Characterizing the Hazard of Rainfall-Diverse Hurricane Profiles in the Southeast United States

Atlantic basin hurricanes act as drivers of serious meteorological hazards for the southeast United States, including rainfall-induced freshwater flooding. The well-known Saffir-Simpson Hurricane Wind Scale (SSHWS) communicates only wind hazard. This creates the potential for low wind, high rainfall storms to be perceived as mild by the public due to misunderstandings of what the SSHWS communicates. Recently, researchers have emphasized the need to include rainfall hazard in hurricane warning messaging. In the interest of this goal, this research investigates the rainfall profiles of three different Atlantic hurricanes: Hurricane Florence (2018), Hurricane Michael (2018), and Hurricane Ian (2022). Each hurricane’s rainfall profile is quantified by using CPC-Unified daily gridded gauge-based data. Wetness is determined on a relative scale as a function of rainfall totals over space and time. Impacts for each hurricane are assessed through this lens of wetness and compared between the three rainfall scenarios using a mixed-methods analysis. This includes discussion of how social vulnerability may correlate with impacted areas. Impacts that are investigated include deaths, monetary damage, and real time impact observations from the Weather Prediction Center’s local storm reports database. As a central component of this project, Excessive Rainfall Outlooks (EROs) that were issued for each hurricane are verified against the actual spatial extent of rainfall impacts in order to evaluate precipitation forecasting in the three scenarios. Results of this study validate the use of EROs for different hurricane wetness scenarios and lay a foundation for a future larger-scale analysis of verifying hurricane rainfall forecasts. This will improve how rainfall hazards from tropical cyclones are communicated and support future work in bridging the gap between citizens, governments, and other stakeholders.