Andrew Stoller
EF5
I came across this video while looking at footage from the April 14th outbreak in Kansas. I think it possibly might be the best footage showing a rear flank downdraft wrapping around the mesocyclone and resultant clear slot producing an RFD gust front, and tornado-genesis. This supercell I believe went on to produce EF-3 damage.
http://www.youtube.com/watch?v=fkAFmk1OBoI
http://www.youtube.com/watch?v=fkAFmk1OBoI