Forecast equations have been developed to predict the probabilities of seven categories of ceiling height. The category definitions are the same as thse used for the the NGM MOS forecasts. The definition of ceiling height categories one through seven are: < 200 ft, 200 - 400 ft, 500 - 900 ft, 1000 - 3000 ft, 3100 - 6500 ft, 6600 - 12000 ft, and > 12000 ft. At the present time, forecast equations have only been developed for the cool season (October through March). A verification of these forecasts was conducted on an independent sample of approximately 90 days (the last half of each month (October - March). Forecasts for 335 sites in the contiguous US, Alaska, Hawaii, and Puerto Rico were included in the verification sample. The P-scores and Ranked Probability Scores (RPS) of the AVN MOS Primary equations, AVN MOS Secondary equations, and operational NGM MOS ceiling height (not developed for Hawaii and Puerto Rico) are presented for projections 6 - 72 hours after the 0000 UTC and 1200 UTC model runs (presently, 1200 UTC only includes results for the contiguous US and Alaska combined). The P-score is analogous to the mean square error, therefore smaller values represent more accurate results. The RPS is analogous to the square error of the cumulative forecast probabilties of the categories: how closely do the forecast probabilities match the verification. Smaller RPS values represent more accurate results.

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Developer: Mitchell Weiss

Last Updated: February 2, 2000