Forecasts, observations, and warning response for flash floods

The COMET® Program at UCAR was established in 1989 and routinely develops training material in collaboration with the NOAA National Weather Service and the university community on flash flood forecasting, quantitative precipitation estimation (QPE) and quantitative precipitation forecasting (QPF), hydrology, mesoscale meteorology, and societal impacts of severe weather and hydrometeorological events. Numerous case studies, online material, and discussions in both onsite and virtual classroom formats examine the relationships between short-fused, high-impact events like flash flooding, the latest scientific advancements, and societal impacts. The distance learning materials are freely available to users worldwide on our MetEd website (www.meted.ucar.edu) courtesy of our sponsors, NOAA (NWS, NESDIS, NPOESS), the Department of Defense (Air Force Weather, Naval Meteorology and Oceanography Command), and the Meteorological Service of Canada. COMET has also received funding from National Environmental Education Foundation as well as NSF, DOT, BLM, the Australia Bureau of Meteorology, and EUMETSAT.

This presentation will focus on relevant issues raised via our training activities specifically in the areas of flash flood forecasting and warning response. Flash flood forecasting involves all of the meso- and storm-scale complexities of severe weather forecasting along with the challenge of forecasting runoff on the small basin scale. The nature of hydrologic response can vary greatly across geographic regions as well as between drainage basins within a region. This hydrologic response variability combined with the spatial and temporal variability of intense convective rainfall results in a wide range in the severity and coverage of flash flood episodes. At times flash floods occur simultaneously with severe weather leading to challenges in appropriate warning response.

This study will review a number of recent flash floods in the United States and look at the meso- and storm scale hydrometeorological processes as well as important issues regarding warning communication and societal response. Cases include very small scale events like the California debris flows of February 2010, the June 2010 Albert Pike Recreation Area flash flood in Arkansas, and the Kansas Turnpike flash flood of August 2003. More widespread cases are also reviewed such as the disastrous September 2009 flash floods in northern Georgia, the Nashville area flooding in May 2010, and the Cheshire County New Hampshire floods of October 2005.

This paper was funded by the University Corporation for Atmospheric Research under the cooperative agreement award #NA06NWS4670013 from the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce. The statements, findings, conclusions, and recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of NOAA or any of its sub-agencies.