Pilot reports of aircraft turbulence and icing were compared with forecasts of those phenomena from the National Aviation Weather Advisory Unit for a 45-day period in the winter of 1992. An observation-driven approach was used because it is considered more appropriate for accomodating the subjective reporting that is characteristic of the observational dataset. A number of comparisons were done for subsets of the data based on the magnitude of the reported event, aircraft altitude, and type of forecast. Positive observations of events compared with forecasts more favorably for the icing data than for the turbulence data. Observations of nonevents compared with forecasts more favorably for the turbulence data than for the icing data. Positive observations of both icing and turbulence compared with forecasts more favorably below 18 000 ft than above 18 000 ft. Null reports for icing appear to be more representative of `'no icing'' than the zero-icing reports.
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