Investigation of the Air-Sea Interaction Processes Simulated with a 1/12-d Regional MOM6 Coupled to the Hurricane Analysis and Forecast System

The representation of the upper ocean is essential to the Tropical Cyclone (TC) intensification. Otherwise, it might lead to false intensification, especially storms transiting over the Gulf of Mexico and Caribbean Sea. It is because they have relatively short lead time to landfall, and yet might potentially have a higher chance of intensification due to high heat contents in the warm oceanic upper layer. Under a favorable environment, a storm could go through rapid intensifications. Hurricane Laura in 2020 is a good example and other examples are the recent storm Hurricane Ian (2022) and Idalia (2023). We investigate the air-sea interaction processes from the coupled ocean-hurricane simulations using two ocean component models in coupled Hurricane Analysis and Forecast System (HAFS). HYbrid Coordinate Ocean Model (HYCOM) is an eddy-resolving, ocean model that has been extensively developed in the past and widely used for the physical and thermodynamical process studies at various scales. In recent years, an effort focuses on developing a high-resolution regional Modular Ocean Model version 6 (MOM6) in order to integrate to HAFS for the 2024 version. We chose Hurricane Laura (2020) for the Gulf of Mexico storm and Fiona (2022) for the case study. The preliminary suggests that MOM6 coupling demonstrated mixed forecast skill in early lead time but improved skill for late lead time for track and intensity by O(10%), compared to HYCOM coupling. However, the ocean simulations show relatively large convective mixing and weak shear mixing for MOM6, compared to HYCOM. We will present detailed analysis, including comparisons with in-situ observations from Saildrones and gliders.