West Pacific/north Indian Ocean Invest Thread 2009

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90W

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90W

[Somerset Squall]

West Pacific:

90W became TS Etau.

Invest 91W has formed, a couple hundred miles east of the Philippines. Deep convection is wrapping into a consolidating LLC, which is showing signs of stronger rotation over time. Waters are ample for further development and shear is low. JTWC are assessing the chances of TC devleopment in the next 24hrs as fair and I reckon there is a good chance of TC formation in the next 48hrs based on the favourable conditions are increased organisation of the system.

Invest 92W has formed, just west of the date line in the far east of the basin. Deep convection has exploded recently in the region but is showing little signs of rotation as yet. Shear is currently moderate to high which may slow or stop further development. Chances for TC development in the near term are poor.

North Indian Ocean:

No invests.

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91W

not looking great either

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91W

looks better

[Somerset Squall]

West Pacific:

Invest 94W is located several hundred miles southwest of TS Maka, around 10N, 160E. Convection is increasing over the system and the LLC is becoming better defined in favourable conditions of low shear and high ocean heat content. There's a good chance of a tropical depression forming later today if this organisational trend continues.

North Indian Ocean:

No invests.

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94W

[Somerset Squall]

West Pacific:

Invest 96W has formed in the south China Sea, just off the west coast of the Philippines. Convection is increasing in the area but is showing little signs of rotation or banding as yet. However, waters are warm and shear is low so further slow development of this system is possible over the next day or two.

North Indian Ocean:

No invests.

[Somerset Squall]

West Pacific:

Invest 90W is located around 20N, 148E, out to sea. A LLC seems to be rapidly developing underneath an expanding area of convection. In addition to the rotation, banding features are beginning to appear too. JTWC have issued a tropical cyclone formation alert on the system based on the current organisation and the fact that the invest is over very warm waters, under low shear and is benifitting from radial outflow. TD12W quite possibly just around the corner.

Invest 92W has formed, just 6 degrees north of the equator and around 163E, which is as far east as where Vamco formed. Disturbances at this lattitude typically don't do very well, there has been a few examples of this this year too. This is due to poor spin due to lack of coriolis force near the equator. Not to say development isn't possible in this area. Convection has truly exploded over 92W this afternoon, but is only showing signs of weak rotation. Shear is fairly low at the moment, however, it may increase furtherthe further west 92W goes. Based on past trends and the possible deterioration of conditions further west, I think chances for TC development in the near term are poor.

North Indian Ocean:

No invests.

[Somerset Squall]

West Pacific;

Invest 90W became TS Krovanh.

Invest 92W dissipated.

Invest 93W has formed, around 700 miles east northeast of the Philippines. 93W consists of a broad and elongated circulation with widespread and persistant convection obscuring it as warm waters and low shear persist, further enhancing it. 93W is experiencing some good outflow, in an equatorward and poleward direction which should allow the LLC to consolidate and tighten. JTWC give the disturbance a fair chance of TC development in the next 24hrs.

Invest 95W has formed in the South China sea, a couple hundred miles southeast of Hainan Island. 95W is showing signs of a consolidating LLC, along with convection flaring and beginning to wrap into the LLC. 95W is sat in a very favourable environment for further development, as shear is set to remain low, waters warm and outflow good. JTWC assess the chances of TC development in the next 24hrs as fair, and I think this system has a good chance of being upgraded beyond this based on the increased organisation and the continued supportive upper level environment.

Invest 97W has formed far out to sea around 8.0N, 158E. A shapeless mass of convection has exploded in the area but is showing only signs of weak rotation at the surface. Shear is low to moderate, equatorward outflow is good but poleward outflow is poor which is preventing convection form forming over the weak mid-low level circulation centre. The ocean heat content in the area support further development, but without poleward outflow further development, if any, will be slow.

North Indian Ocean:

Invest 97B has formed, in the central Bay of Bengal. Disorganised convection has been pulsing in the area, near an ill defined and elongated LLC. Though waters are very warm, shear is moderate to high which is preventing further development. Shear values decrease further north in the northern half of the Bay of Bengal. Unless shear eases or 97B moves into the region of lower shear, TC development appears unlikely.

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busy busy thanks for the updates.€

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97B

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97B has briefly become TC03B, with intensity currently at 35kts, but it is already heading inland and will dissipate soon.

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West Pacific:

Invest 93W became TS Dujuan.

95W came close to tropical depression status before moving westwards inland across the coast of Vietnam. However, 95W has wondered south-southeastwards and is now back over water, just off the coast. The LLC remains well defined, especally as it's been over land, but convection is not directly over the centre and instead resides to the west over land. This could be due to moderate shear. Shear is not expected to increase, so some development of this system is still possible if it doesn't move back inland. Preferably, for a better chance, 95W will need to move a bit further away from the coast. 95W, at the moment, is quasi-stationary.

Invest 97W has dissipated.

Invest 90W has formed, just off the west coast of Luzon in the south China Sea. Disorganised convection is showing signs of broad rotation around an elongated, ill defined circulation. Shear is low and waters warm, so some slow development is possible. Due to the broad nature of the system however, it may really take it's time.

