Category Archives: Indian Ocean

Tropical Cyclone Abela Forms over the South Indian Ocean in the Middle of Winter

Tropical Cyclone Abela formed over the South Indian Ocean in the middle of winter on Sunday.  At 5:00 p.m. EDT on Sunday the center of Tropical Cyclone Abela was located at latitude 12.9°S and longitude 62.4°E which put it about 640 miles (1030 km) northeast of Port Louis, Mauritius.  Abela was moving toward the west-southwest at 18 m.p.h. (29 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.

Enough spiral banding developed in a low pressure system over the South Indian Ocean to allow the system to be classified as Tropical Cyclone Abela.  The circulation is not well organized.  Most of the thunderstorms were located in a thin primary rainband that wrapped around the western side of the center of circulation.  The other rainbands contained shallower clouds.  There was enough convection to produce some upper level divergence.  Winds to tropical storm force extend out about 150 miles (240 km) from the center of circulation.

The environment around Tropical Cyclone Abela is only marginal for further intensification.  It is moving over water where the Sea Surface Temperature (SST) is near 26°C.  Northeasterly winds in the upper levels are creating a moderate amount of vertical wind shear.  The wind shear will limit the potential for intensification during the short term.  In about a day or so Abela will move over cooler SSTs and it should start to weaken.

A ridge of high pressure located east of Abela is steering the tropical cyclone toward the west-southwest and that general motion is expected to continue for another day or two.  On its anticipated track Tropical Cyclone Abela will pass north of Mauritius and La Reunion.  Abela is expected to reach the western end of the ridge and recurve toward the south as it nears the east coast of Madagascar.

Tropical Cyclone Roanu Nearing Bangladesh

Tropical Cyclone Roanu moved closer to the northern coast of the Bay of Bengal on Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Cyclone Roanu was located at latitude 20.3°N and longitude 87.8°W which put it about 200 miles (320 km) south of Kolkata, India and about 355 miles (575 km) west-southwest of Chittagong, Bangladesh.  Roanu was moving toward the northeast at 11 m.p.h. (18 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 983 mb.

On Friday Tropical Cyclone Roanu went through another cycle in which most of the thunderstorms dissipated near the center of circulation and then convection redeveloped rapidly.  Thunderstorm activity is increasing at the core of the circulation and those storms are driving well developed upper level outflow.  Several well formed bands of thunderstorms are rotating around the center of circulation.  Roanu is more organized and it is a little more intense than it was 24 hours ago.

Tropical Cyclone Roanu is in an environment that could support a little more intensification before it makes landfall on the north coast of the Bay of Bengal.  It is over water where the Sea Surface Temperature is near 30.5°C.  Roanu is under an upper level ridge which means the upper level winds are light and there is not much vertical winds shear.  However, Roanu is getting closer to the north coast of the Bay of Bengal and it only has another 12 hours or so to intensify.

A ridge east of Roanu is steering the tropical cyclone toward the northeast and that general motion is expected to continue for the next several days.  On its anticipated track Tropical Cyclone Roanu will be near the coast of Bangladesh in about 12 hours.  Roanu is expected to continue moving toward the northeast after it makes landfall.

Although Tropical Cyclone Roanu could cause some minor wind damage, its main threats will be locally heavy rain and a moderate storm surge.  Tropical Cyclone Roanu could produce locally heavy rainfall, especially if the thunderstorm activity continues to pulse diurnally.  The heavy rain could produce significant fresh water flooding over parts of northeastern India, Bangladesh and Myanmar (Burma).  In addition, the winds on the eastern side of Tropical Cyclone Roanu will be blowing toward the coast of Bangladesh and those winds will push water toward the coast.  The north coast of the Bay of Bengal is particularly susceptible to storms surges and Roanu could bring a moderate storm surge to the coast of Bangladesh.  The surge will be higher in the mouths of rivers and other locations where the shape of the coast funnels the water into specific locations.

Tropical Cyclone Roanu Threatens Northern Bay of Bengal

Tropical Cyclone Roanu intensified on Thursday and it poses an increasing threat to the northern Bay of Bengal.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Roanu was located at latitude 17.9°N and longitude 84.9°E which put it about 125 miles (200 km) east of Visakhapatman, India and about 580 miles (935 km) west-southwest of Chittagong, Bangladesh.  Roanu was moving toward the north-northeast at 14 m.p.h. (23 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 70 m.p.h. (115 km/h).  The minimum surface pressure was 986 mb.

Most of the thunderstorms in Tropical Cyclone Roanu weakened earlier today and at times it did not look much like a tropical cyclone on satellite imagery.  However, a burst of thunderstorm activity near the center of Roanu has occurred in recent hours and an eyelike feature has appeared on conventional satellite imagery.  The structure of the circulation improved as a result of the new burst of thunderstorms.  The primary rainband now coils more tightly about three quarters of the way around the apparent center of circulation.  The thunderstorms near the center of circulation are generating upper level divergence which is pumping out mass in all directions.  Several additional bands of thunderstorms have developed over the eastern half of the circulation and Tropical Cyclone Roanu is stronger than it was 24 hours ago.

Tropical Cyclone Roanu is in an environment favorable for intensification.  It is over water where the Sea Surface Temperature is near 31°C.  Roanu has moved closer to the center of an upper level ridge and the upper levels are not as strong as they were yesterday.  As a result the vertical wind shear is much less and the upper level ridge is actually helping to pump mass away from the center of Roanu.  The center of the tropical cyclone is near the east coast of India, but the core is expected to remain over water on Friday.  Roanu is likely to strengthen further and it could reach hurricane/typhoon intensity.

A ridge east of Roanu is steering the tropical cyclone toward the northeast and that general motion is expected to continue.  On its anticipated track Roanu could be south of Kolkata, India in about 18 hours.  Tropical Cyclone Roanu could be approaching Chittagong, Bangladesh in 24 to 36 hours.

Tropical Cyclone Roanu poses a significant threat to the northern Bay of Bengal.  That area is vulnerable to storm surges.  Since Roanu will approach from the southwest, the winds in its counterclockwise circulation will push water toward the north coast of the Bay of Bengal.  In addition, a strengthening Tropical Cyclone Roanu will be capable of producing locally heavy rain which could cause inland flooding.

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.

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.

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 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.