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Abstract Initially a Category 3 storm, Hurricane Ian (2022) rapidly intensified on the West Florida Shelf reaching Category 5 over the course of about 12 hr. Intensification occurred despite inhibiting factors such as high axial tilt, high vertical wind shear, low atmospheric moisture, and transit over a relatively shallow continental shelf. Using a high‐resolution simulation of Hurricane Ian from the Hurricane Weather Research Forecasting (HWRF) model, we examine the factors that both hindered and supported rapid intensification (RI) by blending various methods. We show that an increase in diabatic heating in the eyewall led to an inward radial advection of momentum, seen in both the absolute angular momentum budget and in the azimuthal wind budget. Analysis of the moist static energy budget indicates that the substantial latent heat flux from the surface was enough to balance heat losses through storm outflow. For instance, surface latent heat fluxes exceeded 1,500 W m⁻²on the West Florida Continental Shelf. As suggested by actual ocean temperature observations that substantially exceeded those in the HWRF simulation, the latent heating may have even been larger. Physical explanations for discrepancies between the simulated Hurricane Ian and observations are provided, particularly those pertaining to the coastal ocean at the time of Ian's passage. This research provides a comprehensive explanation of the RI of a hurricane using momentum budget analyses as part of a coupled air‐sea analysis. Our findings demonstrate the importance of in situ oceanic air‐sea measurements in evaluating the performance of coupled models, especially for hurricanes. 

Abstract Airborne Doppler radar observations of the wind field in the tropical cyclone boundary layer (TCBL) during the landfall of Hurricane Ida (2021) are examined here. Asymmetries in tangential and radial flow are governed by tropical cyclone (TC) motion and vertical wind shear prior to landfall, while frictional effects dominate the asymmetry location during landfall. Strong TCBL inflow on the offshore‐flow side of Ida occurs during landfall, while the location of the peak tangential wind at the top of the TCBL during this period is located on the onshore‐flow side. A comparison of these observations with a numerical simulation of TC landfall shows many consistencies with the modeling study, though there are some notable differences that may be related to differences in the characteristics of the land surface between the simulation and the observations here. 

Abstract Understanding physical processes leading to rapid intensification (RI) of tropical cyclones (TCs) under environmental vertical wind shear is key to improving TC intensity forecasts. This study analyzes the thermodynamic processes that help saturate the TC inner core before RI onset using a column‐integrated moist static energy (MSE) framework. Results indicate that the nearly saturated inner core in the lower‐middle troposphere is achieved by an increase in the column‐integrated MSE, as column water vapor accumulates while the mean column temperature cools. The sign of the column‐integrated MSE tendency depends on the competition between surface enthalpy fluxes, radiation, and vertical wind shear‐induced ventilation effect. The reduction of ventilation above the boundary layer due to vertical alignment is crucial to accumulate the energy within the inner core region. A comparison of the RI simulation with a null simulation further highlights the impact of vortex structure on the thermodynamic state adjustment and TC intensification.