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Mesoscale Discussion 1121
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MD 1121 graphic

   Mesoscale Discussion 1121
   NWS Storm Prediction Center Norman OK
   1150 AM CDT Thu Jun 22 2017

   Areas affected...Central/eastern LA...Central/southern
   MS...Southeast AR...Central/southern AL...FL Panhandle

   Concerning...Tornado Watch 363...

   Valid 221650Z - 221815Z

   The severe weather threat for Tornado Watch 363 continues.

   SUMMARY...Isolated tornado threat continues east of Tropical
   Depression Cindy. New watch issuance is likely before 18Z.

   DISCUSSION...Thus far this morning, the strongest convection (and
   occasional rotation) has been noted across the eastern portion of WW
   363, with a possible waterspout/tornado reported earlier this
   morning near Pensacola. This region is located within the strong
   belt of deep, moist southerly flow to the east of a well-defined
   midlevel dry slot that is wrapping into TD Cindy. While wind
   profiles are southerly through a deep layer, backing of the
   low-level flow is supporting substantial low-level shear, with 0-1
   km shear of 25-35 kts noted per recent mesoanalyses and VWP data.
   Very warm midlevel temperatures and poor lapse rates will continue
   to limit the intensity of convection through the day, but the the
   strongest cells will pose an isolated tornado threat given the
   aforementioned low-level shear magnitude coincident with a very
   moist, tropical airmass and potential for some additional
   destabilization as modest heating continues. Some threat may spread
   north out of the watch by early afternoon, though it is unclear at
   this time whether any northward expansion of the watch will be
   necessary. 

   Further east, closer to the primary circulation of TD Cindy,
   convection has likely been inhibited by very dry midlevel air noted
   on WV imagery. However, greater insolation within the dry slot has
   allowed stronger heating to occur, and convection has begun to
   gradually increase across southern/eastern LA and southern MS.
   Continued destabilization within a low-level environment that is
   very moist and strongly sheared will support a gradual increase in
   the tornado threat through the day across portions of LA into
   western MS. 

   Since some tornado threat is likely to persist through the afternoon
   across WW 363, a new tornado watch will likely be required before
   18Z covering generally the same area from LA eastward through MS,
   and perhaps northward into southeast AR and eastward into portions
   of AL and the FL Panhandle.

   ..Dean/Guyer.. 06/22/2017

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

   ATTN...WFO...TAE...BMX...MOB...JAN...LIX...LZK...LCH...SHV...

   LAT...LON   29169219 33569220 33508875 33198598 30788599 29698617
               29538846 28458880 28599111 29169219 

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Page last modified: June 22, 2017
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