Choi-wan.  Winds to tropical storm force extended out 115 miles (185 km) in the western half of Choi-wan’s circulation.  The winds in the eastern side of Tropical Storm Choi-wan were blowing at less than tropical storm force.

Tropical Storm Choi-wan will move through an environment that will be somewhat favorable for intensification during the next 24 hours.  Choi-wan will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the southern part of an upper level ridge that is south of Japan.  The upper level ridge will produce easterly winds that will blow toward the top of Choi-wan’s circulation.  Those winds will cause some vertical wind shear, but the wind shear will not be enough to prevent intensification.  Tropical Storm Choi-wan will intensify during the next 24 hours.  Choi-wan could strengthen to a typhoon by the end of the week.

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 west-northwest during the next 24 hours.  On its anticipated track, Tropical Storm Choi-wan will move over Alamagan, Agrihan, Pagan, and Anatahan on Thursday.

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.

A Flash Flood Watch is in effect for Tinian and Saipan.

A Tropical Storm Warning is in effect for Tinian and Saipan. 

A Tropical Storm Warning is in effect for Alamagan and Pagan.

A Typhoon Watch is in effect for Alamagan and Pagan.

A Tropical Storm Watch is in effect for Agrihan.

Tropical Storm Saola Forms Northeast of Luzon

Tropical Storm Saola formed over the Western North Pacific Ocean northeast of Luzon during Wednesday night. At 5:00 a.m. EDT on Thursday the center of Tropical Storm Saola was located at latitude 20.5°N and longitude 124.5°E which put it about 250 miles (400 km) northeast of Aparri, Philippines. Saola was moving toward the northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 998 mb.

A small low pressure system northeast of Luzon strengthened during Wednesday night and the Japan Meteorological Agency designated the system as Tropical Storm Saola. The circulation around Saola was small. Winds to tropical storm force extended out 30 miles (50 km) in the southern side of Saola’s circulation. The winds win the northern side of the circulation were blowing at less than tropical storm force.

More thunderstorms were forming near the center of Tropical Storm Saola. Storms near the center began to generate upper level divergence that pumped mass away from the tropical storm. Bands of showers and thunderstorms developed around Tropical Storm Saola. The bands were beginning to revolve around the center of Saola’s circulation.

Tropical Storm Saola will move through an environment mostly favorable for intensification during the next 24 hours. Saola will move over water where the Sea Surface Temperatures are near 30°C. It will move under the southern part of an upper level ridge over South Asia and Southeast Asia. The ridge will produce easterly winds that will blow toward the top of Saola’s circulation. Those winds will cause some vertical wind shear and the wind shear will inhibit intensification. The vertical wind shear will probably not be enough to prevent intensification and Tropical Storm Saola is likely to intensify during the next 24 hours.

Tropical Storm Saola will move around the southwestern part of a high pressure system over the Western North Pacific during the next 12 hours. The high pressure system will steer Saola toward the northwest during that time period. A large counterclockwise monsoon gyre is forecast to develop east of the Philippines. The monsoon gyre will pull Saola back to the south during the next several days. On its anticipated track, Tropical Storm Saola is forecast to make a counterclockwise loop east of Luzon.

Elsewhere over the Western North Pacific Ocean, Tropical Depression 08W was east of the Marianas. At 5:00 a.m. EDT on Thursday the center of Tropical Depression 08W was located at latitude 16.5°N and longitude 149.2°E which put it about 225 miles (365 km) east of Anatahan. Tropical Depression 08W was moving toward the west at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1000 mb. Tropical Depression 08W is forecast to slowly strengthen.