Tropical Storm Soudelor

[Somerset Squall]

Invest 99W has acquired sufficient organsiation to be classified a tropical depression by the JTWC. Initial intensity is 25kts. Deep convection is persisting over the LLC of 05W, but the depression lacks banding features at present. 05W is currently interacting with Luzon, which may hinder development at first. However, 05W is moving generally west-northwestward along the southern periphery of a subtropical steering ridge over China which will take the system away from Luzon and allow it to strengthen into a tropical storm. However, 05W may not have much time to strengthen before landfall in Southern China. JTWC are currently only prediciting a peak of 35kts, and this may be as the depression is feeling the effects of moderate shear, though I would have thought that the good outflow would cancel this somewhat- so it may be possible for 05W to get a little stronger than 35kts prior to landfall.

[Somerset Squall]

Intensity has been increased to 30kts overnight. The convection has waned a little from what is was but banding features are becoming evident in satellite imagery. 05W is still moving westwards along the southern periphery of a narrow ridge to the north. 05W is expected to make landfall in southern China in 48hrs time as the ridge begins to weaken and the system pushes in a more west-northwesterly direction. However, if the ridge holds out then 05W will move to the south and instead strike Hainan Island. Generally favourable conditions of warm sea temps, good outflow but moderate shear should allow a little intensification for the next 24hrs. After this, shear is progged to increase which would cap further development. JTWC are currently forecasting a peak of 40kts prior to landfall.

[Somerset Squall]

05W's intensity has remained at 30kts today. However, latest satellite imagery shows than finally some more concentrated convection is persisting over the LLC, and the depression has better shape than this morning. I expect 05W to become a tropical storm by tomorrow morning, though significant strengthening is unlikely due to increasing shear tomorrow and the fact that the depression doesn't have much time over water before landfall near Hong Kong. Land interaction with Luzon has ceased which probably accounts for the increased organisation occuring now.

[Cookie]

thanks for the great updates mate

like you say not a great deal of time before landfall

[Somerset Squall]

JTWC briefly upgraded the system to a 35kt tropical storm last night, but intensity has now decreased to 30kts as shear is beginning to displace convection away from the centre. However, conflictingly, JMA now have 05W as a 35kt tropical storm named Soudelor. Soudelor, as I mentioned above, is entering an increasingly hostile environment of high shear as it approaches Hainan Island, so it should weaken below tropical storm strength soon. The ridge to the north has strengthened and this has enforced a more westward tracking which now takes Soudelor closer to Hainan Island than mainland China. In fact, I wouldn't be entirely surprised if further southerly adjustments were made to the track and Soudelor misses China entirely. We shall see.

[Cookie]

went from this

to this very fast

[Somerset Squall]

Indeed Cookie, continued high shear and now land interaction with Hainan Island is causing loss of deep convection and is disrupting the core of Soudelor. As I suspected, Soudelor has refused to move north and is still heading westwards directly through Hainan Island. What is left will then make landfall on the coast of northeastern Vietnam and rapidly dissipate.

Edited July 11, 2009 by Somerset Squall

[Cookie]

from watching a tv program am I right in saying a lot of these systems get broken up by Hainan Island?

[Somerset Squall]

from watching a tv program am I right in saying a lot of these systems get broken up by Hainan Island?

Hainan Island certianly can protect a large stretch of the southern coastline of China. Hainan Island is fairly large and can zap the energy out of systems and protect against storm surge for the coast directly north of the island.

Despite the decreasing convection, JTWC have upgraded Soudelor to a 35kt tropical storm again. Soudelor is likely to bring flooding rains to the island itself.

[Cookie]

[Cookie]

[Somerset Squall]

Thanks for the image Cookie. It clearly shows the convection being sheared westwards leaving the LLC partially exposed.

Since then, Soudelor has not recovered, and is just making landfall as a weak tropical depression with sustained winds of 25kts on the coast of Vietnam. The convection is still pulling away from the circulation, effectively leaving it behind to limp across the coast. The LLC itself has become much less defined in the last six hours, and the conclusion of all of this is that Soudelor is rapidly dissipating. I expect full dissipation over Vietnam within the next 12hrs.