Monthly Archives: March 2021

Tropical Cyclone Habana Develops South of Diego Garcia

Tropical Cyclone Habana developed over the South Indian Ocean south of Diego Garcia on Thursday. At 10:00 a.m. EST on Thursday the center of Tropical Cyclone Habana was located at latitude 16.5°S and longitude 73.0°E which put it about 640 miles (1035 km) south of Diego Garcia. Habana was moving toward the east-southeast 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 1000 mb.

An area of low pressure over the South Indian Ocean south of Diego Garcia strengthened on Thursday and the system was designated as Tropical Cyclone Habana. The circulation around Habana was still organizing. A primary rainband wrapped around the eastern and southern sides of the center of circulation. Other bands of showers and thunderstorms were developing. Storms near the center of circulation began to generate upper level divergence which pumped mass away from the tropical cyclone. Winds to tropical storm force extended out 115 miles (185 km) on the eastern side of Tropical Cyclone Habana. Winds to tropical storm force extended out 65 miles (105 km) in the western half of Habana.

Tropical Cyclone Habana will move through an environment favorable for intensification during the next 48 hours. Habana will move over water where the Sea Surface Temperatures will be near 29°C. It will move near the southern part of an upper level ridge. The ridge will produce westerly winds which will blow toward the top of Habana. Those winds will cause some vertical wind shear and the shear will limit the rate at which Tropical Cyclone Habana intensifies.

Tropical Cyclone Habana will move south of a high pressure system over the tropical South Indian Ocean. The high will steer Habana toward the east during the next several days. On its anticipated track Tropical Cyclone Habana will remain far to the south of Diego Garcia.

Elsewhere over the South Indian Ocean Tropical Cyclone Marian was weakening gradually. At 10:00 a.m. EST on Thursday the center of Tropical Cyclone Marian was located at latitude 22.1°S and longitude 94.1°E which put it about 680 miles (1100 km) south-southwest of Cocos Island. Marian was moving toward the south-southeast at 9 m.p.h. (15 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 991 mb.

Tropical Cyclone Niran Strengthens over the Coral Sea

Tropical Cyclone Niran strengthened over the Coral Sea on Wednesday. At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Niran was located at latitude 15.4°S and longitude 149.2°E which put it about 225 miles (365 km) east-northeast of Cairns, Australia. Niran was moving toward the east at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 125 m.p.h. (200 km/h). The minimum surface pressure was 961 mb.

Tropical Cyclone Niran continued to intensify over the Coral Sea on Wednesday. A circular eye with a diameter of 25 miles (40 km) developed at the center of Niran. 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 around the core of Tropical Cyclone Niran. The strongest rainbands were in the northern half of Niran. Storms near the core generated upper level divergence that pumped mass away from the tropical cyclone.

The circulation around Tropical Cyclone Niran expanded in size on Wednesday. Winds to hurricane/typhoon force extended out 60 miles (95 km) from the center of Niran. Winds to tropical storm force extended out 230 miles (370 km) from the center of circulation. The Hurricane Intensity Index (HII) for Tropical Cyclone Niran was 16.5. The Hurricane Size Index (HSI) was 19.7 and the Hurricane Wind Intensity Size Index (HWISI) was 36.2.

Tropical Cyclone Niran will move through an environment favorable for intensification during the next 24 hours. Niran will move over water where the Sea Surface Temperatures will be near 29°C. It will move under an upper level ridge over the Coral Sea. The winds are weak in the ridge and there will be little vertical wind shear. Tropical Cyclone Niran will continue to intensify during the next 24 hours. It is likely to strengthen to the equivalent of a major hurricane.

Tropical Cyclone Niran will move around the southwestern part of a high pressure system over the tropical South Pacific Ocean. The high will steer Niran toward the southeast during the next several days. On its anticipated track Tropical Cyclone Niran could approach New Caledonia in 48 hours. Niran could be the equivalent of a major hurricane when it approaches New Caledonia.

Tropical Cyclone Niran Strengthens to Equivalent of Hurricane/Typhoon

Tropical Cyclone Niran strengthened to the equivalent of a hurricane/typhoon over the Coral Sea east of Queensland on Tuesday. At 10:00 p.m. EST on Tuesday the center of Tropical Cyclone Niran was located at latitude 14.7°S and longitude 148.3°E which put it about 225 miles (365 km) northeast of Cairns, Australia. Niran was moving toward the east at 2 m.p.h. (3 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 976 mb.

The circulation around Tropical Cyclone Niran strengthened over the Coral Sea on Tuesday. The inner end of a rainband wrapped around the center of Niran. Other bands of showers and thunderstorms revolved around the core of Tropical Cyclone Niran. Storms near the core generated upper level divergence which pumped mass away from the tropical cyclone. Winds to hurricane/typhoon force extended out 20 miles (30 km) from the center of Niran. Winds to tropical storm force extended out 120 miles (195 km) from the center of circulation.

