Weekly Severe Weather Discussion

Severe Weather Discussion for November 19 – 25, 2007.
Valid: 11/19/2007.

Highlights:

– Potentially record breaking warmth today and tomorrow. Temperatures plummet on Wednesday in Oklahoma into the 30s with highs in the 40s through Sunday.

– A mixed bag of precipitation is possible Saturday night into Sunday, but confidence is low.

– Tropics are quiet, nothing expected.

Probabilities:

– Severe Thunderstorms in Oklahoma: < 5%
– Storm Chase: < 5%
– Winter Precip: 10%

Discussion:

I hope everyone has enjoyed the recent global warming, because you'll be begging for it in a week. 00z ECMWF/GFS/NAM-WRF continue prior trends of a Canadian cold front moving through Oklahoma on Wednesday. The NAM-WRF is a few hours faster than the GFS and this would not be a shocker. Models can underdo the density of cold air and subsequent motion. For now, cold front passage in Oklahoma City before sunrise Wednesday sounds good. This will make Wednesday a raw and windy day with falling temperatures during work hours. Some people in southern OKC may very well go to work in 60s temperatures and leave in the upper 30s.

Until Wednesday we have a few days left to melt some glaciers. Today and tomorrow will be beautiful by any measure with light winds and warm afternoons. Today may have a slow start given the current fog bank. However, as with what happened yesterday, the fog should burn off by noon allowing for rapid warming during the afternoon. Less fog is expected on Tuesday as winds veer and shallow moisture is advected away. After Wednesday conditions will remain cold with highs generally in the 40s through Sunday. I see little potential for OKC to break 50F and OUN's morning ZFP shows the same. The weekend temperatures may be a little on the high side, but it is a tough call. This is where the 10% winter precip comes in/mixed bag. 00z GFS/ECMWF and 06z GFS advertise a southern stream closed low to develop a few days after the northern stream system moves across the eastern U.S. bringing the expected Canadian cold front. The models are in poor agreement regarding the handling of this
southern feature. The GFS remains progressive, lifting the system out of the region on Saturday/Sunday while the ECMWF keeps it closed/cutoff over the Baja region.

At this point I prefer the GFS progressive solution, but given the strong cold air advection aloft and associated jet maxia, the ECMWF's solution isn't all that crazy. I've gone 10% for winter precip Saturday into Sunday given surface temperatures near freezing and initially dry low levels. This would allow for wetbulb cooling as the upper system moves across. 00z GFS was light on the precip with the 06z more aggressive, especially for eastern OK. So, the short story here is, we don't know. GFS shows some signs of Arctic air loading in Canada by the end of the week. The placement seems to be out of phase for an Arctic dump into this region, but since it is also dependent on model surface/aloft features anything can happen in seven days. I do thing the Arctic air loading is correct, now it is a matter of where it goes.

Nothing of interest in the tropics. 12 days left in tropical storm season.

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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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