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Tropical Depression 16 forms

By: Dr. Jeff Masters, 3:19 AM GMT on October 28, 2007

The surface low pressure system about 150 miles south of the Haiti/Dominican Republic border has gained enough organization to be upgraded to Tropical Depression 16. Long range radar of of Puerto Rico shows bands of heavy rain continuing to affect the region. Satellite loops show most of the heavy thunderstorm activity is to the north and east of the low's center of circulation, but these thunderstorms have shown some impressive development tonight. Wind shear has fallen to 15-20 knots tonight, and is expected to fall below 15 knots on Sunday. This should allow TD 16 to develop into a tropical storm on Sunday.

Figure 1. Latest satellite rainfall estimate for TD 16.

This is a slow moving system that will dump very dangerous amounts of rain along its path. The system will continue to bring heavy rains and the threat of flash flooding and mudslides to Puerto Rico through Sunday night. Heavy rains of up to eight inches have already fallen in southeast Puerto Rico and the Virgin Islands (Figure 1). Heavy rains will also affect the Dominican Republic and Haiti Sunday and Monday, and are likely to trigger life-threatening flash floods in Haiti.

This afternoon's 18Z (2 pm EDT) major intensity forecast models--the GFDL, HWRF, and SHIPS models--all agree that TD 16 will intensify into a hurricane. The 18Z GFDL, HWRF, and UKMET models predict TD 16 will move northwesterly across Hispaniola, then into the Bahamas on Tuesday, and intensify into a Category 1 hurricane over the central Bahamas on Tuesday. A trough of low pressure would then swing TD 16 northeastwards out to sea. This forecast track seems unreasonable, as TD 16 has headed more to the west today than these models predicted.

The ECMWF and GFS models predict TD 16 will track west-northwest along the length of Cuba, then pass within 50 miles of Miami on Thursday before recurving northeastwards out to sea. These models do not intensify TD 16 into a hurricane, due to the amount of time the storm spends over the mountainous terrain of Cuba. This is a reasonable forecast, should TD 16 track over Cuba for a long distance.

I believe the 12Z forecast of the NOGAPS model, which predicts a more southerly track into the Western Caribbean, just south of Cuba, is the most reasonable one. This track would favor TD 16 developing into a hurricane, possibly a major hurricane, since the heat content of the waters in the Western Caribbean is high, and the wind shear will be lower further to the south.

The area of disturbed area of weather in the extreme Western Caribbean, just east of the Yucatan Peninsula now appears to be too insignificant to affect the path or intensity of TD 16 very much.

I'll have an update Sunday morning.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.