Normal and reverse storm surges along the coast of Florida during the September 2022 Hurricane Ian: Observations, analysis, and modelling

The September 2022 Hurricane Ian was among the most destructive hurricanes to hit the US coasts. Ian was one of the rare events that produced both positive (normal) and negative (reverse) surges. We analyse and model the generation mechanism of these surges through studying sea level, air pressure, and wind observations as well as numerical modelling. Analysis of a rich observation dataset helped us to explain their simultaneous generations for the first time. Among the examined data, maximum wind speed was 50-60 m/s and the minimum air pressure was 961.6 hPa. Although three factors of wind, pressure drop, and geometry contribute to surge generation, we found that wind was the dominant factor. Despite the opposing impacts of pressure drop and wind on reverse surge generation, the amplitudes of reverse surges (2.4 m) were larger than those of normal surges (over 1.8 m). Normal and reverse surges were consistently generated by landward and seaward winds, respectively. Reverse surges occurred at parts of the coast under seaward wind that experienced less intensive pressure drop. We successfully modelled both normal and reverse surges. Our model can be employed for forecasting unique storm surges such as those generated during Hurricane Ian.