The National Hurricane Center classified the low East off the Carolinas as a subtropical system, by the name of Beryl. So you ask, "What's a subtropical storm?".
A sub-tropical cyclone is a low-pressure system existing in the tropical or subtropical latitudes (anywhere from the equator to about 50°N) that has characteristics of both tropical cyclones and mid-latitude (or extra tropical) cyclones. Therefore, many of these cyclones exist in a weak to moderate horizontal temperature gradient region (like mid-latitude cyclones), but also receive much of their energy from convective clouds (like tropical cyclones).
Beryl is about 245 miles away from Charleston, SC with 45 mph winds. It is not a healthy looking system as strong upper winds are shearing it apart. Still, some thunderstorm activity persists.
Beryl will begin to move west and make landfall somewhere across North Florida or along the Southeast Coast as far north as South Carolina. Watches and warnings are in effect for that area.
The tail end of the Subtropical storm will also move west. This tail is loaded with moisture and could bring us a chance for storms both Sunday and Monday.