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Somerset Squall

Southern Hemisphere Invest Thread 2010/2011

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South Indian Ocean:

Invest 91S has formed near 10S 86E, some 800 miles east of Diego Garcia. Although this is the second invest of the season (the first, 90S, briefly developed last week), it is the first with a real shot at developent. Sea temperatures have been gradually increasing over the last few weeks, and 91S has found itself in an area of decreasing shear. This has allowed a shallow area of convection to persist near a broad LLC. With the sufficiently warm water and low shear, some slow development is possible this week, and this system has about a 30% chance (IMO) of becoming the South Indian Ocean's first tropical cyclone of the season this week.

South Pacific:

No invests.

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South Indian Ocean:

91S became Tropical Cyclone 01S.

Invest 92S has formed to the northeast of the Cocos Islands. Deep convection is already consolidating over a developing LLC. In addition, banding features are forming readily, wrapping towards the LLC. If current trends continue, then this could become the second tropical cyclone of the season. Shear is low and waters are very warm which should aid further development. BOM mention that the invest (which will probably be a cyclone by this point) will pass very close to the Cocos Islands themselves, so 92S needs watching.

South Pacific:

No invests.

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South Indian Ocean:

92S continues to become better organised and is nearing tropical cyclone strength. The LLC has sustained winds of 30kts this morning, with deep convection wrapping around the southern and western quadrants. Convection is still a little thin on the eastern side due to moderate shear, but 92S is expected to move southwards into lower shear over the next day or two, which should promote intensification. BOM have issued thier first advisory on this system as a tropical low, indicating that the environment is favourable for a fairly potent cyclone near the Cocos Islands. Therefore, 92S still needs to be closely watched by residents.

South Pacific:

No invests.

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South Indian Ocean:

92S became Tropical Cyclone Anggrek.

Invest 95S has formed about 850 miles east-southeast of Diego Garcia, around 10S 86E. Convection is slowly beginning to wrap towards a developing LLC. Moderate shear has impinged on the development of this disturbance over the last day or two, but is expected to ease. This, along with strengthening poleward outflow, should aid further development. JTWC give 95S a FAIR chance of becoming a tropical cyclone over the next 24hrs.

South Pacific:

Invest 96P is located about 250 miles west of Nadi, Fiji and is moving towards the southeast. The invest is not showing any further signs of organisation and as it moves into higher shear and cooler waters, it should dissipate over the next day or so.

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South Indian Ocean:

JTWC have issued a tropical cyclone formation alert on 95S. Convection is expanding quite rapidly and the LLC continues to tighten. 95S' structure looks pretty impressive on satellite imagery with formative banding becoming evident. Shear is easing and will fall to low levels over 95S in the next day or two. If current organisational trends persist, 95S will become a tropical cyclone tomorrow and end the very quiet period worldwide.

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South Indian Ocean:

95S became Tropical Cyclone Abele.

Invest 91S has formed and is now off the coast of northwestern Australia. This invest formed closer to Indonesia and has looked unorganised to this point. However, as 91S has moved southeastwards towards the Australian mainland, the LLC has become much better defined and convection has literally exploded over the centre in the last few hours. Shear is moderate but may lessen tomorrow, and for this reason, 91S could become a tropical cyclone tomorrow. The whole of NW Aus could be in for a soaking over the next day or so regardless of TC formation has 91S is a moisture laden invest.

South Pacific:

No invests.

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South Indian Ocean:

91S remained a monsoon low, moved inland and dissipated without becoming a tropical cyclone.

Invest 97S has formed around 12S, 87E, just out of Australia's area of responsibility. 97S is showing signs of rotation and steadily increasing convection. Shear is low to moderate, but sea temperatures aren't amazing and are only marginally conducive for development. Some slow development is possible with 97S over the next day or so.

Invest 98S has formed over the top end of Australia, a few hundred miles southwest of Darwin. 98S is over land but is showing good signs of organisation which bodes well for this system becoming a tropical cyclone once it moves over water later tomorrow to the north of the Pilbara coast. BOM are keen on some rapid development once this system reaches water, and I would be inclined to agree that this is a possibilty, given the good organisation already over land. Shear is low and waters are very warm along the Pilbara coastline which favours development.

