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  • Writer's pictureBryan Norcross

What happens today with Tropical Storm Fred will determine how it affects South Florida

Tropical Storm Fred is a messy-looking tropical storm just south of the eastern tip of the Dominican Republic. There is a big roadblock is in its way – 10,000-foot mountains that have shredded many a tropical system in the past. The question is, what's going to happen when Fred tangles with those mountains later today.

Fred’s center is hard to pin down. More than one swirl is evident on the San Juan radar, suggesting that the system is not well structured for strengthening. Hurricane Hunters are finding the center somewhat south of its predicted position, which might favor a more direct hit on the mountains. Some land interaction with the Dominican Republic may already be happening, which can make the center bounce around.

The National Hurricane Center forecast and the consensus of the computer forecast models take the storm over the island. Will it slam into the mountains or skirt around to the north? That’s today’s unknown. This a situation where a slight deviation one way or the other would make a big difference what shape the storm is in when it emerges on the other side.

Also, the storm’s current discombobulation adds to the uncertainty. But a discombobulated storm normally has a harder time coming back together if its circulation gets disrupted.

There are other negative factors in play besides the mountains in Fred’s path. That’s why the National Hurricane Center is not forecasting the system to intensify quickly. The biggest issue right now appears to be the dry air surrounding the circulation. The storm is having to fight off the dryness to create thunderstorms, which it needs to generate in order to intensify.

The computer analysis is that dry air will continue to affect the system until it reaches the mountains in the Dominican Republic and Haiti later today.

There is still plenty of moisture to cause heavy rain with the possibility of flash flooding in the Dominican Republic and Haiti, however.

So the big question for Florida is, what is the status of the circulation after it encounters those mountains. The National Hurricane Center is conservatively predicting that a somewhat organized system will remain. It certainly could, but that’s not guaranteed. This is an unforecastable question.

We will just have to see. We have to ready for the circulation to survive well enough that it can regenerate to some degree before it gets near South Florida.

The upper-level winds are forecast to become somewhat hostile when the system, whatever shape it’s in, approaches the Florida peninsula. If the forecast is correct, that would be another factor in favor of it being a weaker system late Friday or early Saturday near South Florida.

In any case, it appears that Fred’s moisture envelope will affect the southern Florida peninsula, no matter what. Periods of heavy rain are expected beginning late Friday, but especially on Saturday. Sunday is a bit of an open question. It depends on Fred's tracks in the Gulf, and whether takes its moisture with it, or a tail of storms lags behind. Most likely the tail of moisture will continue over the peninsula.

The most conducive atmosphere the storm encounters is currently forecast to be in the Gulf to the west of Tampa, but the long-range forecast is full of uncertainties. Some of the long-range computer forecast models indicate that the hostile upper winds they are predicting over and near South Florida will let up farther north over the Gulf. Others indicate the opposite. It’s also very unclear whether the system will stay over water after it finishes its encounter with the mountains in the Caribbean.

As with South Florida, we should have a better idea how things might develop in the Gulf after we see what’s left of the system by tomorrow morning.

Stay tuned.

Elsewhere, a robust-looking system has moved off of Africa and is heading west in the tropical Atlantic. The computer forecast models and the National Hurricane Center are giving it a decent chance to develop into at least a tropical depression this week. It is due to reach the eastern Caribbean islands around this weekend.


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