Weekly Severe Weather Discussion

Severe Weather Discussion for February 16 – 22, 2009.
Valid: 02/15/2009.

Highlights:

– Temperatures in the mid 50s on Monday, warming to the upper 60s on
Tuesday. A slight cool down to the upper 50s on Wednesday with more
cooling on Thursday to the upper 40s behind a cold front. Friday will
see mid 50s before another cold front with temperatures in the low 40s
Saturday and upper 40s Sunday.

– Chance of showers in eastern Oklahoma Tuesday afternoon. There is
also a slight chance of rain Monday night in central sections.

– Extreme fire danger is likely Tuesday afternoon in western
Oklahoma. A fire weather watch has already been issued.

Probabilities:

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

Discussion:

Models are in decent agreement through the forecast week, although
there are a few differences in the daily forecasts. The longwave
pattern will shift this week as the western U.S. longwave trof from
last week weakens and ejects eastward. The resulting southern stream
shortwave trof will shear out as it moves into confluent flow over the
central U.S. amid the development of a northern stream eastern U.S.
longwave trof. With the timing off on the systems and prior Gulf
intrusion, chances of precipitation this week are low. Very slight
chance is put in for Monday night as the GFS develops some QPF.
Tuesday afternoon, the best chance for showers will be in far eastern
Oklahoma. I'm going with the NAM's dewpoints (not dryline position)
Tuesday afternoon as the 1016mb line remains west of Houston. As
such, only marginal moisture return is expected. After Tuesday
northerly flow aloft takes over, which is a dry pattern for this
region. Also, after Tuesday's system, two cold fronts are progged to
move through the region, one Wednesday late afternoon and the second
Friday afternoon.

In the dailies, Monday will warm up as the prior cold surface high
shifts east and return flow sets up. Tuesday will be quite warm
across much of western/central Oklahoma as a dryline rapidly sweeps
eastward in shallow moisture. This is inline with the GFS, which OUN
also picked. Wednesday will be slightly cooler as warm air aloft
cools under northwesterly flow, but not substantially cooler. The
cold front Wednesday evening will bring us back to reality on Thursday
and then briefly warmer on Friday. A second and stronger cold front
is expected Friday afternoon as a shortwave trof dives southeast into
the mean longwave position over the eastern U.S. This will pull a
Canadian cold front with it, bringing highs into the low 40s on
Saturday with some recovery expected on Sunday. I may be a little
high on the temperatures as the cold air could end up being stronger
than I'm forecasting. However, models don't show a lot of cold air in
Canada right now, so I feel okay with the going forecast for the
weekend.

To address last Tuesday, many people ask if the event is a predictor
for an active storm season. To that, I say no. I've seen active
February with busy storm seasons and the opposite. I've seen SPC talk
about above average Gulf depwoints and a busy southern stream, with a
weak storm season. About the only true predictor is La Nina, however
even that may be iffy. We're 28 days before the "official" start,
even though Oklahoma has already had 8 fatalities. After visiting
Lone Grove on Friday, I can say it is quite humbling. I visited the
mobile home park where three people died. Even with the good
forecasting from Norman WSFO and the 40 minute lead time on the
tornado, eight people still died.

—————————————————————-
This message was sent using IMP, the Internet Messaging Program.

Facebooktwittergoogle_plusredditpinterestlinkedinmailby feather

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.
This entry was posted in Severe Weather. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *