On Thursday evening a Mesoscale convective complex (MCC) rolled eastward from the Panhandle and raced into Lake City and into Northeast Florida. A MCC is a thunderstorm complex that has specific characteristics. This storm which brought over 1-2 inches of rain overnight is typical of a MCC. They are nocturnal, last at least 6 hours and the size of the cloud tops are at least 62,000 miles with temperatures measured by a satellite of -26 F or colder.
These pictures show the storm before it reached Jacksonville when it was in the Panhandle. The top two images are base reflectivity from the Tallahassee WSR-88D Doppler radar site. A bowing section of the thunderstorm is approaching St. Marks at 6:40 pm indicating strong mid level air dropping down to the surface due the denser cooler outflow. This gust at the surface spreads out and bows the cell radar signature on the radar.
Twenty minutes later the storms rapid eastward movement is shown in the second picture entering Taylor county. The cell was moving east at 60 mph.
The last picture is the radial velocity product that clearly shows the downdraft moving away from the radar site in red and yellow. The greens are winds moving into the storm in relation to the WSR-88D's location. Notice the moist strong winds coming in off Apalachicola Bay. This fueled the thunderstorms and they remained severe when they blew into the First Coast.
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