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Mid-Atlantic disturbance is likely to develop as it heads toward the Caribbean

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We’re still tracking two tropical disturbances in the Atlantic, but Tropical Disturbance #2 about midway between the Caribbean islands and Africa has most of our interest.

We’ve been watching Tropical Disturbance #1 since it moved off Africa last week. It’s been surrounded by Saharan dust for its whole trip across the tropical Atlantic, and the dry air has taken its toll. The disturbance will move through the eastern Caribbean islands today, likely as a gusty moisture surge.

Murky skies full of Saharan dust will precede the disturbance’s arrival, then periods of gusty squalls with heavy rain causing local flooding and mudslides on the steep terrain are possible as it passes through or by the islands tonight and Thursday.

The odds are that the dust has weaken Disturbance #1 enough that it will have trouble organizing in the Caribbean, but we’ll watch it downstream just in case.

Tropical Disturbance #2, on the other hand, is on the southern edge of the dust plume, so it has access to dust-free air on at least two sides. It’s already showing rotation and some organization.

Atmospheric conditions appear conducive for organization and strengthening downstream, so people in the eastern Caribbean islands need to stay aware. The disturbance in some form – possibly as a strengthening storm – will move through the islands into the Caribbean Sea on Friday.

If you are looking at the computer forecast models online, always bear in mind that the computer simulations are much less accurate when systems are disorganized or just developing. So don’t read too much into them. The key point is that conditions appear to support development of the system.

The red zone on the NHC map is not a forecast cone. It’s the area within which the Hurricane Center forecasters think the system is most likely to turn into a tropical depression or tropical storm. If and when that happens, we will get a traditional forecast cone.

Looking past the potential development point, the future track of the system depends to a large degree on how strong it gets. Since that is unknowable, the possible tracks through the weekend and into next week appear to range from Mexico to near Florida.

Over the weekend, a big dip in the jet stream will be moving through the northeastern U.S. The question is, will that dip nudge the tropical system north, or does is miss? Generally, a stronger tropical system is more likely to get tugged north toward Haiti and Cuba, and a weaker system is more likely to track west in the Caribbean. Until the disturbance has an organized center and circulation, the long-range forecasts are just speculation.

It appears our focus is going to be on Tropical Disturbance #2. Nothing else seems to be in the pipeline right away.


About the Author:

Bryan Norcross is currently a hurricane specialist at Local 10 News, the station where he began his stretch on television in Miami in 1983.