A Measure of the Usefulness of Seasonal Precipitation Forecasts for Agricultural Applications

NOAAs Climate Prediction Center produces experimental climate forecasts that predict total precipitation overthreemonth periods out to a year in advance. The utility of these seasonal forecasts for agricultural applications will dependon a number of forecast characteristics, including dependability, effectiveness, and usefulness. Usefulness is defined as theability of the forecasts to predict conditions significantly different from climatological norms. This definition assumes thatproducers would be more likely to use a forecast if it predicts a large departure from normal conditions. A simple measureof usefulness is developed for the NOAA probability of exceedance seasonal precipitation forecasts. Based on the archivedprecipitation forecasts from 1997 through 2001, this measure is evaluated for 102 forecast divisions covering the continentalU.S. Results vary significantly across the U.S., with some regions showing much larger and more frequent forecasts fordepartures from climatological precipitation than others. For example, at the shortest lead times, precipitation forecastdepartures larger than 10% of climatological means were issued in 45% of the forecasts for southeastern Arizona, but wereissued only 7% of the time for southern Nebraska. Usefulness also varies with lead time, ENSO state and intensity, and season,with the largest forecast departures issued at shorter lead times, during strong ENSO events, and during the fall, winter, andspring seasons. Even if seasonal precipitation forecasts are shown to be dependable and effective, the usefulness of theseforecasts for individual, local agricultural planners and managers will be limited in regions and at lead times where forecastsrarely depart from climatology. Agricultural enterprises that operate at regional scales, and can profitably use predictionsof small shifts in probable outcome (e.g., crop insurance programs, fertilizer production and distribution, and grain storageand transportation) are best suited to benefit in a direct fashion from these forecasts.