Although the mesoscale level of weather action is small in stature, it certainly is huge in impact. The most violent weather on the face of the earth takes place within this scale. Tall cumulonimbus clouds turn into violent thunderstorms, delivering strong winds, torrential rains, and damaging lightning. At the extreme, these clouds can begin to spin and form tornadoes. This severe weather strikes throughout the world, but the United States seems to be world capital for violent thunderstorms and tornadoes. A unique convergence of forces makes them happen with amazing frequency.