Category Archives: South Pacific

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.

Tropical Cyclone Victor Moves Toward Tonga

Tropical Cyclone Victor moved slowly westward toward Tonga as it passed south of Niue on Wednesday.  At 4:00 p.m. EST on Wednesday the center of Tropical Cyclone Victor was located at latitude 21.5°S and longitude 169.8°W which put it about 155 miles (250 km) south of Niue and about 370 miles (595 km) east of Tonga.  Victor was moving toward the west at 4 m.p.h. (6 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 977 mb.

Tropical Cyclone Victor still looks like the equivalent of a hurricane on satellite images.  It has a well formed eye which is surrounded by a ring of thunderstorms.  The thunderstorms near the center of Victor are generating a large area of upper level divergence.  Convection outside of the core of Victor is somewhat asymmetrical.  Most of the stronger thunderstorms are located in bands south and east of the center of circulation.  There are few tall thunderstorms in the northwestern part of Victor.

Tropical Cyclone Victor continues to be in an environment that is favorable for intensification.  Victor is moving over water where the Sea Surface Temperature is near 27°C.  The upper level winds near Victor are light and there is no appreciable vertical wind shear.  Tropical Cyclone Victor has the potential to intensify during the next 24 hours.

A subtropical ridge south of Victor is steering the tropical cyclone slowly toward the west.  The ridge is expected to continue to steer Victor toward the west, but at a faster speed, during the next day or two.  On its anticipated track Tropical Cyclone Victor could be approaching Tonga in about 36 hours.

Tropical Cyclone Victor passed far enough south of Niue that the stronger winds and heavy rain did not affect the island.  Large waves and surf may have affected some of the coastal areas.  Tropical Cyclone Victor could bring wind and rain to Tonga in two or three days.

Tropical Cyclone Victor Intensifies East of Niue

Tropical Cyclone Victor intensified on Monday and it is now the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale.  At 4:00 p.m. EST on Monday the center of Tropical Cyclone  Victor was located at latitude 20.2°S and longitude 166.3°W which put it about 175 miles (280 km) east-southeast of Niue.  Victor was moving toward the south-southwest at 5 m.p.h. (8 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.

Tropical Cyclone Victor has an unusual structure.  It has a very large eye, which is about one degree of longitude across.  The eye is surrounded by a narrow eyewall of strong thunderstorms and a couple of thin, primary rainbands.  Winds to tropical storm force extend out about 200 miles (320 km) from the center of circulation.  The thunderstorms in the eyewall are generating strong upper level divergence which is pumping out mass.  The eye has appeared to contract a bit on recent satellite imagery, which could be a sign of further intensification.

Tropical Cyclone Victor is an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature (SST) is near 27°C.  An upper level ridge located northeast of Victor is producing some light northwesterly winds over the top of the tropical cyclone.  However, the vertical wind shear is minimal and it is not inhibiting intensification at this time.  Victor could continue to intensify on Tuesday.  Later this week Tropical Cyclone Victor will move into an environment with cooler SSTs and more wind shear.  Victor will start to weakening when it enters that environment.

The ridge northeast of Victor is getting stronger and it is forcing the tropical cyclone to move toward the west-southwest.  That general motion is expected to continue for the next several days.  On its anticipated track the core of Tropical Cyclone Victor with the strongest winds will pass south of Niue during the next 48 hours.  However, Tropical Cyclone Victor could bring a period of strong winds and rain to Niue as it moves south of the islands.  The large wind field around Victor could also generate significant waves and surges.  Tropical Cyclone Victor could be approaching Tonga later this week.

Tropical Cyclone Ula Equivalent of Cat. 4 Hurricane

Tropical Cyclone continued to intensify steadily on Saturday and it is now the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  At 8:00 p.m. EDT on Saturday the center of Tropical Cyclone Ula was located at latitude 19.8°S and longitude 171.4°E which put it about 400 miles (640 km) east-northeast of Noumea, New Caledonia.  Ula was moving toward the southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 933 mb.

Tropical Cyclone Ula has circular eye with a diameter of 24 miles (38 km).  The eye is surrounded by a closed ring of thunderstorms.  Other spiral bands are rotating around the center of circulation.

