Monthly Archives: April 2016

Tropical Cyclone Amos Speeds Past Samoa and Weakens

Tropical Cyclone Amos weakened as it sped past Samoa on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Amos was located at latitude 14.0°S and longitude 169.1°W which put it about 15 miles (25 km) north of Luma, Samoa.  Amos was moving toward the southeast at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 970 mb.

A ridge of high pressure east of Amos produced strong northwesterly winds which steered the tropical cyclone rapidly to the east-southeast on Saturday.  Those steering winds carried the core of Amos just north of the larger islands of Samoa.  Since hurricane force winds only extended out about 20 miles (30 km) from the center of circulation, the stronger winds stayed mostly over the open water.  A weather station in Pago Pago, Samoa reported a wind gust of 54 m.p.h. (87 km/h).

Tropical Cyclone Amos is currently bringing wind and rain to the Manua Islands of eastern Samoa which include Olosega, Ofu and Ta’u.  The rapid forward motion of Amos means that conditions should improve within a few hours.

The strong northwesterly winds are causing significant vertical wind shear that is rapidly weakening Tropical Cyclone Amos.  Amos is still moving over water where the Sea Surface Temperature is near 30°C, but the vertical wind shear should continue to weaken the tropical cyclone as it moves farther east of Samoa.

Tropical Cyclone Fantala Weakens Northeast of Madagascar

Thunderstorms near the center of Tropical Cyclone Fantala dissipated and it weakened as moved northeast of Madagascar.  At 5:00 p.m. EDT  on Saturday the center of Tropical Cyclone Fantala was located at latitude 11.5°S and longitude 54.5°E which put it about 350 miles (565 km) east of Antsirañana, Madagascar.  Fantala was moving west-northwest at 10 m.p.h. (16 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.

Tropical Cyclone Fantala reversed course again on Saturday and it is moving over the same part of the South Indian Ocean that it already crossed twice during the past few days.  The winds produced by Fantala mixed cooler water up to to the surface of the ocean during its previous passages over the same region.  The cooler water means that there is less energy available to power the circulation of Tropical Cyclone.  Although the winds continue to rotate around the center of circulation, there are no thunderstorms near the core of Fantala.  There are still several thunderstorms in rainbands farther to the east of the center of circulation.

If new thunderstorms do not develop around the core of the circulation, the winds will gradually spin down and the tropical cyclone will dissipate within a few days.  Upper level winds blowing from the west-northwest are also generating some vertical wind shear, which will make it more difficult for new thunderstorms to form.

A subtropical ridge southwest of Fantala is steering the tropical cyclone toward the west-northwest and that general motion is expected to continue for the next several days.  On its anticipated track Tropical Cyclone Fantala is forecast to pass north of Madagascar and move over the Seychelles.  It could be even weaker by the time it gets to the Seychelles.

Strong Tropical Cyclone Amos Heading Toward Samoa

Tropical Cyclone Amos strengthened as it passed over Iles Wallis and headed toward Samoa on Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Cyclone Amos was located at latitude 12.5°S and longitude 175.4°E which put it about 70 miles (115 km) north-northeast of Iles Wallis and about 360 miles (580 km) west-northwest of Pago Pago, Samoa.  Amos was moving toward the east at 11 m.p.h. (18 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 core of the circulation of Tropical Cyclone Amos is small but it is well organized.  There is a ring of the thunderstorms around an eye, but clouds from the taller thunderstorms are obscuring the eye on conventional satellite imagery.  Multiple bands of thunderstorms are rotating around the core of the circulation.  The thunderstorms are generating well developed upper level divergence which is pumping out mass in all directions.

Tropical Cyclone Amos is an environment favorable for further intensification.  It is moving over water where the Sea Surface Temperature is near 30°C.  The winds in the upper levels are weak and there is not much vertical wind shear.  Amos is likely to intensify during the next 24 hours and it could be the equivalent of a major hurricane when it reaches the western part of Samoa.

A ridge of high pressure is expected to steer Tropical Cyclone Amos toward the east-southeast during the nest several days.  On its anticipated track Amos could be approaching the western islands of Samoa in a little over 24 hours.  It could be the equivalent of a major hurricane at that time.

