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Posted at 2:55 PM ET, 11/ 1/2010

Tropical storm Tomas a goner? Haiti hoping ...

By Greg Postel

* Why last year was snowy | Extreme precip in SE linked to warming *
* A frosty evening: Full Forecast *

Tomas is now a weak tropical storm with maximum winds estimated near 45 mph. Located in the central Caribbean, several hundred miles southeast of Haiti, Tomas is moving basically westward at 14 mph.

Hardly distinguishable on the infrared satellite pictures amidst a seemingly disorganized arrangement of thunderstorm complexes, Tomas has been battling a strong headwind for the last couple of days that has effectively torn the structure apart.

Neither of the two large clusters of thunderstorms associated with the storm sit atop the low-level vortex. According to the National Hurricane Center (NHC), the gap between the nearest storms and the near-surface swirl is over 100 miles. A vertical structure like this, where there's a strong tilt to -or even a complete dismantling of- the vortex tube, is potentially devastating to the system as a whole.

The highly sheared environmental flow over the Caribbean, discussed in my last post as a potential threat to Tomas's survival, is apparently taking its toll.

shear-tomas-110110.jpg
Wind shear over the Caribbean in knots (yellow contours). Source: CIMMS

The solid yellow contours in the picture above indicate that 25-45 mph of wind shear (speed difference between low and high altitudes) occupy much of the Caribbean right now.

NHC predicts the hostile conditions will relax somewhat during the next couple of days and allow for some re-strengthening. The forecast calls for Tomas to become a 65 knot (minimal Category 1) hurricane late this week as it approaches Haiti.

Wall Street Journal blogger Eric Holthaus rightly cautions that:

Tomas could turn into a potentially disastrous situation for Haiti, where more than 1.5 million people remain in tents only nine months removed from the devastating January earthquake. And on top of that, the recent cholera epidemic has humanitarian workers and resources spread thin. On Sunday, the Haitian Government raised the official nationwide alert level to Orange Alert.

But unless conditions change soon, Tomas may never recover to hurricane status. This is because an unseasonably cold, dry, and windy upper air flow - in association with a deep trough over the eastern United States - will likely penetrate to Caribbean latitudes and seal Tomas' fate by the weekend. Though the interaction between a tropical cyclone and an upper trough can occasionally trigger short-lived intensification, a cold front of this magnitude just might shred Tomas to pieces.

By Greg Postel  | November 1, 2010; 2:55 PM ET
Categories:  Tropical Weather  
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Next: PM Update: Frost advisory D.C., east and south

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