Mesoscale Discussion 1860
   NWS Storm Prediction Center Norman OK
   1255 PM CST Sun Dec 20 2020

   Areas affected...west-central Florida and adjacent coastal waters

   Concerning...Severe potential...Watch unlikely 

   Valid 201855Z - 202030Z

   Probability of Watch Issuance...5 percent

   SUMMARY...A thunderstorm capable of producing brief
   tornadoes/waterspouts and strong, gusty winds will continue to
   approach the south Tampa Bay area this afternoon. The isolated
   nature of the current threat should preclude the need for a watch.
   Additional thunderstorms may develop farther northwest later this
   afternoon/evening.

   DISCUSSION...An isolated, thunderstorm exhibiting supercell-like
   characteristics persists across the far eastern Gulf of Mexico to
   the west-southwest of Tampa Bay. MRMS radar trend indicates
   persistent midlevel rotation has increased slightly recently and
   MESH cores have correspondingly increased. This thunderstorm appears
   to reside within the eastern gradient of the greater destabilized
   airmass.

   Tampa Bay VAD indicates the airmass ahead of the storm is
   characterized by 0-3km storm-relative helicity values between
   200-250 m2/s2, with the bulk of that existing within the 0-1km
   layer. This reservoir of enhanced low-level helicity should maintain
   at least a low threat for brief tornadoes/waterspouts with this
   storm.

   As the thunderstorm moves onshore, the severe threat should quickly
   wane given the cooler/more stable airmass across the Florida
   Peninsula.The limited spatiotemporal coverage of this storm should
   preclude the need for a watch in the short term.

   Morning and early afternoon high-resolution numerical guidance
   continues to suggest thunderstorm redevelopment should occur later
   this afternoon/evening across the northeast Gulf of Mexico as a cold
   front approaches the Florida Peninsula. This area will continue to
   be monitored through the afternoon and evening.

   ..Marsh/Guyer.. 12/20/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...TBW...

   LAT...LON   27238346 27538350 27758338 27868306 27888274 27828242
               27598222 27208224 27058238 27018248 26978296 27238346