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Mesoscale Discussion 1106
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MD 1106 graphic

   Mesoscale Discussion 1106
   NWS Storm Prediction Center Norman OK
   0212 AM CDT Wed Jun 21 2017

   Areas affected...Portions of the central Gulf Coast

   Concerning...Tornado Watch 358...

   Valid 210712Z - 210915Z

   CORRECTED FOR WATCH TYPE

   The severe weather threat for Tornado Watch 358 continues.

   SUMMARY...The threat for a few tornadoes along the central Gulf
   Coast should continue to slowly increase towards daybreak.

   DISCUSSION...As Tropical Storm Cindy continues its slow
   northwestward movement, a broad area of showers and thunderstorms
   has advanced near/onshore from Louisiana eastward to the Florida
   Panhandle. Several convective cells (primarily those offshore)
   within this regime have exhibited low-level rotation, with
   occasional waterspouts probable in several of these offshore cells.
   Regional VWP data (e.g., KLIX, KMOB, KEVX) sample low-level winds
   strongly veering with height, bolstering storm-relative helicity and
   the potential for low-level mesocyclogenesis. Additionally, this
   notable veering implies considerable warm-air advection near a front
   stretching from Plaquemines Parish east/northeastward to the Florida
   Panhandle. Near and to the south of this boundary, dew points in the
   mid/upper 70s and temperatures in the upper 70s/lower 80s are
   offering adequate surface-based buoyancy for a tornadic threat.

   VWP data, model analyses, and surface pressure-fall observations
   indicate the strongest branch of the low-level jet currently resides
   from the Alabama Panhandle southeastward into the Gulf. Indeed,
   radar data indicate a band of strong thunderstorms extending
   near/along this axis, likely fostered by warm-air advection and
   speed convergence near the coast. While these cells are currently
   displaced from zones of sufficient onshore destabilization (i.e.,
   Plaquemines Parish, LA and the Apalachicola, FL vicinity), continued
   northward advection of warm/moist air will likely increase the
   tornado threat from southern Mississippi to the western Florida
   Panhandle over the next several hours. Farther west, water-vapor
   imagery and forecast soundings suggest drying aloft is leading to
   shallower/more sparse convection across southeast Louisiana.
   However, further surface destabilization and favorable
   storm-relative helicity will maintain some tornado threat here as
   well through the night.

   ..Picca.. 06/21/2017

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

   ATTN...WFO...TAE...MOB...LIX...LCH...

   LAT...LON   28949102 29299134 29989127 30519081 30918853 31038626
               30898567 30278529 29718530 29448565 29588727 29088876
               28819052 28949102 

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Page last modified: June 21, 2017
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