Emergency and Disaster Information Service.
Atmospheric Optics. What causes tornadoes? Americans know tornadoes like no one else. The U.S. averages at least 10 times more twisters each year than any other country on Earth, and their intensity is infamous — the worst can be a mile wide, rotate at 300 mph and plow along at 70 mph. Yet despite being target practice for these atmospheric power drills, America's tornado mythos is still cloaked in mystery and misunderstanding. That's understandable, considering tornadoes' stealthy nature — sudden appearances, erratic behavior and brief lifespans make them elusive subjects to study — but science has nonetheless learned a lot in recent decades.
Tornadoes can occur any time of year, but they wage all-out war on the U.S. during spring and summer. How tornadoes work Tornadoes produce the strongest winds on Earth, but they owe all their energy to the chaotic clouds that birth them. Before a thunderstorm forms, winds begin quickly changing speed and direction. Where and when tornadoes strike How to survive a tornado. Tornado Videos, Tornadoes, Storm Videos, Storm Chasing, Stormgasm, Hurricanes. NOAA - National Oceanic and Atmospheric Administration.