Chase Discussion for April 25, 2009.
Target area: Shamrock Texas
Departure Time: 14:00 CDT
Expected Risk Area: Slight Risk – 10% tornado, 30$/10% hatched hail,
00z NAM continues prior thinking that a few severe thunderstorms will
develop in the eastern Texas panhandle late Saturday afternoon. While
the threat is conditional, enough of the models suggest convective
development to give decent confidence on activity. Wind fields will
not be particularly strong as the shortwave trof responsible for this
setup will still be in the base of the developing longwave trof.
Despite this, sufficient lift should occur along the dryline in the
Texas panhandle for initiation by late afternoon. NAM UVV fields
collocate from Wellington to Shamrock by 00z. This is just east of
the expected dryline location and appears to be a good spot to stage.
CAPE values will range from 2500-3000 J/Kg just east of the dryline.
It appears the surface low will be shifting westward during the late
afternoon hours and the dryline should retreat also. However, enough
surface convergence should remain to assist storm development. The
threat is conditional due to lack of significant upper support but at
least a few storms appear possible. SPC will likely continue the
slight risk as coverage doesn't seem to warrant a moderate risk.
Sunday continues to have potential but the ultimate threat will
greatly depend on Saturday's activity. I'm not buying into the 00z
NAM's precip prog for late Saturday into Sunday. It may end up
correct, but for now Sunday remains 50/50.
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