Severe Weather Discussion for July 13 – 19, 2009.
– Climatological max temperature starts the 17th for OKC at 94F.
– Temperatures will be around 105F Monday – Tuesday, 101F Wednesday,
upper 90s Thursday, mid 90s Friday-Saturday, and upper 90s Sunday.
Thunderstorms are possible late Thursday through early Saturday across
– Severe Thunderstorms in Oklahoma: 5%
– Storm Chase: < 5%
– Tropical Development: 10%
The first few days of the week will be similar to what we have
experienced this week. A 594dm ridge will be in place across the
central U.S. with 500mb heights running around 597dm in Oklahoma. All
models agree the center of the ridge will shift west around mid week
as a shortwave trof moves across the northern U.S. A cold front will
approach Oklahoma on Thursday and should lead to cooling on Friday
across parts of the state. This may linger into Saturday, but
temperatures will still be in the mid 90s. The 12z ECMWF is
aggressive with the eastern U.S. system and typically I go with it.
For this week I'm siding with the GFS, which slides the ridge a little
east into Oklahoma. As such, I'm warmed temperatures back up on
Sunday. If I'm wrong, I'll be quite happy. Surface boundary,
reducing ridging, and seasonable moisture will provide a chance for
thunderstorms late Thursday into Friday.
I've gone with 10% on the tropical development, given that mid-July is
the usual time for an uptick in activity. However, it appears that El
Nino 2009 has started with a weak El Nino now confirmed. El Nino
typically causes stronger shear in the Atlantic basin, reducing the
tropical threat. We'll see what happens.
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