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New Tropical Depression Thirteen is forecast to intensify as it moves toward Florida

Tropical Depression Thirteen satellite image.
Tropical Depression Thirteen satellite image. (CIRA/RAMMB)

The disturbance we have been watching east of the Caribbean islands has organized into Tropical Depression Thirteen. If trends continue, it will become a tropical storm as soon as later today. Its future is uncertain, but effects in Florida are likely.

Since the system is expected to develop winds over 40 mph in the next day or so, tropical storm alerts are in effect for most the northeastern Caribbean islands.

The official National Hurricane Center forecast indicates a gradually intensifying storm as it quickly tracks toward Florida reaching the vicinity of South Florida on Monday – less than four days from now. In real terms, however, the forecast is annoyingly murky. 

In the short term, the circulation will have to fight off dry Saharan air and somewhat hostile upper winds. This means that the storm is not expected to be terribly strong when it reaches the vicinity of the northeastern Caribbean islands tomorrow, and when it tracks near or just north of the Virgin Islands and Puerto Rico on Saturday.

The trickier part of the forecast comes after that. The atmospheric environment is forecast to become more conducive for development as the system moves into the Bahamas over the weekend and near or over Florida very early next week.

Odds of development.
Odds of development. (National Hurricane Center)

The open question is, exactly what shape will the system be in when it tracks over the warm ocean water near or north of the Dominican Republic and Haiti? A poorly organized circulation might continue to fight the dry air, and might not be able to take full advantage of the favorable upper-wind regime.

Further, even if the system does organize, how close does it track to the tall mountains in the Dominican Republic and Cuba? If it’s too close, it will likely become discombobulated, and again not be able to develop in a significant way. 

A weaker system would still affect South Florida on Monday, but as a gusty moisture surge.

It’s not out of the question, however, that an organized storm tracks just north of the islands and is able to intensify over the weekend as it comes this way. And it could intensify much faster and get stronger than the National Hurricane Center forecast is showing.

Don’t look at the forecast as gospel at this point. The range of possibilities up and down is large.

Unfortunately, the computer forecast models are not helpful. They present all variety of scenarios. In fact, some of the normally reliable models show the system remaining quite weak as it passes Florida for the above reasons, and some other factors that are not obvious. So the signals are decidedly mixed.

The bottom line is, we have to be ready to spring into action over the weekend if necessary. At this point, we can’t rule out an intensifying strong tropical storm or hurricane coming this way.

Satellite image of the tropics.
Satellite image of the tropics. (CIRA/RAMMB)

Elsewhere in the tropics, in the central Caribbean, Disturbance #1 is finally finding its footing. It looks to be on the verge of becoming a tropical depression or tropical storm. In fact, in many ways it looks stronger than Tropical Depression Thirteen. Its best chance to develop should be later today or tomorrow as it slows to a leisurely drift in the western Caribbean Sea with very deep, extremely warm water. 

At the same time, a sharp dip in the jet stream is forecast to plunge into the Gulf of Mexico. If the disturbance can organize and grow some tall thunderstorms, or develop in the northwest part of the Caribbean, it could well be grabbed and pulled toward the northern Gulf coast. If, however, it stays fairly weak, the system or its remnants are more likely to track toward Mexico or South Texas. 

It’s not clear whether Tropical Depression Thirteen or Disturbance #1 will become a tropical storm first. Whichever does, it will be named Laura. The second one to develop will become Marco.

In the far eastern Atlantic, large Disturbance #3 is just moving off the African continent. It has a decent chance of developing into a tropical depression or tropical storm. It does not appear to be a threat to land at the present time, but that forecast is based on it organizing to at least some degree. If it stays weak, it is more likely to continue to track to the west for a while longer, at least.

Plan for the possibility of rapidly changing forecasts over the weekend.


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