In-Flight Icing Forecasts from Two Model Configurations Running in the Icing Product Alaska (IPA) System

The Icing Product Alaska (IPA) will include both diagnoses and forecasts of in-flight icing in Alaska. The forecast product functions in a similar fashion to the currently operational CONUS-based Forecast Icing Product (FIP) by using model output to produce hourly forecasts of icing probability, severity, and supercooled large drop (SLD) potential out to 18 hours. Some differences from the FIP will be necessary to account for the distinctive icing environments in Alaska, but the overall look and feel of the product will not vary. The IPA forecast product and its differences from the FIP will be presented. The Rapid Refresh (RAP) version of the Weather Research and Forecast (WRF) model will provide the grid on which the IPA forecasts are made. A high-resolution version of the RAP being run at the University of Fairbanks (UAF) will also be tested with the IPA forecast. This model version runs at 3-km horizontal resolution and provides more accurate information on topographical effects and air/sea interactions, both of which are strong drivers of icing conditions in Alaska. Icing relevant parameters and the icing products created from both models will be compared to each other and to pilot reports of icing to measure the usefulness of the high-resolution model in a real-time forecasting system. The results of this evaluation will be discussed.

The larger goal of the IPA is to construct a single system to diagnose and forecast in-flight icing conditions in Alaska. The forecast part of the algorithm is discussed here, but work on the IPA diagnosis is progressing. In the diagnostic portion the IPA forecast will serve as the background grid, and icing-relevant weather observations will be added only where they are available to provide useful information.