This bulky, eerily lit wall cloud reveals yet another shape these spinning cloud features take. Wall clouds often pulse through cycles: lowering and becoming well-defined, then flaking apart, then reorganizing. The wall cloud is associated with the mesocyclone, a broad (up to five miles wide) area of rotation at the heart of the storm. Through a narrowing, stretching and quickening of that area of circulation -- when conditions are right -- a tornado can be produced.