Tropical Cyclone Riley Forms West of Australia

Tropical Cyclone Riley formed west of Australia on Wednesday.  At 4:00 p.m. EST on Wednesday the center of Tropical Cyclone Riley was located at latitude 16.7°S and longitude 121.2°E which put it about 110 miles (175 km) northwest of Broome, Australia.  Riley was moving toward the west-southwest at 14 m.p.h. (22 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 997 mb.

The circulation around a tropical low off the coast of Western Australia strengthened on Wednesday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Riley.  A band of thunderstorms wrapped clockwise from northwest to southeast around the center of circulation.  Additional bands of showers and thunderstorms were developing around the western side of the circulation which was over the open water of the south Indian Ocean.  The bands on the eastern side of the circulation were weaker, but portions of those bands were still over Western Australia.  Thunderstorms around the center of circulation were generating upper level divergence which was pumping mass away from the tropical cyclone.

Tropical Cyclone Riley will move through an environment favorable for intensification during the next several days.  Riley will move over water where the Sea Surface Temperature is near 30°C.  It will move through an area where the upper level winds are weak and there will not be much vertical wind shear.  Tropical Cyclone Riley is likely to intensify steadily and it could intensify rapidly once an eye forms and the inner core is well developed.  Tropical Cyclone Riley is likely to strengthen into the equivalent of a hurricane/typhoon within 24 to 36 hours.

Tropical Cyclone Riley will move along the northwestern edge of a subtropical ridge during the next 48 to 72 hours.  The ridge will steer Riley in a general west-southwesterly direction.  On its anticipated track Tropical Cyclone Riley will move parallel to the coast of Western Australia.  However, a southward deviation of the track could bring Riley closer to the coast.