Stan Changnon headed the project, and the Chief Emeritus of the Water Survey recalls that, “the immediate significance of detecting the hook echo was the hope of using radar to provide better tornado warnings. Over the past half century radar technology has improved greatly and has been adopted by weather services throughout the world. Tornado warnings using radar technology have saved thousands of lives.”

It was on the afternoon of April 9, 1953, that staff were operating the Water Survey’s radar for routine collection of rainfall data as part of a project to determine radar’s usefulness for measuring precipitation. A network of many raingages had been established in east-central Illinois to provide ground truth for radar-indicated amounts. The normal procedure was to turn off the radar after precipitation had occurred.

Radar engineer Don Staggs and Changnon were working at the radar, and Staggs decided to leave it on and continue photographing radar echoes. Other key Water Survey personnel for the project were meteorologists Doug Jones, Stuart Bigler, Homer Hiser, and Floyd Huff; head of Meteorology Glenn Stout; and Water Survey Chief Arthur Buswell.

Development, growth, and movement of a fishhook-shaped tornado echo associated with a passing thunderstorm were observed on the radar scope and photographed in detail. This distinct tornado echo near the southwest edge of the associated thunderstorm contained the tornado funnel.

Although Staggs recognized the unusual nature of the radar echo and the possibility of a severe storm, positive identification was not made until the radar film was developed the next day. Floyd Huff then realized that the distinctive hook echo was the signature of the tornado reported the previous afternoon over Champaign and Vermilion Counties.

The discovery garnered widespread attention from the media and the scientific community and led to further major achievements. Changnon notes that “the major scientific significance of this 1953 discovery was that it helped take atmospheric research in new directions. Scientists and engineers sought to use radars to detect all forms of severe weather, but learned that radars of that era were not capable of doing so. Thus, Water Survey staff later designed more powerful radars with longer wavelengths, large antennas, and computerization for severe storm and rainfall measurements.”

Doppler capabilities of these new radars made it possible to measure the direction and speed of airborne particles, a breakthrough for assessing in-cloud development of tornado funnels and strong straight-line winds.

“A dual Doppler radar jointed developed by the Water Survey and the University of Chicago, the CHILL, successfully detected incipient tornado funnels and hail aloft, and served as the prototype for the NEXRAD radars used today by the National Weather Service for advance detection of tornadoes,” says Changnon.

The Water Survey (http://www.sws.uiuc.edu/) is proud of its 50-year history of weather radar research and development. A reception commemorating the 50th anniversary of the first radar observation of a hook echo documented to be associated with a tornado was held at the Water Survey in Champaign from 1-2 p.m. on April 8, 2003. Members of the public were invited. A display at the Water Survey includes photographs of the hook echo, the magnetron used, radar logbook documentation, and details about the actual tornado.