Weekly Severe Weather Discussion

Severe Weather Discussion for September 6 – 12, 2010.
Valid: 09/05/2010.

Highlights:

– Widespread showers and thunderstorms are likely Wednesday and
Thursday. Isolated tornadoes will be possible depending on the
strength of the tropical system as it moves into Oklahoma.

– Temperatures will be in the mid 90s Monday, upper 80s Tuesday, mid
80s Wednesday-Thursday, uppers 80 Friday, low 90s Saturday-Sunday.

– September 10th is the climatological peak in tropical storm season.

– NHC is closely watching an area in the south Gulf of Mexico and the
remnants of Gaston.

Probabilities:

– Severe Thunderstorms in Oklahoma: 15%
– Storm Chase: < 5%
– Tropical Development: 60%

Discussion:

Upper level pattern really isn't that exciting again this week, but
there appears to be a player in the Gulf this afternoon. Whether or
not this system develops enough to became a tropical depression or
storm, it will bring very high precipitable water vapor values into
Oklahoma. This combined with a weakening frontal boundary should
focus heavy rainfall in the state as the system approaches late
Tuesday into Wednesday. Later Wednesday, the remnants will move into
Oklahoma and the excessive rainfall threat should continue. By
Friday, this system is expected to move northeast as a shortwave trof
ejects out of the southwest U.S. Eastern U.S. ridging is likely to
keep the western U.S. shortwave trof from influencing the region and
is also why the first front on Tuesday will be rather weak. After the
tropical system departs on Friday, the mid-level ridge over the
eastern U.S. is progged to shift west, which will raise temperatures.

Highs this week are likely to be tricky Tuesday-Friday. This time
period will see the most influence from the cold front and then
tropical system. Model progs aren't too bad and generally went with
them. I went with likely POPs mid-week as there should be widespread
rainfall across the state. NAM/ECMWF are most bullish with the GFS
lower on QPF. Given the recent model physic changes in the GFS to
reduce QPF bombs, it could be under estimating QPF. Much of Oklahoma
is in a D1 drought, so we'll need a lot of rain to result in a
flooding concern.

Tropics continue to be very active, which is normal this time of year.
The system in the Gulf is being watched closely for development and
could become a tropical storm assuming it can organize. The remnants
of Gaston are also getting organized and this may be a threat to the
US later in the week. As such, went high on the tropical storm
probabilities. Coordination with Andy yields a tornado threat for
eastern Oklahoma on Thursday depending on how organized the system in
the Gulf gets. As these tropical type systems are good at producing
quick and small tornadoes, a 15% seems warranted.

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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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