Tropical Cyclone Savannah formed over the southeast Indian Ocean north of Cocos Island on Wednesday. At 5:00 p.m. EDT on Wednesday the center of Tropical Cyclone Savannah was located at latitude 11.3°S and longitude 96.7°E which put it about 60 miles (100 km) north of Cocos Island. Savannah was moving toward the south-southwest at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 997 mb. The Australian Bureau of Meteorology has issued a Tropical Storm Warning for Cocos Island.
More thunderstorms formed near an area of low pressure over the southeastern Indian Ocean west of Australia and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Savannah. The distribution of thunderstorms around Savannah was asymmetrical. Several bands of showers and thunderstorms developed in the western half of the circulation. Rainbands in the eastern half of the circulation consisted primarily of showers and lower clouds. Tropical Cyclone Savannah was moving south of an upper level ridge. The ridge was generating easterly winds which were blowing toward the top of the circulation. Those winds were causing moderate vertical wind shear and they were contributing to the asymmetrical distribution of thunderstorms.
Tropical Cyclone Savannah will move through an environment favorable for intensification during the next several days. Savannah will move over water where the Sea Surface Temperature is near 28°C. The upper level ridge will continue to cause vertical wind shear, but the shear could decrease during the next 48 hours. Tropical Cyclone Savannah is likely to intensify during the next day or two.
Tropical Cyclone Savannah will move near the western end of a strengthening subtropical ridge over Australia. The ridge will steer Savannah toward the south-southwest during the next day or two. On its anticipated track Tropical Cyclone Savannah will bring gusty winds and locally heavy rain to Cocos Island during the next 24 hours.
Tropical Cyclone Gaja formed over the Bay of Bengal on Sunday. At 4:00 p.m. EST on Sunday the center of Tropical Cyclone Gaja was located at latitude 12.9°N and longitude 86.7°E which put it about 500 miles (805 km) east of Chennai, India. Gaja was moving toward the west-southwest at 8 m.p.h. (13 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 1002 mb.
An area of low pressure moving over the Bay of Bengal strengthened on Sunday and the India Meteorological Department classified the system as Tropical Cyclone Gaja. The circulation around Tropical Cyclone Gaja is still organizing. There is a distinct low level center of circulation. A short band of thunderstorms is west and north of the center. Several other bands of showers and thunderstorms are developing in other parts of Tropical Cyclone Gaja. One stronger band is east of the center of circulation and another stronger band is southeast of the center. Storms near the center are beginning to generate upper level divergence which will pump mass away from the tropical cyclone.
Tropical Cyclone Gaja will move through an environment somewhat favorable for intensification during the next 48 hours. Gaja will move over water where the Sea Surface Temperature is near 29°C. It will move south of an upper level ridge. The ridge will produce easterly winds which will blow toward the top of the circulation. The winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification. Tropical Cyclone Gaja will intensify and it could be nearly equivalent to a hurricane/typhoon in two or three days.
The upper level ridge will steer Tropical Cyclone Gaja in a generally west-southwesterly direction. On its anticipated track Tropical Cyclone Gaja will approach the coast of southern India in about 72 hours. Gaja could be nearly the equivalent of a hurricane/typhoon at that time.
Elsewhere, over the South Indian Ocean Tropical Cyclone Alcide still was moving slowly east of the northern end of Madgascar and Tropical Cyclone Bouchra developed between Diego Garcia and Cocos Island. At 4:00 p.m. EST on Sunday the center of Tropical Cyclone Alcide was located at latitude 12.3°N and longitude 51.9°E which put it about 170 miles (275 km) east of Antisiranana, Madagascar. Alcide was moving toward the northwest at 4 m.p.h. (6 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.
At 4:00 p.m. EDT on Sunday the center of Tropical Cyclone Bouchra was located at latitude 5.4°S and longitude 89.1°E which put it about 700 miles (1130 km) northwest of Cocos Island, Australia. Bouchra was moving toward the east at 2 m.p.h. (3 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 999 mb.
Tropical Cyclone Caleb formed over the South Indian Ocean on Thursday. At 8:00 a.m. EDT on Thursday the center of Tropical Cyclone Caleb was located at latitude 13.0°S and longitude 100.7°E which put it about 255 miles (410 km) east-southeast of Cocos Island. Caleb was moving toward the south-southeast at 6 m.p.h. (9 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 995 mb.
Although there is a well defined low level circulation in Tropical Cyclone Caleb, the distribution of thunderstorms is asymmetrical. The strongest thunderstorms are occurring in the northwestern quadrant of the circulation and they are in the primary rainband. Those thunderstorms contain the strongest winds. There are few thunderstorms in the other parts of the circulation, although there are some bands of lower clouds and showers in those regions. The thunderstorms in the primary rainband are generating upper level divergence which is pumping out mass to the west of Tropical Cyclone Caleb.
Tropical Cyclone Caleb is in an environment that is marginal for intensification. Caleb is moving over water where the Sea Surface Temperature is near 28°C. So, there is enough energy in the upper ocean to support intensification. However, an upper level ridge located southeast of Caleb is producing easterly winds which are blowing across the top of the tropical cyclone. The easterly winds are generating moderate vertical wind shear and the shear is probably the reason why most of the thunderstorms are occurring in the northwestern quadrant of the circulation. The moderate shear will inhibit intensification, but some strengthening may be possible if the upper level winds abate.
A ridge to the east of Caleb is steering the tropical cyclone toward the south-southeast and that general motion is expected to continue for another day or two. Eventually, a second ridge is forecast to strengthen and steer Tropical Caleb back toward the northwest.