As MikeC mentioned above, the low pressure system that may form over the Caribbean later in the week may not be fully tropical, at least in the sense of being a typical tropical storm/hurricane. While the models can't fully resolve a hurricane, the GFS and ECMWF are capable of producing compact tropical cyclones of hurricane strength. Neither of those models do that with the potential Caribbean system... rather the low pressure they develop is a order of magnitude larger than a typical tropical storm and the pressure gradient is pretty flat (rather than ramping up quickly near the center). You can also tell from the forecast precip pattern that it is not a typical tropical cyclone, with no well-defined QPF bullseyes near the center. Anything that gets as far north as FL or the GOM may also become involved with a cold front and undergo some baroclinic interaction.

This is not to say that a true tropical cyclone (of the type that NHC is concerned with) could not form, but it looks like it would be a case of a smaller-scale vortex developing from or within a broad low pressure area, rather than the usual case of a small-scale disturbance growing upscale into a tropical cyclone.

Also, while it seems likely that Matthew will dissipate over land, that can't be taken for granted at this point. The forecast becomes even more complex if that hangs around in some form.