Tropical Cyclone Ula is moving through an environment that is almost perfect for intensification.  The upper level winds are very light and there is almost no vertical wind shear.  Ula is over water where the Sea Surface Temperature (SST) is near 28°C.  It intensified quickly on Saturday and it has the potential to intensify a little more before it moves over cooler SSTs.

Tropical Cyclone Ula is moving around the western end of a subtropical ridge which is steering it toward the southwest.  That general motion is expected to continue for another 12 to 24 hours.  As Ula reaches the western end of the ridge it will start moving more toward the south.  Eventually the mid-latitude westerlies will start to steer Ula toward the southeast.

On its anticipated track Tropical Cyclone Ula could pass near the extreme southeastern islands of Vanuatu.  The greatest risk is to Aneityum and Futuna.  Ula could also bring wind and rain to Tanna, Aniwa, and Erromango.  The core with the strongest winds should pass southeast of Vanuatu, but Ula could bring wind and rain to some of those islands.  The center of Ula is expected to pass east of New Caledonia early next week, but it could also bring wind and rain to the Iles Loyaute.

Tropical Cyclone Ula Intensifies Rapidly, Threatens Vanuatu

Tropical Cyclone Ula intensified rapidly on Friday as it started to move toward Vanuatu.  At 4:00 p.m. EDT on Friday the center of Tropical Cyclone Ula was located at latitude 18.7°S and longitude 173.5°E which put it about 545 miles (880 km) east-northeast of Noumea, New Caledonia.  Ula was moving toward the southwest at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 95 m.p.h, (155 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 963 mb.

Tropical Cyclone Ula intensified rapidly on Friday because it was in a very favorable environment.  Satellite images showed that there is a 15 mile (24 km) wide eye at the center of Ula.  Additional spiral bands are rotating outside the core of the tropical cyclone.  Ula has a very symmetrical structure.  Thunderstorms in the core of Ula are creating upper level divergence, especially to the west of the center of circulation.

Tropical Cyclone Ula is in an environment favorable for further intensification.  It is over water where the Sea Surface Temperature is near 28°C.  An upper level ridge to the east of Ula is producing northeasterly winds over the top of the tropical cyclone.  However, the vertical wind shear is only modest and further intensification is possible.  Tropical Cyclone Ula could become the equivalent of a major hurricane during the weekend.

A subtropical ridge east of Ula is starting to steer the tropical cyclone toward the southwest.  That general motion is expected to continue for the next several days.  On its anticipated track Tropical Cyclone Ula could approach the southern islands of Vanuatu in about 48 hours.  It could be a very strong tropical cyclone when it nears those islands.

Tropical Cyclone Ula Intensifies, Could Threaten Vanuatu

Tropical Cyclone Ula moved into a more favorable environment and it intensified on Thursday.  At 4:00 p.m. EDT on Thursday the center of Tropical Cyclone Ula was located at latitude 18.7°S and longitude 174.4°E which put it about 260 miles (420 km) west of Suva, Fiji.  Ula was moving toward the northwest at 3 m.p.h. (5 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 Ula has been moving slowly equatorward this week and it is now over slightly warmer Sea Surface Temperatures (SSTs).  Ula has extracted additional energy from the warmer water and the strength of thunderstorms near the core of the tropical cyclone increased.  The structure of the circulation is more symmetrical and an eyewall may be forming around the center of Ula.  The thunderstorms are also generating more upper level divergence, especially to the west of the center of the tropical cyclone.

Tropical Cyclone Ula is once again in a region that is favorable for intensification.  It is back over water where the SSTs are near 28°C.  An upper level ridge east of Ula is generating northeasterly winds over the top of the tropical cyclone, but the vertical wind shear is modest.  Tropical cyclone is likely to intensify further during the next 24 hours and it could become the equivalent of a hurricane on Friday.

Ula has been moving slowly northwest around the western end of a subtropical ridge.  The ridge is forecast to slowly strengthen during the next few days.  As the ridge strengthens it will start to steer Ula more toward the west.  On its anticipated track Tropical Cyclone Ula could move toward Vanuatu.