Interesting to note aswell before I talk about the North Indian Ocean invest, is that the West Pacific is still significantly below average in terms of activity. The East Pacific is ahead of the West Pacific (15 TC's so far here compared to the West Pacific's 13) which is unusual in itself. There has been a lack of real intense storms in this basin too, with the strongest storms only having peaks of 115kts (Kujira and Vamco). This compares to 135kts in the East Pacific from Jimena, though it is thought this storm was actually stronger than that and was actually possibly a cat 5. For a moderate El Nino event, the lack of activity in this basin is quite unusual, and intersting to note.

North Indian Ocean:

Invest 98B has formed in the northern half of the Bay of Bengal. The system is moving northwards and is close to moving inland on the Indian/Bangladeshi border. 98B is in a favourable environment, just like 97B was when it briefly became TC03B in the same area, but 98B lacks that same organisation. Despite convection being deep and concentrated, the LLC is still rather elongated and is probably not closed. Therefore, I think development is not that likely before the system moves inland within the next 24hrs.

[Cookie]

interesting read SS.

do you think the East Pacific has peaked yet or do you think it will keep churning them out?

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We are just at peak now for the East Pacific, so the basin may throw some more big storms out this September with a gradual decline in activity in the first half of October with a rapid drop off after that. That is if Mother Nature keeps to plan of course!

The Atlantic peak is the 10th September on average if I remember rightly. We should see some more cape-verde systems like Fred over the next couple weeks if conditions remain favourable.

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thanks, SS, well we all know what mother nature is like with her curve balls and catching us off guard.

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West Pacific:

Invest 95W dissipated, but not before causing serious flooding over the east coast of Vietnam and killing 6 people, with 3 missing

Wiki article (JMA montitored this sytem as a tropical depression): http://en.wikipedia.org/wiki/September_2009_Vietnam_tropical_depression

Invest 90W became Tropical Storm Mujigae.

Invest 91W has developed a couple hundred miles to the southeast of Luzon. Convection is beginning to consolidate around a developing LLC. The environment is marginal, with moderate to high shear over the system but very warm waters and good westward outflow. Looking at the CIMSS shear charts however, shear looks like it is easing in the area which may promote more steady development.

Current shear:

The area we are looking at is just east of the Philippines. As you can see shear is at an unfavourable level of 30kts, but the westward outflow channel is probably combating this to tighten up the LLC and keep convection persistant. However, in the next chart, if you look at the same area you can see the shear is easing, this should allow 91W to further develop:

Therefore, as it currently stands, I think 91W has a good chance of becoming the next tropical depression of the West Pacific season in the next couple of days. JTWC are forecasting a fair chance of formation in the next 24hrs.

Invest 92W has formed, very near 91W, between that disturbance and Luzon in fact. Deep convection is exploding in the area and an LLC appears to be forming. Shear is high as with 91W, but should ease as I have shown above. However, I can't see this one developing. If it goes west, it will interact with Luzon which will probably dissipate over the rugged terrain of Luzon (the only chance of development then is if the disturbance survives and then goes on to develop in the South China Sea. If it moves east, it will likely be absorbed by invest 91W, which is the much larger disturbance. If both disturbances actually manage to develop into tropical depressions, Fujiwhara interaction is very likely. However, I think this chance is poor for 92W.

Invest 93W has formed, around 14N, 155E, out to sea. Waters are warm and shear is currently low over the system, though it increases further north. Disorganised convection is showing signs of increasing and even a little rotation. As long as 93W moves west then some slow development is possible.

North Indian Ocean:

No invests.

Images of the 3 West Pacific invests, from left to right- 91W, 92W & 93W:

[Somerset Squall]

West Pacific:

91W has changed little this evening, and is approaching Luzon. Land interaction with Luzon could potentially halt development in the near term, but as shear is low and waters warm in the area, 91W may be able to develop further once interaction ceases.

92W has been absorbed by 91W.

93W has become much better organised this evening and JTWC have issued a tropical cyclone formation alert on the system. Convection has exploded this evening and become very concentrated over an area of pronounced turning. Conditions are favourable with low shear, warm sea temps and excellent poleward outflow persisting. If current trends continue, then 93W could become a tropical depression tomorrow.

North Indian Ocean:

No invests.

[Somerset Squall]

West Pacific:

Invest 91W became Typhoon Koppu.

Invest 93W became Super Typhoon Choi-wan.

Invest 95W has formed just off the coast of Vietnam. This is a bit of a coincidence, as the last invest 95W formed in the exact same area. 95W is displaying some patchy convection around the weak LLC. Conditions are favourable for development has shear is low and waters warm. However, land interaction could be a possible limiting factor in the long run. As it stands, chances of TC development in the near term is poor due to the disorganised state of the system coupled with the possible land interaction.

Invest 96W has formed to the east of Luzon. Convection is concentrating over a consolidating LLC. The environment is very good, with low shear, warm sea temps and enhanced poleward outflow. I think there is a good chance of this one becoming a tropical depression over the next day or so.

