Severe Tropical Cyclone Alenga

[Somerset Squall]

Invest 99S has become the seasons first tropical cyclone with an intensity of 40kts. 01S is located about 500 nautical miles west of the Cocos Islands. The cyclone has a well defined LLC with a small and persistant area of deep convection directly over it. Shear is low, and waters are warm. This favourable environment is expected to persist over the next few days allowing for strengthening. 01S is moving towards the southwest along the northern extension of a subtropical ridge. Troughing will eventually break down the ridge and recurve 01S to the southeast. When this occurs, the cyclone will move over cooler waters and begin extratropical transition.

[Somerset Squall]

01S has developed a central dense overcast and has been upgraded to Tropical Cyclone Alenga, with intensity rising to 55kts. Alenga seems poised to strengthen, and I think there is a good chance that Alenga will become at least a cat 1 before conditions deteriorate.

Edited December 5, 2011 by Somerset Squall

[Somerset Squall]

Alenga appears to be rapidly intensifying, may have a few surprises up its sleeve!

Edited December 5, 2011 by Somerset Squall

[Somerset Squall]

Alenga weakened somewhat overnight as the cyclone struggled against increasing shear which also restricted outflow. Intensity has plateaued at 45kts today. In the last few hours, eastward outflow has improved which has been lacking so far. This has allowed deeper convection to once more develop over the LLC. Some restrengthening is expected, and Alenga is expected to peak at 55kts for the second time. It no longer appears likely that the system will become particularly intense or rapidly intensify. Alenga has turned to the southeast now in response to the approaching mid-lattitude trough. This will soon bring Alenga over cooler water, which, along with increasing shear, should dissipate Alenga in around 96hrs time.

[Konstantinos]

Alenga is the first cyclone in southern hemisphere this season:

[Somerset Squall]

Alenga has become a cat 1 on the SS scale, with intensity rising to 65kts this evening. Alenga has developed an eye within a solid central dense overcast. I wouldn't be surprised if Alenga strengthens a little more before reaching cooler waters tomorrow afternoon.

[Somerset Squall]

Alenga has continued to intensify at an accelerated rate and has been upgraded to "severe tropical cyclone" status by BOM. Alenga has become a cat 2 on the SS scale with intensity rising to 90kts. The compact cyclone has a fairly well defined eye, and could still strengthen a little more before weakening begins.

[Somerset Squall]

90kts ended up being the peak for Alenga. High shear, dry air and cold sea temps have destroyed Alenga well west of NW Australia.