When questions arise about the threat of tornadoes to Perimeter Technology's Oklahoma City data center, Todd Currie has answers at the ready. Perimeter's vice president of operations and general manager, Currie even has a cutout sample of the data center's roof to use as proof of the sturdiness of the facility, which was built to withstand an EF3 tornado. In the middle range on the Enhanced Fujita scale of tornado strength, whose ratings go from EF0 to EF5, an EF3 tornado has winds of 136 to 165 miles per hour.