Hurricane Ian Intensification on the West Florida Shelf

In September 2022, Hurricane Ian underwent a rapid intensification as it approached the west coast of Florida with a maximum wind speed of 140 kt (72 m s^-1) and a minimum central pressure of 937 mb. This intensification occurred with the storm over shallow water and under the influence of moderate shear. We used a high resolution hurricane model and observations to determine why Ian intensified. The rapid intensification occurred over the West Florida Shelf, where sea surface temperatures were anomalously warm. The warmth is linked to the Gulf of Mexico Loop Current, which had not reached the West Florida Shelf anchoring state in a few years. Without Loop Current induced upwelling of cooler, deeper ocean water onto the West Florida Shelf, the entire shelf water column was warm. Thus, sustained warmth, despite strong wind mixing led to a consistent enthalpy flux into the storm and in turn a radial advection of heat. Both balanced and unbalanced dynamic analyses were conducted to help explain why Ian underwent intensification. Despite what may otherwise have been unfavorable conditions, the enthalpy fluxes were large enough that Ian underwent rapid intensification.