Deadliest tornado season in 50 years - but why?
- There were 506 tornadoes reported in the U.S. through this date last year. It's already more than double that - 1151 - this year."This is just remarkable from a meteorological point of view," says City College of New York's professor Stan Gedzelman. He says superstorms are formed by an instability in the air that usually occurs in the Spring.