Tropical Cyclone Niran will move through an environment favorable for intensification during the next 36 hours. Niran will move over water where the Sea Surface Temperatures will be near 29°C. It will move under an upper level ridge over the Coral Sea. The winds are weak in the ridge and there will be little vertical wind shear. Tropical Cyclone Niran will continue to intensify during the next 36 hours. It could strengthen to the equivalent of a major hurricane.

Tropical Cyclone Niran will move around the southwestern part of a high pressure system over the tropical South Pacific Ocean. The high will steer Niran toward the southeast during the next several days. On its anticipated track Tropical Cyclone Niran could approach New Caledonia in about three days.

Tropical Cyclone Marian Spins Southwest of Cocos Island

Tropical Cyclone Marian continued to spin over the South Indian Ocean southwest of Cocos Island on Tuesday. At 10:00 a.m. EST on Tuesday the center of Tropical Cyclone Marian was located at latitude 18.8°S and longitude 90.0°E which put it about 650 miles (1045 km) southwest of Cocos Island. Marian was moving toward the east-southeast at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h). The minimum surface pressure was 958 mb.

The circulation around Tropical Cyclone Marian remained well organized on Tuesday morning. A circular eye with a diameter of 35 miles (55 km) was present at the center of Marian. The eye was surrounded a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Even though the circulation was well organized, satellite images of Tropical Cyclone Marian suggested that it could be starting to weaken. The temperature of the tops of thunderstorms was warming which indicated that those storms were not rising as high in the atmosphere. Microwave satellite imagery depicted breaks forming in the southwestern part of the eyewall of Marian.

Winds to hurricane/typhoon force extended out 65 miles (105 km) from the center of Tropical Cyclone Marian. Winds to tropical storm force extended out 185 miles (295 km) from the center of circulation. The Hurricane Intensity Index (HII) for Tropical Cyclone Marian was 17.8. The Hurricane Size Index (HSI) was 21.6 and the Hurricane Wind Intensity Size Index (HWISI) was 39.4.

Tropical Cyclone Marian will move into an environment that will be less favorable for tropical cyclones during the next few days. Marian will move over water where the Sea Surface Temperatures will be near 27°C. An upper level trough over the South Indian Ocean will approach Tropical Cyclone Marian from the west. The trough will produce northwesterly winds which will blow toward the top of Marian. Those winds will cause more vertical wind shear. A combination of slightly cooler water and more vertical wind shear will cause Tropical Cyclone Marian to weaken during the next several days.

The upper level trough will begin to steer Tropical Cyclone Marian toward the southeast. On its anticipated track Marian will move farther away from Cocos Island. Tropical Cyclone Marian is forecast to remain west of Western Australia during the next five days.

Tropical Cyclone Niran Develops over Coral Sea

Tropical Cyclone Niran developed over the Coral Sea east of Queensland on Monday. At 10:00 p.m. EST on Monday the center of Tropical Cyclone Niran was located at latitude 15.4°S and longitude 147.0°E which put it about 175 miles (285 km) northeast of Cairns, Australia. Niran was moving toward the northeast at 7 m.p.h. (11 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 991 mb.

The circulation around a low pressure system over the Coral Sea east of Queensland strengthened on Monday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Niran. The circulation around Niran was organizing gradually. The strongest thunderstorms were occurring in bands in the western half of Tropical Cyclone Niran. Bands in the eastern half of the tropical cyclone consisted primarily of showers and lower clouds. Storms near the center of circulation began to generate upper level divergence which pumped mass away to the west of Niran. Winds to tropical storm force extended out 90 miles from the center of circulation.

Tropical Cyclone Niran will move through an environment favorable for intensification during the next 48 hours. Niran will move over water where the Sea Surface Temperatures will be near 29°C. It will move under the northern part of an upper level ridge over the Coral Sea. The ridge will produce easterly winds which will blow toward the top of Tropical Cyclone Niran. Those winds will cause some vertical wind shear and they are contributing to the current asymmetrical distribution of thunderstorms. The wind shear will slow the rate of intensification. Tropical Cyclone Niran will intensify and it could strengthen into the equivalent of a hurricane/typhoon within 48 hours.

Tropical Cyclone Niran will be in an area where the steering winds are weak during the next day or so. Niran could make a slow loop over the Coral Sea east of Queensland during the next 24 hours. A high pressure system over the tropical South Pacific Ocean will strengthen during the week. The high will start to steer Tropical Cyclone Niran toward the southeast on Wednesday. On its anticipated track Niran could approach New Caledonia during the weekend.