Precipitation Probability-Comparing Offices for Skill

Abstract

Using screening regression procedures, an attempt has been made to standardize probability of precipitation Brier scores for difficulty. Climatological factors affecting the difficulty of forecasting used are: precipitation frequency, time persistence and small amount frequency. Standardizing equations were derived for three-month seasons from seven years of data. Four-term regression equations were developed for each season and lead time. Local forecaster improvement over guidance scores varied inversely as the Model Output Statistics (MOS) scores, indicating that poor machine forecasts are easier to improve upon than good machine forecasts.