Severe Weather Discussion – 2008-13-1

Severe Weather Discussion for June 4 – 5, 2008.
Valid: 06/02/2008.

Highlights:

– Isolated severe thunderstorms are possible on Wednesday in western
Oklahoma. Primary threats would be destructive hail and isolated
tornadoes. A heat burst may also occur. Farther north in Kansas more
widespread activity is expected.

– Severe thunderstorms are expected on Thursday across much of Kansas
into Oklahoma.

Discussion:

12z models continue to advertise a large western U.S. longwave trof
developing by Wednesday. As this trof develops wind speeds at all
levels will increase along with directional shear. Moisture is
already in-place and hot afternoon temperatures should yield CAPE
values around 2500 J/Kg. Presence of warm air at 500mb, temperatures
around -5C look to keep CAPES from getting much higher. This would be
a high risk in April or even much of May. However, presence of
summertime temperatures in the atmosphere along with a nuclear cap
make the threat rather conditional on Wednesday. SPC Day 3 is a good
product and I do agree with a conditional threat in Oklahoma. The
better threat is in Kansas as the cap should be weaker and potentially
more directly impacted by small shortwave trofs ejecting out of the
mean longwave position. Any mature thunderstorms will produce
destructive hail and tornadoes. 12z GFS lowers CIN values to -30 J/Kg
across western Oklahoma on Wednesday, this is certainly something to
watch.

Thursday continues to be the interesting day this week. 12z NAM has
significantly slowed the system and is 12 hours slower than the
GFS/ECMWF. Given that the pattern remains in a progressive 5-wave,
maybe 6-wave pattern, I wouldn't expect any more slowing of the upper
system. The upstream kicker it right on its tail. This being said,
the bulk of the upper system impinges on the region at peak heating on
Thursday. This should be sufficient to ignite the dryline and warm
fronts across Kansas and points northeast. The Oklahoma part of this
remains conditional due to the previously mentioned nuclear cap.
500mb heights are 582-576dm across the state and this should help
some. Temperatures may also cool aloft but CAPE values at best appear
to be 2500 J/Kg. SPC Day 4 looks good and no complaints at this
point. I'd have a real hard time with a moderate on the new Day 3,
although they may do it. I don't have all their toys and frankly
there aren't many June case studies to go by. The atmosphere is
unseasonably hot and this may impact the ultimate outcome of this event.

Probabilities:

Risk area for any part of OK/TX (valid: 06/03 Day 2, Day 3):

Slight: 75%, 100%
Moderate: 5%, 40%
High: 0%, N/A

Chase Status:

Level 1 – Normal

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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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