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William E. Klein and Gordon A. Hammons

Abstract

A new automated system of forecasting maximum and minimum surface temperatures in the conterminous United States has been developed. This system is based on the Model Output Statistics (MOS) approach which effectively combines numerical and statistical methods. A series of screening experiments is described, derivation and interpretation of the MOS equations are discussed, and sample statistics are presented. Verification results, comparing the MOS and perfect prog systems, are summarized. Operational aspects such as facsimile and teletype transmissions, are discussed, and recent changes in procedure are explained. The MOS system replaced the perfect prog technique in the operations of the National Weather Service in August 1973. This has resulted in increased accuracy of the autmated forecasts; at the same time we increased the station coverage from 131 to 228 cities in the conterminous United States.

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Gordon A. Hammons, J. Paul Dallavalle, and William H. Klein

Abstract

For the last few years the National Weather Service has been producing centralized guidance forecasts of calendar day maximum and minimum temperatures by applying multiple regression equations derived statistically from numerical model output. At fist the equations were developed from a six-month stratification of the numerical forecasts, but later we were able to stratify the dependent data into three-month seasons. At the same time we added a number of new potential predictors. These two changes increased the skill of the automated guidance. Here we discuss the dependent data statistics for the three-month season equations and compare their forecasts with those made by the older six-month equations. Finally, we present verification statistics on the objective guidance for the fall and winter seasons from August 1973 to February 1976.

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William H. Klein, Frank Lewis, and Gordon A. Hammons

Abstract

Recent changes in the National Weather Service's automated system of forecasting maximum and minimum surface temperatures are described and illustrated. Modifications include use of the primitive equation model, later surface reports, computer-analyzed isotherms, and climatologically-determined forecast limits. Verification figures are presented to show the improvement of the new system over the old and to justify the replacement of centralized subjective temperature forecasts by completely objective ones.

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