Tropical Cyclone 01B Forms Over Bay of Bengal

The structure of a low pressure system north of Sri Lanka changed on Wednesday and it was classified as Tropical Cyclone 01B (TC01B).  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone 01B was located at latitude 15.9°N and longitude 82.3°E which put it about 155 miles (250 km) south-southwest Visakhapatnam, India.  TC01B was moving toward the northeast at 12 m.p.h. (19 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.

A low pressure system developed near Sri Lanka several days ago.  The low moved over the east coast of Sri Lanka, which slowed the organization of the circulation.  A more well defined center of circulation began to organize after the low moved north of Sri Lanka.  A primary rainband started to wrap around the western side of the low and several broken spiral bands formed on the eastern side.  The circulation exhibited enough characteristics associated with tropical cyclones to be classified as Tropical Cyclone 01B.

The circulation of TC01B is still not particularly well organized.  A primary rainband curls around the northern and western sides of the circulation.  However, there are not many thunderstorms in the other parts of the tropical cyclone.  An upper level ridge over the northern Bay of Bengal is generating easterly winds over the top of the tropical cyclone.  Those winds are producing moderate vertical wind shear and are contributing to the fact that most thunderstorms are west of the center of circulation.  The fact that the center of circulation is near the coast of India also means a  portion of circulation is over land, where there is more friction and less moisture.

Tropical Cyclone 01B is expected to move into a more favorable environment during the next two days.  It is over water where the Sea Surface Temperature is near 31°C.  TC01B is expected to move closer to the center of the upper level ridge where the winds are not as strong.  That would reduce the vertical wind shear, which would also be favorable for intensification.  However, the proximity of the center to the east coast of India means that a portion of the circulation will remain over land, which will slow the rate of future intensification.

A ridge is east of TC01B is expected to steer the tropical cyclone toward the northeast during the next two to three days.  On its anticipated track, TC01B could be approaching the coast of Bangladesh in 48 to 72 hours.  TC01B caused heavy rain in parts of Sri Lanka and southeast India.  It could produce more heavy rain in parts of northeast India, Bangladesh and Myanmar (Burma).  TC01B could also generate a significant storm surge along the north coast of the Bay of Bengal as it nears the coast.

Hurricane Season Officially Starts in East Pacific

May 15 is the official start of the hurricane season for the Eastern North Pacific Ocean.  The Sea Surface Temperatures (SSTs) should be cooler than they were in 2015, since the El Niño is dissipating.  That could produce a hurricane season in which the activity is nearer to normal.  In a normal year we might expect 13-17 named storms, 7-10 hurricanes and 3-4 major hurricanes.  Of course, other environmental factors including the location and strength of atmospheric systems will also determine how active the season is.

The National Hurricane Center (NHC) is currently monitoring Invest 90E which is about 950 miles (1530 km) south-southwest of the southern tip of Baja California.  There is a well defined low level circulation in Invest 90E, but there are no deep thunderstorms.  NHC is giving Invest 90E a 20 percent chance of developing into a tropical cyclone during the next five days.

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.