The Hurricane Intensity Index (HII) for Amos is currently 17.8.  The Hurricane Size Index (HSI) is 9.0 and the Hurricane Wind Intensity Size Index (HWISI) is 26.8.  Those indices suggest that the core of Tropical Cyclone Amos will be capable of causing major damage if it moves directly over any of the islands of Samoa.  In addition, Amos will produce locally heavy rain capable of causing flash floods.  It could also generate high waves and surges along the coasts of some of the islands.

Tropical Cyclone Amos to Bring Wind and Rain to Wallis and Samoa

Tropical Cyclone Amos intensified to the equivalent of a hurricane/typhoon on Thursday as it moved eastward across the South Pacific.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Amos was located at latitude 12.4°S and longitude 177.1°W which put it about 80 miles (130 km) northwest of Iles Wallis.  Amos was moving toward the east-northeast at 11 m.p.h. (18 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 974 mb.

Tropical Cyclone Amos is a small, tightly organized storm.  A primary band of thunderstorms wraps almost entirely around the center of circulation and an eyelike feature is visible intermittently on satellite imagery.  Additional bands of showers and thunderstorms are spiraling around the core of the circulation.  The thunderstorms are generating upper level divergence which is pumping out mass in all directions and causing the surface pressure to decrease.

The environment around Tropical Cyclone Amos is very favorable for further intensification.  It is moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds are very weak and there is little vertical wind shear.  Amos will continue to intensify on Friday and it could intensify rapidly.

A subtropical ridge north of Amos is steering the tropical cyclone toward the east and that general motion is expected to continue for several more days.  On its anticipated track Amos will pass near Iles Wallis on Friday.  Although the core of strongest winds will pass north of Iles Wallis, It could still bring strong winds, heavy rain and large waves to those islands.  On its anticipated track Amos could be approaching western Samoa within 36 hours.  It could be a very strong tropical cyclone at that time.

Tropical Cyclone Fantala Stalls East of Madagascar

Tropical Cyclone Fantala moved into an area of weaker steering currents on Thursday and it stalled about 500 miles (800 km) east of northern Madagascar.  At 5:00 p.m. EDT on Thursday the center of Tropical Cyclone Fantala was located at latitude 13.0°S and longitude 56.7°E which put it about 515 miles (830 km) east of Antsirañana, Madagascar.  Fantala was moving toward the southeast at 5 m.p.h. (8 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.

Although Fantala weakened slightly on Thursday, the structure of the inner core of the circulation remained fairly intact.  A thin ring of thunderstorms was wrapped around an that was obscured on conventional satellite imagery.  Other bands of thunderstorms spiraled around the eyewall.  The thunderstorms in the core of Fantala were generating upper level divergence to the north and east of the center of circulation.  It appears that drier air may be getting pulled into the eastern portion of the circulation outside the core of Fantala.  There only only isolated thunderstorms in the rainbands in that part of the circulation.

The environment is marginally favorable for intensification.  The upper level winds are light enough so there is only a moderate amount of vertical wind shear.  Fantala is over water where the Sea Surface Temperature is near 29°C.  However, because Fantala is moving so slowly, it could mix cooler water to the surface which would reduce the energy available to the tropical cyclone.  In addition the drier air will also limit the supply of energy being transported into the core of the circulation.

Tropical Cyclone Fantala has moved into an area where the steering currents are weak.  It may not move much during the next 24 hours.  A subtropical ridge is forecast to develop southwest of Fantala in a day or two.  When the subtropical ridge develops, it is expected to steer Fantala back toward the west again.  On its anticipated track Tropical Cyclone Fantala could be approaching the northern part of Madagascar in 60 to 72 hours.

Tropical Cyclone Amos Forms North of Fiji

A center of circulation developed within a large area of thunderstorms north of Fiji on Wednesday and the system was designated as Tropical Cyclone Amos.  At 5:00 p.m. EDT on Wednesday the center of Tropical Cyclone Amos was located at latitude 12.5°S and longitude 179.4°W which put it about 145 miles (235 km) northwest of Ile Futuna.  Amos was stationary.  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 near the core of Tropical Cyclone Amos is still organizing.  A narrow primary band of thunderstorms is wrapping tightly around the core and an eye may be forming at the center of circulation.  Several other thin bands of showers and thunderstorms are rotating around the outer portions of the circulation.  The thunderstorms are generating some upper level divergence, but it is not well developed yet.

