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Capital Weather Gang

The tropical Atlantic is waking up as the peak of hurricane season approaches

August 29, 2018 at 11:45 AM

Like a bear that instinctively knows when to come out of hibernation, the tropical Atlantic is waking up as the peak of hurricane season approaches. The atmosphere and the ocean have become more favorable for storm development.

Models are suggesting the next named storm, Florence, could form by the weekend off the coast of Africa. They all simulate a tropical storm or hurricane will develop from a wave entering the Atlantic from Africa. However, they suggest the storm will veer northward over open waters and will probably not affect land.

Closer to home and of potentially greater significance, the European computer model indicates a potential storm for South Florida and the northern Gulf Coast early next week. Other models do not signal this threat, but, given the European model’s track record, it would not be wise to dismiss it. The disturbance that could strengthen into a storm is passing through the Lesser Antilles.

The European model forecast indicates a tropical depression or storm could pass over South Florida on Labor Day. It then strengthens the storm a bit upon entering the Gulf of Mexico. Then, it turns the storm northward before it hits the northern Gulf Coast on Wednesday or Thursday next week as a tropical storm or Category 1 hurricane. Keep in mind this is not an official forecast, just output from a single model — but it is worth being aware of and monitoring.

Storm tracks from the latest European global model ensemble. Tracks are colored by wind speed. (UAlbany/)

In addition to the tropical wave exiting Africa and this disturbance in the Caribbean, models agree several more energetic waves will enter the Atlantic from Africa over the coming week, so this burst of activity might just be getting started.

At least two factors are conspiring to provide this invigoration of tropical activity right on cue.

The region of cooler-than-average water that was present much of the year between Africa and the Lesser Antilles is rapidly eroding and even becoming slightly warmer than average in many places.

Sea surface temperature anomalies three weeks ago (left) and this week (right). (NOAA/NESDIS/)

Secondly, a large-scale atmospheric phenomenon called the Madden-Julian Oscillation, or MJO, is forecast to enter a phase that is more conducive for Atlantic activity over the coming week and beyond (in other phases, it can act to suppress it).

The 2018 Atlantic hurricane season featured above-average activity all season up until Aug. 21, and since then it has slipped to just 60 percent of average activity into Tuesday. Should a named storm not form by Labor Day, that number will drop further to 46 percent of average because this is the time of year when it is actually unusual to NOT have at least one named storm somewhere.

For reference, the next two names on 2018’s list of storms are Florence and Gordon — and we may get to use both of them in the coming week.

This hurricane season, only Beryl and Chris began their lives as tropical cyclones (Beryl on July 5 and Chris on July 6). Alberto, Debby and Ernesto, the other three named storms, began as subtropical cyclones. So, amazingly, Florence would be the first storm in eight weeks to form with a tropical pedigree.


Brian McNoldy works in cyclone research at the University of Miami’s world-renowned Rosenstiel School of Marine and Atmospheric Science (RSMAS). His website hosted at RSMAS is also quite popular during hurricane season.

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