Subtropical System Developing off the U.S. Southeast Coast?

Fig. 1: Satellite view of the North Atlantic basin reveals plumes of thunderstorm activity developing off the South Carolina/Georgia Coast this morning.

Is there a subtropical storm forming off the Southeast U.S. Coast: An area of low pressure is forming off the East Coast of Georgia along a quasi-stationary frontal system. Plumes of thunderstorm activity are ahead of this low-pressure area (Fig. 1). Near the low-pressure area, a plume of water ocean surface water associated with Gulf Stream is in the 27C range. The water surface is warm enough to cause the low-pressure area to possibly gain subtropical characteristics over the next 1-2 days. ECMWF indicates an area of heavy rain along and to the north of where this low-pressure area will track over the next 2-3 days (Fig. 2). Rainfall amount in the 2-5 in. range with strong onshore wind is likely off the Carolinas through tomorrow. The system loses subtropical characteristics over cooler waters to the north although still capable of unloading 1-3 in. of rain across Southeast New England Saturday. Additionally, a thundery pattern shifts across the southwest Great Plains, Rio Grande Valley, and Southeast States the next few days.

Fig. 2: ECMWF rainfall forecast through the weekend across the East U.S.