Category Archives: Indian Ocean

Tropical Low Develops Near Coast of Western Australia

A distinct low level center of circulation developed in an area of thunderstorms near the coast of Western Australia on Tuesday and the Australian Bureau of Meteorology classified the system as a Tropical Low.  At 10:00 p.m. EST on Tuesday the center of the Tropical Low as located at latitude 17.2°N and 122.3°E which put it just inland east of Coulomb Point and about 55 miles (85 km) north of Broome, Australia.  The Tropical Low was moving toward the southwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 998 mb.

Although the center of circulation was over land, the circulation of the Tropical Low became much better organized on Tuesday.  There was a well defined center of circulation and weather radar images indicated an eyelike feature at the center of the Tropical Low.  Several bands of showers and thunderstorms wrapped around the center of circulation.  Storms in the core of the Tropical Low were generating well developed upper level divergence which was pumping mass away in all directions.

The Tropical Low will move through an environment favorable for intensification during the next 24 to 36 hours.  The Sea Surface Temperature of the water off the coast of Western Australia is near 30°C.  The Tropical Low is underneath an upper level ridge and the upper level winds are not very strong.  There is little vertical wind shear.  The only factor inhibiting intensification is the fact that the center is still inland over Western Australia.  If the center moves over water as is forecast, the Tropical Low will intensify and it could intensify rapidly.

The Tropical Low is moving around the western end of a mid-level ridge which is steering it toward the southwest.  The ridge is forecast to steer the Tropical Low toward the southwest for another 12 to 24 hours.  When the Tropical Low reaches the western end of the ridge, it will move more toward the south.  On its anticipated track the center of the Tropical Low will move off the coast of Western Australia and over water during the next 6 to 12 hours.  The center of the Tropical Low is expected to pass west of Broome.  The Tropical Low could approach the coast of Western Australia between Bidyadanga and Wallal Downs in about 36 hours.

The Tropical Low will drop heavy rain along the coast of Western Australia during the next 48 hours.  It will also bring gusty winds and a Warning has been issued for the portion of the coast from Cape Leveque to De Grey.

Tropical Cyclone 04B Develops Over Northern Bay of Bengal

Tropical Cyclone 04B developed over the northern Bay of Bengal on Friday.  The circulation around an area of low pressure southeast of India strengthened on Friday and the Joint Typhoon Warning Center (JTWC) designated the system as Tropical Cyclone 04B.  Data from a scatterometer on a satellite indicated there were winds to 45 m.p.h. (75 km/h) in the western part of the circulation.  The Indian Meteorological Department was classifying the low pressure system as a depression and that was why it did not have a name.

At 4:00 p.m. EDT on Friday the center of Tropical Cyclone 04B was located at latitude 18.7°N and longitude 86.9°E which put it about 340 miles (550 km) southwest of Kolkata, India.  It was moving toward the north at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 994 mb.

Although there was a well defined low level center of circulation, the rest of the circulation of Tropical Cyclone 04B was not particularly well organized.  There were no strong thunderstorms near the center of circulation.  The stronger thunderstorms were occurring in a rainband 80 miles (130 km) northeast of the center of circulation.  Other bands revolving around the center consisted primarily of low clouds and showers.

Tropical Cyclone 04B is moving through an environment that is only marginally favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 28°C.  So, there is enough energy in the upper ocean to support intensification, but that is about the only factor favorable for intensification.  Tropical Cyclone 04B is moving underneath the western end of an upper level ridge.  The ridge is producing southeasterly winds which are blowing across the top of the circulation.  Those winds are also causing moderate vertical wind shear and the shear is probably the reason why the band of thunderstorms is displaced northeast of the center of circulation.  It also appears that the western side of the circulation of Tropical Cyclone 04B is also pulling some drier air from over India into the system.  Tropical Cyclone 04B is unlikely to intensify due to the effects of moderate wind shear and drier air.

