Tropical Cyclone Ambali rapidly intensified to the threshold of a Category 5 hurricane on the Saffir-Simpson Scale on Thursday.  At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Ambali was located at latitude 10.8°S and longitude 62.1°E which put it about 740 miles (1190 km) north-northeast of Port Louis, Mauritius.  Ambali was moving toward the south-southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 155 m.p.h. (250 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 932 mb.

Tropical Cyclone Ambali rapidly intensified from a minimal tropical storm to the threshold of a Cat. 5 hurricane in less than 36 hours over the Southwest Indian Ocean.  Nearly perfect environmental conditions including warm water and little vertical wind shear allowed Ambali to strengthen very rapidly.  A small circular eye formed at the center of the tropical cyclone.  The eye was surrounded by a ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Ambali.

The circulation around Tropical Cyclone Ambali was small which also contributed to the rapid intensification.  Winds to hurricane/typhoon force extended out 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extended out 100 miles (160 km) from the center.  The Hurricane Intensity Index (HII) for Tropical Cyclone Ambali was 33.3.  The Hurricane Size Index (HSI) was 7.9 and the Hurricane Wind Intensity Size Index (HWISI) was 41.2.

Tropical Cyclone Ambali may be near its maximum intensity, although it could strengthen a little more during the next six to twelve hours.  Ambali will move over water where the Sea Surface Temperature is near 28°C.  It will remain in an area where the upper level winds are weak during the next six to twelve hours and there will be little vertical wind shear during that time.  Tropical Cyclone Ambali will approach an area where there are strong upper level westerly winds during the weekend.  Ambali will weaken when the wind shear increases.

Tropical Cyclone Ambali will move around the western part of a subtropical high pressure over the South Indian Ocean.  The high will steer Ambali toward the south-southwest during the next several days.  On its anticipated track Tropical Cyclone Ambali will move toward Mauritius.

Elsewhere over the Southwest Indian Ocean, Tropical Cyclone Belna was intensifying north of Madagascar.  At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Belna was located at latitude 7.5°S and longitude 49.0°E which put it about 300 miles (485 km) north of Madagsacar.  Belna was moving toward the southwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 982 mb.

The circulation around Tropical Cyclone Belna exhibited much greater organization on Thursday.  An eye appeared to be forming at the center of circulation on microwave satellite images.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving about the core of Belna.  Storms near the core were generating upper level divergence which was pumping mass away from the tropical cyclone.  Winds to tropical storm force extended out 100 miles (160 km) from the center of circulation.

Tropical Cyclone Belna will move through an environment favorable for intensification during the next 24 to 48 hours.  Belna will move over water where the Sea Surface Temperature is near 28.5°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Cyclone Belna is likely to strengthen into the equivalent of a hurricane/typhoon on Friday.  Belna could intensify rapidly once an eye and eyewall are full formed.  It could strengthen into the equivalent of a major hurricane during the weekend.

Tropical Cyclone Belna will move around the western end of a ridge of high pressure over the South Indian Ocean.  The high will steer Belna toward the south-southwest during the next few days.  On its anticipated track Tropical Cyclone Blena could approach the coast of northwestern Madagascar in three or four days.  Belna could be the equivalent of a hurricane/typhoon when it approaches Madagascar.