Monthly Archives: December 2020

Tropical Cyclone Yasa Rapidly Intensifies to Equivalent of Major Hurricane

Tropical Cyclone Yasa rapidly intensified into the equivalent of a major hurricane on Tuesday. At 4:00 p.m. EST on Tuesday the center of Tropical Cyclone Yasa was located at latitude 14.7°S and longitude 173.8°E which put it about 320 miles (515 km) northwest of Nadi, Fiji. Yasa was moving toward the east at 5 m.p.h. (8 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 922 mb.

Tropical Cyclone Yasa rapidly intensified to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale northwest of Fiji on Tuesday. An eye with at diameter of 23 miles (37 km) was at the center of Yasa. 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 Yasa. Storms near the core generated strong upper level divergence which pumped mass away from the tropical cyclone in all directions.

Winds to hurricane/typhoon force extended out 45 miles (75 km) from the center of Tropical Cyclone Yasa. Winds to tropical storm force extended out 130 miles (210 km) from the center. The Hurricane Intensity Index (HII) for Tropical Cyclone Yasa was 33.3. The Hurricane Size Index (HSI) was 14.8 and the Hurricane Wind Intensity Size Index (HWISI) was 48.1. Tropical Cyclone Yasa was capable of causing regional severe damage.

Tropical Cyclone Yasa will move through an environment favorable for intensification during the next 24 hours. Yasa will be over water where the Sea Surface Temperature is near 29°C. It will be in a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Cyclone Yasa is could strengthen into the equivalent of a Category 5 hurricane during the next 24 hours. If the inner end of a rainband wraps around the existing eye and eyewall, then concentric eyewalls could form. If that happens, then an eyewall replacement cyclone could cause Yasa to start to weaken.

Tropical Cyclone Yasa will move around the southwestern part of a high pressure system near the Equator. The high will steer Yasa toward the southeast during the next two days. On its anticipated track Tropical Cyclone Yasa could approach Fiji in 36 hours. Yasa will be the equivalent of a major hurricane when it approaches Fiji. The center of Tropical Cyclone Yasa could pass between Vanua Levu and Viti Levu. Yasa could bring very strong winds and locally heavy rain to the most populated parts of Fiji. Tropical Cyclone Yasa could cause severe damage to Fiji.

Elsewhere over the South Pacific Ocean, the center of Tropical Cyclone Zazu passed southwest of Niue. At 4:00 p.m. EST on Tuesday the center of Tropical Cyclone Zazu was located at latitude 20.6°S and longitude 170.7°W which put it about 115 miles (185 km) southwest of Niue. Zazu was moving toward the southeast at 15 m.p.h. (24 km/h). The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h). The minimum surface pressure was 979 mb.

Tropical Cyclone Yasa Intensifies Northwest of Fiji

Tropical Cyclone Yasa intensified northwest of Fiji on Monday. At 10:00 p.m. EST on Monday the center of Tropical Cyclone Yasa was located at latitude 14.9°S and longitude 172.5°E which put it about 350 miles (565 km) west-northwest of Nadi, Fiji. Yasa was moving toward the northwest 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 Yasa intensified into the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale northwest of Fiji on Monday. A circular eye with a diameter of 25 miles (40 km) developed at the center of Yasa. 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 center of circulation. Storms near the center generated upper level divergence which pumped mass away from the tropical cyclone. Winds to hurricane/typhoon force extended out 40 miles (65 km) from the center of Tropical Cyclone Yasa. Winds to tropical storm force extended out 150 miles (240 km) from the center.

Tropical Cyclone Yasa will move through an environment favorable for intensification during the next 36 hours. Yasa will be over water where the Sea Surface Temperature is near 29°C. It will be in a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Cyclone Yasa is likely to intensify into the equivalent of a major hurricane during the next 24 hours.

Tropical Cyclone Yasa will move around the southwestern part of a high pressure system near the Equator. The high will steer Yasa toward the southeast during the next several days. On its anticipated track Tropical Cyclone Yasa could approach Fiji in 48 hours. Yasa is very likely to be the equivalent of a major hurricane when it approaches Fiji.

Elsewhere over the South Pacific Ocean, Tropical Cyclone Zazu continued to bring wind and rain to the Vava’u Group of Islands in Tonga. A weather station at Lupepau’u airport in Vava’u reported at sustained wind speed of 45 m.p.h. (75 km/h) and a wind gust of 60 m.p.h. (95 km/h). At 10:00 p.m. EST on Monday the center of Tropical Cyclone Zazu was located at latitude 19.0°S and longitude 173.7°W which put it about 30 miles (50 km) south-southeast of Neiafu, Tonga. Zazu was moving toward the southeast at 4 m.p.h. (6 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 982 mb.

