Development of a new set of web-based tools for drought analysis and prediction

The NIDIS implementation plan has identified the need for additional analysis and forecast tools that provide quantitative, objective, verifiable, and understandable drought early warning information at a range of time scales for decision makers. We are developing a prototype web-based drought analysis and prediction tool that provides information on the probability of future drought conditions over the U. S. and Mexico using multiple accumulation periods for the Standardized Precipitation Index (SPI) as indicators. The tool uses a methodology equivalent to Ensemble Streamflow Prediction (ESP), combining recently-observed precipitation and an ensemble of re-sampled historical precipitation observations to generate a PDF of forecast SPI values in future months. The interface includes maps of the probability of falling below a user-selected SPI threshold in future months and the ability to click on a location to view a time series displaying a probabilistic plume of future SPI conditions. We will show examples of forecasts from the tool and compare to observed conditions. Further development of the tool will include GCM forecasts of precipitation combined with recently-observed precipitation to produce PDFs of forecast SPI.