Invest 99S has formed several hundred miles east-southeast of Cocos Island. Convection has increased in association with the disturbance today but is showing a slanted look meaning moderate shear of around 20kts is impinging on the system. Unless the shear eases, the system will find it hard to develop further. Interaction with invest 90S to the east may well hinder development too.

Invest 90S has formed to the east of invest 99S and to the west of invest 98S. The system is quite small, similar to 99S. However, shear is lower over 90S, which may allow for some steady development. Complicating matters is the rather larger 98S to the east which could well absorb 90S over the next day or so unless the latter makes a hasty exit towards the west.

South Pacific:

No invests.

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South Indian Ocean:

97S has become a little better organised overnight. An LLC appears to be developing, and outflow is gradually improving. Shear is low, and sea temps are marginally conducive. If shear remains low and outflow continues to improve, some further development is likely. JTWC assess the chances of TC formation in the next 24hrs as poor, but chances may raise after that.

98S has raced westwards at a speed of 19kts overnight, almost double the average. This has put the invest right on the coast northwest of Derby. The LLC remains well defined, and convection is exploding over the western quadrant (over water). With low shear and sea temps of 30C, 98S looks poised to develop into a tropical cyclone very quickly as it moves over water this afternoon. JTWC have issued a tropical cyclone formation alert on the system.

99S still has a sheared look this morning. Convection is being sheared west of a weak LLC. The invest is still retaining a fair amount of convection, but unless shear eases, further development will be slow or may not occur at all.

90S is on death's door this morning. Convection has diminished this morning and there is no sign of a well defined circulation now the convective curtain has gone. Shear is becoming unfavourable with 98S approaching from the east, as the latter system develops better outflow. 90S is sandwiched between 98S and 99S which is also reducing the amount of moisture availabilty.

South Pacific:

No invests.

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South Indian Ocean:

97S' convective organisation has remained steady over the last 24hrs, but the LLC has continued to develop and deepen. Shear has risen to moderate levels, placing the majority of the convection to the west and south of the LLC. Shear may dampen development over the next day or so. However, an area of lower shear is evident to the south of 97S, and the invest may move into this improved environment over the next 24hrs. With the increasingly well defined LLC, 97S could develop quite quickly into a tropical cyclone if it were to make it's way south. JTWC have risen chances of TC formation in the next 24hrs from this system to FAIR.

98S has continued to race southwestwards at a speed of 23kts. This fast motion has prevented 98S from fully closing off an LLC, thus the system has remained below tropical cyclone intensity. The window of opportunity for 98S to become a tropical cyclone is rapidly closing as the very fast motion has brought it close to cooler waters and higher shear north of Learmonth. JTWC have downgraded the chances of TC formation to POOR, and though BOM are still forecasting the system to briefly attain TC status, their forecast notes state that the system may struggle to do this and could remain a tropical low.

99S has become better organised over the last 24hrs, though moderate shear is still impinging on the system. Convection has continued to flare over the increasingly well defined LLC, but is not persistant due to the shear. Outflow is improving away from the eastern quadrant which is suffering from the easterly shear, and this may allow the system to develop further. JTWC forecast the chance of TC formation within the next 24hrs from the system as FAIR.

90S has dissipated.

South Pacific:

No invests.

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South Indian Ocean:

Convection has increased this evening with 97S and looks to be a little more centralised in relation to the LLC. Still a fair chance of 97S going on to become a tropical cyclone in the next day or two.

98S has slowed down somewhat this evening. The LLC looks to have deepened a little and shear seems to be easing. There is a slightly greater chance therefore of 98S briefly becoming a minimal tropical cyclone before the environment becomes hostile.

Shear has increased over 99S this evening giving the invest a stretched appearance. Unless this higher shear eases, development will cease. 98S is now directly south of 99S, and the seperation distance between the two invests is only a couple hundred miles, which is hindering the outflow of 99S at present. 98S is moving faster than 99S, so the seperation distance will increase and 99S' outflow should once again improve. For now however, the increase in shear is putting a holt on intensification.

South Pacific:

No invests.

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South Indian Ocean:

97S has changed little as it heads westwards. Convection remains deep, but displaced west of the centre by shear. Further slow development is possible unless shear increases further.

