The Hail Quadrature Parameter (HQP) is a scalar quantity calculated from the co-polar reflectivity (Z_H), the differential reflectivity (ZDR), and the linear depolarization ratio (LDR), as measured by an S-Band dual linear polarization radar system (Kennedy et. al, 30th AMS weather radar conference, Munich, Germany, 2001). It is proposed that the HQP magnitude observed at above-freezing environmental temperatures near the surface may be correlated with important hail fall characteristics (probability of structural damage, categorical hail size discrimination, etc.). Data to test this proposition were collected during a summer 2002 field experiment conducted in Colorado at the CSU-CHILL radar facility. HQP maps plotted from the polarimetric radar data were compared with the hail observations obtained from ground observers during post-storm surveys. This paper will present various correlations between the HQP magnitudes (and several other radar-based hail parameters) and the ground truth hail observations. The theoretical sensitivity of HQP to the effects of melting and particle size distribution variations will also be addressed based the results of a microwave backscattering model.