Tag Archives: SH04

Tropical Cyclone Seth Speeds South

Tropical Cyclone Seth sped toward the south over the Coral Sea east of Australia on Saturday night. At 7:00 p.m. EST on Saturday the center of Tropical Cyclone Seth was located at latitude 25.8°S and longitude 159.0°E which put it about 385 miles (620 km) east-northeast of Brisbane, Australia. Seth was moving toward the south at 25 m.p.h. (41 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 987 mb.

An upper level trough over eastern Australia and an upper level ridge east of the Coral Sea were combining to steer Tropical Cyclone Seth quickly toward the south on Saturday night. The structure of Seth’s circulation was beginning to resemble a subtropical cyclone. The strongest thunderstorms were occurring in bands south of the center of circulation. Bands in the northern half of Tropical Cyclone Seth consisted primarily of showers and lower clouds. The upper level trough and upper level ridge were producing strong northerly winds that were blowing toward the top of Seth’s circulation. Those winds were causing strong vertical wind shear. Drier air was wrapping around the northern side of Tropical Cyclone Seth. The strong vertical wind shear and drier air were causing the asymmetrical distribution of thunderstorms. The distribution of winds around Seth was also asymmetrical. Winds to tropical storm force extended out 205 miles (335 km) in the southern half of Tropical Cyclone Seth. Winds to tropical storm force extended out 90 miles (150 km) in the northern half of Seth’s circulation.

Tropical Cyclone Seth will move through an environment unfavorable for intensification during the next 24 hours. Seth will move over water where the Sea Surface Temperatures are near 26˚C. However, the upper level trough and upper level ridge will continue to cause strong vertical wind shear. Drier air in the northern half of Seth’s circulation will inhibit the formation of thunderstorms. Tropical Cyclone Seth could make a transition to a subtropical cyclone during the next 24 hours. Seth could maintain its intensity during the transition, but it is likely to weaken during the next few days.

The upper level trough will steer Tropical Cyclone Seth quickly toward the south during the next 12 hours. The upper trough could make a transition to a cutoff low during the next day or so. The center of Seth could move under the cutoff low, which would cause Seth to move more slowly. The cutoff low and Tropical Cyclone Seth could drift west toward Australia during the next several days. On its anticipated track Tropical Cyclone Seth could move slowly toward Australia as a subtropical cyclone.

Tropical Cyclone Seth Spins Northeast of Brisbane

Tropical Cyclone Seth was spinning northeast of Brisbane, Australia on Friday night. At 10:00 p.m. EST on Friday the center of Tropical Cyclone Seth was located at latitude 22.6°S and longitude 157.7°E which put it about 465 miles (745 km) northeast of Brisbane, Australia. Seth was moving toward the southeast at 13 m.p.h. (20 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 992 mb.

Tropical Cyclone Seth strengthened on Friday morning, but then it weakened later in the day. An upper level ridge centered northeast of Australia and an upper level trough over eastern Australia were interacting to produce strong northwesterly winds over the Coral Sea on Friday night. Those winds were blowing toward the top of Seth’s circulation and they were causing moderate vertical wind shear. The wind shear was causing an asymmetric distribution of thunderstorms around Tropical Cyclone Seth. The strongest thunderstorms were occurring in bands southeast of the center of Seth. Bands in the northwestern half of the tropical cyclone consisted primarily of showers and lower clouds. Winds to tropical storm force extended out 155 miles (250 km) in the southern half of Tropical Cyclone Seth. Winds to tropical storm force extended out 100 miles (160 km) in the northern half of the circulation.

Tropical Cyclone Seth will move through an environment unfavorable for intensification during the next 24 hours. Seth will move over water where the Sea Surface Temperatures are near 28˚C. However, the upper level trough over eastern Australia and the upper level ridge over the Coral Sea will continue to produce strong northwesterly winds. Those winds will continue to cause strong vertical wind shear. The wind shear is likely to prevent Tropical Cyclone Seth from intensifying during the next 24 hours. There is a chance that the upper level winds could weaken in 24 hours, which might allow Seth to strengthen at that time.

The upper level trough and ridge will steer Tropical Cyclone Seth toward the south-southeast during the next 24 hours. The upper level trough could evolve into a cutoff low, which could pull Seth back toward the west during the second half of the weekend. On its anticipated track Tropical Cyclone Seth could be east of Brisbane in 36 hours.

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.

Weakened Tropical Cyclone Sarai Moves Across Tonga

A weakened Tropical Cyclone Sarai moved across Tonga on Monday.  At 10:00 p.m. EST on Monday the center of Tropical Cyclone Sarai was located at latitude 20.6°S and longitude 174.9°W which put it about 30 miles (50 km) northeast of Nuku Alofa, Tonga.  Sarai was moving toward the northeast 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 989 mb.

