April 24 2007 chase



I preliminarily targeted Hutchinson KS on a pretty classical severe weather day.  Extensive warm sector convection was

possible by mid-day, but a synoptic dry slot would likely wrap in its wake and allow for dpva-driven initiation along the dryline.

I stopped along I-70 for data at 1030am.  Unfortunately, the 12Z models indicated 1km agl flow would significantly wane

across the central plains between 18-00Z as the storm system began to occlude over  CO.  Previous forecasts of low-level shear

in the warm sector had been marginal to begin with, so I'd already entertained the idea of playing the stationary front where

hodograph curvature would be enlarged.  Given the strength of the dry slot on satellite, boundary layer destabilization

looked like a decent bet along the front.  Thus I adjusted my target to 30 N of Hays KS.






It just "looked" like tornadoes in Hays by early afternoon, with fair weather cu bubbling beneath the dry slot nose.

Performed a quick hand analysis of surface obs in MS-Paint.  Luray and Concordia were a hair south of the stationary boundary, with ESE winds and low 70s over low 60s at 1pm.  However, elevated convection kept erupting locally right on the boundary and moving north, which strongly reinforced the cold sector and sharpened the frontal boundary.  Not good.
The dryline appeared to be mixing eastward faster than progged.  I repositioned to Russell.  Since convective initiation would be delayed, I drove north 15 miles to Waldo to try and find the front.  A bank of stratus laid on the northern horizon (as in photo), which I presumed to be the boundary.  Then, as I stood outside the car, the wind suddenly switched from SE to NW and the temperature dropped at least 20 degrees F.  It was frigid!  Was the front pushing southward?
Individual CBs began popping near I-70 as the band of ascent finally hit the dryline.  This one became dominant, viewed looking SW from Lucas.
The storm developed a decent core (not shown here) but remained multi-cellular and very high-based. 
I experienced another wind shift; the front was definitively oozing south despite weak pressure falls across the board.  (Interestingly, the 12Z NAM forecast this and I had discounted it.)  I let the first storm go as additional cells built SSE.  I sampled them one by one, and noted an expanding cold pool beginning to undercut all of them.  Here's a shot of the strong gust front pushing out ahead of the northernmost cells, looking NW from I-70.
This photo shows a dreaded moustache cloud beneath the next cell in line over Wilson KS (510pm).  Some neat inflow/outflow interactions took place with this storm, but I could smell the raging outflow and regardless I was "done" with the stationary front play.  I had to take my chances farther south in the warm sector despite the marginal low-level shear.
I dove southward away from the outflow bonanza as five more closely-spaced cells began to develop on down the dryline.  A tornado warning was issued about halfway down the line, and I intercepted the cell along the Ellsworth-Rice county line just after 600pm.  I was truly ecstatic to find a storm with supercell characteristics (photo).  Inflow was respectable.
A narrow beaver tail developed and streamed into the storm.
Though cloud base rotation was weak, by 615pm the storm was getting "the look" (cue Roxette song), as in photo.  Then, two minutes later, the wall cloud detached itself from the RFB and the updraft started to look like outflowish trash.  I headed south without thinking twice.
This was storm number four in line, looking south from near Lyons KS.  I actually watched this updraft for some time; it had a steady state radar appearance and was rock-solid visually, whereas the tail-end charlie to my south was struggling via radar.
A new radar image showed tail-end charlie finally having developed a strong precip core, as well as slowing down markedly.  I committed to it and drove south to intercept.  Its forward flank core contained very little hail.  I crossed the Reno county line just as a tornado warning was issued, and came out of the core in a perfect position to view the storm's strengthening updraft.  Only moments later, the storm produced its first tornado, as in photo (701 pm).
I jogged two miles south on Hodge Rd to 56th Ave.  The tornado had dissipated, but the updraft structure was becoming quite beefy and a clear slot was evolving at cloud base.
A large-ish nub funnel formed.
A stout inflow fin was condensing on the inside edge of the updraft.
Another funnel.
The clear slot continued to advance.

I was wishing for a wide angle lens right about now.  Stormchasers farther away took some excellent structure photographs of the bell-shaped, LP/classic hybrid updraft.


A ropey funnel descended to the right of the persistent nub funnel and rotated fairly quickly 180 degrees around to the left side (as in photo).  A debris swirl was evident at ground level as the funnel tightened up and spun itself apart.  I may not have even have noticed the debris had a car full of local youngsters not started shouting "I see it!" just down the road.
I moved 0.8 miles west and let the lowering nub funnel pass just to my south.  Several frogs were croaking loudly in this location.
Cloud material eroded around the funnel, revealing a tall cylinder.  The RFD reached my location at this time, and a tornado was born (715pm).
A good amount of debris (primarily dirt) was kicked up as the tornado passed just behind a stand of trees.
Tornado moving ENE.
The waterfalling RFD was fairly cool, which was unexpected given the high boundary layer RH.
The tornado began to weaken, and probably dissipated near Hodge Rd. at ~718pm.
The mesocyclone continued NE at 20mph.
Skinny funnel cloud (722 pm).
Violent rotation suddenly ensued within scuddy tendrils at cloud base (725pm).
One final small & dusty tornado occurred beneath the nose of the RFD and persisted from 729-731pm.
The storm passed north of Hutchinson, displaying a nice "whale's mouth."  I stayed well behind it as tornado potential looked to be over.
One final shot of the weakening supercell at sunset.



Maps, weather data


observed supercells


observed tornadoes (paths estimated)


18Z LMN RAOB (should be roughly representative of storm environment)

Sfc T/Td: 73/67 F

MLCAPE: 2317 J/kg

MLCINH: 0 J/kg

0-3 km MLCAPE: 79 J/kg

MLLCL: 719 m

MLLFC: 767 m


representative hodograph via Hillsboro profiler

storm motion: 234 deg @ 24 kts

0-1 km SRH: 143 m2/s2

0-3 km SRH: 66 m2/s2

0-1 km bulk shear: 16 kts

0-6 km bulk shear: 64 kts

7-10 km SR flow: 70 kts