"I've seen strong tornadoes going through open fields, and they don't really do a whole lot of damage," Wurman says. "They just break some grass, even though the wind might have been very, very strong. So it's difficult to rate them."
Wurman's Doppler on Wheels (DOW) provides meteorologists with detailed, on-site tornado analysis, but only a few radar systems of this kind exist. There's simply too much storm activity to cover. Even the 2009 VORTEX2 program, the largest field study of tornadoes in history, could only study a small fraction of U.S. tornadic activity.
What Would It Take?
What would it take for widespread tornadic activity to increase? According to Brooks, it essentially comes down to three key ingredients: warm moisture at low levels, cold air at high levels and changes in wind direction that produce rotation.
Meteorologists can predict how these ingredients might change in the future with the help of computer climate models.
"The big signal in North America will be an increase in the low level moisture," Brooks says. "So that's a favorable thing for tornadoes. The temperatures aloft will probably warm a little bit, but not enough to counterbalance. So we'll have a more favorable thermodynamic profile for tornadic storms."