Tropical Cyclone Wasi Develops Near Samoa

Tropical Cyclone Wasi developed near Samoa on Friday night.  At 10:00 p.m. EST on Friday the center of Tropical Cyclone Wasi was located at latitude 13.6°S and longitude 172.9°W which put it about 20 miles (35 km) west of Falealupo, Samoa and about 185 miles (300 km) west-northwest of Pago Pago, American Samoa.  Wasi was moving toward the southeast at 11 m.p.h. (17 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 993 mb.

Tropical Cyclone Wasi spun up out of the same elongated trough of low pressure near Samoa that produced Tropical Cyclone Vicky on Thursday.  A small center of low pressure developed west-northwest of Samoa on Friday.  More thunderstorms formed near the center of circulation and the system was classified as Tropical Cyclone Wasi.  Microwave satellite imagery indicated that there was a tight inner core in the tropical cyclone.  Storms near the core were generating upper level divergence which was pumping mass away from Tropical Cyclone Wasi.  The circulation around Wasi was even smaller than the circulation around Tropical Cyclone Vicky.  Winds to tropical storm force only extended out about 50 miles (80 km) from the center of Tropical Cyclone Wasi.

Tropical Cyclone Wasi will move into an environment somewhat favorable for intensification during the next 24 to 36 hours.  Wasi will move over water where the Sea Surface Temperature is near 28°C.  It will move under the western end of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the tropical cyclone.  Those winds will cause moderate vertical wind shear, but the winds may not be strong enough to prevent intensification.  Tropical Cyclone Wasi could strengthen during the next 24 to 36 hours.  Since the circulation around Wasi is so small, if the tropical cyclone moves into an area where the upper level winds are stronger, it could weaken quickly.

Tropical Cyclone Wasi will move around the western end of a high pressure system over the South Pacific Ocean.  The high will steer Wasi toward the southeast during the next 12 hours.  Wasi will move more toward the south later in the weekend.  On its anticipated track Tropical Cyclone Wasi will bring gust winds and locally heavy rain to portions of Samoa during the next 24 hours.

Elsewhere over the South Pacific Ocean, Tropical Cyclone Vicky weakened as it passed near Niue on Friday.  At 10:00 p.m. EST on Friday the center of Tropical Cyclone Vicky was located at latitude 19.7°S and longitude 168.7°W which put oit about 95 miles (150 km) southeast of Niue.  Vicky was moving toward the south-southeast at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1001 mb.