Tropical Storm Debby and other tidbits

August 23, 2006

– Tropical Depression 4 was upgraded to Tropical Storm Debby at 11 PM last night based on satellite imagery.  As expected the storm has struggled to intensify further. As I wrote yesterday, the storm’s best prospects lay in the future once it gets north of 20 N and I think it will manage to get further west than the current forecast track indicate, which, when extrapolated, indicates it getting no further than 55 W. Even if it does get significantly further west, the only possible threat would be Bermuda, and that’s a bit of a long-shot.

– The more immediate potential threat is the tropical wave that is currently about 400 miles east of the Leeward Islands.  There’s been a marked increase in thunderstorm activity associated with the wave this morning and afternoon and it appears that the reconnaisance flight that was penciled in for tomorrow afternoon will be a necessity. The QUIKSCAT satellite will be passing over itat around 6 PM EDT this evening and its imagery helps to ascertain what kind of circulation there is at the surface.

Climatology shows that development would be a ‘right now’ event or something a few days later.  There have been plenty of storms that form right at or just east of the Leeward Islands, but very few that develop in the box that extends from southeast of Jamaica to the islands.

There is Saharan dust to the north and the west of the system, but there is not an uninterrupted flow from Africa to the Caribbean; Debby lies in between, so this won’t get the full brunt of the Saharan Air Layer the way that the wave that was in this area three weeks ago did.

The one thing that could inhibit development if this were to form ‘now’ are the upper level winds in the eastern Caribbean. At the moment shear is at an unfavorable 20-30 knots. The latest output from the SHIPS intensity model inputs a low amount of shear and strengthens the system into a hurricane into just over two days.  That expectation of low shear may be unrealistic, but it does show what is possible if the system catches a break.

Definitely something for people with interests in Jamaica and points west to keep an eye on.

–  The Honolulu Star Bulletin that an Air Force research vessel took refuge on Johnston Island from the central Pacific Hurricane Ioke. How on earth the vessel managed to get caught in that situation is beyond me.

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