On the Combination of Forecast Probabilities for Consecutive Precipitation Periods

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  • 1 Department of Soil, Crop, and Atmospheric sciences, Cornell University, Ithaca, New York
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Abstract

The performance of the method of Hughes and Sangster (1979) for combining precipitation probabilities pertaining to standard 12-h forecast periods is examined for 100 stations in the conterminous United States. Precipitation probabilities for both 24- and 36-h periods are investigated. Although originally derived for a small number of stations by using data from a limited time period, the original formulation is found to be remarkably robust. There is a tendency for overforecasting in the lower half of the probability range, which is most pronounced for the 36-h forecasts. A modification of the original procedure is suggested which largely corrects this problem.

Abstract

The performance of the method of Hughes and Sangster (1979) for combining precipitation probabilities pertaining to standard 12-h forecast periods is examined for 100 stations in the conterminous United States. Precipitation probabilities for both 24- and 36-h periods are investigated. Although originally derived for a small number of stations by using data from a limited time period, the original formulation is found to be remarkably robust. There is a tendency for overforecasting in the lower half of the probability range, which is most pronounced for the 36-h forecasts. A modification of the original procedure is suggested which largely corrects this problem.

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