Invest 98S and 99S have merged off the coast of Australia near Learmonth. 99S moved unexpectedly southwards due to Fujiwhara Interaction and merged with 98S. The resultant disturbance is moving southwestwards over colder water and high shear, therefore further development is not expected.

South Pacific:

No invests.

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South Indian Ocean:

97S dissipated.

98/99S dissipated.

Invest 91S has formed in the NW Australian waters. Convection is exploding west of a developing LLC. This convection is being sheared by 30kt upper level winds. Much lower shear is present to the south, and 91S may well move south over the coming days. If the southerly track materialises, 91S has a good shot at becoming a tropical cyclone.

South Pacific:

Invest 93P has formed about 100 miles east-northeast of Port Villa, Vanuatu. This disturbance has been very slowly organising over the last several days, originating from the monsoon trough to the near the equator. The circulation is still broad at present, though winds have been increasing in association with the low and pressure dropping very slowly. Conditions are favourable with low shear, warm sea temperatures and good radial outflow. However, the majority of the convection resides in the northern quadrant of the LLC, and 93P will need to wrap this convection around the southern side if it wants to go on to become a tropical cyclone.

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TD03F looks like it will have a significant impact on both Vanuatu and New Caledonia even if it fails to make TC strength. But Nadi have a high potential of it becoming a TC, and it wouldn't be surprising if it were being named in the next 24 hours.

Often a sign things may kick off when we get very strong highs in the mid latitudes or further south, combined with a surge of equatorial westerlies. Both of these things happened a few days ago.

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Interesting J07, hopefully there will be some more storms to track then, with no loss of life of course!

South Indian Ocean:

91S continues to suffer from strong easterly shear which is prohibiting transition into a tropical cyclone. Convection has been fairly persistant through the day, but resides mostly west of the LLC. The invest is expected to turn towards the southeast into lower shear in the next 24hrs, and therefore JTWC have issued a tropical cyclone formation alert on the system as 91S already has a well defined LLC so should strengthen quickly once the lower shear is found. 91S could be a threat to the Pilbara coast later down the line so needs to be watched.

Invest 92S has formed on the other side of the South Indian Ocean, around 12S, 64E, several hundred miles east of Madagascar. Although waters are warm, the air is fairly dry which is suppressing convection. However, shear is low (only about 5kts at present) so if 92S can find some moisture then some development could occur. The limited convection present is actually showing pretty good signs of rotation suggesting a low is forming.

South Pacific:

93P has become Tropical Cyclone 05P.

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South Indian Ocean:

91S has become Tropical Cyclone Vince.

92S looks rather unimpressive. Convection has increased a little but remains rather lacking. As a consequence, the rotation looks to be not as strong as yesterday. Shear remains low and waters warm so some slow development is still possible.

South Pacific:

TC05P has been named Vania.

Invest 94P has formed off the east coast of Queensland. Convection has persisted throughout the day and the LLC is deepening with time. Shear is low and waters are hot at around 32C. In addition, outflow is excellent as the system sits beneath an upper level anticyclone. JTWC have issued a tropical cyclone formation alert on the system and BOM are also keen for this invest to become a tropical cyclone. Thankfully, it looks like 94P will move away from flood stricken Queensland and roughly follow Vania out to sea.

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South Indian Ocean:

92S has almost reached the east coast of Madagascar. Convection has exploded over the LLC which has deepened to 30kt sustained winds overnight. 92S has a shot at becoming a tropical cyclone this afternoon before it makes landfall in Madagascar tonight or tomorrow. It will probably then dissipate over land.

South Pacific:

94P became Tropical Cyclone Zelia.

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South Indian Ocean:

92S has crossed Madagascar and didn't develop into a tropical cyclone before crossing the east coast. However, the invest is now emerging into the Mozambique Channel and convection is increasing considerably over the hot water. However, JTWC remark that the well defined LLC that was attached to 92S is no longer eveident after the trek over mountainous terrain. Conditions are marginally favourable in the Mozambique Channel, with very warm waters but moderate shear. Unless this shear eases, 92S may not have enough time to develop into a tropical cyclone before making landfall in Mozambique. Certainly a little fighter this one, tracked it halfway across the South Indian Ocean but it has never found a favourable enough environment to become a tropical cyclone. Maybe, just maybe, it now might be able to over the hottest waters of the basin.

