Ensemble Flood Forecasting in the U.S. Middle Atlantic Region

Track 3A: Forecasting Droughts and Floods
Thursday, October 12, 2017, 3:40 pm – 5:10 pm

Sanjib Sharma
Ph.D. Candidate
Department of Civil and Environmental Engineering
Penn State University

We demonstrate the application of a regional hydrologic ensemble prediction system (RHEPS) to generate improved flood forecasts in the U.S. middle Atlantic region. The RHEPS is comprised here by the following six components: 1) National Centers for Environmental Prediction 11-member Global Ensemble Forecast System Reforecast version 2(GEFSRv2); 2) NOAA’s Hydrology Laboratory-Research Distributed Hydrologic Model (HL-RDHM); 3) statistical weather preprocessor; 4) statistical postprocessor; 5) multisensor precipitation estimates, gridded surface temperature, and gauged streamflow as the observed data; and 6) a comprehensive verification strategy. To study the role played by preprocessing and postprocessing in flood forecasts, the RHEPS is implemented under the following four forecasting scenarios: raw, preprocessed, postprocessed, and joined preprocessing and postprocessing. Verification of the different scenarios indicate that the benefits of preprocessing and postprocessing vary depending on the forecasting conditions, e.g., season, lead time, basin size, etc. Overall, the analysis shows that postprocessing alone can result in significant gains in forecast skill and reduced biases.