Severe Weather Discussion – 2008-13-3

Severe Weather Discussion for June 4 – 5, 2008.
Valid: 06/04/2008.

***Significant Severe Weather Episode on Thursday***
***Affecting much of Oklahoma northward to Iowa***

Highlights:

– Isolated severe thunderstorms are expected late this afternoon into
the early evening hours across northwest Oklahoma. Generally west of
a line from Medford to Weatherford. The threat is conditional upon
storms developing. However, any mature thunderstorms will produce
destructive hail, destructive winds, and maybe an isolated tornado.

– A much more significant and potentially life threatening episode is
developing for Thursday across much of Oklahoma. Unlike today, storm
development is much more likely Thursday late afternoon into the
evening hours. Initial development will feature supercells capable of
destructive hail, isolated long-track tornadoes, and damaging winds,
primarily in west-central through north-central Oklahoma. The threat
should transition to a widespread destructive wind event for the
remainder of the state during the evening hours. While damaging winds
are the primary threat during this time period, large hail and
isolated tornadoes cannot be ruled out.

– Chase Status is increased to Level 3 for Thursday.

Discussion:

12z model data continues to develop isolated severe thunderstorms
later today. Most likely time for development will be between 4-7pm
in northwest Oklahoma. Only a few storms are expected but any mature
storm will have high-impact potential. Primarily destructive hail to
softball size, winds to 80mph, and isolated tornadoes. The tornado
threat appears low today, but that can rapidly change. The Storm
Prediction Center has issued a slight risk for areas west of a line
from Medford to Weatherford through the evening hours.

Model data also continues to hint at a significant severe weather
event on Thursday. Wind fields at all levels will be very strong for
early June and when combined with modest instability makes for an
extreme severe weather setup. The longwave trof responsible for this
setup will move east into the region late Thursday. Until this happen
a cap, layer of warm air aloft, should hold down the atmosphere
allowing for hot and humid conditions to develop east of the dryline.
As the upper system moves into the region, the cap will weaken and
allow for explosive development during the late afternoon hours.
Storms may initially be isolated, which will enhance the severe
weather threat. In this scenario long-track tornadoes are possible.
Later in the evening, and potentially from the beginning, a squall
line will develop. This scenario would yield widespread destructive
winds as the line of storms moves east across Oklahoma.

This setup is very dynamic and in cases like this the event can
quickly go from discrete storms to a squall line. In rare events
there is too much wind shear and the updrafts are ripped away. There
is little way to determine what will be the actual scenario, however
the potential is there. I think SPC should have done a high risk for
NE/KS and parts of Iowa, and further I think the moderate should come
down to the Red River.

Probabilities:

Risk are a for any part of OK/TX (valid: 06/05 Day 1):

Slight: 100%
Moderate: 100%
High: 50%

Chase Status:

Level 3 – Thursday

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About Putnam Reiter

Putnam has been storm chasing since 1990 and is a co-founder of Hook-Echo.com. For his day job, Putnam works in emergency management for information technology.
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