Saturday, November 06, 2010

Hurricane Tomas: November 5, Update A

In the early hours of this morning Tomas officially became a hurricane. He passed between Haiti and Cuba as a mid-sized cat 1 storm with winds of 85mph (range: 74-95 mph). The interaction with land on either side knocked some steam out of him (puns always intended! ;-)) and he's barely a cat 1 storm now, heading towards the southern Bahamas/Turks and Caicos region, with winds of 75mph and a central pressure of 994mb. He is moving NE at 13mph, and is centered at 20.8N, 72.8W.
He looks pretty ragged at the moment, but where there is convection it is still very strong so I agree with the hurricane classification. Haiti and the Turks and Caicos are really experiencing a lot of strong thunderstorms at the moment. It's too soon to say what the impact on Haiti has been because they are still in the thick of things. So far I see a somewhat inaccurate news report from an unamed news source (with three letters in the title and from my homeland ... tut tut, I expected better - the earthquake was less than a year ago!) saying four people have died. Hopefully that's the worst of it, despite people riding out the storm in their tents.
The vorticity in the upper troposphere has decreased a bit. Although he looks like a tropical storm in the middle levels of the troposphere, the vorticity in the lowest levels is now connected to a front that extends north all the way from the storm to Canada. I've attached a picture (from the University of Wisconsin) to show you this - the red areas indicate higher vorticity. You can see the front quite clearly. Normally a tropical storm will look like an isolated area of high vorticity.

The forecast calls for Tomas to continue moving northeastward, and for him to get weaker and eventually dissipate by Tuesday. I agree with this. I think the NHC have been pretty good on the track with this storm - at least from the point just before he made that turn towards the north.
More tomorrow!
Adieu for now,
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These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I was there and was going to "run away, run away" (Monty Python), I'll let you know.

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