Severe Weather Discussion 2010-6-2

Severe Weather Discussion for May 10-12, 2010.
Valid: 05/08/2010.


– Active severe weather day is likely on Monday across western/central
Oklahoma. Primary threats are tornadoes, some possibly strong, and
destructive hail.

– Severe thunderstorms are possible on Tuesday in southern Oklahoma.

– Severe thunderstorms are possible on Wednesday across Oklahoma.

– Chase Readiness is increased to Level 2.


Very complex and volatile forecast is on-tap for the forecast period.
12z/18z models agree on disagreeing, which continues the trend of the
past several days. In general the GFS/ECMWF progress the upper system
eastward into south-central Kansas by Monday evening. The GFS pulls a
dryline to near HWY 81 as a function of the rapid shortwave trof
movement. The NAM is slower and holds the dryline along the TX/OK
border. Given the NAM's consistency with the upper system, I'm
following that solution.

Deep layer moisture will return ahead of the upper system on Monday
with the NAM finally settling on a warm front in Kansas. GFS/NAM want
to develop showers and thunderstorms along the front, slowing its
northward track somewhat. While there is no reason to dispute this,
time of year would certainly argue against it. Even if precipitation
does develop along the front, a continued northward movement is
expected. This places all of Oklahoma in the warm sector on Monday.
The warm front seems to range from I-70 to near the OK/KS border, so
not sure where to place it right now. There is little question that
deep layer moisture will return, the question remains where and how
much. NAM shows 850mb dewpoints around 15C but has a dewpoint min
over north-central Texas. This seems to be a downstream impact from
earlier southwest winds at this level via model progs. NAM has done
this several times this year and I'm not jumping on it right now.
Using the above reasoning, CAPE values are expected to be AOA 3000
J/Kg and LIs AOB -8. EHI values are impressive, but not a shocker
given the awesome winds with this system.

There remains concern for a widespread severe weather event, but model
issues with QPF make this part of the forecast difficult. Both the
NAM and GFS want to keep areas well east of the dryline cool due to
earlier precipitation. This looks suspicious given time of year and
how quickly we can warm-up. Granted, the NAM showed this for
04/22/2010 event in western OK and it was correct. However, we are
2.5 weeks later and certainly a lot more sun/warmth. We'll see what
actually happens, but certainly have to be on-guard for dangerous
supercells entering central Oklahoma after dark.

My chase target is currently between Elk City and Vici. I'm not high
on the warm front as I've never been a fan of them. The triple point
looks to be SW KS and this is certainly a consideration. However,
there is seemingly no difference between my area and farther north,
other than being closer to the upper system, which is another thing I
don't like. I like the subtle nature of the lift in western Oklahoma
given moisture and heating. A small bump on the dryline is usually
more than enough to make things go boom.

I don't think SPC will do a high risk given the QPF issues earlier in
the day on Monday. If we see a high risk, it will be 3pm on Monday.
I do expect a moderate on the Day 2 and will continue with 100%.
Granted, I can't make SPC do it, but I'm putting my opinion out there
for everyone to read and bash.

Tuesday isn't that tough other than figuring out where the frontal
boundary ends up. Where ever this happen, there are likely to be
storms along it Tuesday afternoon. Mid-level winds are decent, but
low-level winds are weak seemingly leading to QLCS structures near the
warm front. Since the NAM and GFS show the front in Oklahoma, I've
placed southern Oklahoma in the threat area. I don't see it
warranting a moderate risk at this point.

Wednesday looks like another potentially significant severe weather
day, but way too many issues to resolve before getting there.


Risk area for any part of TX/OK (valid: 05/09 Day 2, Day 3):

Slight: 100%, 100%
Moderate: 100%, 10%
High: 0%, N/A

Chase Readiness:

Level 2 – Monitoring Monday.

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About Putnam Reiter

Putnam has been storm chasing since 1990 and is a co-founder of For his day job, Putnam works in emergency management for information technology.
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