The environment is favorable for continued intensification.  Amos is moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds are not very strong and there is little vertical wind shear.  As the core of the circulation becomes more well organized, it will convert energy from the ocean more efficiently and the wind speeds will increase.  Tropical Cyclone Amos could intensify into the equivalent of a hurricane/typhoon within 24 to 36 hours.

Tropical Cyclone Amos is currently in an area where the steering currents are weak.  An upper level ridge is forecast to develop north of Amos and begin to steer the tropical cyclone toward the east.  On its anticipated track Amos could pass near Iles Wallis in 24 to 36 hours.  It could be approaching Samoa in two or three days.

Tropical Cyclone Fantala Reorganizes Northeast of Madagascar

Tropical Cyclone Fantala reorganized northeast of Madagascar on Tuesday.  At 8:00 p.m. EDT on Tuesday the center of Tropical Cyclone Fantala was located at latitude 10.0°S and longitude 52.0°E which put it about 240 miles (385 km) northeast of Antsirañana, Madagascar.  Fantala was moving toward the east-southeast at 8 m.p.h. (13 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. (220 km/h).  The minimum surface pressure was 952 mb.

The core of the circulation of Tropical Cyclone Fantala became more organized on Tuesday.  A ring of strong thunderstorms surrounded a circular eye that was visible on satellite imagery.  It did still appear that some drier air was wrapping around the eastern and southern sides of the circulation, but the drier air did not appear to be spiraling into the center of the circulation.  Upper level divergence appeared to increase throughout the day.

The environment around Tropical Cyclone Fantala is favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is not much vertical wind shear.  The only inhibiting factor is the presence of a band of drier air on the eastern and southern sides of the circulation.  Given the improved organization of the core of the circulation, Tropical Cyclone Fantala could intensify further on Wednesday.

A ridge north of Fantala is steering the Tropical Cyclone toward the east-southeast and that general motion is expected to continue for another day or two.  A new subtropical ridge could develop southwest of Fantala and turn it back toward the west later this week.  Tropical Cyclone Fantala could still have an impact on northern Madagascar in a few days.

Tropical Cyclone Fantala Stalls and Weakens North of Madagascar

Tropical Cyclone Fantala stalled north of Madagascar on Monday and it weakened below Category 5 on the Saffir-Simpson Scale.  At 8:00 p.m. EDT on Monday the center of Tropical Cyclone Fantala was located at latitude 9.2°S and longitude 49.6°E which put it about 200 miles (320 km) north of Antsirañana, Madagascar.  Fantala was nearly stationary.  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (265 km/h).  The minimum surface pressure was 933 mb.

The structure of the circulation of Tropical Cyclone Fantala deteriorated on Monday.  An eye was no longer visible in satellite imagery and the ring of thunderstorms that was around the eye appeared to have a gap on the east side.  There were still bands of thunderstorms spiraling around the outer portion of the circulation.  However, it appeared that some drier air may have been pulled into the northeastern part of Fantala.  Thunderstorms were still generating upper level divergence, but it was mainly to the south of the tropical cyclone.  The upper level divergence pumped out less mass than the amount of mass that converged in the lower levels and the surface pressure rose about 20 mb on Monday.

The environment around Tropical Cyclone Fantala contains a mixture of favorable and unfavorable features.  Fantala is over water where the Sea Surface Temperatures are near 29°C.  Upper level winds are blowing a little more strongly from the northeast, but the vertical wind shear is still not too significant.  Fantala does seem to be pulling in some drier air into its circulation.  The tropical cyclone is nearly stationary and its strong winds may be mixing some cooler water to the surface.  Drier air and cooler water would reduce the energy available to drive the circulation of Fantala and it is likely to weaken further on Tuesday.

Fantala is in an area where the steering currents are weak and it may not move much during the next 12 to 24 hours.  Eventually, a ridge is expected to develop northeast of Fantala and start to steer the tropical cyclone toward the southeast.  On its anticipated track the core of strongest winds would pass north of Madagascar.  However, there is still uncertainty about the future track of Fantala and it could still have an impact on northern Madagascar.

