The tropical Atlantic, the Caribbean and the Gulf of Mexico are covered in dust, though two robust tropical disturbances are slogging their way west just south of the Saharan Dust belt. One is in the Caribbean, the other is between Africa and the Caribbean islands. Next month, we will be keeping a close eye on this type of disturbance, but for now the dry, dusty air is keeping them from developing further, so they are simply moisture surges in the trade-wind flow.
As the disturbances pass through the Caribbean, the northern ends might increase the moisture over South Florida – over the weekend from the first one, and mid to late next week from the second.
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No organized development is expected in the tropics through the weekend, at least.
Of interest today is a non-tropical low-pressure system spinning over the South Carolina coast. This is the same low that spawned the system that became Tropical Storm Edouard, and also the swirl the National Hurricane Center tracked over the Gulf before it came inland over the Florida Panhandle.
The center of this circulation is forecast to cover the North Carolina coast, and from there move north, over or just offshore of the Mid-Atlantic and the Northeast coastline.
In the winter, we would call this a nor’easter – a coastal storm that produces northeast winds at the coast. And even in July, normally this would just be a coastal low that would briefly disrupt summer beach plans along the coast.
The odd thing this year is that the ocean water is unusually warm just off the shoreline from North Carolina north to New England. In spots, it’s several degrees warmer than normal. As a result, if the system moves far enough offshore, it could acquire some tropical characteristics – it could turn into a subtropical or tropical depression or storm.
It’s going to move pretty quickly to the north, so its impact on the coast is largely dependent on exactly how far offshore it tracks. Where Long Island, New York sticks out to the east, more direct effects could be felt about Friday. But, slight deviations in the track make a lot of difference in what happens at the coast, and somewhere on Long Island and in Southern New England is likely to get a lot of tropical rain in a short period of time.
In any case, it’s not expected to become super strong, but there’s potential for local problems where the tropical rains come ashore, if they do.
If it were to acquire some tropical characteristics, it would be a rare event. I don’t find anything comparable in the record book. There have been tropical storms that move up the coast in July, but not that originate as a broad non-tropical low over land. If it happens, it will be the unusually warm ocean water that makes it possible.