Hurricane Paths Shape Estuarine Flushing in Florida’s Multi-Inlet Systems

Hurricanes can substantially alter estuarine circulation, residence time, and bay–ocean exchange, yet the mechanisms controlling storm-driven bay-ocean exchanges and flushing rate in multi-inlet estuaries remain incompletely characterized. We investigated the transport and flushing responses of two estuaries along the west coast of Florida to Hurricanes Helene and Milton (2024) using advanced numerical modeling in barotropic mode with sensitivity experiments, momentum diagnostics, and Lagrangian particle tracking. The results show that winds associated with these two successive hurricanes were the dominant driver of bay–ocean exchange. Wind forcing dominated storm-driven transport and flushing in both estuaries; however, tidal exchange substantially enhanced flushing in Tampa Bay during portions of the Helene period, whereas tidal influences remained comparatively minor in Charlotte Harbor. Despite affecting the same region within two weeks, Hurricanes Helene and Milton produced contrasting exchange patterns because of different storm tracks and wind orientation relative to estuarine inlet orientations. Helene generated a transition from landward intrusion to oceanward flushing, whereas Milton produced the opposite sequence, demonstrating that transport pathways are strongly dependent on storm trajectory. Momentum analysis indicate that inlet-scale exchange was controlled primarily by barotropic pressure-gradient forcing setup by winds, which was balanced by residual resistance. Hurricanes related winds influenced transport indirectly through water-level setup and setdown that generated strong pressure gradients across the inlet systems. Charlotte Harbor–Pine Island Sound exhibited substantially larger exchange fluxes, stronger wind-driven exchange flux, and shorter residence times than Tampa Bay, reflecting greater hydrodynamic connectivity to the coastal ocean. Estimated surface-parcel residence times ranged from 10–37 days in Tampa Bay and from 3–11.5 days in the Charlotte Harbor–Pine Island Sound system. These findings demonstrate that hurricane-track-dependent wind forcing regulates pressure-gradient-driven exchange, flushing efficiency, and hydrologic connectivity in multi-inlet estuaries. The results provide a physical framework for predicting hurricane impacts on bay-ocean exchanges, estuarine flushing, and water-quality resilience in hurricane-prone coastal environments.