February 28 2007 chase







Departed at 325pm with a rough target of Independence KS.  Clumpy cumulus off to my southwest began to tower significantly by the time I reached Iola.  Conditions were extremely hazy along the leading edge of the robust moisture advection, and with the poor visibility I wrote off the towers as high-based junk based above the cap.  It gradually became apparent they were rooted far nearer the surface than I'd thought.  I continued toward Chanute, having the distinct feeling I'd be back up around Iola again later... but wanting to get a closer view before sundown rather than hang back and wait for a nocturnal intercept.

I headed west out of Chanute toward this absolute bomb of an updraft (527pm).  Radar reflectivity at this time verified the explosive nature of this convection--from no echoes to a pair of 55+ dbz storms in 4 scans.  Meanwhile, the evening sun blazed just above the low-visibility murk of the advancing moist sector.
I moved north from Buffalo toward Yates Center, pacing two high-based thunderstorms sailing NNE at 40kts atop the Kansas Flint Hills.  I parked southwest of Yates Center to get a look at the southernmost updraft at 550pm.  A mid-level inflow stinger was already streaming in from the east-northeast, as at photo top.  A wall cloud was also present, but the infant storm was clearly undercut. 
553pm - the storm continued moving briskly from a direction just east of due north.  Unless faster moisture advection and/or rightward storm deviance began to occur, I feared it would remain hopelessly high-based and outflow dominant amidst increasingly weak BL moisture content.
559pm - the updraft intensified and assumed supercell characteristics.
603pm - the RFB lowered and darkened further as the storm continued to mature.  After snapping this photo, I jogged back into and then north of Yates Center.  What happened over the next five minutes was rather shocking.
609pm - just as though someone had "flipped a switch," the supercell updraft became more rounded and a wall cloud rapidly condensed.  The last time I observed this sort of near-instantaneous cloud base evolution was with the Hallam NE tornadic supercell early on, near Hebron.
612pm - an increasingly distinct collar cloud marked the location of the low-level mesocyclone, while bits of scud began wrapping into it.  The colors I observed in this scene were simply amazing.
614pm - though the wall cloud was losing its bulbous shape, it was now displaying violent rotation.  The storm was likely going nuts in conjunction with significantly enlarging sr-hodographs; the Neodesha KS wind profiler sampled 500 m agl flow increasing from 25 kts to 40 kts by 0100 UTC.
615pm - the supercell had obviously turned to the right and was moving from about 240 degrees.  I didn't particularly like the road availability (or lack thereof) northeast of this area, which is something I'd realized about half an hour ago.  I headed east on gravel roads.
618pm - the low-level meso became a little less organized from a visual standpoint as it scooted away from me across the nothingness of northern Woodson county.  However, in time, lightning flashes revealed pronounced lowerings/possible funnels on its inside edge.  Meanwhile, the RFD advanced from behind and filled with dense precipitation, effectively shrinking the visible portion of the updraft base.  It looked to me like the storm was evolving into an HP supercell.  I stairstepped back to the blacktop running between Yates Center and Iola with hopes of regaining some ground on the storm.  A tornado warning was issued soon after by NWSICT.
637pm - dusk had fallen and I snapped my last digital still from west of Iola.  The dark feature at lower left is the top of an enormous inflow fin that had taken shape over the past 15 minutes.
Tail end of the inflow band streaming south-to-north into the supercell.

Just north of Iola, the HP character of the storm was very apparent courtesy of lightning flashes.  I continued north and parked 2 miles south of the small town of Colony, which marked my next east option.


Lightning suddenly became extremely limited from my vantage point.  The storm was quickly cycling a new updraft... but the structure itself was so elevated and flat at cloud base that it was really difficult to tell what was going on at the time.  I cautiously drove into Colony.  Halfway through town, a bunch of dead leaves began literally floating in the street a few feet off the ground as the developing tornadocyclone passed ahead of me.
Just east of Colony, lightning flashes revealed the tornadic circulation a couple miles to my northeast.  In hindsight, the tornado was initially quite nondescript... more than likely just a nub funnel with debris cloud south of and/or masked by lots of scud (as in video capture), per a couple of other stormchasers.  Just down the road I came upon some significant damage, which NWSTOP later surveyed as the initial touchdown point of the tornado.  Powerlines were down and two barbed wire fences blown entirely across the road.  The RFD surge hadn't yet reached this location, so it made sense that this was tornadic damage.  I cleared the first fence from the road, but was held up a few minutes until a volunteer fireman cut the wires of the second fence.
As I continued eastward to Lone Elm, lightning flashes revealed the shape-shifting tornado again ~5 miles to my northeast... far better defined by this point.  It transitioned from dusty cone to multiple-vortex barrel and back again.  Shown is one of the better looks I got of the tornado as I caught back up with it again...view looking north-northeast.  An enormous RFD erosion was also evident (top third of image).  The overall change in the supercell's structure over the past 30 minutes was nothing short of remarkable.  The tornado dissipated around 718pm.  (Will have to check my cell phone bill for the start time.)
I headed east on Highway 59/31 and noticed a full moon had risen from behind the supercell updraft.
Shortly after I passed through the town of Kincaid, the storm cycled a new, toothy wall cloud to my northeast.  Around the time of this video capture (737pm... telephone poles in foreground), the "Blue Mound tornado" was born.
Within a minute and a half, two distinct stovepipe tornadoes appeared to be emanating from the ugly, descending wall cloud.
Another lightning flash ~30 seconds later revealed much the same structure... with the positions of the two vortices having not changed.  Ultimately, it's inconclusive to me whether this was two separate tornadoes or one big multi-vortex circulation, due to the paucity of the lightning flashes.
739pm - I pulled over to try to get some better video ~2 miles west of Blue Mound.  The tornado was taking on a wedge shape. 
My camcorder captured a well-defined powerflash a couple seconds later.  Note the incredibly stout updraft structure above the tornado.
740pm - violent wedge tornado 4 miles to my north.  Backlighting via lightning flashes was at its peak during this period.  There appeared to be a possible secondary (satellite?) tornado off to its right, as in the image.  I drove east to Blue Mound and then north on County Road 1077. 
746pm - this image captures the last good look I got via backlighting as I pulled within a mile or two of the tornado...view looking northeast.  A hint of a clear slot was nosing in from the west, and the tornado's appearance was rather ominous given significant lowering of the parent cloud base.  Soon after, I encountered a destroyed home strewn across the highway at a point five miles north of Blue Mound.  The owner, David Matthes, sought shelter in his basement and blessedly survived without injury.



Soundings, maps, radar


chase route in green, observed tornado paths in black per NWS storm surveys


Base reflectivity & storm-relative velocity as tornado passed due north of Blue Mound (NWSEAX)



20Z OUN special RAOB (which ultimately was what pushed me out the door to chase!); and 00Z & 04Z SGF RAOBs



00Z Topeka KS RAOB modified for 01Z conditions at Blue Mound KS

(used TOP to achieve an appropriate pressure surface; sounding created via 21-06Z LMN/OUN/SGF RAOBs and 00-02Z RUC model trends)

Sfc T/Td: 64/55 F

MLCAPE: 1075 J/kg

MLCINH: 28 J/kg

0-3 km MLCAPE: 46 J/kg

MLLCL: 949 m

MLLFC: 1559 m


representative hodograph via Neodesha KS profiler

storm motion: 246 deg @ 32 kts

0-1 km SRH: 363 m2/s2

0-3 km SRH: 466 m2/s2

0-1 km bulk shear: 33 kts

0-6 km bulk shear: 62 kts

7-10 km SR flow: 54 kts