Influence of inner‐core dynamics regulating the intensity decay of landfalling tropical cyclones over the eastern coast of India

Abstract During the last 30 years (i.e., 1995–2024), postmonsoon (October–December) landfalling tropical cyclones (TCs) over the Bay of Bengal (BoB) exhibited a 51% slower intensity decay rate (33.55 hours) compared to the premonsoon (March–May) TCs (22.16 hours). Moreover, a significantly slower decay rate is noticed for the recent two decades. Therefore, to understand the role of inner‐core dynamical processes and associated intensity changes, four postmonsoon landfalling TCs are simulated using the Weather Research and Forecast (WRF) model assimilating radar reflectivity (Rf). The intensity, convective structure, and rainfall skills are markedly improved by assimilating Rf observations, as it captures the convective‐scale details of the TCs during landfall. Further analysis reveals that the diabatic heating maxima within the eyewall during the mature stage are confined within the radius of maximum wind (RMW). This diabatic heating in the inner core induces cyclonic potential vorticity (PV), maintaining the eyewall ring structure. However, the landfall process can induce small‐scale perturbations in the PV field, affecting the inner‐core structure. A TC eyewall with an axisymmetric structure and strong inertial stability supported by the lateral supply of moisture flux can sustain the adverse effect of the landfall, therefore slowing down the decay process. Conversely, radial influx of anomalously low PV is found to cause rapid weakening of eyewall convection and consequently intensity decay. Overall, this work comprehensively explains the inner‐core evolution associated with the intensity decay of landfalling TCs. These results will improve the understanding of the landfall processes, and consequently have direct implications for improving the early‐warning systems.