Gabe Garfield (@WxGabe on Twitter) is a research meteorologist for the National Weather Service. In the video below he talks about the May 31, 2013 El Reno tornado the widest tornado in recorded history that occurred over rural areas of Central Oklahoma. Tragically, eight people died in this tornado, including four storm chasers. The video is definitely worth 30 minutes of your time. What truly makes this video exceptional is starting at 2:41-8:40, he discusses the physics of how tornadoes form.