Invest 97W has formed a few hundred miles south-southeast of Tokyo, Japan. Whilst shear is currently low, waters are marginally warm and cold, dry air is wrapping around the LLC. The effects of this are clearly shown on satellite imagery; the LLC is well defined but it is lacking any significant convection. Shear rapidly increases further north. All considered, I think this system has a poor chance of TC formation.

Invest 98W has formed, around 7N, 170E. Deep convection is flaring widely in the disturbed area, and is showing signs of weak rotation though it is unclear if it is at low level. Shear is low and waters are gradually becoming warmer on the westerly heading. Some slow development is possible over the next day or two.

North Indian Ocean:

No invests.

[Somerset Squall]

West Pacific:

95W has become better organised over the last 24hrs, and convection appears to be slowly consolidating around a broad LLC. However, it may be too little too late for this system. 95W is located in the Gulf Of Tonkin and is very close to land, and more than likely will move inland before it has time to organise into a tropical depression.

96W has changed little in organisation over the last 24hrs. Deep convection persists in the vicinty of the LLC, but has not fully wrapped around it yet. Conditions are still ok, shear is moderate and waters warm. JTWC have issued a tropical cyclone formation alert on the system. Despite the modest increase in shear, I still think this one has a good chance of spawning a tropical depression over the next day or so.

97W remains unimpressive. The LLC is well defined, and even closed. If this system had even a modest amount of convection it would be upgraded. However, 97W is still battling dry air, and shear is also rapidly increasing over the LLC. Chances for further development remain poor.

98W is slowly organising. Deep convection is consolidating over an increasingly well defined LLC. Shear is low and waters are warm in the area. This system has a fair chance of becoming a tropical depression in the next few days IMO, though not in the next 24hrs as the LLC needs to consolidate a little bit more first.

Invest 99W has formed, a few hundred miles west of 98W- around 6N, 150E. Deep convection is showing signs of rotation suggesting a low pressure area could be forming. However, shear is moderate and may increase further towards the west, perhaps up to 30kts. This will likely hamper further development. If shear lessens however, 99W already has the deep convection as a base for development. In terms of TC development currently, poor chance at best IMO.

North Indian Ocean:

No invests.

[Cookie]

Busy busy

96W

THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 14.7N

129.4E, IS NOW LOCATED NEAR 14.5N 128.9E, APPROXIMATELY 455 NM EAST

OF MANILA, PHILIPPINES. RECENT ANIMATED INFRARED SATELLITE IMAGERY

INDICATES THAT CENTRAL CONVECTION CONTINUES TO ORGANIZE AND BUILD

AROUND A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) THAT

IS ELONGATED IN AN EAST TO WEST ORIENTATION. THE DEEPEST CONVECTION

IS CURRENTLY FOUND TO THE WEST OF THE LLCC, AND IS BEGINNING TO WRAP

TOWARDS THE CENTER FROM THE SOUTHWEST. A 241201Z ASCAT IMAGE

INDICATES VERY STRONG WESTERLIES (20+ KNOTS) TO THE SOUTH OF AN

ELONGATED AND CONSOLIDATING LLCC. UPPER LEVEL SUPPORT IS MARGINAL

FOR CONTINUED DEVELOPMENT WITH LOW TO MODERATE VERTICAL WIND SHEAR

ASSESSED AT 10 TO 20 KNOTS. BROAD EQUATORWARD VENTING IS LIKELY TO

BE THE MAIN EXHAUST MECHANISM AS THE LLCC CONTINUES TO CONSOLIDATE.

MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS.

MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 MB. THE

POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE

WITHIN THE NEXT 24 HOURS REMAINS GOOD.

97W

strange little system this one.

98W

looking good

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98W

[Somerset Squall]

West Pacific:

95W dissipated.

96W became Tropical Storm Ketsana.

97W dissipated.

98W continues to develop. The LLC is becoming better defined and convection is persistant over the LLC. Shear is low and waters remain warm, and for this reason JTWC have issued a tropical cyclone formation alert on the system. The eighteenth TC of the West Pacific season seems to be just around the corner.

99W has not changed in appearance since I last posted. Though convection is deep, rotation is still weak at best showing the lack of a decent LLC. The LLC probably hasn't developed due to the high shear, but the shear is now easing which may allow for some slow development over the next day or two.

North Indian Ocean:

No invests.

[Somerset Squall]

West Pacific:

98W became TD18W.

99W became TD19W.

Invest 90W has formed well southeast of TD18W, not far west of the dateline and just 4 degrees north of the equator. Shear is moderate which may slow development, and the fact that the disturbance is located so near the equator may also slow development due to lack of spin. Despite this, a weakly defined LLC appears to be forming with patchy convection over this centre. In addition, a weak convectional band stretches out towards the southwest. Some slow development is possible over the coming days.

North Indian Ocean:

Invest 99B has formed in the northern Bay of Bengal. Waters are warm and shear is low which supports the idea of further development. A weak LLC is present, but there is currently little convection associated with the disturbance. In addition, 99B is close to land and could make landfall at any time, which adds some uncertainty to future intensity. With the developing LLC and favourable conditions, some slow developement is likely but only if the circulation stays over water.