What Drives Variability in Tropical Cyclone Landfall Patterns in the Eastern North Pacific? Environmental Drivers and Implications

In 2023, two northward-moving Tropical Cyclones (TCs) in the Eastern North Pacific (ENP), Hurricane Hilary and Otis, caused significant damage. Hilary led to unprecedented flooding in areas previously unaffected by such weather, while Otis had devastating category-five winds in the economically vulnerable southwest coast of Mexico. Despite the ENP having the world's highest TC density, its TC variability receives relatively little research attention. Previous work in this region has studied TC Activity and track densities modulated by different climate drivers such as ENSO, MJO, and the Central America Gap Winds. Research has yet to understand what drives variability in TC landfalls along Mexico’s west coast. This work examines how landfall count variability depends on genesis and landfall probability (steering flow). We quantitatively decompose total landfall counts into spatial contributions from genesis location and landfall probability due to the steering flow. Applying this framework to IBTrACS and ERA5 reanalysis datasets, we conducted a monthly composite analysis to examine key environmental differences between high and low landfall probability years. Our results show that years with lower landfall rates actually exhibited a higher number of TC genesis during most months, indicating that variations in steering flow play a major role in landfall variability. In contrast, the high landfall years are characterized by a concentration of landfalls in Southwestern Mexico primarily attributed to two factors: stronger easterly wind reversals in June and September associated with the ENP tropical monsoon and anomalous southerly winds in October, augmenting landfall probability in the region. Preliminary findings suggest that TC landfall probability also increases in the basin during transitional ENSO years. This study provides crucial insights into the atmospheric conditions that could produce a high landfall hurricane season, providing the foundation for improving subseasonal to seasonal hurricane landfall predictability.