Weekly Severe Weather Discussion

Severe Weather Discussion for March 16 – 22, 2009.
Valid: 03/15/2009.

Highlights:

– Temperatures will be in the upper 70s on Monday, low 80s
Tuesday-Wednesday, mid 60s Thursday, 60F Friday, low 70s Saturday, mid
70s Sunday.

– Showers are possible late Wednesday into Thursday with another
chance on Friday.

– Fire danger will be high all week, but especially on Tuesday and Saturday

– Vernal equinox is on Friday (i.e. spring begins).

Probabilities:

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

Discussion:

The last few days of winter will feel more like mid-spring. A cold
front and some weak shortwave trofs will be the main weather events
the next few days. Overall, sensible weather will be at a minimum.

ECMWF is the preferred model this week, although in a few areas the
GFS was helpful. Weak shortwave trof will continue moving east
through the southeast U.S. by Tuesday. Zonal flow will replace this
system for a few days before the jet stream buckles late in the week.
This eventuality is where the models start to differ. The 12z GFS
develops shortwave ridging across the central U.S. as a clipper type
system moves quickly southeast through the great lakes late Thursday.
The GFS is more amplified with this system than the ECMWF and creates
more ridging in the central U.S. A cold front will move south in
response to the eastern U.S. system and lower temperatures briefly
across the region. Low POPs are added for the cold front late
Wednesday into Thursday. Models show a weak shortwave trof moving
across the region on Friday. This will likely cause some cloud cover
and keep temps a little lower. All of this while a trof develops off
the California coast.

The GFS is much more progressive with the western U.S. system than the
ECMWF and dampens it out as it moves east into the central U.S. While
a decent surface low develops, little moisture is drawn north as a
result of ridging along the Gulf coast. The ECMWF is similar with the
majority of features, it is also 12-18 hours slower than the GFS with
the western U.S. trof. I'm picking this solution, which would
seemingly delay precipitation chances just beyond this forecast
period. Additionally, I think the ultimate evolution might be even
somewhat slower than the ECMWF's 12z progs. Semi-permanent ridging
along the Gulf seems to be a problem so far in 2009. If moisture can
return and system timing is better, a more robust event does seem
possible just beyond the forecast period on 03/23. I'll watch 03/22
for now, but not going with precip chances as of yet.

12z/18z NAM BUFKIT numbers are used through Wednesday and in general
GFS numbers through Sunday. I see no major reason to disagree with
what the models have provided. Drought conditions do continue,
although Texas got a nice round of rain this past week.

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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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