Submitted to: Precipitation Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 2001
Publication Date: June 30, 2001
Technical Abstract: The National Oceanic and Atmospheric Administration's Climate Prediction Center issues experimental forecasts monthly for 3-month total precipitation, at the scale of forecast divisions (roughly 100,000 square kilometers), for lead times from 0.5 months to 12.5 months. A multifaced investigation of the utility of these forecasts to support planning and decision making in agricultural and natural resource management is underway. The forecasts consist of probability of exceedance functions for each division at each lead time, with associated contour maps of the best- guess prediction of departure from normal conditions (climatology). These best-guess predictions are the difference between the center values of the forecast and climatological probability of exceedance functions, essentially the shift at the midpoint of the function toward wetter or drier conditions. This shift is a very simplified representation of the full probability of exceedance forecast, but is the aspect of immediate interest in this user community. Small variations away from climatology are rarely significant in agricultural and natural resource applications, so predictions of near-normal precipitation are of little value, having no impact on the planning and decision making process. Accordingly, an evaluation of the ability of the seasonal precipitation forecasts to predict shifts from normal/climatology was performed. The evaluation was done on a division by division basis, for the seasonal precipitation forecasts from 1995 through 1999. Results for the 0.5 month lead time forecasts show that the ability to predict shifts in 3-month precipitation varied by forecast division, ans was of limited value in some regions.