Weekly Severe Weather Discussion

Severe Weather Discussion for May 17 – 23, 2010.
Valid: 05/16/2010.

Highlights:

– Severe thunderstorms are possible across southern Oklahoma on
Wednesday. Threats are difficult to discern, but a medium-end event
is possible.

– Severe thunderstorms are possible across northwest Oklahoma on Saturday.

– Severe thunderstorms are possible across Oklahoma on Sunday.

– Thunderstorms are possible Monday – Wednesday and again Saturday-Sunday.

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

Probabilities:

– Severe Thunderstorms in Oklahoma: 50%
– Storm Chase: 40%

Discussion:

Complex forecast this week as a 500mb ridge is progged to develop
across the eastern half of the U.S. Additionally, a weak southern
stream trof is expected to undercut said ridge and move into the
region on Wednesday. Expected moisture, heat, and wind fields with
the upper system argue for a medium-end event. However, there are
significant differences among the models. The NAM keeps the warm
front south of Oklahoma with mainly elevated hailers across the state.
The GFS is more robust with the warm front moving north and would
argue for severe thunderstorms along the dryline and warm front across
the southern half of the state. At this point, I'm not too confident
on what will happen, but Wednesday will need to be monitored. Special
discussions may be needed starting tomorrow. One seemingly important
difference among the two models is the GFS has higher temperatures at
850mb/700mb than the NAM. This does appear more reasonable given time
of year. It would also suppress the widespread precipitation the NAM
is showing Wednesday.

Cold front moves south of the state on Thursday with a cool-down
likely. Front should move quickly back north on Friday as a western
U.S. longwave trof develops. GFS is rather progressive with this trof
while the ECMWF holds it to the west through Sunday. The ECMWF is
likely the correct solution owing to the GFS's tendency to be overly
progressive and recent trends. Presence of deep layer moisture and
seasonable temperatures will yield a severe weather threat. A
developing cap will likely prevent widespread thunderstorm activity
outside of mid-level support. With the current disagreement among the
models and subtle nature of mid/late May severe weawher events, I've
gone with severe potential next weekend. If a medium-end event does
develop, it will be handled with special discussions. Given the ridge
near the area and east, tough to say how far into Oklahoma favorable
winds will move.

I didn't do much temperature forecasting again this week due to
ongoing severe weather in Oklahoma City and complex nature of the
forecast. I did go much higher than some for next weekend given the
expected trof to our west. I'm not biting on the GFS's cold front at
this juncture.

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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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