Southern Hemisphere: Invest Thread 2009

[Cookie]

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

this is an invest thread for the Southern hemisphere

I'm currently keeping an eye on

invest 90s near NW Australia

and

invest 91s near MADAGASCAR.

Edited February 14, 2009 by Ross B

[Somerset Squall]

Let's comment on 90S, which has now been reclassified 92S (due to the LLC dissipating and reforming), first. This disturbance moved over water yesterday to the northeast of Karratha, NW Australia. 92S is suffering from shear at the moment which is disrupting the circulation at present. BOM are forecasting that the low has a moderate chance of development from Sunday onwards, however, this heavily relies on the shear easing.

As you say Cookie, there is another invest, 91S, in the Mozambique Channel. This invest is also suffering from shear which is displacing convection to the southwest of the centre. 91S is moving westwards towards the Mozambique coast, where it could move inland. Chances for development are poor if this motion continues. However, 91S has been showing modest signs of organisation, and although convection is not widespread, what exists is quite deep and trying to reform near the centre in the face of the shear. JTWC are flagging this systems' potential for development as poor.

[Cookie]

91s has now been classed as poor chance of developing into a tropical storm in the next 24 hrs.

[Somerset Squall]

South Indian Ocean:

91S has now moved inland, therefore further development is not expected.

92S remains disorganised. However, convection has really flared up today and 92S is providing heavy rains to Karratha, right down the coast to Exmouth. This system is still suffering some moderate shear and is getting increasingly closer to land. Chances for TC development is poor.

South Pacific:

Invest 93P has developed near Viti Levu, Fiji. The system is currently very disorganised and it is hard to pick out any discernable LLC near the deep, sporadic convection. 93P is in an area of moderate shear but high sea temps. Based on the current state of organisation, quick development seems unlikely but conditions may improve a little later down the line.

(Interesting to note, the South Pacific has only has had one TC so far, the very short lived Hettie. Unless things pick up, we must be heading for one of the quietest, if not the quietest South Pacific season on record.)

Edited February 14, 2009 by Somerset Squall

[Cookie]

a few hours old now but here is 93P

[Somerset Squall]

South Indian Ocean:

92S is moving parrallel to the NW Australian coast, and is now providing heavy rains to Exmouth. Some lively storms have been flaring up around 92S and the system has provided a good dose of rainfall to a large stretch of coastline. However, the system has little or no chance of becoming a tropical cyclone. Shear remains strong, the system is now interacting with land and JTWC has analysed the system to find it has multiple circulation centres. All of these centres are battling for dominance, and as a consequence, the system is not becoming any better organised.

South Pacific:

93P has become a little better organised today. The LLC has slowly become better defined and convection is persisting near the centre. However, moderate shear is preventing any rapid development of the invest but 93P is certainly slowly becoming better organised. I think the chances of tropical cyclone development in the next couple days is fair.

Image of 93P:

[Somerset Squall]

South Pacific:

93P has really ramped up during the last few hours. In latest satellite imagery you can clearly see a well defined LLC, along with good banding features to the north attempting to wrap around the centre. JTWC have just issued a tropical cyclone formation alert on the system, noting that the shear has eased and an upper level anticyclone is forming over the system, enhancing outflow. Waters remain plenty warm enough, and based on current organisation we could well have the 2nd tropical cyclone of the South Pacific season very soon.

[Cookie]

thanks for the update, its great having this thread and watching these systems.

[Cookie]

THE POTENTIAL FOR THE DEVELOPMENT

OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS GOOD.

3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED

BY 162130Z.//

[Somerset Squall]

South Indian Ocean:

Invest 92S has moved further inland. However, just because this isn't strong enough to be a TC doesn't mean it can't be dangerous. The system has been dumping copious amounts of rainfall between Karratha, down the coast to Exmouth, and now much further inland too. The ill defined LLC is well inland now, but convection continues to flare in large amounts which is causing flash floods. TC development is not expected.

South Pacific:

Invest 93P remains well organised today. Convectional banding has improved and the LLC remains well defined. However, some moderate shear has left the LLC partially exposed, and this is probably the main reason the system hasn't been upgraded to a tropical cyclone yet. An anticyclone is still forecast to build over the system, and this should lessen the shear. Conditions are otherwise favourable with warm sea temps and good amounts of moist and unstable air. Therefore the chances for tropical cyclone development in the next 24 hours remains good.

Edited February 16, 2009 by Somerset Squall

[Somerset Squall]

South Indian Ocean:

Invest 94S has formed, and the LLC is about 50 miles south-southwest of Diego Garcia according to the JTWC. The LLC is currently in formative stages, and convection is being sheared to the west. Therefore, unless conditions improve, tropical cyclone development appears unlikely, and if it does occur, it will be slow.

South Pacific:

The remnant low of Innis continues to zip generally southwards. Convection has built again by the centre but this isn't expected to persist as the remnant low is in a high shear, low sea temperature environment now.

