moist air. so cool outflow on the backside you see the rotation going on and voila, we have a tornado. preceding a tornado there's another feature we have to talk about. it's a wall cloud. it's the base of the thunderstorm beginning to lower, tremendous violent motion sometimes these whole wall clouds are rotating. sometimes you just see the air coming up into the wall cloud. when the wall cloud produces a funnel and when the funnel is on the ground or not, when you see debris on the ground you know you have a tornado. and the debris cloud is the last place you want to be because within that you have trees, homes, cars and sometimes you have humans and that debris of course, is being rotated around the storm and eventually sentry centrifuged out. in some of the stronger tornados, we see common features around that immediate funnel. that is upward motion on the outside of that tornado followed by inward sinking motion on the inside. this is an amazing feat of