Severe Weather Discussion for April 24, 2008.
– Active severe weather expected this afternoon and tonight across
much of Oklahoma northward into Nebraska. Primary threats are
tornadoes, destructive hail, and strong winds.
– Chase Status is increased to Level 4.
Little time for a discussion, attempting to spin up on the weather
Northern stream longwave trof is taking shape just west of the
region this afternoon. This feature will continue moving east the
remainder of today into tonight. Afternoon surface analysis shows a
dryline in western Oklahoma with a windshift boundary farther east.
Winds across the western parts of Oklahoma westward to the dryline are
slightly veered at 200 degrees. Winds in central sections are more
170 to 180 degrees. Temperatures are commonly in the upper 70s to low
80s with dewpoints in the mid 60s. This is yielding CAPE values near
3200 J/Kg in parts of central Oklahoma, with LIs to -7. Low and mid
level wind speed/directional shear are quite favorable for rotating
updrafts and organized storms.
Two parameters are of concern at this point. 1) is the EML, cap.
However, CIN values are below 25J?kg as of 19z and only a little more
cap erosion is needed for storm initiation. As such, the cap is not
expected to be a problem and may help things as it keeps storms
isolated. 2) Upper level winds. To me this is the biggest limiting
factor we face right now as these winds are generally 40-60kts across
the state. However, one bright side is the WSW to ENE orientation of
the mean 300/200mb flow. This should limit anvil seeding and the
overall expected isolated nature of storms should help also.
The NWS is focusing on northern Oklahoma where low level shear will be
best. However, I think there is a general threat along the I-35
corridor, especially near Oklahoma City given the 3400 J/Kg CAPE max
just southwest of the metro at 19z. This is the primary reason we’re
going to hug I-40 today. Things could get real interesting around
19:00-20:00 as the low level jet develops.
Level 4 – Heading to Weatherford around 16:00.
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