Use of HPC QPF confidence interval forecasts to produce an ensemble of river forecasts

The North Central River Forecast Center (NCRFC) has been using the HPC deterministic Quantitative Precipitation Forecasts (QPF) in its hydrologic modeling since 1994 with reasonable success; however we have received a number of requests from our users over the years for alternative QPF inputs (i.e. less or more) or multiple QPF solutions. Although we were able to meet some of these requests by manually manipulating the data, it was cumbersome, introduced significant overhead to the forecast process, and resulted in questionable, subjective results and lacked consistency.

The NCEP HPC began producing 95% Confidence Interval (CI) QPF in early 2004. These forecasts continue to be under review and refinement based on verification results and user feedback. In 2005, the NCRFC began a project to utilize the Maximum 95% CI QPF and Minimum 95% CI QPF as routine additional inputs to the National Weather Service River Forecast System (NWSRFS). With these additional inputs we now produce a three member ensemble of river forecasts for selected locations. The results of the analysis of these ensembles will be presented.