Saturday, May 7, 2005






309pm - view looking southwest at building cumulus clouds along dryline.  This was somewhere north of Hill City KS, as I rode Highway 283 north toward my target of Beaver City NE.  A severe thunderstorm watch was in effect, with severe cells ongoing farther to the northwest along the cold front.

338pm - a CB glaciated just ahead of me between Norton KS and Beaver City NE, which was to be the storm of the day.
Linear configuration initially tried to form
407pm - view from back side of the storm
416pm - storm was already producing golfball-sized hail northwest of Oxford NE
433pm - obtained a little clearer view of the updraft, which was exhibiting rapid vertical growth northwest of Orleans NE

Flanking line. 

450pm - storm developed strong supercell characteristics as it approached Holdredge, with a nice rounded RFB and distinct/vigorous clear slot
The storm earned a tornado warning just as a piece of scud reached for the earth
456pm - The RFD hit me at about this time, and was very cold... not a surprise given dewpoint depressions around 18F. 
Though the supercell appeared to be undercut by outflow, a few brief tornadoes occurred soon after in and east of Holdredge.  I didn't observe anything tornadic before turning away from the storm.  I backtracked to Highway 4 east (experiencing a little de ja vu from May 22 2004), rather than heading north to Holdredge. 



View west-southwest at a second updraft trailing behind the supercell

View north-northwest as I re-approached the supercell updraft along Highway 44.  The storm was "trucking right along," due to 500mb flow around 60 kts.
5:19pm - well-defined collar cloud, with brisk inflow kicking up a lot of dust.  Brief tornado was reported at this time... couldn't see it from my low-contrast vantage point.
Just west of Axtell
I made the "coin-flip" decision to break eastward toward Minden (rather than north toward Kearney) in an attempt to gain some extra ground on the storm.  I headed north from Minden on Highway 10.  The storm looked increasingly messy at that time, and reports came over the radio of a tornado touchdown near Kearney.  I became a bit frustrated as my timing repeatedly seemed to be way off.
5:37pm - I parked just south of the Platte River in extreme northern Kearney county, and my frustation was replaced by awe as the storm rapidly cycled a new mesocyclone right in front of me.  View is looking due west.
Low-level mesocyclone morphed/tightened quickly into an indistinct wet blob.
545pm - blobular wet thing preceded by well-defined mesocyclonic lip.
553pm - Experienced westerly winds again at my location, so I knew the focus was shifting away to the northeast along with the tight low-level meso.  I drove north across I-80, but upon reaching my east option (Highway 30) a train held me up for 3 minutes.  Ironically, a very interesting piece of scud drifted along behind the train.
It wasn't rotating.  The train wouldn't tell me whether it was tornadic or not; I kind of doubt it.


When I headed east-northeast on Highway 30, I immediately noted dust being rapidly lifted beneath the forward lip of the mesocyclone.

I initially diagnosed this as being created by inflow... but as the meso pinwheeled rapidly north-northeast away from me, the area of dust became more focused and developed vertical walls beneath an agitated lowering above.  As time went on, I became more and more certain this had been--or was becoming--a tornado.
I primarily focused on video as I blasted eastward toward my next north option, but was able to snap off one low-contrast photo of the Gibbon tornado at 600pm sharp.  View is due NW.
607pm - I drove north of the town of Shelton on a gravel road, and verified that the tornado had dissipated.  However, the rear-flank gust front had organized and surged forward, creating a gorgeous little clear slot.
610pm - The occlusion downdraft focused a second tornado about 7 miles NNW of Shelton.  Motions at ground level were respectable via violent churning of dirt within summer fallow fields.
Beautiful storm structure above was eroded quickly away by the downdraft as I found a vantage point free of telephone lines.
One other chaser or spotter was up the road a ways in a white sedan, and was able to enjoy the tornado along with me.  Never did figure out who it was.
613pm - dirt was wrapped WAY up into the air as the tornado began to rope out.
Tornado dissipated by 617pm.  A friendly guy in a pick-up drove up and we talked briefly.  He asked how far away it was, and I guessed about three miles.



630pm - storm became outflow dominant near Cairo NE.
810pm - a younger supercell storm behind the departing HP near Fullteron NE.  Beautiful lighting on the anvil.
One of the most lovely storms I've seen.  This was a great way to end the chase day.



Maps, weather data


observed tornadoes (paths estimated)


23Z modified RUC sounding at Gibbon NE

Sfc T/Td: 74/57 F

MLCAPE: 1502 J/kg

MLCINH: 7 J/kg

0-3 km MLCAPE: 104 J/kg

MLLCL: 1282 m

MLLFC: 1777 m


representative hodograph via UEX VWP/McCook-Neligh profilers

storm motion: 225 deg @ 43 kts

0-1 km SRH: 208 m2/s2

0-3 km SRH: 242 m2/s2

0-1 km bulk shear: 23 kts

0-6 km bulk shear: 38 kts

7-10 km SR flow: 28 kts