Until a few years ago, tornado researchers had very few direct measurements of winds in a tornado. That's because very few tornadoes ever pass right over a place that has weather instruments.

But with Doppler Radar, it's possible to get fairly precise estimates of tornado winds without being in the twister's path. Some Doppler Radars are even small enough to be mounted on vehicles and driven to within a few miles of tornadoes, to get up-close-and-personal measurements. Two years ago today, one such "Doppler-on-Wheels" measured the world record for highest wind speed - 318 mph - in a tornado near Oklahoma City.

This is what that record-setting tornado looked like to meteorologists on Doppler Radar. In this image, different colors correspond to different wind speeds. The white square in the upper left marks the location of the radar. Red and pink correspond to fast winds blowing away from the radar, while purple and blue indicate even speedier winds blowing toward the radar. Between these oppositely-blowing winds lies the core of the tornado, and itˆ‚s there that meteorologists detected the world-record wind of approximately 318 mph.