Hydrometeorological Forcing Errors for a Real-Time Flood Forecast System in the Ohio River Valley

An examination of the magnitude of hydrologic model forcings errors in the form of Quantitative Precipitation Estimate (QPE) and Quantitative Precipitation Forecast (QPF) over the Ohio River Valley at the National Oceanic and Atmospheric Administration (NOAA), National Weather Service (NWS) Ohio River Forecast Center (OHRFC) is presented. Analyses of QPE biases, which are limited to the OHRFC area of forecast responsibility, are made with respect to Parameter-elevation Regressions on Independent Slopes Model (PRISM) estimates on a monthly, seasonal, and annual basis. QPE biases are shown to be quite variable monthly and seasonally over the 1997-2016 analysis period. QPF analyses, relying on data from the NOAA/NWS National Precipitation Verification Unit (NPVU), are reported for NWS River Forecast Centers (RFCs) within the Continental United States (CONUS) and are compared to QPF from several numerical weather prediction (NWP) models and the NOAA/NWS Weather Prediction Center (WPC). Improvements in Next Generation Radar (NEXRAD) based QPE over the OHRFC area have been dramatic from 1997 through 2016, but QPF estimation remains problematic. From the perspective of meeting hydrologic forecasting needs, QPF shows marginal improvement over the analysis period. A case study illustrating the sensitivity of hydrologic forecast error to QPF is presented. These findings have important implications on real-time forecast operations at the OHRFC and, potentially, other NWS River Forecast Centers and forecast operations elsewhere.