Severe Weather Discussion – 2008-13-2

Severe Weather Discussion for June 4 – 5, 2008.
Valid: 06/03/2008.

Highlights:

– Isolated severe thunderstorms are possible across the western 1/4 of
Oklahoma on Wednesday. The threat is very conditional, but if storms
do form damaging hail and isolated tornadoes would be the primary
threats.

– Active severe weather day is expected on Thursday across much of
Oklahoma northward to Iowa. A significant severe weather episode
appears to be in the offering for parts of the central U.S.

– Severe thunderstorms may be ongoing Friday, but this threat is also
conditional.

– Chase Status is increased to Level 2 for Thursday.

Discussion:

Little change to forecast reasoning from yesterday's discussion.
Wednesday appears to be a very conditional day, but with very strong
speed and directional shear on top of a hot/moist boundary layer, the
threat still exists. Any mature storm will have the potential to
produce damaging hail and isolated tornadoes. The threat shouldn't
extend very far east as mid-level lift will not be supportive of this
given nuclear cap.

Models seem to be in better synch on the 12z runs with respects to
Thursday afternoon and evening. The 12z NAM/GFS both develop
precipitation along the dryline, although at different times. The NAM
is earliest with convection around 7pm, while the GFS is seemingly a
little later. The cap is the main issue for Thursday and progs would
certainly indicate a very stout one. Despite this the 12z NAM erodes
CIN across a wide area, however this is a characteristic bias of this
model so I think it is probably over doing it. The GFS may be closer
showing -30 J/Kg CIN across much of western Oklahoma at 7pm Thursday.
This amount of CIN would require dynamic support to breach the cap.
Said support looks to be there given impressive UVV's on both models.
The GFS's 90kt 400mb jet is pretty amazing for this time of year. If
this was a few weeks ago, I'd call for a high risk on Thursday.
However, given the strong cap and still unseasonable warmth of the
mid-levels, I'm not sure how all of it will play out. Either way with
the models picking on QPF, I think a moderate is warranted on the new
Day 2.

With all this said, the chase status is increased to Level 2 for Thursday.

Probabilities:

Risk area for any part of OK/TX (valid: 06/04 Day 1, Day 2):

Slight: 50%, 100%
Moderate: 0%, 100%
High: 0%, 0%

Chase Status:

Level 2 – Watching 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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