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.






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.
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.
5:13: supercell updraft became linear and nondescript thereafter, with the trailing gust front shown here... beautiful laminar banding
5:13: same



Maps, weather data


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