November 5 2008 chase
This will probably be the
last chase of the year. The area of interest on November 5 was in advance
of a dryline from southcentral KS through central Oklahoma.
Severe storms were
forecast to develop off the boundary and move northeastward through a fairly
narrow moisture/instability axis, as vertical motion and
a coupling upper jet
structure evolved downstream of a strong mid-level trough. Discrete mode
looked most probable in central and southern targets, where deep layer
shear vectors crossed the
dryline with the largest angle; however, deep mixing would be quite destructive
to LCL heights and low-level speed/directional shear
farther south as well.
Thus my plan was to play the northern third of OK and far southern KS, where
weaker mixing/backed low-level winds and proximity to
incoming
CAA above the boundary layer were forecast to produce a localized area quite
favorable for tornadoes if discrete mode could occur.
Unfortunately, the
corridor of significant low-level destabilization--sampled by the 00Z TOP/LMN
RAOBs--was just too narrow to allow my storms to become
strongly surface-based
before outrunning it. Also, the primary LLJ core had developed
northeastward away from the area... with SRH accordingly
not as impressive as I'd
have liked, and a definitive weakness present in the 1.5-2 km flow per regional
RAOBs/profilers. Low-level shear began to
increase dramatically
across the warm sector by 00Z, but by that time messy clustering and linear mode
had pretty much taken over everywhere.
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426pm: I was a
bit lazy and got left later than I wanted to. After a quick datastop
in Wellington, I quickly moved southeast toward Sedan as initiation was
already underway. An early cell coming out of Osage county OK received
a tornado warning. I thought I could skirt entirely around the
northern edge of it, but I ended up traversing the core near Cedar Vale and
got several large "handfuls" of pea to marble size hail. I came out of
the core and a looked back west to see the hind end of the updraft crossing
the highway. |
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4:30pm:
surprisingly, a blocky wall cloud came out of the rain and organized with
weak to moderate rotation. |
 |
4:30pm: another
shot of the wall cloud |
 |
4:31pm: wall
cloud then became ragged as a massive wall of rain associated with upstream
convection began to overtake it |
 |
4:46pm: I let
the storm go and jogged east to near Sedan to watch the tail-end cell of the
short convective line go by. Looking to my southwest, I immediately
saw the storm approaching @ 50mph. Soon after it received a tornado
warning. The updraft remained disogranized and relatively high-based
though. |
 |
5:03pm: the
supercell briefly put on a show to my north, with localized cyclonic
rotation at the occlusion point of the updraft and surging rear flank
gustfront... and a cute little tail cloud too. Sunset scenes like this
one, with orange sky and blue/violet clouds, are some of my favorites. |
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5:13: supercell
updraft became linear and nondescript thereafter, with the trailing gust
front shown here... beautiful laminar banding |
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5:13: same |
observed supercells
21Z subjective surface analysis
22Z modified
sounding for Sedan KS (primarily
used trends on 18Z/00Z LMN
RAOBs)
Sfc
T/Td: 73/59 F
MLCAPE:
1118 J/kg
MLCINH:
4 J/kg
0-3 km
MLCAPE: 25 J/kg
MLLCL:
1119 m
MLLFC:
1924 m
representative
hodograph via Neodesha KS profiler
storm
motion: 230 deg @ 41 kts
0-1 km SRH: 195 m2/s2
0-3 km SRH: 251 m2/s2
0-1 km bulk shear: 21 kts
0-6 km bulk shear: 51 kts
7-10 km SR flow: 22 kts