 

Tropical Cyclone Fantala Reaches Cat. 5 North of Madagascar

Tropical Cyclone Fantala continued to intensify on Sunday and it reached the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  At 5:00 p.m. EDT on Sunday the center of Tropical Cyclone Fantala was located at latitude 9.7°S and longitude 50.5°E which put it about 190 miles (305 km) north-northeast of Antsirañana, Madagascar.  Fantala was moving toward the west-northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 175 m.p.h. (280 km/h) and there were wind gusts to 205 m.p.h. (335 km/h).  The minimum surface pressure was 911 mb.

Fantala is an extremely well organized tropical cyclone.  There is a solid ring of thunderstorms surrounding a clear eye.  Other bands of thunderstorms spiral into the core of the circulation.  Hurricane force winds extend out about 30 miles (50 km) south of the center.  The thunderstorms are generating enough upper level divergence to cause the surface pressure to decrease to 911 mb.

Fantala is a very powerful tropical cyclone.  The Hurricane Intensity Index (HII) is 40.4, the Hurricane Size (HSI) is 10.5, and the Hurricane Wind Intensity Size Index (HWISI) is 50.9.

The environment around Tropical Cyclone Fantala is very favorable.  It is over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Fantala could intensify a little more, but it is likely near its maximum intensity.  Any increase in the speed of the upper level winds would generate more vertical wind shear and start to weaken Fantala.

A subtropical ridge southwest of the tropical cyclone is steering Fantala toward the west-northwest.  That general motion is expected to continue for another 12 to 24 hours.  Guidance from numerical models predicts that in a day or so a second ridge located northeast of Fantala will begin to steer the tropical cyclone back to the southeast.  There is variability in the location and sharpness of the turn to the southeast.  If there is a sharp turn to the southeast, the core of Fantala could remain north of Madagascar.  If the turn occurs later and/or is more gradual the core of Fantala could come closer to the northern end of Madagascar.

Tropical Cyclone Fantala is a very dangerous storm.  It would be capable of causing catastrophic damage if it were to make landfall.

Tropical Cyclone Fantala Almost Equal to Cat. 5 Hurricane

Tropical Cyclone Fantala intensified further on Saturday and it is almost the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  At 8:00 p.m. EDT on Saturday the center of Tropical Cyclone Fantala was located at latitude 11.1°S and longitude 53.4°E which put it about 620 miles north of St. Denis, La Reunion.  Fantala was moving toward the west-northwest at 12 m.p.h. (19 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 Fantala increased in both intensity and size again on Saturday.  Hurricane force winds now extend out about 60 miles (95 km) south of the center of circulation.  The Hurricane Intensity Index (HII) for Fantala is 33.3.  The Hurricane Size Index (HSI) is 18.7 and the Hurricane Wind Intensity Size Index (HWISI) is 52.0.

The circulation of Tropical Cyclone Fantala is very well organized.  It has a clearly visible eye on satellite imagery.  The eye is surrounded by a ring of strong thunderstorms.  Additional bands of thunderstorms are rotating around the core of the circulation.  The thunderstorms are generating strong upper level divergence which is pumping out mass in all directions.

The environment around Tropical Cyclone Fantala is favorable.  It is over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Fantala could intensify a little more during the next 24 hours.  If one of the rainbands wraps around the existing eye, and eyewall replacement cycle could cause fluctuations of intensity.

A subtropical ridge southwest of Fantala is steering the tropical cyclone toward the west-northwest.  That general motion is expected to continue for another 24 to 36 hours.  In a day or so Fantala will move into an area where the steering currents are weaker and it could slow down or stall.  Eventually a northwesterly flow is forecast turn Tropical Cyclone Fantala back toward the southeast.  However, guidance from numerical models differs on when and where the southeasterly turn will occur.

On its anticipated track Tropical Cyclone Fantala could be near the northern end of Madagascar in a day or two.  The current size and intensity of Fantala means that it could produce regional significant damage if it were to hit land.  The future track of Fantala will determine if the tropical cyclone has an impact on Madagascar.