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Posted at 2:40 PM ET, 11/ 4/2010

Tropical storm Tomas taking torrential rains to Haiti

By Greg Postel and Jason Samenow

Water vapor image of Tropical Storm Thomas from 1:45 p.m. Thursday

Disaster-stricken Haiti faces an unwelcome challenge as Tropical Storm Tomas makes its approach. Already, the outer bands of Tomas are moving ashore the country's southwest coast.

As of Thursday at 2 p.m., the low-level swirl associated with Tropical Storm Tomas was located roughly 295 miles southwest of Port Au Prince, Haiti. Maximum sustained winds are estimated to be near 50 mph. The system is moving north at approximately 8 mph, and the National Hurricane Center (NHC) predicts it will make its closest approach to Hispaniola early Friday morning as a strong tropical storm.

Five to ten inches of rain are possible over Haiti with isolated amounts to 15 inches in the mountains. This would likely trigger mudslides and devastating floods. Fortunately, Tomas' current projected track is sufficiently west of Haiti such that the worst rains may miss the earthquake ravaged part of the country. Nonetheless, several inches of rain and flooding remain possible in those areas.

At this time, Haiti is particularly vulnerable to natural hazards. Not only are more than one million people homeless from January's earthquake , but a cholera outbreak has claimed 446 lives according to CNN. Efforts to move homeless into school, churches and hospitals are in progress but available space is unlikely to be sufficient to shelter all those in need.

Countries neighboring Haiti will also have to contend with Tomas' heavy rains. The National Hurricane Center states:


Tropical storm and hurricane warnings are in effect for all of these regions (see map).

Fortunately, the toll from Tomas in the central Caribbean may not be as bad as once feared.

Tomas has spent days battling a hostile environment over the Caribbean, with just enough of a dry crosswind to mangle the system's integrity. For much of its recent lifetime, the system has been hardly distinguishable on the satellite pictures amidst a seemingly disorganized arrangement of thunderstorm complexes. The dramatic diurnal (night-to-day) swings in thunderstorm organization that we've seen lately (nocturnal flareup followed by morning weakening) continue to suggest Tomas's circulation has yet to mature.

As suggested by the comma-shaped cloud field in the most recent visible satellite imagery, the low-level swirl is still dislocated from primary mid-level circulation associated with the strongest thunderstorms.

A vertical structure like this, where there's a strong vertical tilt to -or even a complete dismantling of- the vortex tube, has been observed over the past several days. It is a symptom of a storm that is being torn apart by strong winds aloft. The sheared environmental flow (the wind speed difference between low and high altitudes) over the Caribbean, that has been discussed in our recent posts as a potential threat to Tomas's survival, has apparently taken its toll.

After Tomas exits the Caribbean back into the Atlantic Ocean, the atmosphere will become even less supportive of its development. This is because an unseasonably cold, dry, and windy upper air flow -in association with a deep trough over the eastern United States- will penetrate to these latitudes and seal Tomas' fate over 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 will likely shred Tomas to pieces, devolving the circulation into a non-tropical windbag.

By Greg Postel and Jason Samenow  | November 4, 2010; 2:40 PM ET
Categories:  International Weather, Tropical Weather  
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Next: PM Update: Raw rains to gradually diminish


"current projected track" link returns a 403 "Access forbidden!" error.

Posted by: wiredog | November 4, 2010 3:11 PM | Report abuse



Posted by: Jason-CapitalWeatherGang | November 4, 2010 3:45 PM | Report abuse

Tomas caused massive flooding in Curacao. They got a year's worth of rain in only a few hours.
My parents are still trying to dry out their house, and some of their friends reported 3 feet of water inside their home. We've never experienced anything like this there!

Posted by: lgc77 | November 4, 2010 3:46 PM | Report abuse

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