The upper level ridge is steering Tropical Cyclone 04B toward the north.  On its anticipated track Tropical Cyclone 04B could make landfall near Kolkata in 24 to 30 hours.  The primary risk is locally heavy rain which could cause flooding.  The rain is likely to reach northeastern India a few hours before the center of circulation makes landfall.

Tropical Cyclone Ockhi Moves Closer to India

Tropical Cyclone Ockhi moved closer to India on Monday.  At 10:00 p.m. EST on Monday the center to Tropical Cyclone Ockhi was located at latitude 17.9°N and longitude 70.7°E which put it about 170 miles (270 km) west-southwest of Mumbai, India and about 250 miles (400 km) southwest of Surat.  Ockhi was moving toward the northeast at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 983 mb.

An upper level trough over the northern Arabian Sea was producing strong southwesterly winds which were blowing across the top of Tropical Cyclone Ockhi.  Those winds were causing significant vertical wind shear.  Microwave satellite imagery was indicating that the shear may be strong enough to push the upper part of Ockhi’s circulation to the northeast of the lower part of the tropical cyclone’s circulation.  The circulation in the middle and upper levels continued to show evidence of an eye surrounded by a ring of strong storms.  Several bands of strong storms were occurring north of the center of circulation.

The upper level trough is steering Tropical Cyclone Ockhi toward the northeast and that general motion is expected to continue for several more days.  On its anticipated track Ockhi will make landfall in Gujarat along the coast of the Gulf of Khambhat within 24 hours.  Strong vertical wind shear will continue to weaken Tropical Cyclone Ockhi.  Ockhi is likely to make landfall as the equivalent of a tropical storm.  Drier air is wrapping around the southern side of the circulation.  The heavy rain will fall over parts of Gujarat before the center of circulation reaches the coast.  Locally heavy rainfall could create the potential for flash floods in some places.

Tropical Cyclone Ockhi Turns Back Toward India

Tropical Cyclone Ockhi turned back toward India on Sunday night as it moved over the eastern Arabian Sea.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Ockhi was located at latitude 14.6°N and longitude 68.9°E which put it about 405 miles (650 km) southwest of Mumbai, India.  Ockhi was moving toward the north-northeast at 7 m.p.h. (11 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 976 mb.

Tropical Cyclone Ockhi started to weaken on Sunday.  An upper level trough over the northern Arabian Sea was producing southwesterly winds which were causing moderate vertical wind shear.  In spite of the weakening trend, the structure of Tropical Cyclone Ockhi remained well organized.  There was a circular eye at the center of Ockhi.  A ring of strong storms surrounded the eye, but the ring was broken east of the center of circulation.  Several bands of showers and thunderstorms were occurring north of the core of Tropical Cyclone Ockhi.  The bands in the other parts of the circulation consisted primarily of low clouds and showers.  It appeared that some drier air might be wrapping around the southern and western parts of the circulation.  Winds to hurricane/typhoon force extended out about 50 miles (80 km) from the center or circulation.  Winds to tropical storm force extended out about 180 miles (290 km) from the center.

Tropical Cyclone Ockhi is likely to continue to weaken.  The upper level trough will continue to produce significant vertical wind shear over Ockhi.  The wind shear and drier air will weaken Ockhi to the equivalent of a tropical storm on Monday.  Some models dissipate the circulation of Ockhi before it makes a landfall in India, while other models move a weakened Tropical Cyclone inland before it dissipates.

The trough over the northern Arabian Sea will steer tropical cyclone Ockhi toward the northeast during the next several days.  On its anticipated track the center of Tropical Cyclone Ockhi could make a landfall on the coast of India between Mumbai and Veraval in 36 to 48 hours.  Ockhi could bring gusty winds and heavy rain to the Gulf of Khambhat and surrounding land areas in Gujarat.

Powerful Tropical Cyclone Ockhi Churns West of India

Powerful Tropical Cyclone Ockhi churned over the Arabian Sea west of India on Saturday night.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Ockhi was located at latitude 12.1°N and longitude 69.1°E which put it about 535 miles (860 km) south-southwest of Mumbai, India.  Ockhi was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 963 mb.

