Tropical Cyclone Intensity Sensitivity to Sea Surface Temperature and Mixed Layer Depth

Rapidly intensifying tropical cyclones (TCs) are among the most dangerous and least predictable weather systems. In this work, we focus on two intense Atlantic TCs that showed rapid intensification (RI, defined as at least 36 hPa deepening in 24 h) and which impacted the coast of the Gulf of Mexico. This study focused on how sea surface temperature (SST) and ocean mixed-layer depth (OMLD) modulate the rapid intensification (RI) and maximum intensity (MI) of two hurricanes, Wilma and Rita (2005). Using the Weather Research and Forecasting (WRF) model coupled with a simplified 1D ocean model, 20 simulations were performed to systematically vary SST (±1–3 °C) and OMLD (doubled or halved), as well as remove observed SST anomalies (SSTA). Results show that SST dominates TC intensity changes from around 15–20 hPa °C−1, and correspondingly higher deepening rates. Warmer simulations also exhibit an increased energy transfer from the ocean, supporting increased near-surface equivalent potential temperature, a more symmetrical wind field and elevated accumulated cyclone energy (ACE). By contrast, deeper OMLD enhances thermodynamic support but is constrained by SST conditions, limiting the total surface heat flux in the storm's vicinity. Results also stress that remote heat fluxes across a broader region, not just beneath the storm core, play a crucial role in determining maximum intensity and deepening. Westward landfall shifts up to 300 km are observed in +3 °C scenarios, emphasizing the potential of ocean heat in altering trajectories. These findings highlight the critical importance of accurately representing upper-ocean thermal structures to improve predictions of TC intensity and trajectories, particularly as warmer future SSTs may lead to more frequent and dynamically evolving hurricanes.