Monthly Archives: February 2016

Tropical Cyclone Winston Stalls Between Vanuatu and Fiji

Steering currents weakened on Sunday and Tropical Cyclone Winston stalled about half way between Vanuatu and Fiji.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Winston was located at latitude 18.0°S and longitude 172.5°E which put it about 300 miles (480 km) east of Port Vila, Vanuatu.  Winston was moving toward the west-southwest at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 135 m.p.h. (215 km/h).  The minimum surface pressure was 952 mb.

Vertical wind shear over Winston decreased on Sunday and the organization of the tropical cyclone improved.  The eye has become more visible on satellite images and thunderstorms surrounding the eye are generating more upper level divergence.  Easterly winds which were blowing over the top of Winston diminished and the upper level divergence is again flowing out in all directions.

Tropical Cyclone Winston is in an environment that favors intensification.  It is over water where the Sea Surface Temperature is near 30°C.  There is not much vertical wind shear and Winston is likely to intensify during the next 24 hours.

Winston has moved into an area that is between two subtropical ridges.  As a result, it is in an area where the steering winds are not very strong.  The forward motion of Winston has slowed and there is some indication that it may be turning southward.  The guidance from numerical models is forecasting a southerly or southeasterly motion during the next 24 to 48 hours.  On its anticipated track Tropical Cyclone Winston is predicted to stay east of Vanuatu.  However, a more westerly track could bring it closer to that country.

Tropical Cyclone Winston Hits Viti Levu Then Moves West of Fiji

The eye of destructive Tropical Cyclone Winston moved over the northern part of Viti Levu and then continued west of Fiji.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Winston was located at latitude 17.5°S and longitude 174.4°E which put it about 425 miles (685 km) east of Port Vila, Vanuatu.  Winston was moving toward the west at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 937 mb.  Winston was the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.

The core of intense Tropical Cyclone Winston was disrupted as it moved across the northern portion of Viti Levu.  However, the core reorganized once it moved back over water.  It has a well formed eye surrounded by a circular eyewall.  Several rainbands are spiraling around the core.  Thunderstorms in the core of Tropical Cyclone Winston are generating upper level divergence.

The environment surrounding Tropical Cyclone Winston is a little less favorable for intensification.  Winston is still moving over water where the Sea Surface Temperature is near 30°C.  However, an upper level ridge located to the southeast of Winston is generating easterly winds that are inhibiting upper level divergence to the east of the tropical cyclone.  There is still strong upper level divergence in the western half of the circulation.  The vertical wind shear has caused Winston to weaken slowly, but the shear has not been strong enough to disrupt the reorganization of the circulation.  Tropical Cyclone Winston could maintain its intensity or even strengthen somewhat during the next day or two.

The subtropical ridge southeast of Winston is steering the tropical cyclone toward the west and that general motion is expected to continue for at least another 24 hours.  Guidance from numerical models suggest that Winston will turn toward the south early next week.  However, the guidance from the models has consistently forecast a turn to the south that has not yet occurred.  The guidance predicts that Tropical Cyclone Winston will turn south before it can affect Vanuatu, but people in that country should monitor the progress of Winston closely.

Radar and satellite information indicate that the northern eyewall of Tropical Cyclone Winston may have moved over the southern part of Vanua Levu.  The eye moved across the northern part of Viti Levu.  Press reports indicated Winston produced significant wind damage and power outages in parts of Fiji.

Destructive Tropical Cyclone Winston Hits Fiji

Destructive Tropical Cyclone Winston hit parts of Fiji on Friday.  At 10:00 p.m. EST on Friday the center of Tropical Cyclone Winston was located at latitude 17.1°N and longitude 179.6°E which put it about 125 miles (205 km) east-northeast of Suva, Fiji.  The eye was just south of Vanua Levi.  Winston was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 185 m.p.h. (295 km/h) which made Winston the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  There were wind gusts to 225 m.p.h. (360 km/h) and the minimum surface pressure was 903 mb.

Winston is a compact symmetrical tropical cyclone.  It has a very well formed eye with a ring of very strong thunderstorms surrounding the eye.  Several spiral bands curl into the eyewall.  Thunderstorms around the eye are generating strong upper level divergence which pumped out mass and allowed the pressure to decrease rapidly during the past few hours.

