A weak tropical disturbance and its tail are pulling moisture across Florida as it moves north in the Atlantic. It will be absorbed into a northern-type low-pressure area forming off the Carolinas. Its main effect on Florida will be to keep us wet for a couple days and then push in drier air late in the week.
In a complicated mix, the Caribbean tropical disturbance that moved over South Florida yesterday, a developing low-pressure system/coastal storm off the Carolinas, a cold front stretching from the Northeast to the Gulf, and a strong dip in the jet stream will combine into a formidable nor'easter-type storm offshore of the Mid-Atlantic and Northeast.
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The coastal storm will bring high surf, dangerous ocean conditions, blustery winds, and potentially very heavy rain to some coastal sections, depending on where and how all of the ingredients come together.
There is a chance that it will eventually find warm enough ocean water and become somewhat tropical in structure before it gets swept out to sea. That would be a technical meteorological change, but wouldn't significantly alter the effects on the Northeast coast. If it gained enough tropical characteristics, and it had strong enough winds, it would get a name.
The National Hurricane Center gives that the tropical or sub-tropical transition a 30% chance of happening, but the chance of the nor'easter-type storm forming is near 100%.
Tropical systems get their energy from the warm ocean. Non-tropical systems run on the contrast between cold air to the north and warm tropical air to the south. A hybrid system – called sub-tropical – use both sources of energy. Tropical and sub-tropical storms are assigned names by the National Hurricane Center.
If the system developing off the Mid-Atlantic/Northeast coast gets strong enough, it could strong push drier air into South Florida late week. It wouldn't dramatically cool the temperatures, but the humid air might get pushed to the south. It's going to be a close call. There are so many atmospheric ingredients going into the storm, the details of the forecast are iffy.
A separate low-pressure system in the middle of the Atlantic is also developing. This one also started out as a non-tropical system. It, however, has a better chance of eventually becoming tropical and getting a name. It is not likely to affect land areas, however.
The next two names on the list are Melissa and Nestor.
In October, we watch the western Caribbean, but there currently are no signs of any tropical development.