Severe Weather Discussion for April 6, 2010.
– Severe thunderstorms are expected across the eastern 2/3rds of
Oklahoma this afternoon and evening. Primary threats with initial
convection will be damaging hail and tornadoes. Later in the evening,
the threat will shift to damaging winds.
– Chase Readiness is increased to Level 4.
12z models are consistent with prior runs and there are no major
changes to prior thinking. At this point the models are not that
useful and will turn to observational tools for decisions later today.
Current thinking continues to be the dryline ending up near HWY 81
at convective initiation. Storms should rapidly go severe given CAPE
values AOA 1500 J/Kg. NAM has finally resolved the 850mb moisture
issue and seems inline with other models. This has been noted on the
NAM in past events and as recent as December 24th snow storm (seems to
be a NAM bias).
15z SPC analysis and Mesonet data indicate the dryline is on TX/OK
border with CAPE values in this area around 1500 J/Kg. Normalized
CAPE is very low, but not a shocker this early in the game. Clouds
are thinning across the region and would expect surface heating to
increase during the late morning and afternoon hours. Surface winds
are veering a little in northern Oklahoma and this is expected and
shown by the models. Winds should back a little later today as the
influences from the first shortwave trof leaves the area.
12z NAM shows no QPF on the dryline today whereas the GFS does. GFS
has slowed the dryline movement and appears more inline with the NAM.
GFS also has a 2000 J/Kg CAPE max just east of OKC, so this will have
to be watched. QFP remains limited across the state with models
having great variability. I think this is a good thing since it
certainly implies isolated storms. Of course I've seen no QFP
forecasts turn into a squall line.
The chase target is quite variable right now and will truly center on
what observational analysis shows around 2pm. There is no reason to
flop all over the place at this point. My interest is to hang close
to OKC but be flexible enough to drop south a little or scream north.
I'm not that interested in going too far south given same instability
but less mid-level flow. GFS shows deep layer UVV's entering central
Oklahoma around 00z, which could certainly enhance ongoing activity.
Storms are expected to develop between 4-6pm.
Level 4 – heading out around 15:00 CDT. The target area remains
unknown, but somewhere around Yukon, Kingfisher, Guthrie, OKC.
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