The 4th Annual Flash Flood and Intense Rainfall Experiment: Evaluating Emerging Atmospheric and Hydrologic Guidance for Probabilistic Flash Flood Forecasting

The 4th Annual Flash Flood and Intense Rainfall (FFaIR) Experiment was held at the Weather Prediction Center (WPC) Hydrometeorology Testbed (HMT) in College Park, MD over four weeks during the period from June 20 to July 22.  The FFaIR Experiment brings together participants from across the weather enterprise to simulate a pseudo-operational environment in an effort to create experimental probabilistic forecasts and evaluate emerging models, tools, and datasets with the ultimate goal of improving flash flood forecasting.  During the experiment, participants utilized and evaluated the latest experimental deterministic convection allowing models (CAMs) and CAM ensemble systems.  In addition to this atmospheric guidance, a major theme of the 2016 FFaIR Experiment was to expand the hydrologic forecasting toolbox beyond Flash Flood Guidance to include fields such as soil saturation at various depths, streamflow anomalies, runoff, and precipitation annual recurrence intervals.  

The 2016 FFaIR Experiment evaluated ways to maximize the utility of high resolution CAMs and ensembles for short-term flash flood forecasts, identify the most effective forms and proper usage of available hydrologic guidance for the prediction of flash floods, and further explore proposed changes to WPC’s operational Excessive Rainfall Outlook (ERO).  After testing the previous three years, a 2% probabilistic contour was introduced operationally on August 1.  In the 2016 FFaIR Experiment, the experimental ERO definition continued to be tested as the probability of a flash flood occurring within 40 km (25 miles) of a point.  This presentation will show the performance results of both the experimental atmospheric and hydrologic guidance for several significant flooding events that occurred during the experiment as well as the statistical calibration results of the ERO probabilistic contours which are defined by the number of flash flood reports captured.  The FFaIR Experiment serves as a probabilistic proving ground for improvement and expansion of operational products offered by WPC.