Tornadoes are capable of completely destroying well-made structures, uprooting trees and hurling objects through the air like deadly missiles. Tornado intensities are classified on the Fujita Scale with ratings between F0 (weakest) to F5 (strongest). The National Weather Service classified the twister that hit Moore as an EF-5, the most powerful type of tornado.
In this image, flipped vehicles are piled up outside the heavily damaged Moore Medical Center. (Photo: Brett Deering/Getty Images)