this is a hook echo, a monster cell. but it wasn't a tornado on the ground until it got right there. when the tornado got on the ground it ripped through joplin, missouri, got bigger and bigger. at some point in time at 200 miles per hour, even if you are in your safe spot in your house, if you are not under ground in a storm shelter you can't survive it. >> we have seen so many tough storms this season. is there something about this season or something about the particular storms that we are just unlucky? this one hit joplin, another hit tuscaloosa. >> a few things that are different. we won't know for years exactly what all happened until somebody's master thesis figures it all out. let's go through things that are different this year than in a normal year. this is a normal jet stream. how is 2011 spring different? it's colder than normal on the