2/25/98 Chase Summary by Mike Umscheid


From: Mike Umscheid (mscheid@SOUND.NET):

Chase Account:  "The Pre-Season Chase"
February 25, 1998 -- Northeast Kansas (Topeka)

[taken off my web page.. sorry about the late-ness :-)]

A very impressive negative-tilt axis trough was barrelling out of the
Rockies overnight Tuesday and Wednesday morning.  A rapid surface
cyclogenesis was occuring in the high plains of Colorado and the
Nebraska Panhandle... (LBF, 978.0mb at 16z).  In response to this
vigorous system pulling northeast into the northern plains, low-level
moisture was advecting northward into central and eastern Kansas, and
as far north as around Lincoln, NE by the noon hour.  Low and mid
level clouds had kept surface surface T's from jumping into the lower
70s in eastern Kansas.  The surface instability was the only key to
determining if and how much convection fired in northeast Kansas.
Upper level dynamics and shear was in place for the storms to really
get going once they developed.  After taking a look at surface maps
and model progs at school Wednesday, we knew that we needed some
decent heating to get things going.

My chase partner, Jon Smith, and I decided to sit at bay and wait for
the activity to develop.  The firing line (which was a retty sharp
dryline) extended from a ICT/MHK/OMA line.  By shortly after 20Z,
nothing had fired yet.  2015Z High-Res. Visible showed a decend line
of TCU developing along the dryline in eastern Kansas, so we expected
convection to fire at anytime from the OK border to southeastern NE.
Around 2030Z, a couple cells initiated around the EMP vacinity, and
quickly faded.  More organized storms developed right around, and just
west of, Topeka.  At that time some of the cells southeast of Holton
took interesting v-notch signatures, and appeared to be splitting
cells, by one of the local TV dopplars (KSHB-TV, KC).

By 2045Z, we were out the door and heading west on I-70.  At Lawrence,
we decided to take a jog northeast on US-59 to just north of TOP.  The
problem with these storms and such a vigorous upper system was that
the storm motion was entirely too fast, playing catch up with the
storms was a chore, at best (mean storm vector was approx. 190/45!).
We went north on US-75 a couple miles and headed west again on a
county road to place ourselves just west of the line of developing
congestus.  Approximately 2315Z we took about 15-25 minutes of video
of low topped convection ust to our east.  Around 2330Z, some of the
congestus were beginning to shape into decent low topped Cb's, and
becoming quite interesting, but were just racing off north/northeast.
About 20 minutes later, they pretty much dissipated.  There was just
not enough heating at the surface to keep these storms fueled.  Some
of the low topped storm structure looked interesting north of TOP from
about 2330Z to 26/0030Z, but the fact that there were only CAPE values
to about 700-800 J/kg limited the the chance of substantial severe
activity...  keep in mind that we aren't even in March yet!  All in
all, for the time of year, it was a decent chase, we didn't expect to
really see anything more than we did, it was a good pre-season chase
just to get "broken in" for the upcoming season!

Mike Umscheid
mscheid@sound.net

My New Updated Web Site -->  www.sound.net/~mscheid/wallcloud.htm
(includes video freeze-frames and other images on 2/25 chase)


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