Tropical Cyclone Winston is in a nearly perfect environment for a tropical cyclone.  It is over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and there is almost no vertical wind shear.  Winston could continue to intensify for another 6 to 12 hours.  It is hard for a tropical cyclone to remain as strong as Winston is for an extended period of time.  An eyewall replacement cycle, or movement over one of the large islands of Fiji could disrupt the circulation and cause Winston to weaken.

A subtropical ridge south of Winston is steering the tropical cyclone to the west and that general motion is expected to continue for the next day or two.  On its anticipated track the center of Tropical Cyclone Winston could pass very near the south coast of Vanua Levu and the north coast of Viti Levu.

Winston is an extremely dangerous tropical cyclone.  The Hurricane Intensity Index for Tropical Cyclone Winston is 44.1.  The Hurricane Size Index is 12.9 and the Hurricane Wind Intensity Size Index is 57.0.  These indices mean the Tropical Cyclone Winston is capable of producing regional catastrophic damage.  In addition to wind damage heavy rain will cause inland flooding and storm surges will inundate low lying portions of the coast.  The eye of Winston passed over Vanua Balavu and Yacata earlier on Friday and it is currently just south of Vanua Levi.

Strong Tropical Cyclone Winston Heads for Fiji

Strong Tropical Cyclone Winston passed over northern Tonga as it moved closer to Fiji on Thursday.  At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Winston was located at latitude 17.6°N and longitude 175.1°W which puts it about 460 miles (740 km) east of Suva, Fiji.  Winston was moving toward the west at 14 m.p.h. (23 km/h).  The maximum sustained wind speed was 125 m.p.h. (205 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 941 mb.  Tropical Cyclone Winston is the equivalent of a Category 3 hurricane on the Saffir-Simpson Scale and it would be considered a major hurricane if it were over the Atlantic Ocean.

Winston is a small, compact tropical cyclone with a well organized inner core.  It has an eye with a diameter of 15-20 miles (24-32 km) which is surrounded by a ring of strong thunderstorms.  A couple of bands of convection spiral into the core, but Tropical Cyclone Winston possesses some of the characteristics of an annular hurricane.

Winston continues to move through a very favorable environment.  The Sea Surface Temperature is near 30°C and upper level winds are relatively light.  There is not much vertical wind shear.  Tropical Cyclone Winston could intensify further on Friday.

A subtropical ridge to the south of Winston is steering the tropical cyclone toward the west-southwest.  That general motion is expected to continue for another day or two.  On its anticipated track Tropical Cyclone Winston could be very near the Lau Group of islands in eastern Fiji within 24 hours.  Winston is expected to move across the Koro Sea and it could be near Suva within 48 hours.

Winston is a strong tropical cyclone and it could bring destructive winds and heavy rain to parts of eastern Fiji.  It could also bring a storm surge and large waves, which may create dangerous conditions in low lying coastal areas.

Tropical Cyclone Winston Gets Stronger and Turns Back Toward Tonga

Tropical Cyclone Winston intensified into the equivalent of a Major Hurricane on Wednesday before it made a slow turn back toward Tonga and Fiji.  At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Winston was located at latitude 17.1°N and longitude 171.2°W which put it about 160 miles (255 km) north-northwest of Niue and about 240 miles (390 km) east-northeast of Neiafu, Tonga.  Winston was moving toward the west at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 944 mb.

A very favorable environment of Sea Surface Temperatures near 30°C and little vertical wind shear allowed Tropical Cyclone Winston to intensify quickly into the equivalent of a Major Hurricane on Wednesday.  Winston is a small, symmetrical tropical cyclone.  There is a small, well formed eye at its center.  The eye is surrounding by a ring of strong thunderstorms and there are several spiral bands rotating outside the eyewall.  Hurricane force winds extend out about 40 miles (65 km) from the center and tropical storm force winds extend out about 140 miles (225 km) from the center.

