(Part 1 of 3) Inner and outer vortex components are evident in this tornado from Deuel County of the southeastern Nebraska Panhandle. If viewed in a cross-section, or a mobile Doppler radar image, it may have looked like two concentric rings with a "moat" between. This idea is much like the eyewall replacement cycle of a hurricane, and actually, that's how this tornado behaved. As when a hurricane replaces its inner eyewall with an outer one, the outer vortex ring here became dominant and the tornado expanded in size, as evident in the next image.
2 N Big Springs NE (10 Jun 4), Looking NW