Tropical Cyclone Fantala Intensifies to Equivalent of Cat. 4 Hurricane

Tropical Cyclone Fantala continued to get stronger on Friday and it is now the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  At 5:00 p.m. EDT on Friday the center of Tropical Cyclone Fantala was located at latitude 12.4°S and longitude 57.6°E which put it about 530 miles (860 km) north of Port Louis, Mauritius.  Fantala was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed  was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 926 mb.

Tropical Cyclone Fantala is very well organized.  There is a ring of strong thunderstorms surrounding a well formed eye.  Other spiral bands are rotating near the core of the circulation.  Thunderstorms are generating upper level divergence which is pumping out large amounts of mass and allowing the surface pressure to decrease further.  The Hurricane Intensity Index (HII) for Tropical Cyclone Fantala is 31.6.  The Hurricane Size Index (HSI) is 18.4 and the Hurricane Wind Intensity Size Index (HWISI) is 50.0.

Fantala continues to exist in an environment favorable for intensification.  It is over water where the Sea Surface Temperature is near 30°C.  The upper level winds are weak and there is little vertical wind shear.  Fantala could become the equivalent of a Category 5 hurricane during the next 24 hours.  Fantala appeared to go through an eyewall replacement cycle on Thursday and further cycles could produce additional fluctuations in intensity.

A subtropical ridge located southwest of Fantala is steering the tropical cyclone toward the west.  Movement toward the west or west-northwest is expected during the next 24 to 48 hours.  On its anticipated track Tropical Cyclone Fantala could be northeast of the northern tip of Madagascar by the end of the weekend.  Fantala is a powerful, dangerous tropical cyclone and it would be capable of doing regional serious damage if it made landfall.

Tropical Cyclone Fantala Gets Bigger and Stronger

Tropical Cyclone Fantala grew in size and intensity on Wednesday.  At 8:00 p.m. EDT on Wednesday the center of Tropical Cyclone Fantala was located at latitude 12.7°N and longitude 64.2°E which put it about 700 miles (1130 km) northeast of Port Louis, Mauritius.  Fantala was moving toward the west at 10 m.p.h. (16 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. (200 km/h).  The minimum surface pressure was 956 mb.  The Hurricane Intensity Index (HII) was 17.8, the Hurricane Size Index (HSI) was 14.6 and the Hurricane Wind Intensity Size Index (HWISI) was 32.4.

Both the organization and size of the circulation of Fantala increased on Wednesday.  A complete eyewall formed around an eye at the center of the tropical cyclone.  Other well formed bands of thunderstorms developed and wrapped around the core of Fantala.  The structure of the tropical cyclone is much more symmetrical and there are thunderstorms in all quadrants of the circulation.  Winds to hurricane force extended out 35 miles (55 km) from the center of circulation.  Thunderstorms around the core of Fantala generated upper level divergence which pumped out mass and allowed the surface pressure to decrease.

Tropical Cyclone Fantala is an environment favorable for further intensification.  Fantala is over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and there is very little vertical wind shear.  The structure of Fantala will allow it to use the energy from the ocean very efficiently.  Fantala is likely to continue to intensify on Thursday and it could become the equivalent of a major hurricane.  As Fantala gets stronger, concentric eyewalls could develop and the resulting eyewall replacement cycles could produce fluctuations in intensity.

A subtropical ridge located to the south of Fantala is steering it toward the west and that general steering motion is expected to continue during the next several days.  On its anticipated track Fantala will pass north of Mauritus and La Reunion during the weekend.  Tropical Cyclone Fantala could be near northern Madagascar in a few days.

Tropical Cyclone Fantala Intensifies and Heads Slowly West

Tropical Cyclone Fantala intensified into the the equivalent of a hurricane/typhoon as it headed slowed west across the South Indian Ocean on Tuesday.  At 5:00 p.m. EDT on Tuesday the center of Tropical Cyclone Fantala was located at latitude 12.8°S and longitude 68.5°E which put it about 465 miles (755 km) south-southwest of Diego Garcia.  Fantala was moving toward the west-northwest at 5 m.p.h. (8 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 975 mb.

