May 13, 2017: Mesocyclogenesis Near Florida/Georgia Border

Описание: This animation shows evolution of a cluster of thunderstorms near the Florida/Georgia border, one of which warranted a tornado warning in southern Ware and Charlton counties in Georgia and northeastern Baker County in Florida, on the evening of May 13, 2017. Several scattered thunderstorm clusters had already been moving through this region which had provided a complex array of outflow and thermodynamic boundaries. As storms interacted with these boundaries, it is likely low-level helicity was enhanced causing the generation of a mesocyclone embedded within the cluster of thunderstorms. This storm with the mesocyclone is the one that became tornado warned.

What is interesting about this particular storm is that almost exactly the moment this storm passed over the West Mims Fire in southern Ware and Charlton counties, the storm greatly intensified. It is tough to tell if the fire had any play in the sudden increase in intensity as this is was such a small scale interaction that the current network of surface observations, radar, and satellite data would be hard to verify the fire's role. It does raise some questions as this would be quite the coincidence, although I personally believe it is more coincidence than some pyro-meteo symbiosis.

Here is what I believe are the major players in this mesocyclogenesis: an outflow boundary and the presence of horizontal convective rolls (HCRs), two convective cells noted on radar ahead of the cluster of storms, and a cell merger prior to the intensification of the mesocyclone. The outflow boundary set in place would serve as an anchor for the first convective cell to embed itself on. This convective cell formed from what I believe to be an HCR noted on radar as well as satellite (not shown). As this first convective cell matured on the outflow boundary, another convective cell merged with the stationary first cell. Immediately after this point, the mesocyclone rapidly intensifies.

Regarding the collocation of this storm and the West Mims Fire, the first convective cell started to intensify over the southwestern portion of the fire as it was attaching itself to the outflow boundary. The storm then intensified as it trekked eastward along the southern extent of the fire's burn scar. One note about the fire, however, is that a previous storm moved over the fire a couple hours prior to mesocyclone's life. Could there have been added surface based energy in the form of locally enhanced moisture? If the ground was locally heated, could there have been enough heat to evaporate the previous storms rainfall locally increasing dew points? Again, the current network of in situ and remote sensing instruments cannot provide the answer. If you have any comments on the matter, feel free to comment. Some very interesting meteorology at play here!

Top: 0.5 deg base reflectivity
Bottom: 0.5 deg base velocity
Left: KVAX
Right: KJAX

Time of loop:
Start: 22:13 Z
End: 00:34 Z

Software: McIDAS-V from Space Science Engineering Center at the University of Wisconsin
http://www.ssec.wisc.edu/mcidas/softw...