What are the danger sign a tornado approaching?

Warning signs of a potential tornado include rotation in the clouds, a lowering of the cloud base, a funnel or cone shape hanging from the clouds, and swirling debris near the ground. If you are looking at the radar image a hook shape, usually in the southwestern portion of the storm, means that the storm may produce a tornado or may have already done so. If you look at a storm relative velocity image and bright green and red colors are right next to each other in a small area it means that there is strong rotation the may produce a tornado.