The core of Tropical Cyclone Fantala continued to get better organized on Tuesday.  The primary rainband wrapped entirely around the center of circulation and a small eye appeared intermittently on some satellite imagery.  Thunderstorms around the center of circulation began to produce more upper level divergence and high clouds could be seen fanning out in all directions.  The upper level divergence pumped out mass and allowed the surface pressure to decrease.

Fantala is a small tropical cyclone.  Tropical storm force winds only extend about 100 miles (160 km) from the center of circulation.  The Hurricane Size Index for Tropical Cyclone Fantala is only 8.1.

Tropical Cyclone Fantala is in an environment that appears to be mostly favorable for intensification.  It is over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and there is not much vertical wind shear.  The only possible negative factor is the presence of some drier air around the periphery of the circulation.  Tropical Cyclone Fantala is likely to intensify further and its small size could allow it to intensify rapidly at times.  Tropical Cyclone Fantala could become the equivalent of a major hurricane later this week.

A subtropical ridge located south of Fantala is steering the tropical cyclone toward the west and that general motion is expected to continue for the next several days.  On its anticipated track Tropical Cyclone Fantala could pass north of La Reunion in a few days.  Fantala could be northeast of Madagascar in four or five days.

Tropical Cyclone Fantala Forms South of Diego Garcia

A well organized center of circulation developed within a small area of thunderstorms south of Diego Garcia on Monday and the system was designated Tropical Cyclone Fantala.  At 8:00 p.m. EDT on Monday the center of Tropical Cyclone Fantala was located at latitude 13.0°S and longitude 70.8°E which put it about 420 miles (675 km) south-southwest of Diego Garcia.  Fantala was moving toward the west at 9 m.p.h. (14 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 989 mb.

The circulation of Tropical Cyclone is still organizing.  A primary rainband is wrapping around the southern and western sides of the center of circulation.  Most of the thunderstorms are near or in the primary rainband.  There are few thunderstorms east of the center of circulation.  The thunderstorms are generating upper level outflow to the west side of the circulation.

The environment is favorable for further intensification.  Fantala is over water where the Sea Surface Temperatures are near 30°C.  An upper level ridge south of Fantala is generating light easterly winds over the core of the circulation.  The easterly winds are producing a little vertical wind shear.  The shear is strong enough to contribute to the asymmetrical distribution of thunderstorms, but it is not strong enough to prevent intensification.  Tropical Cyclone Fantala could become the equivalent of a hurricane/typhoon within 24 hours.

A subtropical ridge south of Fantala is expected to steer the tropical cyclone in a general westerly direction during the next few days.  On its anticipated track Tropical Cyclone Fantala could be northeast of La Reunion later this week.

Tropical Cyclone Zena Shears Apart South of Fiji

Strong upper level winds blew the upper portion of the circulation east of the surface circulation of Tropical Cyclone Zena as it passed south of Fiji.  At 8:00 p.m. EDT on Wednesday the center of Tropical Cyclone Zena was located at latitude 21.5°S and longitude 176.0°W which put it about 60 miles (95 km) west of Nuku’ Alofa, Tonga.  Zena was moving toward the east-southeast at 36 m.p.h. (58 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 988 mb.

Although Tropical Cyclone Zena briefly reached hurricane/typhoon intensity on Tuesday, it always consisted of a very small circulation which was very susceptible to vertical wind shear.  When an upper level ridge northeast of Zena increased west-northwesterly winds over the top of the tropical cyclone, those winds blew the upper portion of the circulation east of the center. The circulation of Zena lost its vertical integrity and it was difficult to find a well defined center of circulation at the surface by late Wednesday.  The remnants of Tropical Cyclone Zena are on a trend of rapid weakening.  The vertical wind shear is expected to continue and Zena could dissipate within 24 to 36 hours while it passes south of Niue.

Tropical Cyclone Zena Forms Near Vanuatu and Moves Toward Fiji

Tropical Cyclone Zena formed near Vanuatu on Tuesday.  After several weaker circulations developed within a large trough of low pressure that extended from Tonga west-northwest to near Vanuatu during the past few days, a stronger center of circulation organized near Espiritu Santo on Tuesday.  Thunderstorms consolidated around the center of circulation and the system was designated at Tropical Cyclone Zena (18P).

