77 replies to this topic

[cookie]

Thought it was time for a brand spanking new thread.

This thread is to discuss all invests (disturbances suspect for tropical cyclone development) that occur during 2009 and 2010. A thread will be made for all invests that are upgraded to Tropical Cyclone status.

This is an invest thread for the Southern hemisphere.

[Somerset Squall]

South Indian Ocean:

Invest 99S has formed nearly a 1000 miles northeast of Northern Madagascar. The invest has a consolidating LLC with convection gradually becoming more persistant near the centre. Conditions are favourable in the area with low shear, warm sea tempertures and good outflow, particularly in a poleward direction. JTWC give the disturbance a fair chance of developing into a TC within the next 24hrs, so we could well have our first TC of the season if current trends continue.

South Pacific:

96P has changed little in organisation overall through the last several days. Convection has waxed and waned and any circulation has remained poorly defined as the disturbance track westwards towards Australia. Conditions are marginal for development, with warm sea temps but moderate shear over the system. Based on it's performance so far, I can't see this one developing further.

Invest 90P has formed a long way to the east, around 12S 178E. Convection is exploding around an area of mid level turning, though the invest lacks a low level centre. Conditions are favourable for some slow development as shear is low currently, and sea temperatures are sufficiently warm.

[Somerset Squall]

South Indian Ocean:

99S looks a bit worse for wear this evening. Convection has diminshed and the LLC has become distorted. Looking at the CIMSS charts, it appears 99S has entered and area of upper level convergence which is causing subsidence over the LLC, choking convection. Without convection, the LLC has weakened. Looking unlikely now that a TC will form.

South Pacific:

96P has dissipated.

90P has dissipated.

[cookie]

the lights have been switched back on, the southern hemisphere is slowly waking up

99S

[cookie]

ignore I put something in the wrong place

Edited by cookie, 04 November 2009 - 23:34 .

[cookie]

91S

Quote

THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT
TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS FAIR.

[Somerset Squall]

South Indian Ocean:

99S has dissipated.

Invest 91S has formed, a few hundred miles north-northeast of Diego Garcia. The system has a fairly well defined LLC, and convection is currently exploding over the LLC. Conditions are marginal for further development, with warm sea temps, but moderate shear and weak outflow. Based on current organisation though, JTWC indeed have given 91S a fair chance of becoming a TC within 24hrs.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

91S has continued to become better organised overnight. Deep convective banding is wrapping into a well defined LLC. Despite moderate shear and weak outflow, 91S seems to be well on the way to becoming the first tropical cyclone of the South Indian Ocean season. JTWC have issued a tropical cyclone formation alert on the system. As 91S is so far north, the disturbance should remain over very warm waters of around 29C. If upper level conditions improve further, then don't rule out a strong tropical storm occuring.

South Pacific;

No invests.

[cookie]

not far off becoming a tropical storm

[Somerset Squall]

South Indian Ocean:

91S had a lull in activity overnight, and the convection became sporaic around a partially exposed LLC. This was due to poor outflow and increased upper level convergence. This caused some weakening of the LLC aswell. However, in the last few hours convection has exploded over the LLC again and is taking on the appearance of an early central dense overcast. If this persists, then expect 91S to be upgraded to a tropical storm tonight. Upper level support isn't amazing and shear is moderate, but waters are very warm this far north, and is certainly fuelling some intense convection at present. As a result, if 91S doesn't become a tropical storm tonight then it has every chance tomorrow.

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[cookie]

93S

poor chance

[Somerset Squall]

South Indian Ocean:

93S has become considerably better organised, particularly in the last 6 hours. Shear previously effecting the system has eased. Waters are warm also, supporting development. Deep convection is wrapping into a well defined LLC, therefore, JTWC have issued a TCFA on the system.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

93S became TC Anja.

Invest 95S has formed around 10S, 172E, directly north of the remnants of Anja. The invest is showing an impressive flare up of convection currently, but this is already showing signs of being sheared by moderate to high shear. Waters are warm, but shear is likely to slow or even stop further development over the next few days unless it eases. Chances in the near term at least, are poor for TC formation until this shear lets up.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

95S has dissipated.