Tropical Cyclone Ula Bringing Strong Wind to SE Fiji

Tropical Cyclone Ula is bringing strong winds, heavy rain and high surf to the extreme southeastern islands of Fiji.  At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Ula was located at latitude 19.4°S and longitude 178.0°W which put it about 265 miles ( 430 km) east-southeast of Suva, Fiji.  Ula was moving toward the southwest at 9 m.p.h. (15 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 961 mb.  Tropical Cyclone Ula was the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale.

The inner core structure of Tropical Cyclone Ula changed on Saturday and it may have gone through an eyewall replacement cycle.  Ula started the day with a small pinhole eye, but recent visible satellite imagery indicates that it has a larger, symmetrical eye.  Even though the inner core structure has changed, Tropical Cyclone Ula maintained its intensity.  The structure of Ula is still symmetrical, but most of the stronger thunderstorms are south and west of the center of circulation.

Tropical Cyclone Ula remains in an environment that is favorable for intensification.  It is over water where the Sea Surface Temperature (SST) is near 28°C.  The upper level winds are light and there is not much vertical wind shear.  The favorable environment could allow Ula to maintain its intensity for another 12 to 24 hours.  After that time the tropical cyclone will move into an area where the SSTs are cooler and the upper level winds are stronger.  Cooler water and more vertical wind shear will cause Tropical Cyclone Ula to weaken.

A subtropical ridge is steering Tropical Cyclone Ula toward the southwest.  Ula is nearing the western end of the ridge and it is likely to turn more toward the south in a day or two.  The center of Tropical Cyclone Ula is near Vatoa, Ogea Levu and Ogea Driki.  It is bringing strong winds, heavy rain and large waves to those islands.  It will move near Ono-i-lau, Tuvana-i-colo and Tuvana-i-ro during the next few hours and conditions will get worse on those islands.

Tropical Cyclone Ula Bringing Wind and Rain to Northern Tonga

Tropical Cyclone Ula is bringing wind and rain to islands in northern Tonga.  At 10:00 p.m. EST on Friday the center of Tropical Cyclone Ula was located at latitude 18.3°N and longitude 175.6°W which put it about 100 miles (160 km) north-northwest of Tongatapu, Tonga.  Ula was moving toward the west-southwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 115 m.p.h. (150 km/h) and there were wind gusts to 135 m.p.h. (215 km/h).  The minimum surface pressure was 959 mb.

Lupepau’u airport on Vava’u reported maximum sustained winds of 65 m.p.h. (105 km/h) and wind gusts to 100 m.p.h. (160 km/h) when the center Tropical Cyclone Ula passed north of it.  Ula also brought strong winds and heavy rain to Tafahi, Fonaulei and Toku in northern Tonga.

Tropical Cyclone Ula intensified quickly during the past few hours and a pinhole eye is visible on conventional satellite images.  The eye is surrounded by a tight ring of strong thunderstorms.  Several spiral bands are rotating around the center of Ula.  One of the primary rainbands may be wrapping around the pinhole eye and concentric eyewalls may be developing.  Thunderstorms in the core of Tropical Cyclone Ula are generating upper level divergence that is pumping out mass in all directions.

Tropical Cyclone Ula is in an environment favorable for intensification.  Ula is moving over water where the Sea Surface Temperature (SST) is near 28°C.  The upper level winds are relatively light and there is not much vertical wind shear.  Ula could intensify further during the next few hours, although an eyewall replacement cycle could cause fluctuations in intensity.  Tropical Cyclone Ula could move into an area where the upper level winds are stronger in 24 to 48 hours.  Ula will also move over cooler SSTs in several days.  The combination of more wind shear and cooler SSTs will weaken the tropical cyclone.

A subtropical ridge is steering Tropical Cyclone Ula toward the west-southwest and that general motion is expected to continue for another day or so.  After that time Ula will reach the western end of the ridge and turn more toward the south.  On its expected track Tropical Cyclone Ula could be approaching the southeastern islands of Fiji in about 24 hours.