Impact of Land Friction on Surface Wind Structure During Hurricane Landfall

This study employs a diagnostic three-dimensional Hurricane Boundary Layer (HBL) wind model to understand the evolution of surface wind structure changes during hurricane landfall in an idealized setting. Our approach focuses on the role of dynamical boundary layer processes in governing the changes in surface wind structure. Model results show that offshore wind changes develop in the front-left quadrant even when the hurricane center is relatively far (100–200 km) from the coastline. Notably, as the hurricane nears land, both its radial inflow and tangential wind speeds intensify over the ocean (by 80% and 13%, respectively) in the storm’s front-left and rear-left quadrants. The storm’s maximum surface wind speed is enhanced (by 14%) before landfall and shifts to the left of the storm track. Momentum budget analysis indicates that land-induced friction reduces tangential wind speed over land, which is advected offshore, increasing the imbalance between the pressure gradient force and the combined Coriolis and centrifugal forces. This imbalance, along with radial and azimuthal advection, drives the development of offshore wind asymmetry. As the storm center moves closer to land, enhanced angular momentum advection due to enhanced radial inflow further strengthens the tangential speed in the rear-left quadrant. Sensitivity experiments reveal that slower-moving hurricanes develop offshore wind asymmetry earlier, while increased land roughness amplifies its effects, leading to stronger maximum radial, tangential, and total wind speeds at landfall. These findings enhance our understanding of hurricane wind evolution near landfall and underscore the need to consider multiple factors in forecasting and disaster preparedness.