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| Mesoscale Discussion 1692 |
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Mesoscale Discussion 1692
NWS Storm Prediction Center Norman OK
0523 PM CDT Tue Sep 15 2020
Areas affected...Southern AL and the FL Panhandle
Concerning...Severe potential...Tornado Watch likely
Valid 152223Z - 160030Z
Probability of Watch Issuance...95 percent
SUMMARY...A tornado threat will continue into the evening and
overnight hours along the FL Panhandle coastal region. A new tornado
watch will be issued to replace WW 489 by 23 UTC.
DISCUSSION...Per recent NHC guidance, Hurricane Sally continues to
move north towards southern AL at around 2 mph. This slow motion
will allow a strongly sheared environment (around 600 m2/s2 0-1 km
SRH noted on the KEVX VAD) to linger over southern AL and the FL
Panhandle. However, the tornado threat may be somewhat conditional
on sufficient instability to support inland convection. Recent IR
satellite trends show numerous convective towers developing offshore
over the Gulf Coast, but only weak/transient convection inland. This
trend is reflected in recent RAP Mesoanalysis, which shows only
250-500 J/kg MLCAPE inland - largely due to persistent stratiform
rain over the region. Confidence in sufficient instability is lowest
across southern AL/the Mobile Bay area where easterly low-level
trajectories are advecting in lower theta-e air from the FL
Panhandle into the region and reducing instability. However,
sufficient instability immediately offshore will continue to support
the potential for waterspouts moving inland along the coastal areas
in the coming hours for the FL Panhandle. As mid-level dry air
continues to move inland overnight and low-level onshore flow
increases, the potential for sustained inland convection may
increase and support a tornado threat.
..Moore/Thompson.. 09/15/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TAE...MOB...
LAT...LON 30628751 30908746 31168715 31188660 31038580 30798488
30238372 29868364 29728378 29718418 29468468 29468512
29908578 30218662 30208688 30258716 30378738 30628751
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