Tropical Cyclone Winston could remain in a favorable environment for another 12 to 24 hours.  It has the potential to intensify further during that time.  After that time vertical wind shear could start to increase.  Since the circulation of Winston is relatively small, fluctuations in intensity could occur more quickly.

A subtropical ridge south of Winston turned the tropical cyclone back toward the west on Wednesday.  The ridge is expected to steer Winston slowly westward on Thursday.  The subtropical ridge will steer it toward the west-southwest at a faster speed on Friday.  On its anticipated track Tropical Cyclone Winston could approach the northern islands of Tonga in about 36 hours.  It could be a very strong tropical cyclone at that time and Winston could bring strong winds and heavy rain to those islands.  Winston could be approaching Fiji in about three days.

Tropical Cyclone Winston Intensifies Rapidly East of Tonga

Tropical Cyclone Winston intensified rapidly on Tuesday as it moved east of Tonga.  At 10:00 p.m. EST on Tuesday the center of Tropical Cyclone Winston was located at latitude 17.5°N and longitude 171.5°W which put it about 165 miles (270 km) northwest of Niue.  Winston was moving toward the east at 7 m.p.h. (11 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 956 mb.

The upper level winds that were blowing over the top of Tropical Cyclone Winston diminished on Tuesday.  The decrease in vertical wind shear allowed Winston to intensify rapidly and it is now the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale.  Tropical Cyclone Winston remains in a favorable environment.  It is over water where the Sea Surface Temperature is near 30°C.  Winston has a well formed eye surrounded by an eyewall containing strong thunderstorms.  Multiple spiral bands are rotating around the core of the circulation.  Winston should continue to intensify and it could intensify rapidly on Wednesday.

A subtropical ridge to the northeast of Winston is slowing the eastward motion of the tropical cyclone.  Winston could continue to move a little farther east on Wednesday before the ridge blocks its motion.  The ridge is forecast to strengthen and extend to the west later this week.  As the ridge extends westward it will force Winston to start to move back toward the southwest.  On its anticipated track Tropical Cyclone Winston could move between Niue and Samoa on Wednesday.  Winston could approach Tonga from the northeast as a much stronger tropical cyclone on Friday.

Tropical Cyclone Winston Moving Through Tonga

Tropical Cyclone Winston brought wind and rain as it moved through Tonga on Monday.  At 10:00 p.m. EST on Monday the center of Tropical Cyclone Winston was located at latitude 18.9°S and longitude 175.0°W which put it about 405 miles (650 km) east-southeast of Suva, Fiji and about 140 miles (225 km) north of Nuku’ Alofa, Tonga.  Winston was moving toward the east-northeast at 15 m.p.h. (24 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 990 mb.

The structure of Tropical Cyclone Winston improved on Monday.  A primary rainband wrapped much of the way around the eye and a nearly complete eyewall reformed.  Additional bands of thunderstorms formed mainly in the eastern half of the circulation.  Thunderstorms increased the upper level divergence to the northeast of Winston.

The environment remains marginal for intensification.  A subtropical ridge is generating southwesterly winds over the top of Tropical Cyclone Winston.  Those winds are generating moderate vertical wind shear and are inhibiting re-intensification of Winston.  However, the tropical cyclone is moving over water where the Sea Surface Temperatures are near 30°C.  If the upper level winds diminish, then Tropical Cyclone Winston could re-intensify during the next several days.

The subtropical ridge is steering Winston toward the east-northeast and that general motion is expected to continue for another 24 to 48 hours.  On it anticipated track Tropical Cyclone Winston will move through the Vava’u Group of Tonga.  It could bring strong winds and locally heavy rain to those islands.  Winston could be between Samoa and Niue later this week.

Tropical Cyclone Winston Turns Back Toward Fiji

Tropical Cyclone Winston turned northeastward on Sunday and it began to move back toward Fiji.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Winston was located at latitude 22.6°S and longitude 179.9°E which put it about 345 miles (560 km) south-southeast of Suva, Fiji.  Winston was moving toward the northeast at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 70 m.p.h. (115 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 978 mb.