Tropical Cyclone Ockhi intensified again on Saturday and it was the equivalent of a strong Category 2 hurricane on the Saffir-Simpson Scale.  There was an elliptical eye at the center of circulation.  A ring of strong thunderstorms surrounded the eye, but there was a weaker area in the eastern side of the ring.  Bands of showers and thunderstorms were revolving around the core of the circulation.  The storms around the center of circulation were generating strong upper level divergence which was pumping mass away to the northeast of Tropical Cyclone Ockhi.  Winds to hurricane/typhoon force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.

Tropical Cyclone Ockhi has been moving through an environment favorable for intensification, but it will move into a less favorable environment on Sunday.  Ockhi will continue to move over water where the Sea Surface Temperature is near 29°C.  So, there will be enough energy in the upper ocean to support a strong tropical cyclone.  Tropical Cyclone Ockhi could intensify a little more during the next 12 hours.  However, an upper level trough over Saudi Arabia will approach Ockhi from the west.  Southwesterly winds ahead of the trough will increase the vertical wind shear over Tropical Cyclone Ockhi and the increased shear is likely to cause the tropical cyclone to start to weaken later on Sunday.

Tropical Cyclone Ockhi is moving around the western end of a ridge centered over the Bay of Bengal.  The ridge is steering Ockhi toward the northwest.  Tropical Cyclone Ockhi will turn more toward the north on Sunday when it moves around the western end of the ridge.  The upper level trough approaching Ockhi from Saudi Arabia will steer the tropical cyclone toward the northeast in about 24 hours.  On its anticipated track the center of Tropical Cyclone Ockhi will approach the west coast of India north of Mumbai in about 60 hours.

Tropical Cyclone Ockhi Strengthens to Hurricane Equivalent

Tropical Cyclone Ockhi strengthened to the equivalent of a hurricane/typhoon on Friday as it moved over the Arabian Sea west of India.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Ockhi was located at latitude 9.4°N and longitude 71.7°E which put it about 655 miles (1055 km) south of Mumbai, India.  Ockhi was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 969 mb.

Tropical Cyclone Ockhi continued to intensify on Friday and it is now the equivalent of a hurricane or typhoon.  An eye has appeared intermittently on satellite imagery.  A ring of strong storms surrounded the eye, although there have been occasional breaks in the northeastern segment of the ring.  Additional bands of showers and thunderstorms were occurring outside the core of the circulation.  There were more showers and thunderstorms in the western half of the circulation.  Storms near the core of Tropical Cyclone Ockhi were generating strong upper level divergence which was pumping mass away to the west and north of the cyclone.

Tropical Cyclone Ockhi will continue to be in an environment favorable for intensification for another 24 to 48 hours.  Ockhi will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge east of Ockhi is producing southeasterly winds which are blowing toward the top of the circulation.  Those winds may be the reason why more of the stronger rainbands are in the western half of the circulation.  The winds are also causing some vertical wind shear, but the shear is not strong enough to prevent intensification.  Tropical Cyclone Ockhi is likely to continue to intensify for another 24 to 36 hours and it could become the equivalent of a major hurricane during the weekend.

The upper level ridge is steering Tropical Cyclone Ockhi toward the west-northwest.  Ockhi will move more toward the north when it reaches the western end of the upper level ridge.  Tropical Cyclone Ockhi will approach the midlatitude westerly winds in two or three days and those winds will start to steer Ockhi more toward the northeast.  On its anticipated track Tropical Cyclone Ockhi could approach the west coast of India in three or four days.

Tropical Cyclone Ockhi Strengthens Quickly Southwest of India

Tropical Cyclone Ockhi strengthened quickly southwest of India on Thursday.  At 7:00 a.m. EST on Thursday the center of Tropical Cyclone Ockhi was located at latitude 8.0°N and longitude 76.2°E which put it about 810 miles (1305 km) south-southeast of Mumbai, India.  Ockhi was moving toward the 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.

