This spring, more than 100 scientists gathered from all over the world to chase tornados in the plains states. From May 1 to June 15, researchers roamed "tornado alley"--Oklahoma, Kansas, Nebraska and nearby states---in a flotilla of 10 mobile radars and 25 other weather vehicles. Their goal was to determine how tornadoes form and how to better predict them.

Each day, teams staked out a potential tornadic storm about an hour ahead and stayed there until the storm passed. The project, called VORTEX2, extended last year's efforts, when the roaming armada of scientists caught up with a tornado and successfully deployed all of their instruments. Their measurements have become some of the most intensely studied tornado data in history.