Tropical Cyclone Sarai moved south of an upper level ridge on Monday.  The upper level ridge produced strong westerly winds which blew across the top of Sarai.  Those winds caused strong vertical wind shear and they blew the tops off of thunderstorms in Tropical Cyclone Sarai.  The circulation in the lower levels of Sarai remained intact, but it consisted of showers and lower clouds.  The wind speed gradually decreased during Monday.

The center of Tropical Cyclone Sarai passed just north of the Tongatapu Group of islands.  Sarai passed over the Ha’apai Group of islands.  Tropical Cyclone Sarai brought winds to tropical storm force and squally weather to parts of Tonga.  Rainfall amounts were relatively light because the wind sheared the tops off of any thunderstorms which started to form.

Tropical Cyclone Sarai will move through an environment unfavorable for intensification.  Sarai will move over water where the Sea Surface Temperature is near 27°C.  The upper level ridge will continue to cause strong vertical winds shear.  The wind shear will make it very difficult for new thunderstorms to form.  Tropical Cyclone Sarai is likely to weaken slowly as the circulation in the lower levels spins down.

Tropical Cyclone Sarai will move south of a subtropical high pressure system over the South Pacific Ocean.  The high will steer Sarai toward the east during the next several days.  On its anticipated track Tropical Cyclone Sarai will move south of the Vava’u Group of Islands during the next 24 hours.  Sarai could reach Niue in less than 30 hours.

Tropical Cyclone Sarai Moves Toward Tonga

Tropical Cyclone Sarai moved toward Tonga on Sunday.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Sarai was located at latitude 20.7°S and longitude 178.3°E which put it about 220 miles (355 km) west of Nuku Alofa, Tonga.  Sarai was moving toward the east-southeast 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 985 mb.

Tropical Cyclone Sarai weakened on Sunday.  An upper level ridge north of Sarai produced strong westerly winds which blew toward the top of the circulation.  Those winds caused strong vertical wind shear which disturbed the circulation around Tropical Cyclone Sarai.  The inner core became less well organized and there was no evidence of an eye on satellite images.  The stronger thunderstorms were occurring in bands in the eastern half of the circulation.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  The circulation around Tropical Cyclone Sarai was still large.  Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation.

Tropical Cyclone Sarai will continue to move through an environment unfavorable for intensification during the next several days.  Sarai will move over water where the Sea Surface Temperature is near 28°C.  However, the upper level ridge will continue to produce strong westerly winds and vertical wind shear is likely to cause Tropical Cyclone Sarai to weaken further.

Tropical Cyclone Sarai will move south of a subtropical high pressure system over the South Pacific Ocean.  The high pressure system will steer Sarai toward the east during the next several days.  On its anticipated track Tropical Cyclone Sarai will move across Tonga in about 24 hours.  Although Sarai will weaken, it will bring winds to tropical storm force and heavy rain to parts of Tonga.

Tropical Cyclone Sarai Moves Across Southern Fiji

Tropical Cyclone Sarai moved across southern parts of Fiji on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Sarai was located at latitude 19.9°S and longitude 179.1°E which put it about 30 miles (50 km) southwest of Matuku, Fiji.  Sarai was moving toward the east at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 976 mb.

Tropical Cyclone Sarai strengthened into the equivalent of a hurricane/typhoon on Saturday as it moved across the southern part of Fiji.  The center of Sarai passed south of Kadavu, but raindbands on the northern side of the circulation brought gusty winds and heavy rain to the island.  A ragged eye appeared intermittently on satellite images.  The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Tropical Cyclone Sarai had a large circulation.  Winds to hurricane/typhoon force extended out 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extended out 200 miles (320 km) from the center.

Tropical Cyclone Sarai will move into an environment that will become increasingly unfavorable for intensification.  Sarai will move over water where the Sea Surface Temperature is near 28°C.  So, there will be enough energy in the upper ocean to support a strong tropical cyclone.  Tropical Cyclone Sarai will move south of an upper level ridge.  The ridge will produce westerly winds which will get stronger during the next several days.  Those winds will cause moderate vertical wind shear.  When the shear gets stronger, Tropical Cyclone Sarai will start to weaken.

Tropical Cyclone Sarai will move south of a subtropical high pressure system over the South Pacific Ocean.  The high will steer Sarai toward the east during the next 48 hours.  On its anticipated track Tropical Cyclone Sarai will move across Matuku, Fiji during the next few hours.  Sarai will reach the Lau Group of Fiji Islands during the next 24 hours.  Tropical Cyclone Sarai could reach parts of Tonga within 48 hours.  Sarai will bring gusty winds and heavy rain to all of those places during the next 48 hours.

