Jet streams play a key role in how tornadoes are formed. When it comes to tornadoes, you’ve seen them, and you’ve seen what they can do. But do you really know how a tornado forms into that monstrous ...

Nearly 900 tornadoes have torn through more than 30 states so far this year, killing dozens of people, shredding buildings and landscapes across big chunks of the Eastern U.S., and costing billions.