The core of the circulation of a tropical depression that developed near Sri Lanka on Wednesday organized quickly on Thursday.  A primary rainband wrapped most of the way around the center of circulation and an eye began to appear on some satellite imagery.  The storms in the eyewall were strongest west of the eye and weakest north of the eye.  Additional bands of showers and thunderstorms formed outside the core of the circulation.  Thunderstorms in the core of Ockhi generated strong upper level divergence which was pumping mass away to the north and west of the tropical cyclone.  The divergence was allowing the surface pressure to decrease and the wind speeds to increase.

Tropical Cyclone Ockhi will be moving through an environment favorable for intensification during the next several days.  Ockhi will move over water where the Sea Surface Temperature is near 29°C.  Tropical Cyclone Ockhi is near the western end of an upper level ridge.  The ridge is producing southeasterly winds which are blowing toward the top of the circulation.  Those winds are causing some vertical wind shear, but they are also enhancing the upper level divergence to the north and west of Tropical Cyclone Ockhi.  The positive effects of enhanced divergence will exceed the negative effects of the vertical wind shear.  Tropical Cyclone Ockhi will continue to intensify and it could intensify rapidly.  Ockhi will likely become the equivalent of a hurricane/typhoon within the next 24 hours.

The upper level ridge is currently steering Tropical Cyclone Ockhi toward the west-northwest.  Ockhi will turn more toward the north in a day or two when it reaches the western end of the ridge.   On its anticipated track Tropical Cyclone Ockhi will move farther away from the coast of India during the next 24 to 48 hours.  The outer rainbands on the eastern side of Ockhi will drop locally heavy rain over portions of southern India and flash floods could occur in some places.  Tropical Cyclone Ockhi is likely to turn toward the northeast in three or four days and it could eventually make landfall in western India.

Tropical Depression Forms Near Southern Tip of Sri Lanka

A tropical depression formed near the southern tip of Sri Lanka on Wednesday.  At 7:00 a.m. EST on Wednesday the center of Tropical Depression 96S was located at latitude 6.2°N and longitude 80.0°E which put it about 20 miles (30 km) northwest of Galle, Sri Lanka.  It was moving toward the west-southwest at 4 m.p.h.  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1004 mb.

A center of circulation formed within a cluster of thunderstorms also designated as Invest 91B and the Indian Meteorological Department classified the system as a Depression.  The circulation in the tropical depression was still organizing.  A large, primary rainband wrapped around the southern and western sides of the center of circulation.  Additional bands of showers and strong thunderstorms were forming in the western half of the circulation.  Bands of showers and isolated thunderstorms were developing in the eastern half of the circulation.  Thunderstorms in the primary rainband were generating upper level divergence which was pumping away mass to the west of the depression.

The depression will move through an environment favorable for intensification during the next several days.  It will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge over India is generating easterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear which is probably the reason why most of the stronger thunderstorms are occurring in the western half of the depression.  The vertical wind shear will inhibit intensification, but it is not likely to prevent strengthening.  The depression is likely to intensify into a stronger tropical cyclone during the next several days.

The ridge over India is steering the tropical depression toward the west-southwest.  The ridge is forecast to steer the depression in a generally westerly direction during the next several days.  On its anticipated track the depression will move away from Sri Lanka and the center will pass south of India.  The depression could cause locally heavy rain and flash floods in parts of Sri Lanka and southern India.

Tropical Cyclone Dahlia Forms Southwest of Indonesia

Tropical Cyclone Dahlia formed southwest of Indonesia on Wednesday.  At 10:00 a.m. EST on Wednesday the center of Tropical Cyclone Dahlia was located at latitude 8.4°S and longitude 101.5°E which put it about 320 miles (520 km) west-northwest of Christmas Island.  Dahlia was moving toward the east at 5 m.p.h. (8 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 999 mb.

