Many residents of Western Massachusetts were personally affected by the rare occurrence of a tornado in our region last year. Even 9 months later, a drive through Springfield still shows the effects of the June 1 storm.  Why was the 2011 tornado season in the U.S. so extreme? NOVA: “Deadliest Tornadoes” will air at Wednesday, April 11, 2012 at 9pm on WGBY.  Learn more about tornadoes on NOVA’s website.  Here’s a preview of the episode: