Category Archives: Indian Ocean

Tropical Cyclone Vardah Reaches Hurricane Intensity

Tropical Cyclone Vardah intensified into the equivalent of a hurricane on Saturday as it moved across the Bay of Bengal toward India.  At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Vardah was located at latitude 13.0°N and longitude 84.8°E which put it about 290 miles (470 km) east of Chennai, India.  Vardah was moving toward the west at 13 m.p.h. (21 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 974 mb.

The circulation of Tropical Cyclone Vardah is well organized, but the distribution of thunderstorms is asymmetrical.  There is a broken ring of thunderstorms around the center of circulation.  Outside of that ring most of the thunderstorms are forming in the western half of the circulation.  It appears that an upper level ridge to the north of Vardah is producing easterly winds which are causing moderate vertical wind shear.  The wind shear seems to be the primary cause of the asymmetry of the convection.  The thunderstorms are generating upper level divergence which is pumping out mass to the west of the cyclone.

The environment around Tropical Cyclone Vardah is marginal for further intensification.  Vardah is moving over water where the Sea Surface Temperature is near 29°C.  However, the moderate vertical wind shear may be strong enough to inhibit further intensification.  There are some indications that the upper level winds may be getting stronger and the shear could increase.  If the shear increases, then Tropical Cyclone Vardah could start to weaken even though it is over warm water.

The same ridge that is causing the wind shear is also steering Tropical Cyclone Vardah toward the west and that general motion is expected to continue.  On its anticipated track Tropical Cyclone Vardah could make landfall near Chennai, India in about 36 hours.  Tropical Cyclone Vardah will bring gusty winds and locally heavy rain to portions of southern India.  The heavy rain could cause flooding and mudslides.  Vardah will also cause a storm surge along the coast near and to the north of where the center makes landfall.

Tropical Cyclone Vardah Turns Toward India and Strengthens

Tropical Cyclone Vardah turned toward India and strengthened on Friday.  At 4:00 p.m. EDT on Friday the center of Tropical Cyclone Vardah was located at latitude 12.5°N and longitude 88.7°E which put it about 500 miles (800 km) southeast of Visakhapatnam, India.  Vardah was moving toward the west-northwest at 13 m.p.h. (21 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 985 mb.

Many more thunderstorms formed around the core of Tropical Cyclone Vardah and it exhibited a more symmetrical, circular shape on Friday.  The increasing organization of the circulation include multiple spiral rainbands in the outer portions of the cyclone.  The thunderstorms near the core of Vardah generated strong upper level divergence which pumped out mass and allowed the pressure to decrease more quickly.  An increased pressure gradient force generated stronger winds.

The environment around Tropical Cyclone Vardah has become much more favorable for intensification.  An upper level ridge to the east of Vardah was causing southeasterly winds and was producing moderate vertical wind shear.  Those winds have diminished and the wind shear is much less.  Since Vardah is moving over water where the Sea Surface Temperature is near 29°C, it is efficiently extracting energy from the ocean.  Tropical Cyclone Vardah will continue to intensify during the next 24 hours and it could intensify rapidly.  Vardah is likely to become the equivalent of a hurricane on Saturday.

A subtropical ridge north of Vardah is strengthening and building toward the west.  The ridge is steering Tropical Cyclone Vardah toward the west-northwest and that general motion is expected to continue.  On its anticipated track Tropical Cyclone Vardah could approach the coast of southeast India in two or three days.

Tropical Cyclone Vardah could bring strong winds and heavy rain to parts of southeastern India in three or four days.

Tropical Cyclone Forms Near Andaman Islands

A tropical cyclone formed near the Andaman Islands over the Bay of Bengal on Wednesday.  At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone 05B was located at latitude 11.6°N and longitude 92.1°E which put it about 710 miles (1145 km) southeast of Visakhapatnam, India.  The tropical cyclone was moving toward the north-northeast at 5 m.p.h. (8 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 997 mb.

An area of thunderstorms moved from the western Pacific Ocean into the southeastern Bay of Bengal.  The area of thunderstorms turned slowly northward near the Nicobar and Andaman Islands.  A distinct center of circulation began to organize inside the area of thunderstorms.  The Indian Meteorological Department classified the low pressure area as a depression and the Joint Typhoon Warning Center designated the system as Tropical Cyclone 05B.

The circulation of Tropical Cyclone 05B is still organizing.  A primary band of thunderstorms wraps around the northern and western side of the center of circulation.  Additional bands of thunderstorms are forming in the eastern half of the circulation.  Microwave satellite imagery suggests that an eye could be developing in the middle levels of the circulation.  The thunderstorms near the center are generating upper level divergence that is pumping out mass toward the northeast of the tropical cyclone.

Tropical Cyclone will be moving through an environment that is favorable for intensification.  It will be moving over water where the Sea Surface Temperature is near 29°C.  An upper level ridge to the west of the cyclone is producing northerly winds which are blowing across the top it.  However, the vertical wind shear is not significantly inhibiting the organization of the tropical cyclone.  Tropical Cyclone 05B could reach hurricane intensity in a couple of days.