South Pacific:

Severe Tropical Cyclone Zelia is still active, but there are no other invests in the basin.

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South Indian Ocean:

92S dissipated.

South Pacific:

Invest 95P has formed around 13S, 178W, 400 miles west-northwest of Pago Pago. Convection has been steadily increasing over a developing LLC through the day. Conditions are favourable for further development as waters are warm, shear is low and outflow is generally good. This should allow the convection to continue to build and the LLC to deepen further. There is a fair chance IMO of this system becoming a tropical cyclone over the next day or so.

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South Indian Ocean:

Invest 98S has formed near Kununurra, over the Top End of Australia. 98S is over land but is forecast to move northwards over water in the next day or two. High shear resides to the north but looking at CIMSS shear tendency charts it looks like it is easing. Therefore, some slow development of 98S appears likely.

South Pacific:

95P has become better organised over the last 24 hours, with convection continuing to build over a well defined LLC. JTWC have issued a tropical cyclone formation alert on the system, and Fiji Met are indicating a high chance of this low becoming a cyclone soon. Conditions remain favourable for development and I think 95P will become a tropical cyclone tomorrow.

Invest 96P has formed to the southeast of 95P. The invest is showing little signs of rotation, but convection is increasing in the area. Shear is moderate, and sea temps are warm. However, the invest is at 22 degrees S and cooler waters are not far to the south. The convective mass is pushing southeastwards so may not have time to consolidate, especially as the rotation is lacking at present.

Invest 97P has formed just off the coast of Queensland, 40 miles northeast of Cairns. Convection is lacking but steadily increasing around a forming low. Shear is low, waters are steaming hot at 32C, and outflow is strong already to the south. Therefore, further development seems likely and the system may become a tropical cyclone in the next couple days, if it moves away from land.

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South Indian Ocean:

98S has changed little in organisation since I last posted. Moderate shear and land interaction is preventing further organisation, but the shear is easing as predicted and 98S should move westwards over water over the next few days. JTWC and BOM seem quite keen on the system developing into a tropical cyclone as it moves down the NW Australian coast.

South Pacific:

95P has become Tropical Cyclone Wilma.

96P dissipated.

97P has become Tropical Cyclone Anthony.

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South Indian Ocean:

98S became Severe Tropical Cyclone Bianca.

Invest 91S has formed a couple hundred miles southeast of Madagascar. Convection is poorly organised and the LLC is ill defined. In addition, at lattitude 25 degrees S, the invest is not far away from colder water. Chances for TC formation are pretty poor IMO. The complete absence of tropical cyclones this side of the South Indian Ocean is ASTONISHING to me. Meteofrance certainly hasn't had much to warn about!

South Pacific:

Invest 90P has formed northeast of Vanuatu. The LLC associated with 90P is rapidly deepening, and the convection is well organised and expanding. Conditions are favourable for further development with low shear, warm sea surface temperatures and good outflow in all quadrants. JTWC have issued a tropical cyclone formation alert on the system and the Fiji Met are keen on transition to a tropical cyclone too.

EDIT: Well worth noting is the fact this system is modelled to closely follow Anthony and impact the Queensland coast as a fairly intense cyclone. Long way off at the point but 90P really needs watching.

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South Indian Ocean:

91S dissipated.

Invest 94S has formed a few hundred miles east of the eastern coast of Madagascar. Convection has been flaring today in the vicinity of a weak LLC. 94S is located in a reasonably favourable environment of low to moderate shear and warm sea surface temperatures. Therefore, some slow development is possible. Will we finally see a cyclone this side of the South Indian Ocean? We shall see.

Invest 95S has formed off the coast of NW Australia. The invest is disorganised and may well be swallowed up soon by a disturbance to the east. It's the latter disturbance that BOM are keen on developing into a tropical cyclone over the next few days, so this needs watching.

South Pacific:

90P became Severe Tropical Cyclone Yasi.

93P became Tropical Cyclone Zaka.

No invests.

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