The world’s biggest tornado hunt is stuck. I’m at an improvised command center in the conference room of the Holiday Inn Express in Perry, Oklahoma, and 35 scientists are trying to decide where, on this cloudy May morning, to deploy the 50 equipment-laden trucks parked outside. The first major storm system of the expedition is forming southwest of us, in Texas, and it’s likely to lead to supercells, massive rotating thunderstorms that may in turn spin off one or more twisters. Very promising. But Lou Wicker, a team leader from the National Severe Storms Laboratory, sees a problem. He looks up from a radar screen. “Fifty miles per hour,” he says. Too fast.