A subtropical ridge located northwest of Winston generated southwesterly winds over the top of the tropical cyclone.  The southwesterly winds produced moderate vertical wind shear, which caused Winston to weaken on Sunday.  The circulation of Tropical Cyclone Winston remains fairly intact.  A narrow band of thunderstorms is wrapped around the center of circulation and a remnant eyewall persists.  Other bands of thunderstorms are rotating around the eastern side of the cyclone.  Upper level divergence is still pumping mass out from the northeastern side of the circulation.

Tropical Cyclone Winston is currently over water where the Sea Surface Temperature is near 28°C.  As Winston moves northward it will move over warmer water.  It will also move into an area where the upper level winds are not as strong.  Tropical Cyclone Winston could continue to weaken slowly for another 12 to 24 hours.  It may re-intensify in about two or three days.

The subtropical ridge is likely to continue to steer Winston toward the northeast for anther two or three days.  After that time the subtropical ridge may shift position and allow Winston to turn back toward the west.  On its anticipated track Tropical Cyclone Winston could move over the extreme southeastern islands of Fiji on Monday.  It could bring strong winds, heavy rain and large surf to Vatoa, Ono-i-lau, Tuvana-i-colo, and Tuvana-i-ra.  Tropical Cyclone Winston could affect portions of Tonga during the middle of the week.

Tropical Cyclone Winston Turning East

Tropical Cyclone Winston turned eastward on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Winston was located at latitude 25.2°S and longitude 175.3°E which put it about 545 miles (880 km) south-southwest of Suva, Fiji.  Winston was moving toward the east-southeast at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 967 mb.

A subtropical ridge located north of Winston generated easterly winds over the top of the tropical cyclone.  The vertical wind shear caused Tropical Cyclone to weaken on Saturday.  Thunderstorms around the western side of the eyewall weakened and the eye became obscured at times as clouds blew over the top of it.  The vertical structure of the circulation is tilted toward the east with height because of the wind shear.  Tropical Cyclone Winston is likely to continue to weaken on Sunday.  However, it is moving over water where Sea Surface Temperature is near 29°C.  If the circulation maintains its integrity for another 48 hours, the wind shear could diminish and Winston could start to intensify again.

The subtropical ridge is steering Tropical Cyclone Winston toward the east.  The ridge is forecast to move toward the north and that will allow Winston to move more toward the northeast.  On its anticipated track Tropical Cyclone Winston could be near the southeastern islands of Fiji in about three days.

Tropical Cyclones Winston and Tatiana Form over SW Pacific

A pair of tropical cyclones named Winston and Tatiana formed over the southwestern Pacific Ocean on Thursday.  At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Winston was located at latitude 18.4°S and longitude 171.6°E which put it about 445 miles (720 km) west of Suva, Fiji.  Winston was moving toward the south at 7 m.p.h. (11 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 974 mb.

At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Tatiana was located at latitude 17.3°S and longitude 159.0°E which put it about 620 miles (1000 km) northwest of Noumea, New Caledonia.  Tatiana was moving toward the east-southeast at 6 m.p.h. (10 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 Winston is the stronger and more well organized storm.  It has a well developed eye surrounded by a ring of strong thunderstorms.  Winston is in a very favorable environment.  It is moving over water where the Sea Surface Temperatures are near 31°C.  There is an upper level ridge over Winston and so the upper level winds are light and divergence is occurring in all directions.  Winston is likely to continue to intensify rapidly on Friday and it could become the equivalent of a major hurricane.

Tropical Cyclone Tatiana is smaller and not as well organized.  Tatiana is moving over water where the Sea Surface Temperatures are near 30°C.  However the western end of the same upper level ridge that is over Winston is generating brisk northerly winds over the top of Tropical Cyclone Tatiana.  As a result, vertical wind shear is inhibiting upper level divergence to the north of the center of Tatiana and it is also tilting the circulation toward the south with height.  Wind shear is likely to prevent Tatiana from intensifying significantly.

A subtropical ridge is steering both Winston and Tatiana toward the south.  Tropical Cyclone Winston will pass west of Fiji, but it could come close enough to the extreme southeastern islands of Vanuatu to bring wind and rain to some of those islands.  Tropical Cyclone Tatiana is likely to pass west of New Caledonia, but it could bring rain and higher surf to the west coast of that island.