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Mesoscale Discussion 1839
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   Mesoscale Discussion 1839
   NWS Storm Prediction Center Norman OK
   0138 AM CDT Wed Sep 28 2022

   Areas affected...Portions of south/central FL

   Concerning...Tornado Watch 545...

   Valid 280638Z - 280915Z

   The severe weather threat for Tornado Watch 545 continues.

   SUMMARY...An isolated tornado threat will continue early this
   morning. A new Tornado Watch will likely be needed before 09Z (5 AM
   EDT), with more of central Florida included.

   DISCUSSION...Hurricane Ian will continue moving north-northeastward
   early this morning off the coast of southwest FL. Multiple outer
   rain bands persist on the eastern flank of Ian's circulation across
   parts of south FL. Some of these low-topped cells have achieved
   enough vertical depth to induce charge separation, with recent cloud
   to ground lightning flashes noted. The environment across south FL
   will remain favorable for isolated tornadoes through the early
   morning hours. Recent VWPs from KAMX and a 06Z sounding from KMFL
   show strong speed shear in the boundary layer, with modest veering
   as well. Even stronger low-level flow is present along/near the
   southwest coast of the FL Peninsula, which is closer to Ian's core.
   Resultant 0-1 km SRH of 200-400+ m2/s2 will allow any low-topped
   supercells that can persist to rotate and produce an occasional
   tornado. The greatest tornado threat in the next 1-2 hours should
   exist with a band of convection arcing from near Miami FL northward
   toward Lake Okeechobee.

   Persistent influx of a very moist low-level airmass and greater
   theta-e air from the FL Straits will likely support continued
   surface-based thunderstorms. Current expectations are for this moist
   and unstable airmass to gradually develop northward over the next
   several hours into more of the central FL Peninsula in tandem with
   Ian's movement. The threat for isolated tornadoes will likewise
   shift slowly northward as well. A new Tornado Watch will be needed
   before the scheduled expiration of WW 545 at 09Z (5 AM EDT). This
   new watch will likely include a bit more of the central FL Peninsula
   as well.

   ..Gleason/Guyer.. 09/28/2022

   ...Please see for graphic product...


   LAT...LON   25248041 25128068 25138114 25328118 25618131 25798152
               25918174 26478218 27178251 27738219 28448145 28788064
               28198053 27478023 26707997 25488016 25248041 

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