Tropical Cyclone Sarai Brings Wind and Rain to Fiji

Tropical Cyclone Sarai brought wind and rain to Fiji in Friday.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Sarai was located at latitude 19.3°S and longitude 177.0°E which put it about 100 miles (160 km) west-southwest of Kadavu, Fiji.  Sarai was moving toward the southeast at 12 m.p.h. (19 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 983 mb.

The center of Tropical Cyclone Sarai passed west of Nadi, Fiji on Friday, but rainbands in the eastern side of the circulation produced gusty winds and heavy rain.  A surface weather station in Nadi measured a sustained wind speed of 44 m.p.h. (70 km/h) and wind gusts of 67 m.p.h. (107 km/h).

Tropical Cyclone Sarai continued to intensify on Friday.  The inner end of a rainband wrapped much of the way around the center of circulation.  The rainband had not wrapped entirely around the northwestern part of the center,  A clear area at the center began to appear on satellite images, which could be evidence of formation of an eye.  Storms around the center were generating upper level divergence which was pumping mass away to the east of the tropical cyclone.  The circulation around Tropical Cyclone Sarai was large.  Winds to tropical storm force extended out 200 miles (320 km) from the center of Sarai.

Tropical Cyclone Sarai will move through an environment favorable for intensification for another 24 to 36 hours.  Sarai will move over water where the Sea Surface Temperature is near 28°C.  It will move south of an upper level ridge.  The ridge will produce westerly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear.  The wind shear will inhibit intensification, but it will not be strong enough to keep Tropical Cyclone Sarai from strengthening into the equivalent of a hurricane/typhoon.

Tropical Cyclone Sarai will move south of a subtropical high pressure system over the South Pacific Ocean.  The ridge will steer Sarai toward the east.  On its anticipated track the center of Tropical Cyclone Sarai will pass south of Suva, Fiji.  The core of Sarai will pass near Kadavu, Fiji in about 12 to 18 hours.  Tropical Cyclone Sarai will bring gusty winds and locally heavy rain to Kadavu.  Heavy rain could cause flash floods in some locations.

Tropical Cyclone Sarai Forms Northwest of Fiji

Tropical Cyclone Sarai formed northwest of Fiji on Thursday.  At 10:00 a.m. EST on Thursday the center of Tropical Cyclone Sarai was located at latitude 14.9°S and longitude 175.8°E which put it about 220 miles (355 km) north-northwest of Nadi, Fiji.  Sarai was moving toward the south at 14 m.p.h. (22 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.

The circulation around a low pressure system northwest of Fiji exhibited greater organization on Thursday and the Fiji Meteorological Service designated the system as Tropical Cyclone Sarai.  The circulation around Tropical Cyclone Sarai was still organizing.  A band of showers and thunderstorms wrapped around the southern and western sides of the center of circulation.  Other bands of showers and thunderstorms were developing and the bands were starting to revolve around the center.  Storms near the center were generating upper level divergence which was pumping mass away from the tropical cyclone.  The circulation around Tropical Cyclone Sarai was large.  Winds to tropical storm force extended out 150 miles (240 km) from the center of circulation.

Tropical Cyclone Sarai will move through an environment favorable for intensification during the next 48 hours.  Sarai will move over water where the Sea Surface Temperature is near 28°C.  It will move under the western end of an upper level ridge.  The ridge will produce northerly winds which will blow toward the top of the circulation.  However, there will be northerly winds at most levels of the troposphere, which means that there will not be a lot of vertical wind shear.  Tropical Cyclone Sarai will intensify during the next 36 to 48 hours and it could strengthen into the equivalent of a hurricane/typhoon.

Tropical Cyclone Sarai will move around the western end of a subtropical high pressure system over the South Pacific Ocean.  The high will steer Sarai toward the south during the next 24 hours.  Tropical Cyclone Sarai will turn more toward the east in a day or so when it rounds the end of the ridge.  On its anticipated track the center of Sarai could approach western Fiji in 24 to 36 hours.

Tropical Low Forms Over Western Australia

A Tropical Low formed over Western Australia on Monday and a Tropical Cyclone Watch was issued for a portion of the coast.  At 2:00 p.m. EST on Monday the center of the Tropical Low was located at latitude 15.9°S and longitude 126.1°E which put it about 135 miles (220 km) west-southwest of Wyndham, Australia.  It was moving toward the southwest a 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 20 m.p.h. (30 km/h) and there were wind gusts to 50 m.p.h. (85 km/h).  The minimum surface pressure was 1005 mb.  The Australia Bureau of Meteorology has issued a Tropical Cyclone Watch for the portion of the coast of Western Australia from Kuri Bay to Wallal Downs including Broome.

