April 24 2008 chase



A decent start to the chase season... my latest start of any year except 2004 when I was laid up after surgery.  Departed at 11am and

reached Norton KS by 5pm.  I anticipated late initiation near a diffuse dryline, as strong ascent downstream of a mobile upper trough

overspread areas roughly north of the Highway 24 corridor.  If storms could survive into the deeper moisture and stay out ahead of

a plunging cold front , a decent tornado threat seemed likely to the north of a fairly hallacious cap crossing southern KS and OK...

particularly since a deep moist layer was likely to advance northward through the evening.  My forecast thoughts the night before,

when models were a little more favorable with the magnitude of moisture return/CAPE and 850mb flow, were that a significant tornado threat

might exist over far southcentral NE/northcentral KS between 02-06Z.  I should have kept that in mind!






From west of Oberlin, I watched a non-descript leading storm cell begin wrap north and then northwest.


Dropped south of Oberlin, and by ~01Z the tail end of evolving convection became beefy/cellular with several inflow bands from multiple directions/altitudes.
Same.  This was just northwest of Seldon KS.
At ~0115Z, inflow into the updraft suddenly became tremendous and a wall cloud condensed.  Surface conditions here were likely ~67/52F.  A tornado warning from WFO GLD followed.
The kiss of death came in the form of outflow-driven sheets of dirt ahead of the dissolving wall cloud.  Softball hail reported in Seldon not long after.  I moved south and east and tried to beat the now ESE-bound supercell storm to Hill City.
Obvious HP characteristics became apparent via lightning flashes... with a large/dense dump of precip beneath a laminar updraft base.  Model soundings showed a surge of elevated warming coming in from the south, which would make sense given the appearance of the updraft.  This may have had an impact on the storm given the otherwise favorable shear profile and increasing near-surface moisture with eastward extent.  I let the wet/messy storm go south of Hill City ~03Z since it had cut my east option off and paved roads were limited downstream.  Also, surface temps had fallen into the 62-64F range, increasing CINH to surface parcels... and the tornado warnings were dropped.  A few hours later, deeper moisture backed up into northcentral KS along with a surge of 66-70F surface temps.  This apparently decreased CINH just enough to allow the supercell to re-organize and produce a large damaging tornado north of Beloit between midnight and 1 AM, in a high SRH environment within the stronger-than-progged LLJ nose.  This is a rather common pattern for violent nocturnal tornadoes, and one I wish I had better anticipated that evening... though the poor road network likely wouldn't have allowed me to stick close to the storm through the night.


Maps, weather data



WFO GLD weather story including radar imagery

WFO GID weather story including Beloit tornado survey

modified RUC sounding for Beloit KS at 05Z

Sfc T/Td: 67/64 F

MLCAPE: 2185 J/kg

MLCINH: 68 J/kg

0-3 km MLCAPE: 52 J/kg

MLLCL: 702 m

MLLFC: 2067 m

0-1 km SRH: 490 m2/s2