A subtropical ridge is currently steering Tropical Cyclone 05B toward the north.  The center is moving just to the west of the Andaman Islands.  The subtropical ridge is forecast to strengthen and build toward the west.  As the ridge strengthens and extends farther west, it will start to steer the tropical cyclone toward the west.  On its anticipated track Tropical Cyclone 05B could approach the east coast of India in three or four days.

Tropical Cyclone 05B will continue to bring gusty winds and heavy rain to parts of the Andaman Islands on Thursday.  The tropical cyclone could bring strong winds, locally heavy rain, a storm surge and mudslides to southern India in a few days.

Tropical Cyclone Nada Develops Near Sri Lanka

Tropical Cyclone Nada developed over the Bay of Bengal near Sri Lanka.  At 10:00 a.m. EDT on Wednesday the center of Tropical Cyclone Nada was located at latitude 10.1°N and longitude 83.5°E which put it about 295 miles (475 km) east-southeast of Chennai, India.  Nada was moving toward the west-northwest at 14 m.p.h. (23 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 997 mb.

Microwave satellite imagery indicates that Tropical Cyclone Nada has a well organized, circular low level circulation.  However, most of the thunderstorms are occurring in bands southwest of the center and north of the center.  There are mostly low clouds and showers in the circular bands south and east of the center of circulation.  An upper level ridge over the northern Bay of Bengal is producing easterly winds which are causing moderate vertical wind shear.  The upper level easterly flow is inhibiting the development of thunderstorms east of the center of Tropical Cyclone Nada and those winds may be tilting the circulation toward the west.

The environment surround Tropical Cyclone Nada consists of factors that are favorable for intensification and factors that are unfavorable.  Tropical Cyclone Nada is moving over water where the Sea Surface Temperature is near 29°C.  So, there is sufficient energy in the upper ocean to support intensification.  However the easterly winds in the upper levels are restricting upper level divergence to the east of the tropical cyclone.  Moderate vertical wind shear will limit intensification unless the upper level winds weaken.  If the upper level winds do weaken, then Nada could strengthen given its well developed low level circulation.  Tropical Cyclone Nada only has about 24 to 30 hours before it reaches the coast of India and it will start to weaken once it moves over land.

A subtropical ridge north of Nada is steering the tropical cyclone toward the west-northwest and that general motion is expected to continue.  On its anticipated track the center of Tropical Cyclone Nada will pass north of Sri Lanka and it will approach the southeast coast of India in 24 to 30 hours.  Nada is likely to make a landfall south of Cheannai, India near Pondicherry.  Tropical Cyclone Nada is expected to continue to move to the west and it could emerge over the Arabian Sea in two or three days.

Tropical Cyclone Nada will bring gusty winds and locally heavy rain to northern Sri Lanka and southern India.  Locally heavy rain could cause flooding and mudslides in parts of northern Sri Lanka and Tamil Nadu, Kerala and Karnataka states in India.

Tropical Cyclone Kyant Forms Over Bay of Bengal

Tropical Cyclone Kyant formed over the Bay of Bengal on Tuesday.  At 11:00 a.m. EDT on Tuesday the center of Tropical Cyclone Kyant was located at latitude 16.6°N and longitude 90.4°E which put it about 480 miles (770 km) east of Vishakhapatnam, India.  Kyant was moving toward the west at 7 m.p.h. (11 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 994 mb.

A cluster of thunderstorms persisted over the eastern Bay of Bengal during the past few days, but strong upper level easterly winds prevented the development of the system.  The upper level winds began to diminish on Monday and a low level circulation center began to develop on the eastern edge of the area of thunderstorms.  When the upper level winds became weaker, then thunderstorms were able to develop closer to the center of circulation.  The system acquired the structural characteristics associated with a tropical cyclone and the India Meteorological Department named it Kyant.

The circulation of Tropical Cyclone Kyant is still organizing.  Some vertical wind shear continues because of easterly upper level winds being generated by a ridge northeast of the tropical cyclone.  The shear is causing more of the thunderstorms to form in the western half of the circulation.  However, additional thunderstorms have developed closer to the center in recent hours and some spiral rainbands have formed.  The thunderstorms near the center are generating upper level divergence which is starting to pump out mass in all directions.

Tropical Cyclone Kyant will be moving through a favorable environment during the next several days.  It will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds should remain weaker, and the vertical wind shear will not be strong enough to prevent strengthening.  Tropical Cyclone Kyant is likely to intensify and it could undergo a period of rapid intensification.

The upper level ridge is steering Tropical Cyclone Kyant toward the west and that general motion is expected to continue.  On its anticipated track Tropical Cyclone Kyant could approach the east coast of India in about 48 hours.  It could bring strong winds and very heavy rain to portions of eastern India later this week.

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.