Differentiating Freezing Drizzle and Freezing Rain in HRRR Model Forecasts

Abstract Supercooled large drop (SLD) icing poses a unique hazard for aircraft and has resulted in new regulations regarding certification to fly regions of known or forecast SLD conditions. The define two categories based upon the maximum supercooled liquid water diameter (Dmax): freezing drizzle (100–500 μm) rain (> 500 μm). Recent upgrades U.S. operational numerical weather prediction models lay foundation provide more relevant guidance including potential predict explicit size. primary focus this paper is evaluate proposed method estimating size from model data differentiate Using in-situ cloud microphysical measurements collected conditions during field campaigns between January March 2017, study shows that High-Resolution Rapid Refresh capable distinguishing using Dmax extracted category microphysics output. It shown correctly predicted observed as much 99% time when HRRR accurately conditions; however, performance varied by campaign dataset used verification.