Tropical Cyclone Zazu Brings Wind and Rain to Northern Tonga

Tropical Cyclone Zazu brought wind and rain to northern Tonga on Monday. At 10:00 a.m. EST on Monday the center of Tropical Cyclone Zazu was located at latitude 18.9°S and longitude 174.4°W which put it about 40 miles (65 km) west of Neiafu, Tonga. Zazu was moving toward the south-southwest at 6 m.p.h. (10 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 Zazu brought wind and rain to the Vava’u Group of islands in northern Tonga on Monday. The circulation around Zazu was intensifying. The inner end of a rainband wrapped partly around the eastern side of the center of circulation. Storms near the center generated upper level divergence which pumped mass away from the tropical cyclone. Thunderstorms were occurring in bands in the eastern half of Tropical Cyclone Zazu. Bands in the western half of the circulation consisted primarily of showers and lower clouds. Winds to tropical storm force extended out 150 miles (240 km) on the eastern side of Zazu. Winds to tropical storm force extended out 75 miles (120 km) in the western half of the circulation.

Tropical Cyclone Zazu will move through an environment favorable for intensification during the next 24 hours. Zazu will move over water where the Sea Surface Temperature is near 29°C. It will move south of an upper level trough over the South Pacific Ocean. The trough will produce westerly winds which will blow toward the top of Zazu. Those winds will cause some vertical wind shear and they are contributing to the asymmetrical distribution of thunderstorms. The shear will inhibit intensification of Tropical Cyclone Zazu, but the shear will not be strong enough to prevent Zazu from intensifying. Tropical Cyclone Zazu could strengthen into the equivalent of a hurricane/typhoon during the next 24 hours. The vertical wind shear will increase in a day or so, and Zazu will start to weaken when that happens.

The upper level trough will start to steer Tropical Cyclone Zazu toward the southeast during the next 24 hours. On its anticipated track Zazu will move between Tonga and Niue. Tropical Cyclone Zazu will continue to cause gusty winds and heavy rain over parts of Tonga during the next 24 hours. Rainbands on the eastern side of Zazu could affect Niue on Tuesday.

Elsewhere over the South Pacific Ocean, Tropical Cyclone Yasa strengthened to the equivalent of a hurricane/typhoon west-northwest of Fiji. At 10:00 a.m. EST on Monday the center of Tropical Cyclone Yasa was located at latitude 15.5°S and longitude 171.6°E which put it about 400 miles (640 km) west-northwest of Nadi, Fiji. Yasa was moving toward the north-northwest at 3 m.p.h. (5 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. Tropical Cyclone Yasa is forecast to move toward Fiji and to intensify into the equivalent of a major hurricane.

Tropical Cyclone Yasa Strengthens between Fiji and Vanuatu

Tropical Cyclone Yasa strengthened between Fiji and Vanuatu on Sunday. At 4:00 p.m. EST on Sunday the center of Tropical Cyclone Yasa was located at latitude 15.7°S and longitude 172.1°E which put it about 380 miles (610 km) west-northwest of Nadi, Fiji. Yasa was moving toward the west-southwest at 4 m.p.h. (6 km/h). The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h). The minimum surface pressure was 982 mb.

Tropical Cyclone Yasa strengthened on Sunday after the circulation of former Tropical Cyclone 04P was absorbed by the larger circulation around Yasa. The inner end of a rainband wrapped around the eastern side of the center of circulation. Other bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Yasa. Storms near the center generated upper level divergence which pumped mass away from the tropical cyclone. Winds to tropical storm force extended out 120 miles (195 km) from the center of circulation.

Tropical Cyclone Yasa will be in an environment favorable for intensification during the next several days. Yasa will be over water where the Sea Surface Temperature is near 29°C. It will be in a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Cyclone Yasa will likely intensify into the equivalent of a hurricane/typhoon during the next 18 hours. It could strengthen to the equivalent of a major hurricane in about three days.

Tropical Cyclone Yasa will be in an area where the steering winds are weak during the next 24 hours. Yasa is forecast to make a slow clockwise loop during the next 24 to 36 hours. Eventually, a high pressure system over the South Pacific Ocean will start to steer Tropical Cyclone Yasa toward the southeast. On its anticipated track Tropical Cyclone Yasa could approach Fiji in about four days.

Elsewhere over the South Pacific Ocean, Tropical Cyclone 06P developed north of Tonga. At 4:00 p.m. EST on Sunday the center of Tropical Cyclone 06P was located at latitude 17.8°S and longitude 173.9°W which put it about 60 miles (95 km) north of Neiafu, Tonga. It was moving toward the south-southwest at 9 m.p.h. (15 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.

Tropical Cyclone Developing East of Vanuatu

A tropical cyclone was developing east of Vanuatu on Friday night. The large low pressure system contained two smaller circulation. One circulation was already designated at Tropical Cyclone 04P by the Joint Typhoon Warning Center. At 10:00 p.m. EST on Friday the center of Tropical Cyclone 04P was located at latitude 14.9°S and longitude 175.8°E which put it about 220 miles (360 km) north-northwest of Nadi, Fiji. It was moving toward the west-southwest at 17 m.p.h. (28 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 994 mb.