The circulation of the Tropical Low is still organizing.  There is a broad low level center of circulation, but there are not many showers and thunderstorms near the center.  There are numerous bands of showers and storms developing in bands on the eastern and western peripheries of the circulation.  The strongest wind gusts are occurring in those storms.  The lack of storms near the center of circulation is keeping the system from generating much upper level divergence.

The core of the Tropical Low is likely to remain over land for another 12-24 hours, which will inhibit the organization of the circulation.  When the center moves off the coast and over the South Indian Ocean, it will move into an environment favorable for intensification.  The Sea Surface Temperature of the water west of the coast of Western Australia is near 30°C.  The Tropical Low is moving north of the axis of a subtropical ridge.  The ridge is producing easterly winds which are blowing toward the top of the circulation, but there is not a lot of vertical wind shear.  The Tropical Low is likely to strengthen when it moves over water and it could intensify rapidly if a more concentrated center of circulation develops.

A subtropical ridge is current steering the Tropical Low toward the southwest, but a general motion toward the west-southwest is expected during the next 24 to 48 hours.  The Tropical Low will reach the western end of the ridge in about two days and then it will turn more toward the south.  On its anticipated track the center of the Tropical Low is expected to move off the coast between Kuri Bay and Derby on Tuesday.  The center is forecast to pass near Cape Leveque and then turn south toward Wallal Downs.

Elsewhere over the South Indian Ocean, Tropical Cyclone Ava continued to swirl near southern Madagascar and stronger Tropical Cyclone Irving was passing well to the south of Diego Garcia.  At 4:00 p.m. EST on Monday the center of Tropical Storm Ava was located at latitude 27.7°S and longitude 46.8°E which put it about 180 miles (295 km) south of Farodofay, Madagascar.  Ava was moving toward the west-southwest at 17 m.p.h. (27 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.

At 4:00 p.m. EST on Monday the center of Tropical Cyclone Irving was centered at latitude 19.6°S and longitude 76.1°E which put it about 875 miles (1415 km) south-southeast of Diego Garcia.  Irving was moving toward the west-southwest at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 960 mb.  Tropical Cyclone Irving was the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale.

Tropical Cyclone Ava Drops Heavy Rain on Madagascar

Tropical Cyclone Ava dropped heavy rain over Madagascar on Saturday.  At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Ava was located at latitude 21.4°S and longitude 48.2°E which put it about 70 miles (110 km) north-northwest of Mananjary, Madagascar.  Ava was moving toward the south-southeast at 11 m.p.h. (17 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 Ava weakened into the equivalent of a tropical storm during the day it spent moving over Madagascar.  The strongest winds were occurring in bands of thunderstorms over the water.  The center made landfall on Friday near Toamasina.  The center then passed near Moramanga, Anosibe An’ala, and Marolambo.  There is still a distinct center of circulation and several bands of showers and thunderstorms are revolving around the center.  Some of the storms dropped heavy rain over parts of Madagascar.  There was stronger rising motion in places where the winds blew up the sides of mountains and the rainfall was heavier in those locations.  The potential for flooding exists in places that received heavy rain.

The center of Tropical Cyclone Ava is likely to move back over the water of the South Indian Ocean during the next few hours.  Tropical Cyclone Ava will move into an environment that is favorable for intensification when it moves back over water.  The Sea Surface Temperature of the water east of Madagascar is near 28°C.  Ava is moving under the axis of an upper level ridge and the upper level winds are relatively weak.  So, there is not a lot of vertical wind shear.  Tropical Cyclone Ava is likely to strengthen once the center moves back over water.

Tropical Cyclone Ava is moving around the western end of a subtropical ridge which is steering Ava toward the south-southeast.  The ridge is forecast to steer Tropical Cyclone Ava toward the south for another day or two.  When Tropical Cyclone Ava moves farther to the south in about 48 hours, an upper level trough will cause northwesterly winds, which will start to steer the tropical cyclone toward the east-southeast.  On its anticipated track the center of Tropical Cyclone Ava is expected to move off the coast of Madagascar near Mananjary in a few hours.

Elsewhere over the South Indian Ocean, Tropical Cyclone Irving was strengthening east-southeast of Diego Garcia.  At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Irving was located at latitude 13.3°S and longitude 87.5°E which put it about 1145 miles (1845 km) east-southeast of Diego Garcia.  Irving was moving toward the west-southwest at 13 m.p.h. (21 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.

Satellite imagery suggested that Tropical Cyclone Irving could be strengthening rapidly.  A primary rainband was wrapping around the center of circulation.  An eye appeared to be forming at the center of Irving.  Tropical Cyclone Irving will move through an environment favorable for intensification.  Irving is likely to intensify into the equivalent of a hurricane/typhoon while it passes well to the south of Diego Garcia during the next several days.