[Somerset Squall]

South Indian Ocean:

94S has dissipated, as signs of rotation in the convection located near Diego Garcia has gone and all that is left is some disorganised convection sat along a trough. There is certainly a lot of convection for a LLC to work with if one were to form but at the moment nothing is going on out there.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

Invest 95S has formed off the coast of Madagascar. It's origins come from a LLC which contains the remains of former TC Freddy. The LLC has been tracked across half of the Indian Ocean before Freddy's remnant low merged with another low pressure area. The remnant system has been tracking quite quickly towards Madagascar with very little convection. However, convecton has increased a lot today and is attempting to wrap around the LLC. Wind shear is low and sea temps plenty warm, the only limiting factor for 95S is proximity to land. I think there is a fair chance of a weak TC forming here in the next couple days, perhaps before the system moves inland.

South Pacific:

No invests.

[Cookie]

thanks for the updates mate, sorry my updates have been a bit lacking back at work so makes it a little harder to update as much

[Somerset Squall]

thanks for the updates mate, sorry my updates have been a bit lacking back at work so makes it a little harder to update as much

No worries mate, good to have your input. As you may have guessed by my frequent updates that I'm on my holiday from work at the moment, going back on Monday. But unfortunately there is still very little to write about.

[Cookie]

I did say it was going to be quite and apart from innes it has been.

this part of the forum really dose feel like are own

[Somerset Squall]

South Indian Ocean:

Invest 94S has re-developed as a new LLC has formed in the remnant convection near Diego Garcia. The LLC is currently elongated and ill defined it is providing some weak rotation in the disorganised convection in the area. Shear is currently hindering further development but is forecast to ease. However, anymore development will be slow due to the highly disorganised nature of the disturbance.

Invest 95S has become much less organised than yesterday. Then, convection was attempting to wrap into an increasingly well defined centre. Now, that centre is difficult to locate and the convection has become more patchy and disorganised. This is more than likely due to interaction with the east coast of Madagascar. I think chances of development of this system are poor, at least in the short term.

South Pacific:

No invests.

Edited February 20, 2009 by Somerset Squall

[Somerset Squall]

South Indian Ocean:

Invest 94S has become better organised today, as the LLC has become better defined and convection is now wrapping into this centre. JTWC assess the chances for develppment into a TC in the next 24 hours as fair, as outflow is good, waters are warm and shear is now low. The disturbance is in it's formative stages, I say the chances for development after 24 hours is good as 94S should continue to get better organised in the favourable conditions.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

94S continues to get it's act together today, and convection is persisting and wrapping healthily into the obvious and well defined circulation centre. JTWC mentions that both poleward and equatorward outflow is good which is facilitating quick development. Sea temps are high and shear is forecast to remain low, so JTWC have upgraded this system's chances of TC development to good for within the next 24 hours. MeteoFrance are in agreement and also predict a TC to form within the next 24 hours.

South Pacific:

No invests.

[Cookie]

thanks for the updates,

what dose equatorward outflow mean again?

[Somerset Squall]

thanks for the updates,

what dose equatorward outflow mean again?

Outflow is the exhaust for a tropical cyclone. Similar to a thunderstorm, you get inflow at the base (also known as convergence) which then rises and disperses at the upper levels. The rising air lowers the pressure of the storm whilst also condensing and increasing convection. When a storm has good outflow it means that it is maintaining the rising of the unstable air within the system and releasing any dry or stable air, and stopping air subsiding (which is turn causes convection to decrease). Therefore, having good outflow allows the system to intensify. If outflow is good, it's a sign the storm is healthy.

Equatorward outflow just means that the direction of the air exiting the storm is towards the equator, in this case, north. When the term dual outflow is used, it means that the air at the upper levels is dispersing in more than one place, which means pressure can fall away quicker and more convection can build, and may cause rapid intensification.

Hopefully that answers your question. I'm not overly confident with the concept myself

[Cookie]

thanks for explaining mate, makes more sense now

[Somerset Squall]

South Indian Ocean:

Invest 95S has formed, a couple hundred miles west of Darwin, Australia. The disturbance is currently located over land, though is expected to emerge over water tommorrow. Waters are very hot off the coast of NW Aus, exceeding 32C in some spots which may facilitate rapid development. Shear is forecast to be low for the next couple days, but BOM have hinted that whilst they expect a tropical cyclone to form on Friday or Saturday, they don't expect it to be all that strong as the low is forecast to moves southwestwards along the coast. Whether the system develops or not, the Pilbara Coast is at risk of significant rainfall over the weekend and into early next week.

South Pacific:

No invests.

[Somerset Squall]

South Indian Ocean:

95S is rapidly becoming better organised. Formative banding features are becoming better defined, and deep convection is persisting over a tightening LLC. And the LLC itself is still over land! JTWC assess the risk of TC development in the next 24 hours as fair. If the system is rapidly deepening over land, then it'll be interesting to see what it does over the hot ocean!

South Pacific:

No invests.

[Cookie]

thanks for the updates.