The following comes from a press release issued by the National Weather Service...
The Weather Surveillance Radar-1988, Doppler (WSR-88D) system operated by the Chicago National Weather Service Forecast Office serving northern Illinois and northwest Indiana will be enhanced with the latest dual polarization technology beginning October 17th for approximately 12 days through October 28th. This $40 million program will result in several benefits such as: better estimation of precipitation amount, size and type; better detection of hail; and in some situations additional information on whether and where a damaging tornado has touched down (as indicated by a “debris ball”).
Dual polarization radar technology can better detect heavy rainfall in flooding events, improve hail detection in thunderstorms and improve classification of precipitation types (rain, snow, ice). It can also detect the presence of airborne tornado debris, giving a forecaster a higher degree of confidence that a damaging tornado is occurring. This helps a forecaster confirm and track the location of a tornado, which is especially helpful at night when tornadoes are difficult to spot with the human eye.
“This is the most significant upgrade to the nation’s weather radar network since Doppler radar was first installed in the early 1990s,” said Jack Hayes, director of NOAA’s National Weather Service. “Dual polarization technology provides significantly more information and clearer pictures of current weather conditions, helping National Weather Service meteorologists provide more accurate and timely forecasts.”
Current National Weather Service radars provide forecasters information on precipitation intensity and movement (direction and speed). Dual polarization technology adds new information about the size and shape of an object, which will improve estimates of how much rain is falling, improving flash flood detection and warnings. During winter weather, dual polarization radar can tell the difference between rain, snow and ice, which gives forecasters a much better idea of what to expect at the ground.
"For the residents of northern Illinois and northwest Indiana, this radar upgrade will help us provide better identification of heavy rainfall, hail and tornadoes, and better distinguish mixed precipitation during the cold season," said Edward Fenelon, meteorologist-in-charge of the Chicago National Weather Service Forecast Office in Romeoville, IL. "It will also aid us in identifying areas of icing aloft for aviation weather interests," added Fenelon. Installation will begin October 17th and will last about two weeks. During the upgrade, adjacent National Weather Service radars in Milwaukee/Sullivan, WI, Quad Cities, IA, Central Illinois and Northern Indiana will provide coverage. Installation of dual polarization technology in all 122 National Weather Service radars is expected to be completed in 2013. Thirty eight other Doppler radars owned by the Air Force and Federal Aviation Administration will also be upgraded.