In 1948, radar was a fairly new technique applied in meteorology to detect rainstorms and determine their location and movement. That summer, ISWS meteorologists Glenn Stout and Floyd Huff collaborated with the Pfister Hybrid Corn Company in El Paso, IL to study the ability to induce rain from an aircraft and, for the first time in Illinois, to evaluate the effectiveness of radar equipment for precipitation studies.
To induce rain, an AT-6 single-engine aircraft that could reach an altitude of more than 27,000 feet was to be used to distribute dry ice through a hatch in the bottom of the fuselage. Dry ice dispersed in a cloud produced ice crystals by cooling the water vapor.
Despite their careful plans, the meteorologists collected no data that summer because precipitation was adequate, and no flights were scheduled. Data from previous flights sponsored by Pfister were also severely limited, so meteorological analysis was impossible.
The ISWS originally purchased a radar set from a war-surplus dealer in Chicago to track the plane and confirm if precipitation had occurred. Instead, the equipment was used for this project to track natural rainstorms. A University of Illinois electrical engineering student who had radar experience in the Navy built the cables connecting the elements together. The radar was installed on the roof and third floor of a Pfister factory building in El Paso.
The equipment was operated during July and August, with a log time of 108.75 hours. It was out of order for about one-third of the days it was used, and repairs took time because spare parts had to be found.
The project also needed daily weather forecasts to schedule flights. Stout and Huff set up a weather station at their Urbana offices, installing weather teletype circuits to provide data used in preparing weather maps and charts. This data would inform their weather forecasts. At 10 a.m. each day, scientists issued a forecast for the next 24 hours.
A 200 square-mile network of 51 raingages also provided data, along with observations from residents. Twelve 7-day recording and 35 stick gages were installed that summer, and two permanent ISWS gages and two U.S. Weather Bureau gages were used. Observers used the stick gages to record total rainfall in a 24-hour period, the beginning and ending time of precipitation, the type, and the occurrence of strong winds. Daily observations were made from May 1 to Sept. 15.
In the 1949 ISWS Report of Investigation 3, Radar and Rainfall, authors Stout and Huff concluded that radar was successful in detecting storms during the summer season. Radar analysis was used to determine if laborers should be sent to the fields in inclement weather. In one instance, dark clouds signaled imminent rain, but the radar showed that the rain showers were moving away from the work area.
The authors wrote, “With radar, rainstorms can be kept under observation for several hours. This makes possible a warning system, by which, some day, radar will serve our everyday needs.”
Incidentally, in 1953, while testing radar equipment to measure rainfall rates, ISWS operators were the first in the United States to detect and photograph a “hook echo,” the telltale sign of a tornado, using radar. ISWS subsequently designed and developed the nation’s first Doppler weather radar in 1968.