An evaluation of the performance of the Current Icing Potential at high altitudes

The Current Icing Potential (CIP) is an algorithm that provides a diagnosis of icing and supercooled large drop (SLD) potential over the CONUS. CIP currently is an operational diagnostic only for altitudes below 18,000 feet because initial verification studies indicated relatively poor performance at higher altitudes. In this study, a new evaluation of CIP above 18,000 feet using both standard and supplemental PIREPS is described. The PIREPs used in this study were the regularly archived reports as well as a special PIREP data set collected by SkyWest Airlines from 13-25 August 2003. The SkyWest PIREPs were not only a valuable addition to the observation data set but also provided a reliable comparison to the somewhat less consistent regular PIREPs. A second evaluation of CIP over the 1 January - 31 March 2003 period was also performed. Standard verification statistics were computed for both of these time periods for CIP values and PIREPs between 18,000 and 30,000 feet. The results indicate that CIP performed very well at high altitudes during the August 2003 time period but was somewhat less successful during winter 2003. The results are also broken down into 3,000 ft. layers to evaluate vertical consistency and are compared to results for levels below 18,000 feet. Case studies are used to investigate situations in which CIP performance at high altitudes is notably poor or good.