That's a heavy line of thunderstorms. Just east of Ft Pierce.
The line is moving toward the SE.
Affiliated with Franklin? I can't really tell at this point. Seems to be something of an outflow boundary...but from where.

Looking at a IR shortwave loop. The thunderstorm complex apparently developed in an area between Franklin and the mid-upper level Low over S Florida.
Similar to the area in front of a electric hand mixer.
Converging winds mixing/ forcing their properties together.
http://www.srh.noaa.gov/radar/loop/DS.p38cr/si.kmlb.shtml