Tornado

Tornadoes are violently rotating columns of air extending from a thunderstorm to the ground — the most intense atmospheric vortices on Earth. Wind speeds in the most violent (EF5) tornadoes can exceed 500 km/h, powerful enough to drive straw into steel and carry freight trains hundreds of meters. The United States experiences about 1,200 tornadoes annually — more than any other country — concentrated in 'Tornado Alley' stretching from Texas to South Dakota. Tornadoes form when warm, moist air from the Gulf of Mexico meets cold, dry air from Canada in the presence of wind shear — change in wind speed and direction with altitude. The 2011 Joplin, Missouri tornado killed 158 people and caused $2.8 billion in damage. Tornado forecasting has improved dramatically, with warnings now averaging 13 minutes.