At 10:00 p.m. EDT on Tuesday the center of Tropical Cyclone Zena was located at latitude 17.6°S and longitude 173.1°E which put it about 300 miles (480 km) west of Nadi, Fiji.  Zena was moving toward the east-southeast at 27 m.p.h. (44 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 978 mb.

Tropical Cyclone Zena is a small system.  Tropical storm force winds only extend out about 100 miles (160 km) from the center of circulation.  The Hurricane Size Index (HSI) for Zena is only 6.4  A primary rainband wrapped around the center of circulation and a tiny pinhole eye has appeared intermittently on satellite imagery.  There is a circular ring of thunderstorms at the core of Zena.  The outer portion of the circulation is asymmetrical.  Most of the bands of thunderstorms are east of the center of circulation.

The environment around Tropical Cyclone Zena is somewhat favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C to 30°C.  An upper level ridge is generating moderate west-northwesterly winds around the tropical cyclone.  Much stronger upper level winds are south of Tropical Cyclone Zena.  The upper level winds are inhibiting outflow to the west of the center of the circulation, but they did not inhibit intensification on Tuesday.  Rapid motion of Tropical Cyclone Zena toward the east-southeast appears to have offset some of the effects of the vertical wind shear.  Zena could continue to intensify in the short term, but its small size could make it very vulnerable to the effects of vertical wind shear, if the speed of the upper winds increase.

An upper level ridge located northeast of Zena is steering the tropical cyclone rapidly toward the east-southeast.  That general motion is expected to continue for the next several days.  On its anticipated track Tropical Cyclone Zena will be nearing Fiji in about 12 hours and it could be near Tonga in about 36 hours.  The center of Zena and the strongest winds could pass south of Viti Levu on Wednesday.

Tropical Cyclone Zena could bring strong winds to any of the southern islands of Fiji including southern Viti Levu, Beqa, Kadavu, Lau and the Lomaiviti group.  It could also cause heavy rain and floods.  Tropical Cyclone Zena could bring wind and rain to Tonga on Thursday.

Tropical Cyclone 16P Forms Over Gulf of Carpentaria

After a quiet period of several weeks in the tropics Tropical Cyclone 16P formed over the Gulf of Carpentaria on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Cyclone 16P was located at latitude 16.4°S and longitude 140.3°E which put it about 75 miles (120 km) east-northeast of Mornington Island and about 115 miles (185 km) southwest of Kowanyama, Australia.  Tropical Cyclone 16P was moving toward the east-southeast at 12 m.p.h. (18 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 996 mb.

An upper level ridge persisted over the Gulf of Carpentaria during the past few days.  The upper level ridge generated upper level divergence which enhanced rising motion and supported the development of thunderstorms.  Eventually, the upper level divergence pumped out enough mass to allow the surface pressure to decrease and the thunderstorms began to consolidate around a low level center.  The system developed enough organization on Tuesday to be classified as a tropical cyclone.

The organization of Tropical Cyclone 16P improved on Tuesday.  Spiral bands of thunderstorms wrapped around a low level center.  Strong thunderstorms near the center of circulation generated upper level divergence, especially to the east of the tropical cyclone.

The environment is favorable for intensification as long as the center of circulation remains over water.  The Sea Surface Temperatures are near 31°C in the southern Gulf of Carpentaria.  An upper level ridge to the east of the tropical cyclone is generating some vertical wind shear, but the ridge is also enhancing upper level divergence.  The primary inhibiting factor is the proximity of the center of circulation to land.  Tropical Cyclone 16P could intensify further during the next 12 hours before it makes landfall.

The upper level ridge is steering Tropical Cyclone 16P toward the southeast coast of the Gulf of Carpentaria.  On its anticipated track Tropical cyclone 16P is expected to make landfall in Queensland near the mouth of the Gilbert River in about 12 hours.  The potential track after landfall is much more uncertain.  Some guidance suggests that the tropical cyclone could move across the Cape York peninsula toward the Coral Sea.  Other guidance suggests that the tropical cyclone could turn back toward the northwest and move back out into the Gulf of Carpentaria.

Although Tropical Cyclone 16P is likely to cause minor wind damage, it could produce locally heavy rainfall and flooding when it moves over northeastern Queensland.

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.