June 7 2008 chase

 

 

I was on a day shift on this day.  The event had kind of a unique synoptic pattern (at least one I'd never chased before), with a sagging cold front progged to stall

and slowly return northward on its west end as strong pressure falls occurred over CO.  I honestly wasn't too sure about tornado potential given possible linear mode

along the front and SSW boundary layer winds in the warm sector.  However, surface flow was progged to back and 1km flow increase around 00Z, which could

potentially improve low-level shear enough for a tornado threat given discrete convection.  I actually wasn't sure if the cap would even break much before evening

closer to home (i.e., not the northern IA/IL or WI targets) and headed home from work at 2:45pm without planning on chasing.  Around 3:45, cells started popping

on the stalling front in far northcentral KS, and I threw my stuff together and headed that way.  With cloud bases and CAPE seemingly better farther east, it seemed

a reasonable strategy to pick off the first (northeasternmost) storms I encountered along Highway 36... but these cells shriveled one by one as I got within ~50 miles

of them.  My fear of "being late for a tornado"gradually shifted to a fear of the final, persistent, tail-end charlie storm evaporating before I even got a chance to view

significant convection!  Lucky for me, that last cell held on till I got there, and put on quite a show after I did.  I took the same highway south through

Mitchell county to intercept it as I did to intercept the May 29 beast near Glen Elder.  Those folks must be getting awfully tired of the severe weather this spring.

 

 

 

Images

 

8:01pm: initial view of supercell from 5 miles west of Downs KS, looking down Highway 24.  An outflow shelf was apparent at cloud base, and I initially thought the show would go "downhill" from here.
8:01pm
8:07pm: at about this time, the updraft literally exploded with visible rising convection, while easterly inflow began to pick up a bit
8:11pm: note the difference after 4 minutes had elapsed
8:16pm: I rushed two miles east, then further east still, to try and get more of the updraft structure photographed.  Kicking myself for not trying a photo stitch... didn't even think of it.
8:17pm: occluding wall cloud in lower left
8:22pm
8:22pm - imagine this photo as representing the right hand/inside edge of a perfectly circular/symmetrical, crown-shaped updraft... that is what the supercell looked like at this time.  It was easily one of the top 3 storm structures I have ever seen.  Looking into getting a wide angle lens soon.
8:25pm - updraft exploded outward/upward into the vault region, disrupting the symmetry a bit.  I apparently missed a brief tornado around this time due to gawking at the structure.  I soon moved back in closer as some funny business was happening at cloud base.
8:30pm - don't honestly know much about DRCs, but wonder if this was visual evidence of one.  Collar cloud developed in foreground.
8:32pm - pronounced funnel with strong rotation, but became rain-wrapped and weakened
8:35pm - rainy area cleared as RFD slot surged in front of a developing wall cloud
8:37pm - two funnels.  Rightmost one developed violent rotation.
8:37pm - local residents at the intersection behind me started cheering on the tightening/descending funnel
8:38pm - complete condensation into a rope tornado along with a debris swirl at ground level occur after I snap this photo.  The tornado occurred near Portis KS and lasted about 8 seconds, with a somewhat segmented ropeout.
8:41pm
8:42pm - complete occlusion of low-level meso

8:52pm - this updraft base was trailing behind the main supercell the entire time, even producing an occasional funnel.  The lead supercell ultimately began to weaken while this one took over.  Wall cloud shown developing.

8:53pm

9:06pm

9:17pm - second wall cloud rapidly condensed.  Dual wall clouds persisted, but showed no rotation.  Along with a LEO, I followed the storm up Highway 181 as darkness fell... then continued east back on Highway 36 as the storm shriveled into a tiny LP and died.

 

 

Maps, weather data

 

observed supercells

 

00Z subjective surface analysis

 

00Z modified NAM 01-hr forecast at RSL (storm inflow assumed to be on warm side of surface front)

Sfc T/Td: 85/68 F

MLCAPE: 3012 J/kg

MLCINH: 44 J/kg

0-3 km MLCAPE: 5 J/kg

MLLCL: 1470 m

MLLFC: 2570 m
 

representative hodograph via models/regional profilers

storm motion: 240 deg @ 24 kts

0-1 km SRH: 297 m2/s2

0-3 km SRH: 438 m2/s2

0-1 km bulk shear: 35 kts

0-6 km bulk shear: 39 kts

7-10 km SR flow: 22 kts