Polarimetric radar and surface observation of a flash flood

On the night of 28 July 1997, the city of Fort Collins, Colorado experienced a devastating flash flood that caused five fatalities and extensive property damage across the western side of the city. The CSU-CHILL radar was operating on that particular evening, providing an unprecedented documentation of the convection and rainfall associated with a flash flood from the view point of an S-band dual-polarized radar. Hydrologically, saturation of the soil in the surrounding area occurred in association with heavy rainshowers that developed on 27 July and lasted through the morning of 28 July. These rains were later followed by a series of convective cells that propagated through the region during the afternoon and evening of 28 July. The storm resulted in rainfall amount of about 10 inches over 5 hours on the southwest side of Fort Collins. This paper presents comparison of various radar algorithms with gage estimates of rainfall. The specific algorithms compared are R(Z_h), R(Z_h, Z_dr), R(K_dp), R(K_dp, Z_dr) and neural network based estimates