Tag Archives: Tropical Cyclone 09S

Anggrek Transitions to an Extratropical Cyclone

Former Tropical Cyclone Anggrek made a transition to an extratropical cyclone over the South Indian Ocean during Tuesday night. At 4:00 a.m. EST on Wednesday the center of former Tropical Cyclone Anggrek was located at latitude 33.3°S and longitude 84.8°E which put it about 1925 miles (3105 km) south-southeast of Diego Garcia. Anggrek was moving toward the east-southeast at 40 m.p.h. (65 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h). The minimum surface pressure was 983 mb.

Former Tropical Cyclone Anggrek made a transition to a powerful extratropical cyclone over the South Indian Ocean. Anggrek moved over water where the Sea Surface Temperatures are near 22°C. It moved under the eastern side of an upper level trough that is east of Madagascar. The upper level trough produced northwesterly winds that caused strong vertical wind shear. The combination of colder water and strong wind shear caused formal Tropical Cyclone Anggrek to make a transition to an extratropical cyclone.

The transition to an extratropical cyclone also caused changes to the structure of former Tropical Cyclone Anggrek. The strong northwesterly winds in the upper levels of the atmosphere blew the tops off of many of the thunderstorms in Anggrek’s circulation. Thunderstorms were still occurring in bands in the southern part of former Tropical Cyclone Anggrek. Bands in the northern part of the circulation consisted primarily of showers and lower clouds. Winds to hurricane/typhoon force extended out 70 miles (110 km) in the eastern side of former Tropical Cyclone Anggrek. Winds to tropical storm force extended out 140 miles (220 km) from the center of Anggrek’s circulation.

The upper level trough east of Madagascar will steer former Tropical Cyclone Anggrek quickly toward the east-southeast. On its anticipated track, Former Tropical Cyclone Anggrek could approach southwestern Australia later this week.

Elsewhere over the South Indian Ocean, a tropical depression formed east of Rodrigues. At 10:00 a.m. EST on Wednesday the center of the tropical depression was located at latitude 19.9°S and longitude 66.2°E which put it about 175 miles (280 km) east of Port Mathurin, Rodrigues. The tropical depression was moving toward the south-southeast at 3 m.p.h. (5 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 996 mb.