Invest 96S has formed around 13S, 65E, a few hundred miles southwest of Diego Garcia. Convection seems to be organsing to the west of a poorly defined circulation. Moderate shear is keeping the circulation and convection seperate currently, and any further development will be slow. Sea temperatures are favourable so development will occur if shear eases.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

96S is becoming better organised due to a relaxation in shear. Convection is persisting over the centre, and convectional banding can be seen on satellite imagery. Surface winds are at 30kts- so it shouldn't be long before this system becomes a tropical cyclone. MeteoFrance are quite keen on making it a strong tropical storm to the north of Madagascar in a few days time. Could be an interesting watch, as 96S' westerly track could keep it over the warmest waters of the basin.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

96S became TC Bongani

Invest 90S has formed in the eastern south Indian Ocean, and is located about 400 miles west-northwest of Cocos Islands. Convection is persisting but not directly over the LLC, which appears weakly defined at present. Conditions appear ok for development, with low shear and warm sea temps, but outflow is not that great which is probably why the LLC is lacking right now. Some slow development is possible over the next few days. TCWC Jakarta gives a medium risk (20-40%) of a TC forming here.

South Pacific:

Invest 98P has formed in the Coral Sea, around 10S, 170E. The LLC appears well defined as evidenced by the rotation of the thunderstorms, however, convection is lacking. Waters are marginal at best, and quickly become to cool for development to the south of the invest. However, shear is low and there does appear to be some good outflow, particularly in an equatorward direction. If 98P avoids heading south and continues west, then further development will occur. It's worth noting however that the models don't seem too keen on making this system a tropical cyclone. It's the best looking low so far however in this new season.

[Somerset Squall]

South Indian Ocean:

90S has become better organised overnight. Although convectional coverage is still small, a small lobe of convection is persisting over an increasingly well defined LLC. In addition, weak banding features are beginning to show signs of wrapping towards the LLC. JTWC have upgraded the chances of TC formation to fair, and MeteoFrance are also forcasting 90S to become a tropical storm within the next 48hrs. With low shear and warm sea temps, I can't see why further development won't occur, unless the environment deteriorates.

South Pacific:

98P has dissipated.

Invest 99P has formed to the west of where 98P dissipated. Deep convection is flaring over an ill defined LLC. Over the last 12hrs, convection has exploded over the disturbance, but now has gone back to being minimal. The flaring nature of the convection is due to moderate to high wind shear which is definitely disrupting development by preventing the LLC tightening up and stopping the convection being persistant. Sea temps are also marginal in the area. Such an environment isn't really conducive for development, but there is a small risk of TC forming in the next couple days.

[Somerset Squall]

South Indian Ocean:

90S looks close to becoming a tropical cyclone. Deep convection has expanded over the LLC, and banding features are slowly becoming stronger. JTWC have issued a TCFA on the system, indicating a good chance of TC formation within the next 12hrs (the alert was issued at 11.30am).

South Pacific:

99P is highly disoargansied. In fact, there is little evidence of an LLC at all now- it was ost likely destroyed by shear. All that remains is an area of messy convection. Chances for further development are poor.

[cookie]

92P

[Somerset Squall]

South Indian Ocean:

Invest 90S became Intense Tropical Cyclone Cleo.

Invest 93S has formed to the northeast of dissipating TC Cleo. 93S is in a similar environment to Cleo (except the waters are warmer) with moderate to high shear and some dry air abundant in the area. 93S has a sheared look, with convection pulsing on the western side of an ill defined LLC. As for the future, it looks bleak. Continue high shear is likely, though it may taper off to moderate levels in a few days time. Question is, will 93S be able to survive that long? As always, shear forecasts are difficulat and slow development may occur if it unexpectedly eases. But, don't expect any rapid development as the LLC leaves a lot to the imagination right now.

South Pacific:

Invest 99P has dissipated.

Invest 90P has formed, several hundred miles north of Fiji. Deep convection is flaring over a slowly consolidating LLC. The LLC has slowly become a little better defined in the last 24hrs, and convection, though still not persistant, has increased. This is due to shear relaxing, and outflow improving. In addition, sea temps are very warm right now, around 30C in fact. JTWC give 90P a fair chance of TC formation in the next 24hrs, and indeed, if conditions remain favourable then chances are good thereafter.

Invest 92P has formed in the northern territories of Australia, near Darwin. An ill defined LLC has been tracked over the last couple days moving in from the Gulf Of Carpentaria- in fact, this low may have been associated with invest 91P that spawned and dissipated rapidly all the way east in the Coral Sea. 92P is currently over land, and as a result, convection is currently subsiding. For this reason, TC development is unlikely in the near term. However, as Cookie's track forecast from BOM indicates, 92P is likely to move back over water into the Indian Ocean, where it will be greeted by low shear and high sea temperatures. Some rapid development could occur in these hot waters, so don't be surprised to see a TC form quite quickly once the LLC emerges over waters. Further discussion on this invest will be under the South Indian Ocean section as 92P crosses basins.