FHICS – Successful forecast of Hurricane Ian impacts

Hurricane Ian was the first 2022 hurricane to make landfall in the continental USA with strong Cat 5 winds and large amounts of rain. The team of Deltares USA, Deltares Netherlands, USGS and NRL successfully applied the COSMOS modelling system to forecast hurricane Ian’s flood and morphological impact.

The Cosmos system consists of a chain of models to compute the surge and waves in US coastal waters, in order to estimate the flooding due to surge and direct rain fall, as well as dune erosion and breaching along the sandy shores (see previous posts about the model chain).

Using the Navy’s COAMPS forecasts of windspeed, pressure and rainfall we drove the model chain for the case of Hurricane Ian, providing 12 hr updates of flooding and erosion on our website (Note that the results displayed are experimental and should not be used to make any decisions).

The COAMPS wind field just prior to landfall showed intense Cat 5 winds at Naples, FL, and Ft. Myers, FL.

Figure 1: Snapshot of windfields just prior to landfall.

The resulting forecasted flood map showed extensive flooded areas from the coast to well inland due to a combination of surge (seawater flooding over land) but also due to direct rainfall.

Figure 2: Predicted flooding in the Ft. Myers area.

The initial results showed that the modelling system captured the signature of the flood curve well, but in fact overpredicted the surge at the Ft. Myers station. The team will further investigate the nature of this overestimation. We predicted the set down of very low water levels in Tampa Bay well.

Figure 3: Computed water levels (orange) at Ft Myers, with observations in green and the “normal” tidal fluctuations in blue.

Furthermore, we predicted extensive coastal erosion (in red) and breaching along the SW Florida coasts.

Figure 4: Estimates of dune erosion (red) and breaching (blue) along the SW Florida coasts.

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