The parent thunderstorm had developed on the south-facing slope of the Caprock in the Canadian River Valley northeast of Amarillo.
Great structure is evident in the wall-cloud with the cloud striations indicative of a mesocyclone.
See Bruce Haynie's excellent photo showing this storm at a distance. Excellent view of the structure from a different perspective. Note also the rain and some large hail which had been wrapping around the back side of the mesocyclone. There are two additional pages.