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 National Weather Service forecasters rely on radar and ground truth reports to evaluate the potential for thunderstorms to produce tornadoes. The examples below illustrate some of the differences between radar information available to warning forecasters 20 years ago and those available to them today.

  Radar Then...

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The WSR-57 radar (named for the year in which it was built) was the system used during the Novermber 1992 tornado outbreak. It was installed at the Jackson Weather Bureau Office at Thompson Field in 1969. It produced coarse reflectivity data that consisted of gray or green blotches on the radar screen. No storm motion or velocity data was available so the ability to forecast tornadoes was limited. Weather features were traced across the radar scope using grease pencils, or copied onto paper maps, to determine their development and motion from scan to scan. Forecasters had to manually turn a crank to change from one radar scan elevation to another. The last WSR-57 was retired in 1996.


Radar Now...

The radar currently used by the National Weather Service is called the WSR-88D, which stands for Weather Surveillance Radar - 1988 Doppler (the prototype radar was built in 1988). The WSR-88D is a Doppler radar, meaning it can detect movements toward or away from the radar as well as the location of precipitation areas. Although the Doppler technology has allowed meteorologists to observe storm motion and how air is moving within the clouds, the heightened sensitivity, improved resolution and scanning capabilities of the Doppler radars—combined with new, sophisticated computer programs—have given forecasters the ability to detect and issue warnings for tornadoes much earlier and, in most cases, before the tornadoes form. is the U.S. government's official web portal to all federal, state and local government web resources and services.