A Climatological Geospatial Analysis of Storm-Based Flash Flood Warnings across the CONUS

Since the implementation of storm-based warnings in October 2007, there has been little research on nationwide geospatial statistics related to the National Weather Service’s (NWS) Flash Flood Warnings (FFWs). As such, this study provides an initial climatological geospatial analysis of FFWs across the contiguous United States (CONUS) from October 2007 to May 2019. We examined statistics at the national, NWS regional, and NWS Weather Forecast Office scales, and included the average warning size, duration, number of counties included, and percent overlap with urban areas. Additionally, we computed time series statistics, such as the number of FFWs per month and time of issuance, to note any seasonal and diurnal signals. Results from analysis of these parameters will provide insight into FFW practices across the NWS and highlight specific recommendations for national training initiatives.