A center of circulation developed in a cluster of thunderstorms previously designated as Invest 96S and the Australian Bureau of Meteorology named the system Tropical Cyclone Dahlia.  The circulation of Dahlia is still organizing.  A primary rainband wrapped around the southern and western sides of the center.  Additional bands of showers and thunderstorms formed in the western half of the circulation.  Fewer thunderstorms formed in the eastern half of Dahlia.  The thunderstorms near and to the west of the center were generating upper level divergence which was pumping mass away to the west of the tropical cyclone.

Tropical Cyclone Dahlia will be moving through an environment favorable for intensification during the next several days.  Dahlia will move over water where the Sea Surface Temperature is near 29°C.  Dahlia is underneath the northern part of an upper level ridge.  The ridge is producing easterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear, which may be the reason why most of the thunderstorms are west of the center of circulation.  The shear is strong enough to slow the intensification of Dahlia, but it is not strong enough to prevent the tropical cyclone from strengthening.  Tropical Cyclone Dahlia is likely to likely to intensify during the next 24 to 48 hours.

The steering winds around Dahlia are relatively weak and the tropical cyclone is moving slowly toward the east.  The upper level ridge is forecast to shift north and stronger westerly winds are likely to steer Tropical Cyclone Dahlia toward the east at a faster speed.  When Dahlia reaches the southern portion of the upper level ridge in a couple of days, northerly winds diverging from the ridge are likely to steer the tropical cyclone toward the south.

Tropical Cyclone Cempaka Develops South of Java

The organization of a small area of low pressure (also known as Invest 95S) south of Java increased early on Monday and the Badan Meteorologi Klimatologi Dan Geofisika (BMKG) Tropical Cyclone Warning Center in Jakarta designated the system as Tropical Cyclone Cempaka.  At 7:00 a.m. EST on Monday the center of Tropical Cyclone Cempaka was located at latitude 8.8°S and longitude 110.8°E which put it about 70 miles (115 km) south-southeast of Yokyakarta, Indonesia.  Cempaka was moving toward the east- northeast at 5 m.p.h. (8 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 997 mb.

Tropical Cyclone Cempaka has a small but well developed center of circulation.  Radar images from BKMG showed an eyelike feature at the center of circulation.  The strongest winds are occurring in a ring of showers and thunderstorms that surrounds the center.  The stronger storms are in the eastern half of the ring.  Other narrow rainbands are developing outside the core of Cempaka.  Thunderstorms around the center are generating some upper level divergence which is pumping mass away from the tropical cyclone.  Winds to tropical storm force extend out about 40 miles (65 km) from the center of circulation.

Tropical Cyclone Cempaka will be in an environment somewhat favorable for intensification during the next 24 to 48 hours.  Cempaka will move over water where the Sea Surface Temperature is near 29°C.  Tropical Cyclone Cempaka is under an upper level ridge and the upper level winds are weak.  There is little vertical wind shear over the tropical cyclone.  The core of Tropical Cyclone Cempaka is near Java.  Part of the circulation is flowing over Java and nearby islands and friction from those islands is slowing the winds.  Interaction with land is the primary factor inhibiting intensification.  If the center of Tropical Cyclone Cempaka remains south of Java, then it has a chance to intensify.  If Cempaka moves closer to Java, then it could weaken.  Also, since Cempaka is a very small tropical cyclone, an increase in the speed of the upper level winds could blow the top off of the circulation.

Since Tropical Cyclone Cempaka is underneath an upper level ridge, the steering winds are weak.  Cempaka is south of the center of the ridge and weak westerly winds are steering the tropical cyclone slowly toward the east-northeast.  Tropical Cyclone Cempaka is forecast to meander south of Java for several more days because of the weak stearing winds.

Tropical Cyclone Cempaka is producing locally heavy rain over parts of Java, Bali and nearby islands.  The locally heavy rain could cause flash floods as Cempaka meanders south of Java during the next day or two.