SPC MD 1574


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Mesoscale Discussion 1574
NWS Storm Prediction Center Norman OK
0747 AM CDT Sat Oct 13 2018

Areas affected...Portions of central/northern Texas

Concerning...Tornado Watch 412...

Valid 131247Z - 131445Z

The severe weather threat for Tornado Watch 412 continues.

SUMMARY...Some threat for damaging winds, isolated large hail, and a
couple of tornadoes is expected to persist through the morning as
thunderstorms develop east/northeast. Downstream watch issuance is
probable within the next 2-3 hours, in addition to the recent
replacement of Severe Thunderstorm Watch 411 with a Tornado Watch.

DISCUSSION...A supercellular cluster south of San Angelo has
produced at least two tornadoes early this morning, confirmed by
polarimetric debris signatures in southern Tom Green Co around
7-730am CDT. Recent KSJT VWP data exhibit clockwise-looping
hodographs characterized by considerable streamwise vorticity for an
eastward storm motion. Given moist/saturated boundary-layer
profiles, occasional/cyclic low-level mesocyclones may persist for a
few more hours, supporting a threat of a couple of tornadoes. To
account for this threat, Severe Thunderstorm Watch 411 has been
replaced with Tornado Watch 412.

Through the morning, broad warm advection ahead of this cluster may
yield sufficient new development for a forward-propagating line of
storms and/or embedded supercells, given gradual surface-based
destabilization and favorable low-level shear. Damaging winds, a
couple of tornadoes, and isolated large hail would all be possible
with these cells as they lift east/northeast. Therefore, a new
downstream watch is probable within the next few hours.

..Picca.. 10/13/2018

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


LAT...LON   31099722 30889734 30629786 30519844 30449931 30480027
            30690064 31180074 31310071 31829997 32099890 32189825
            32069776 31789748 31349725 31099722 

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