A second larger circulation designated Invest 91P was located northwest of Tropical Cyclone 04P. At 10:00 p.m. EST on Friday the center of Invest 91P was located at latitude 12.6°S and longitude 170.1°E which put it about 310 miles (500 km) east-northeast of Vanuatu. It was moving toward the east at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1002 mb.

Tropical Cyclone 04P and Invest 91P will rotate around each other during the next several days. The circulation around Invest 91P was larger, but the wind speeds were weaker. Upper level divergence from Invest 91P was creating vertical wind shear over Tropical Cyclone 04P. The shear was inhibiting the intensification of Tropical Cyclone 04P. The two circulations are forecast to eventually merge, but numerical models differ on which circulation will become the dominant center of circulation.

The larger environment around Tropical Cyclone 04P and Invest 91P will be favorable for intensification after the two circulations merge. The merged tropical cyclone will be over water where the Sea Surface Temperature is near 29°C. It will be in a region where the upper level winds are weak and there will be little vertical wind shear. Once Tropical Cyclone 04P and Invest 91P consolidate into a single circulation, then the tropical cyclone will intensify. It could strengthen into the equivalent of a hurricane/typhoon early next week.

Tropical Cyclone 04P and Invest 91P will rotate clockwise around each other during the weekend. The overall circulation containing the two systems is forecast to drift slowly toward the south during the next several days. On its forecast track the developing tropical cyclone will move slowly toward the south between Fiji and Vanuatu.

Tropical Cyclone 03S Makes Landfall in Western Australia

Tropical Cyclone 03S made landfall on the coast of Western Australia on Thursday night. At 10:00 p.m. EST on Thursday the center of Tropical Cyclone 03S was located at latitude 20.4°S and longitude 117.8°E which put it about 55 miles (90 km) west of Port Hedland, Australia. It was moving toward the southeast at 28 m.p.h. (45 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 994 mb.

Tropical Cyclone 03S made landfall on the coast of Western Australia west of Port Hedland on Thursday night. The tropical cyclone intensified slightly just before landfall. Winds to tropical storm force extended out 125 miles (200 km) from the center of circulation. The tropical cyclone brought gusty winds to the area around Port Hedland. A weather station in Port Hedland reported a sustained wind speed of 44 m.p.h. (71 km/h) and a wind gust of 56 m.p.h. (91 km/h).

Tropical Cyclone 03S will drop heavy rain over parts of Western Australia as it moves rapidly inland. Flood Warnings were in effect for the Pilbara Coastal Rivers, the Fortescue River, the De Grey River catchment, the Salt Lakes District Rivers, the Sandy Desert, and the Warburton District Rivers.

Elsewhere over the South Indian Ocean, Tropical Cyclone Bongoyo weakened east of Rodrigues. At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Bongoyo was located at latitude 22.2°S and longitude 74.8°E which put it about 640 miles (1035 km) east of Rodrigues. It was moving toward the southwest at 7 m.p.h. (11 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.

Tropical Cyclone 03S Moves Toward Western Australia

Tropical Cyclone 03S moved toward Western Australia on Wednesday. At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone 03S was located at latitude 14.5°S and longitude 111.8°E which put it about 595 miles (955 km) northwest of Port Hedland, Australia. It was moving toward the southeast at 9 m.p.h. (15 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.

There was a well defined low level center of circulation in Tropical Cyclone 03S, but the distribution of thunderstorms was asymmetrical. The strongest thunderstorms were occurring in bands southwest of the center. Bands north and east of the center consisted primarily of showers and lower clouds. Tropical Cyclone 03S was under the western part of an upper level ridge. The ridge was producing northeasterly winds which were blowing toward the top of the circulation. Those winds were causing moderate vertical wind shear and the shear was contributing to the asymmetrical distribution of thunderstorms. Winds to tropical storm force extended out 75 miles (120 km) from the center of circulation.

Tropical Cyclone 03S will move through an environment somewhat favorable for intensification during the next 36 hours. The tropical cyclone will move over water where the Sea Surface Temperature is near 29°C. The upper level ridge will still cause vertical wind shear, but the shear could decrease a little. The wind shear will inhibit intensification, but Tropical Cyclone 03S could strengthen during the next 36 hours.

Tropical Cyclone 03S will move around the southwestern part of a high pressure system over Australia. The high will steer the tropical cyclone toward the southeast. On its anticipated track Tropical Cyclone 03S will make landfall on the coast of Western Australia near Port Hedland in about 36 hours. The tropical cyclone will bring gusty winds and locally heavy rain to parts of Western Australia later this week.

