The icing diagnostics that are currently computed and shown on this web site are all based solely on the AFWA MM5 T1A model run. In the very near future, we will display the diagnostics from the UAF local MM5 run as well.

Currently, we show icing diagnostics solely from a slightly modified version of the Schultz/Politovich (1992) model-based temperature and relative humidity algorithm. In the algorithm, each grid column is searched between the 500 hPa pressure level and the surface. Likely areas for in-flight icing are considered to be those where all of the following are satisfied: the relative humidity is greater than 55 %, the temperature is between 0 ^oC and —20 ^o C, and upward vertical motion is present.

While the diagnostic can be evaluated as a columnar or three-dimensional quantity, for display purposes we choose to show only the columnar diagnostic, which indicates if in-flight icing is possible anywhere within the atmospheric column.

Verification statistics from the Schultz/Politovich algorithm (using Pilot reports) as well as diagnostics from the MM5 supercooled liquid water algorithm will also follow at a future date, as will diagnostics from an Alaska MM5-based version of the NCAR Integrated Icing Diagnostic Algorithm.

Schultz-Politovich diagnostic for the current analysis

Schultz-Politovich diagnostic for the current 12 hour MM5 forecast

Schultz-Politovich diagnostic for the current 24 hour MM5 forecast