May 19, 2001: Arrival

Arrival at KDIA. Frustrating attempt to get in favorable area of shear and buoyancy in the northern Texas Panhandle, but stymied by United Airlines and Hertz. First, 1 1/2 hour delay at Oakland due to minor electrical problem in the aircraft. Second, spectacularly slow attendants at Hertz counter (where we rented our 2001 Chase Vehicle, a Subaru Outback) left us exiting the airport at 2:30 PM CDT instead of 11:30AM CDT. Because of this, we did not drop into the Panhandle until 9PM, missing several (though non-tornadic) supercells.

May 20, 2001: Supercells in Southeastern Oklahoma
and Encounter With Weak Tornado

Here is a plot (courtesy of Greg Stumpf, NSSL) of all the radar noted mesocyclones and tornado reports on this day. Note the Wilburton storm.
An obvious focus in southeastern Oklahoma took us to south of the Oklahoma City area by early afternoon. A feed of very high dew points into the area in combination with somewhat favorable shear suggested a good day for supercells.
The 1800 UTC KOKC sounding showed the explosive instability and favorable shear. Note the veering and increasing speeds with height. However, the hodograph initially was straight, suggesting splitting storms, and also suggesting that we should hope for local wind fields contributing to hopefully more curved hodographs in the afternoon.
A tongues of very high surface based CAPE was over the area, with very little CIN by early afternoon.
Storm relative helicity was somewhat favorable for rotating storms, while deep layer shear (not given) was also favorable in the same area as the region experiencing highest CAPE in Oklahoma.
Here was the intial explosion of towering cumulus near Pauls Valley. They formed along the convergence line evident on the hourly plot above.

AThe first storm in our area developed a nice wall cloud, with moderate cyclonic rotation. Note the forming funnel.

This storm may have produced a tornado, and a warning was issued for it, but we never did see a tornado. Other storms in the area (and where we were not, of course, were producing tornadoes at this time).

Supercells broke out over the whole area. We drove into the storm near the town of Willburton. Note the hook.

Radar Animation

(In the animation, note that the Wilburton storm and several others in the area were "deviate" ["hard right"] movers)

We drove towards the rainfree base at sunset, noted staccato lightning, and decided that the hail risk was high, so we drove into Wilburton and took refuge in a Car Wash. Little did we know that we were in the midst of a tornado cyclone the entire time, and the circulation , which we feel was a weak tornado, passed directly over the Car Wash. Note the sheet metal roof portion moving past the car. Unfortunately, the movie does not start until we were in the car wash for about 25 seconds.