Elsewhere over the South Indian Ocean, Tropical Cyclone Bongoyo moved slowly toward Rodrigues. At 4:00 p.m. EST on Wednesday the center of Tropical Cyclone Bongoyo was located at latitude 20.7°S and longitude 75.8°E which put it about 835 miles (1345 km) east of Rodrigues. Bongoyo was moving toward the southwest 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.

Tropical Cyclone Bongoyo Forms Southeast of Diego Garcia

Tropical Cyclone Bongoyo formed over the South Indian Ocean southeast of Diego Garcia on Monday. At 4:00 a.m. EST on Monday the center of Tropical Cyclone Bongoyo was located at latitude 14.8°S and longitude 81.4°E which put it about 870 miles (1350 km) southeast of Diego Garcia. Bongoyo was moving toward the west-southwest at 13 m.p.h. (20 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.

More thunderstorms formed near the center of a low pressure system southeast of Diego Garcia on Monday and the system was designated as Tropical Cyclone Bongoyo. The inner end of a rainband wrapped around the southern and western sides of the center of Bongoyo. Other bands of showers and thunderstorms developed in the southern half of the circulation. Bands in the northern half of Tropical Cyclone Bongoyo consisted primarily of showers and low clouds. Storms near the center started to generate upper level divergence which pumped mass away to the west of the tropical cyclone. Winds to tropical storm force extended out 100 miles (160 km) in the southern half of Bongoyo. Winds to tropical storm force only extended out 35 miles in the northern half of the tropical cyclone.

Tropical Cyclone Bongoyo will move through an environment favorable for intensification during the next several days. Bongoyo will move over water where the Sea Surface Temperature is near 27°C. It will move under the northwestern part of an upper level ridge over the Southeast Indian Ocean. The ridge will produce northeasterly winds which will blow toward the top of the circulation. Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent Bongoyo from intensifying. Tropical Cyclone Bongoyo will intensify during the next 48 hours.

Tropical Cyclone Bongoyo will move around the northwestern part of a high pressure system over the Southeast Indian Ocean. The high will steer Boyongo toward the west-southwest during the next several days. On its anticipated track Tropical Cyclone Bongoyo will pass well south of Diego Garcia. Bongoyo could approach Rodrigues in five days.

Tropical Cyclone Burevi Stalls over Gulf of Mannar

Tropical Cyclone Burevi stalled over the Gulf of Mannar on Friday. At 4:00 p.m. EST on Friday the center of Tropical Cyclone Burevi was located at latitude 9.0°N and longitude 79.4°E which put it about 80 miles (130 km) east of Toothukudi, India. Burevi was nearly stationary. The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1003 mb.

Tropical Cyclone Burevi stalled over the Gulf of Mannar between Sri Lanka and the southern tip of India on Friday. Although the center of Burevi was over water, the tropical cyclone weakened since some of the circulation passed over Sri Lanka or southern India. The parts of the circulation that were over land experienced increased friction and were unable to extract as much energy from the surface. The wind speeds around Tropical Cyclone Burevi decreased gradually as a result of more friction and less available energy.

Tropical Cyclone Burevi dropped locally heavy rain over parts of southern Tamil Nadu and Kerala in India. Persistent rain fell in some locations because Burevi stalled. If the rain continues to fall over the same locations, then flash floods are likely to occur.

A high pressure system over India could start to push Tropical Cyclone Burevi toward the west during the weekend. Burevi will weaken further if the center moves across southern India. Tropical Cyclone Burevi could strengthen slowly next week, if the circulation is still relatively intact when it reaches the Arabian Sea.

Tropical Cyclone Burevi Rains on Sri Lanka and Southern India

Tropical Cyclone Burevi dropped rain on northern Sri Lanka and southern India on Wednesday night. At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Burevi was located at latitude 9.1°N and longitude 80.4°E which put it about 50 miles (80 km) south-southeast of Jaffna, Sri Lanka. Burevi was moving toward the west 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 center of Tropical Cyclone Burevi made landfall on the coast of Sri Lanka north of Trincomalee on Wednesday. The center moved westward across northern Sri Lanka after it made landfall. Bands of showers and thunderstorms in the northern and western parts of Burevi dropped rain over northern Sri Lanka, southern Tamil Nadu and southern Kerala. Prolonged rain could cause flash floods in some locations.

Tropical Cyclone Burevi could weaken during the next few hours while the center is over northern Sri Lanka. The center of Burevi will move over the Gulf of Mannar in a few hours. The center of Tropical Cyclone Burevi could make another landfall on the coast of southern India near Thoothukudi in about 18 hours. Burevi will move across the southernmost parts of Tamil Nadu and Kerala. Tropical Cyclone Burevi could move over the Arabian Sea in about 36 hours. Burevi could slowly strengthen when it moves over the Arabian Sea.