View full lesson: http://ed.ted.com/lessons/how-do-tornadoes-form-james-spann Tornadoes are the most violent storms on Earth, with wind velocities that can exceed 200 miles per hour. How do these terrifying cyclones form? Meteorologist James Spann sheds light on the lifespan of tornadoes as they go from supercell thunderstorms to terrible twisters before eventually dissolving back into thin air. Lesson by James Spann, animation by Província Studio.