Severe Weather Discussion – 2007-11-1

Severe Weather Discussion for June 5 – 8, 2007.
Valid: 06/02/2007.

Highlights:

– Severe thunderstorms are possible Tuesday – Friday with some potential for at least one or more medium-end events.

Discussion:

Analysis of 12z model data continues to point towards an active and potentially deadly week across the region. Current emphasis is on Wednesday. Conventional wisdom dictates that available guidance will shift during the upcoming days, but I cannot ignore the high-end signals presented by the models at the juncture.

Tuesday looks to be a continuation of the atmosphere we currently have and an MCS is the primary threat. However, northwesterly flow will provide ample shear across west Texas for supercells in initial development. Activity may congeal into an MCS during part of the night. Though question on how organized it can get given lack of a shortwave trof. Once again, this far out, wouldn't be surprised if the models are missing something. Either way, SPC Day 4 has a good lock on Tuesday and I agree with the outlook. One big limiting factor may be the presence of shortwave ridging ahead of western U.S. trof.

Wednesday is the more interesting day so far. Many parameters appear to be in-place for what could be a significant severe weather event for north Texas into the Dakotas. Kansas and Nebraska appear to be at the greatest threat. Models agree that the atmosphere will under go a significant change as a progressive and unseasonably strong shortwave trof moves into the region by late Wednesday. At the surface a low is progged to develop in northeast Colorado and move northeast during the day. The resulting dryline should advance east somewhat during the day and be located near the edge of the cap rock. To the east dewpoints of at least 65F are expected with resulting CAPE values above 3500 J/Kg. Certainly seems possible that the region may experience some of the warmest air this season as this system approaches. GFS is showing mid/upper 90s just west of the dryline. Presence of strong speed and directional shear, combined with impressive thermodynamics points to a significant
supercell threat for parts of the region. The cap will be an issue, but strong daytime heating should be enough to breach it in several places across the state. If a chase does occur, our tactic will like be to pick the storm north of tail-end Charlie. Charlie will likely be a meat-grinder due to high T/Td spreads and very cold downdrafts.

Thursday also has significant potential but may be a little more complex as by this time the upper system has shifted east of the region. Current progs have the dryline in Oklahoma with strong wind fields aloft in place. Would expect additional storm development along the dryline by late afternoon. For now I'm not going to get aggressive on discussing Thursday.

Models diverge significant for Friday and Saturday, and for now will just note there is potential.

SPC 4-8 outlook looks good and will continue to monitor trends the next few days. Discussions are expected to continue unless models revert to a 600dm ridge over the region.

Probabilities:

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

Slight: 100%
Moderate: 0%
High: 0%

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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