An Overview of the Performance and Operational Applications of the MRMS and FLASH Systems in Recent Significant Urban Flash Flood Events

The Multi-radar/Multi-sensor System (MRMS) is an operational state-of-the-science hydrometeorological data analysis framework that combines data streams from multiple radar networks, satellites, surface observational systems, and numerical weather prediction systems to produce a suite of real-time decision-support products every two minutes over the contiguous United States. The Flooded Locations and Simulated Hydrograph (FLASH) component of the MRMS system was designed for the monitoring and prediction of flash floods across small time and spatial scales required for urban areas given their rapid hydrologic response to precipitation. Developed at the National Severe Storms Laboratory in collaboration with the Cooperative Institute for Mesoscale Meteorological Studies (CIMMS) and other research entities, the objective for MRMS and FLASH is to be the world’s most advanced system for severe weather and stormscale hydrometeorology, leveraging the best science and observation systems to produce the most accurate and reliable hydrometeorological and severe weather analyses. NWS forecasters and other public and private sector meteorologists utilize a variety of products from the MRMS and FLASH systems for hydrometeorological situational awareness and to provide warnings to the public and other users about potential impacts from flash flooding. Several major urban areas experienced significant flash floods during rush hour commuting periods in 2019, including Washington, D.C., Baltimore, MD, St. Louis, MO, and Minneapolis, MN. This article will examine the performance of hydrometeorological products from the MRMS and FLASH systems, and provide perspectives on how forecasters used these products in the provision of warnings services for these events. Additionally, other potential applications of MRMS and FLASH products for enhanced warning and decision support information will be explored.