Weekly Severe Weather Discussion

Severe Weather Discussion for September 17 – 23, 2007.
Valid: 09/17/2007.

Highlights:

– Temperatures above normal all week.

– Thunderstorms are possible tonight through Wednesday.

– Tropics are quiet, somewhat unseasonably so.

Probabilities:

– Severe Thunderstorms in Oklahoma: 15%
– Storm Chase: < 5%
– Winter Precip: < 5%

Discussion:

Atmospheric pattern will amplify part of this week with Oklahoma influenced by a mid-level ridge. Lack of cold fronts and southwesterly mid-level flow will warm things up this week, as noted by today. As such, temperatures will be above normal (currently 84F in OKC) all week.

The main weather maker for Oklahoma will be the west coast trough. Dewpoints have recovered to the mid-60s and temperatures are in the upper 80s. Combination of these factors, along with weak flow aloft has allowed line segments to develop in the Texas panhandle. Storms should continue until sunset and then weaken. Primary movement is towards the north-northeast, so little affect on Oklahoma is expected.

Better chances for Oklahoma exist on Tuesday as the shortwave trof ejects east and the overall trof axis moves through the region into Wednesday. Mid-level flow will strengthen to 15-20kts with some shear in the area. Thermodynamics are favorable for isolated severe thunderstorms. Primary limiting factor will be lack of surface boundaries as the dryline should remain in the Texas panhandle. Main threat from any storms that develop will be excessive rainfall. However, I wouldn't be surprised to see a few isolated severe reports through Wednesday.

After the trof moves east a strong closed low develops just off the southwest California Coast. Said trof will remain there for several days as the 588dm ridge dominates the weather across Oklahoma. This ridge will keep the area warm and dry through Saturday. Model issues by Saturday make this a complex forecast for Sunday. I'm not going to worry that much about Day 7. The GFS would keep the area warm and dry on Sunday, although some influence from a weak easterly wave may cause some rain. The ECMWF breaks the system in by Sunday and could provide an opportunity for rainfall. I really do not expect much from the SW US closed low, but we'll see.

Ingrid died a horrific death due to southwesterly shear. NHC is monitoring a few areas, but for the most part the tropics are quiet. Seasonably the tropics are a little too quiet as we're still in the peak for another 15 days. Should be interesting to see what happens.

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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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