The cover of Volume 1 has the original Wichita Falls, TX photographs. There was a time when Wichita Falls had the reputation of being THE city for violent tornadoes. Moore, OK has since taken over that role in the public eye. A century ago, St. Louis, MO had that reputation.
The cover of Volume II has photographs that are more personal. The upper photo is Aaron Rigsby's shot of the twin F4 tornadoes near Pilger, NE on June 16, 2014. The two tornadoes crossed paths. Many old newspapers told of tornadoes on the plains with huge multiple funnels and complex movements. It was impossible to draw the path properly. The 2014 NWS Pilger, NE maps are here.
The lower one was taken of a good friend, by a good friend, during one of the most successful tornado chases of all time. The photo was taken by my teacher/mentor (during the 1990's) in the art of storm chasing, Matt Biddle, on June 11, 2004. Watching the tornado near Storm Lake, IA was (on the left) Tim Samaras with his chase partner Carl Young, both of whom died in the El Reno tornado on May 31, 2013. Tim prepared a segment for me on setting probes for detecting tornado-generated seismic waves. It was to be used in a video project that never happened. He was an amazing person, eager to help the Tornado Project. Here, Tim was watching a tornado pass over his seven-camera "turtle" probe, getting ground level velocity measurements. The effort was covered in the June 2005 issue of National Geographic.
The main page is here:
Inside Tornadoes, Direct Hit - National Geographic Magazine
The photo gallery is here
Many thanks to all mentioned above,