Do not watch this video if you are at all sensitive, and I suggest not playing it for children. There is almost no visual, the chilling effects are in the sound. It is almost 6 minutes long, and if you don't watch the whole thing, around 2 minutes in is where it gets truly intense. The video is taken on a cell phone, and is a group of survivors who huddled in a gas station as the Joplin Tornado hit, they were pretty much in its direct path.
There is much more about the Joplin Tornado here, and please consider a donation to the Red Cross if you can manage it. The folks in that area are getting hit very hard this year, and could use a hand.
Update: he went back to the gas station and filmed what was left: