REGIONAL PERFORMANCE OF NOAA/CPC SEASONAL CLIMATE TEMPERATURE FORECASTS

Authors: Schneider, Jeanne; Garbrecht, Jurgen

Submitted to: Environmental and Water Resources Institute World Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/12/2004
Publication Date: 6/27/2004
Citation: Schneider, J.M., Garbrecht, J.D. 2004. Regional performance of NOAA/CPC seasonal climate temperature forecasts. In: Proceedings of the Environmental and Water Resources Institute World Congress, June 27-July 1, 2004, Salt Lake City, UT. 2004 CDROM.

Interpretive Summary: Operational climate forecasts for 3-month average temperature are issued monthly by the National Oceanic and Atmospheric Administration's Climate Prediction Center. The forecasts appear to support a wide range of applications in agriculture, and possibly water resource management. However, the adoption and use of the forecasts has been limited, partly due to a lack of user-oriented measures of forecast utility on a regional basis. An assessment of regional forecast performance was made across the contiguous United States for the years 1997-2002. The measures used were usefulness (degree and frequency of departures from normal conditions), and dependability (the ability of the forecasts to correctly predict the direction of departures). The results of this analysis show that the mean temperature forecast performance does not vary much with region or the state of the El Niño Southern Oscillation. This is distinctly different from the performance of the corresponding precipitation forecasts. Forecasts for warmer than average conditions have been dependable for much of the U.S., especially in the northern Great Plains and Rocky Mountains. This success appears to be the result of persistently warmer than average conditions during the study period, so continued dependability can be expected as long as the trends continue. Relatively few forecasts were offered that predicted cooler than average conditions, and most of those were not dependable.

Technical Abstract: Operational climate forecasts for 3-month mean temperature are issued monthly by the NOAA Climate Prediction Center. Among these forecasts, the Probability of Exceedance forecasts present information on expected shifts in the probability distribution of mean temperature relative to climatological distributions. The forecasts appear to support a wide range of applications in water resource management and agriculture, especially in regions where growing season length, snow pack, and lake or river ice processes are important. These temperature forecasts have been reported to have modest skill when skill is assessed across the entire U.S. However, the adoption and use of the forecasts has been limited, partly due to a lack of user-oriented measures of forecast utility on a regional basis. We examine forecast performance over the years 1997-2002, for all forecast divisions in the contiguous U.S. at the shortest lead time (0.5 months). Performance is assessed using two measures of forecast utility: usefulness (degree and frequency of departures from climatological distributions), and dependability (correspondence between the direction of forecast departures and actual occurrences). The results of this analysis shows that the mean temperature forecast performance does not vary much with region and ENSO state. Forecasts for warmer than average conditions have been dependable for much of the contiguous U.S., especially in the northern Great Plains and Rocky Mountains. This success appears to be the result of persistently warmer than average conditions during this period. There were relatively few forecasts offered predicting cooler than average conditions, and most of those were not dependable. As a result, forecast users should not expect reliable forecasts for cooler than average conditions.