Seasonal Precipitation Forecasting with a 6 to 7 Month Lead Time in the Pacific Northwest Using an Information Theoretic Model

摘要

An entropy minimax analysis to forecast seasonal precipitation with a 6-7 month lead time was performed for two regions in the Pacific Northwest. A model to forecast winter precipitation in the Willamette Valley, Oregon was developed using the 92 year period 1854-1945 for model building. Predictions made for the reserved test years 1946-1982 were found to have a 74% accuracy. Statistical tests established a 99% confidence that this success is not due to chance. Models to forecast winter and spring precipitation in eastern Washington were developed using the 73 year period 1873-1945. The winter model was found to have 69% predictive accuracy on the test years, with a 97% confidence against chance. The spring model was found to have an accuracy of 54%, which is statistically indistinguishable from chance. The accuracies of the winter models for both western Oregon and eastern Washington show fair uniformity throughout the 37 year test period, with a slight downward trend in the later portion.