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Mesoscale Discussion 1107
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   Mesoscale Discussion 1107
   NWS Storm Prediction Center Norman OK
   0747 AM CDT Wed Jun 21 2017

   Areas affected...Portions of the central Gulf Coast

   Concerning...Tornado Watch 358...

   Valid 211247Z - 211445Z

   The severe weather threat for Tornado Watch 358 continues.

   SUMMARY...The threat for a few tornadoes near the coast continues
   this morning. Additionally, new watch issuance may be required prior
   to the 15Z (10AM CDT) expiration of Watch 358.

   DISCUSSION...Although the center of Tropical Storm Cindy is
   progressing farther away from the ongoing Tornado Watch, conditions
   remain modestly favorable for a few brief tornadoes this morning.
   Very slow northward movement of a warm front overnight has brought
   weak, but adequate surface-based buoyancy to parts of the central
   Gulf Coast. Combined with enhanced storm-relative helicity (noted
   most clearly in recent KMOB VWP data and the 12Z LIX sounding),
   low-level mesocyclones will likely persist in semi-discrete/cluster
   modes within confluent bands approaching the coast. Indeed, KEVX
   data likely detected a tornado near Fort Walton Beach, FL via a
   dual-pol debris signature around 1120Z (620AM EDT).

   Persistent moist south/southeasterly flow and pockets of weak
   diurnal heating will lead to further inland advancement of
   sufficient surface-based buoyancy this morning. However, the
   low-level jet peripheral to Cindy will evolve westward through the
   day, likely shifting the highest tornado threat closer to the
   Mississippi River. While mid-level drying over this part of the
   watch has kept convection shallower and more sparse in coverage so
   far, the westward evolution of the low-level jet (and related warm
   advection) today will likely combine with further destabilization to
   foster renewed convection along one or more confluence bands from
   Alabama to Louisiana. Recent visible satellite/lightning data
   suggest the initial stages of this evolution may be underway across
   the central Gulf. Considering the aforementioned environmental
   parameters, storms approaching the coast later this morning may
   still yield an increased tornado threat. Therefore, a new watch may
   be coordinated within the next two hours.

   ..Picca.. 06/21/2017

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

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

   LAT...LON   29589261 30599042 31008778 30898595 30448555 29988576
               29798761 28878907 28849084 29049243 29249267 29589261 

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Page last modified: June 21, 2017
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