The 2013 Flash Flood and Intense Rainfall Experiment

In addition to its traditional responsibility of providing national quantitative precipitation forecast (QPF) guidance, NCEP's Weather Prediction Center (WPC) recently began issuing short-term Mesoscale Precipitation Discussions (MPDs). MPDs are event-driven forecasts that highlight regions where heavy rainfall may lead to flash flooding in the next 1-6 hours. In support of this new function, the Hydrometeorological Testbed at WPC (HMT-WPC) collaborated with NOAA's National Severe Storms Laboratory (NSSL) and Earth Systems Research Laboratory (ESRL) to host the Flash Flood and Intense Rainfall Experiment (FFaIR) from 8-26 July 2013. The experiment brought together a total of 26 forecasters, researchers, and model developers, including 8 participating remotely, to explore the challenges associated with short-term QPF and flash flood forecasting during the warm season.

During the experiment, participants used a combination of operational and experimental numerical model guidance to issue several short-term probabilistic QPF and flash flood forecasts. The experimental guidance included a new version of the operational North American Model (NAM, 12 km with 4 km nest), the High Resolution Rapid Refresh (HRRR, 3 km), the Storm Scale Ensemble of Opportunity (SSEO, 7 members, 4 km), and the Experimental Regional Ensemble Forecast System (ExREF, 8 members, 9 km). Both experimental ensembles featured a variety of point and neighborhood exceedance probabilities, including probabilities of QPF exceeding flash flood guidance. Participants were also asked to subjectively evaluate their experimental forecasts, the quality of various flash flood indicators, and the experimental model guidance. As part of the evaluation process, participants were introduced to Flooded Locations and Simulated Hydrographs (FLASH), a high resolution rapidly updating hydrologic model used to identify locations of flash flood events.

The 2013 Flash Flood and Intense Rainfall Experiment highlighted the numerous challenges associated with short-term flash flood forecasting. This presentation will provide an overview of the experiment, show preliminary results from the subjective evaluations, and highlight lessons learned.