Severe Weather Discussion for May 13, 2008.
– Active severe weather day expected for the eastern half of Oklahoma.
Tornadoes, destructive hail, and damaging winds are all possible.
– Leaving around 16:00. Toying with Pauls Valley due to frontal movement.
MCD just issued for southern OK and north Texas, watch likely.
Afternoon visible imagery shows cumulus east of a dryline extending
from just east of Ponca City to Oklahoma City to Walter and on
south-southwest into Texas. East of this boundary temperatures are in
the low 80s with dewpoints near 70. This is creating SBCAPEs of 3000
J/Kg with 100mb MLCAPE around 2000 J/Kg and LIs to -8. 12z RAOB data
indicated a very strong cap and this is currently suppressing
development area wide. Elevated showers and isolated thunderstorms
are occurring in Texas, but this should not be a problem relative to
12z NAM/RUC indicates that low level winds will weaken near an just
west of I-35 by 7pm. This has been the general forecast the past few
days and I do agree with this. The front has slowed significantly the
past hour and it/dryline should make very limit progress east. NWS
OUN thinks these boundaries may even retreat to the west a little.
Analysis of the events the past few weeks would put the best threat
near the wind shift from S to SW and before the true dryline, west
winds. This is counter-intuitive but has been the pattern recently.
Storms should still move into decent low level winds near and east of
I-35, mid/upper level winds are good statewide. Any storm(s) that
manages to move deviant to the mean flow will increase helicity and
tornado potential. Storms may tend to split early in their life cycle
with the left moves remaining elevated and presenting a destructive
hail threat. Right movers and especially deviant right moves will
have a tornado and destructive hail threat.
PRIND: Explosive development will occur around 4pm near the SW
winds/dryline interface. Storms will rapidly become severe as they
move east and northeast. Currently only scattered storms are expected
as the cap should keep much of the atmosphere down. Later tonight the
front should start moving south again with a squall line developing
along it. The primary threat from these storms will be damaging winds.
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