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The radar relies on a phenomenon first explained by the 19th century physicist Christian Doppler, who observed that sound waves from an approaching source—say the whistle on a speeding train—rise in pitch (or frequency), while the waves from a departing source decrease in pitch. Applying the same principle to radio waves, Doppler radar uses shifts in frequency of the electromagnetic echoes from a storm system to measure motions within it. The research station in Oklahoma is capable of making almost 1 million measurements in a minute. These data are digested by a powerful computer and displayed as color-coded patterns on screens in the center's control room.
The first important revelation about tornadoes from Doppler radar was identification of the characteristic patterns of large, rotating air masses, known as mesocyclones, which frequently spawn twisters. Forecasters have since learned to spot even smaller areas of rapid rotation that represent actual incipient tornadoes, and have predicted within a kilometer (0.6 mile) where they will touch down. Since 1977, when they began sustained testing of their skills, the Oklahoma scientists spotted tornadoes aborning an average of 21.4 minutes before they struck. By contrast, warnings issued by the Weather Service's regular Oklahoma City office on the basis of ordinary radar preceded the twisters by an average of only 2.2 minutes.
Still, all of the new technology is useless if the public does not know how to respond properly to a warning. Many people in Wichita Falls, hearing advance alerts, made for their cars instead of shelters, hoping to outrace the funnel. As a result, the majority of the storm deaths were associated in one way or another with motor vehicles. Noted a federal report: "In 16 of the vehicle-related deaths, the victims had got into their cars or trucks specifically to escape the tornado's path. The homes of eleven of these victims did not have major damage." ∎