Mesoscale Discussion 0815
NWS Storm Prediction Center Norman OK
1122 AM CDT Tue May 23 2017
Areas affected...Portions of northern Florida and southern Georgia
Concerning...Tornado Watch 257...
Valid 231622Z - 231745Z
The severe weather threat for Tornado Watch 257 continues.
SUMMARY...Strong to occasionally severe thunderstorms will continue
east/northeastward across Watch 257 through the early afternoon,
with an attendant threat for a couple tornadoes and damaging wind
DISCUSSION...Along and ahead of a line of thunderstorms (near the
AL/GA border as of 16 UTC/12 EDT), pockets of heating have brought
surface temperatures into the mid/upper 70s and low 80s. In turn,
with rich boundary-layer moisture present, mixed-layer CAPE values
have risen to upwards of 1000 J/kg, based on forecast and modified
observed sounding data. Radar/lightning observations have indicated
a gradual upward trend in intensity over the last hour, and storms
should persist in this relatively favorable thermodynamic
environment for several hours.
Deep-layer shear profiles remain favorable for occasional
low/mid-level rotation, as a southwesterly low-level jet crosses the
region and winds veer with height from the surface to mid levels.
Recent KVAX and KTLH VWP data depict the presence of approximately
150-200 m2/s2 of 0-1km storm-relative helicity, suggesting
occasional low-level mesocyclogenesis potential (either
line-embedded or in semi-discrete cells). Indeed, a dual-pol
tornadic debris signature was observed in southern Randolph County,
Georgia around 1545-1555 UTC, confirming this environmental
potential. As such, a threat for damaging winds and a couple
tornadoes will persist as storms spread east across Watch 257 this
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 31868481 32368339 32638263 32518217 31918228 30918273
30458304 30148410 30118510 30388573 31418521 31868481