Investigating the Dynamics of Recurving Tropical Cyclones in the Eastern North Pacific

Eastern North Pacific tropical cyclones (EPAC TCs) can significantly impact North America's West Coast, leading to impacts such as urban and agricultural flooding. This study merges insights from two complementary approaches to investigate the atmospheric dynamics driving EPAC TC recurvature and their associated impacts. The first approach focuses on unraveling the linkages between large-scale flow patterns in the North Pacific (NPAC) and the recurvature of EPAC TCs. By utilizing 6-hourly best-track data from the National Hurricane Center's HURDAT2, we identify TC recurvature events and determine their relationship with Rossby wave breaking events that modulate the large-scale variability of the NPAC. Through storm-relative composite analyses, we construct a comprehensive analysis of the large-scale flow patterns associated with EPAC TC recurvature.

The second approach investigates the structures of upper-tropospheric troughs and their dynamic contributions to EPAC TC evolution. We quantify the distribution of maximum upper-tropospheric potential vorticity (PV) anomalies surrounding EPAC TCs and objectively define TC-trough interactions. Subsequent quasi-geostrophic analyses, incorporating low-level warm-air advection and moisture flux convergence, evaluate the strength and duration of dynamic interactions between EPAC TCs and upper-tropospheric troughs. We will present representative case studies to illustrate our methodology and showcase notable instances of EPAC TC-trough interactions, enhancing the generality and applicability of our findings with practical insights into our approach. Moreover, we use a time-lagged composite analysis to illustrate the environmental and dynamic impacts of midlatitude troughs on recurving EPAC TCs that move into high PV environments.