Weekly Severe Weather Discussion

Severe Weather Discussion for August 24 – 30, 2009.
Valid: 08/23/2009.

Highlights:

– Quick warm-up and then cool down for the latter half of the week.
Chance of rain Wednesday – Friday. Temperatures will be in the low
90s Monday, mid 90s Tuesday-Wednesday, upper 80s Thursday, mid 80s
Friday, upper 80s Saturday-Sunday.

– Fire weather threat Monday, western Oklahoma.

– Models shows at least a tropical system making a run at the eastern
U.S. late this week. We'll see, but right now NHC is tracking only
one tropical wave.

Probabilities:

– Severe Thunderstorms in Oklahoma: 15%
– Storm Chase: < 5%
– Tropical Development: 30%

Discussion:

Pretty nice late-summer week on-tap for the region as the subtropical
ridge over the central U.S. fails to become anchored. Not a surprise
given the copious amounts of rainfall the past two weeks and potential
for more rainfall this week. Climate temperature drop is nearing a
delta of -1F/3 days. The normal high on Monday is 91F.

In general the models agree on the 500mb pattern with some differences
noted in the lower levels. As the ridge attempts to build-in part of
the eastern U.S. longwave trof will break off and move southwest and
west into Texas/LA. At the same time a southern stream shortwave trof
moves through the somewhat dirty ridge. What this seems to mean at
this point will be 2-3 days of warm temperatures followed by a cool
down as with rain chances. Rain cooled air and a cold front will keep
temperatures near or just below normal the latter part of this week.
Assuming we'll be 90F by the weekend.

I have a real tough time going with the temperatures the models and
OUN are using. I'll risk taking the bust; given I got several last
week for being too high and I was event below them! While the upper
ridge will be over Oklahoma on Tuesday, there is a lot of moisture in
the ground and air to battle against. Not withstanding that we have
80 minutes less sunlight than early July. Just real tough to build up
that much heat without southwest flow. Now, I'm going for OKC. Areas
in southwest Oklahoma will likely get quite toasty Monday-Tuesday. In
fact, OUN is watching western Oklahoma for a fire weather threat on
Monday.

Models show a tropical system mid-week, racing near the east coast.
Lack of a strong ridge in this area should protect the U.S. No other
activity noted right now, but August 20th is the ramp-up to peak
tropical season on 09/10. As such, I've bumped up the probabilities
and will keep them at least 30% through mid September.

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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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