A Dynamical Model of the Inner-Core Evolution of Landfalling Tropical Cyclones. Part II: Applications to Idealized Landfall Scenarios and Evaluation against Radar Observations

This two-part study proposes a simple dynamical model, TRACE (Total Relative Angular-Momentum and Energy Constrained Evolution), to describe the intensity decay and structural changes of a tropical cyclone (TC) inner core during landfall. The model’s behavior is investigated both analytically and through comparison with observations. In Part II, we apply the TRACE model to idealized landfall scenarios and compare its intensity predictions with the empirical inland decay model of Kaplan and DeMaria (1995). For initially intense TCs, the TRACE-predicted intensity decay agrees remarkably well with the empirical model over a 42-h post-landfall period, whereas for weaker TCs, TRACE predicts a faster decay during the later stages. Consistent with Part I, the simulations confirm that lower free-tropospheric winds decay more rapidly for storms that are initially stronger, more compact, and moving over rougher surfaces. Additionally, in cases with rough land, outer-core friction causes a rapid loss of relative angular momentum, inducing pre-landfall core contraction and spin-up as analytically predicted. Finally, the TRACE framework is applied to simulate the structural evolution of Typhoon Faxai (2019) during landfall. The model predictions show good agreement with the lower free-tropospheric axisymmetric tangential winds derived from dual-Doppler radar analysis. Notably, during the period of pronounced observed expansion of the radius of maximum wind (RMW), the phase-space analysis indicates that the inner-core total swirling kinetic energy decays fractionally about twice as fast as, or faster than, the total relative angular momentum. This behavior is consistent with the analytical condition for RMW expansion derived in Part I for self-similar profiles.