Weekly Severe Weather Discussion

Severe Weather Discussion for November 29 – December 5, 2010.
Valid: 11/28/2010.

Highlights:

– Showers are possible in eastern Oklahoma Monday afternoon.

– Temperatures will be in the upper 50s on Monday, mid 40s Tuesday,
low 50s Wednesday, upper 50s Thursday, mid 60s Friday, upper 50s
Saturday, and low 50s Sunday.

Probabilities:

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

Discussion:

Longwave trof progged to translate eastward across the central U.S.
tomorrow. Strength of trof and moisture return points to likely
showers across eastern parts of Oklahoma. Prior Canadian cold front
has limited moisture return in areas west of I-35, so do not expect
much in that area. Upper system will pass quickly east while dragging
a Pacific cold front across the state Monday night. This will setup a
cool day on Tuesday under northerly flow. Models show northwesterly
flow continuing into Wednesday as a weak shortwave trof moves rapidly
southeast. RH fields at 300mb – 500mb seemingly support cloud cover
and I have tempered the warmup just a little.

500mb flow becomes zonal later in the week with a warmup likely.
Models are in decent agreement through Friday, but rapidly diverge
going into the weekend. This does not have huge implications for
Saturday, but does for Sunday. This relates to a southern stream
shortwave trof approaching the southwest U.S. by Sunday shown on the
ECMWF. The GFS has no such feature. An unlikely northern stream
shortwave trof dislodges a piece of Arctic air on Sunday and this
slams south into the region. If these parameters do come together,
winter weather would certainly be possible at D8-D9. However, luckily
it is beyond this forecast period and I can defer to the next forecast
shift to deal with it. I am a little nervous about Sunday as WAA
could be occurring that day or a frontal passage or both. I have
lowered temperatures on Sunday to account for this possibility. For
now, bust factor does seems higher than normal for the weekend.

NAM/SREF seem in decent agreement on temperatures through Tuesday and
these are used. I undercut the GFS for Wednesday and went with it
Thursday and above on Friday (more inline with the NWS here). I did
also stay with the GFS on Saturday and then my own direction for
Sunday. Disturbingly so, my forecast matches up with Andy's.

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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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