Dynamic Forcing Behind Rapid Intensification of Hurricane Lidia

TL;DR

This paper investigates the dynamical mechanisms behind Hurricane Lidia's rapid intensification in the northeastern Pacific, emphasizing the role of an upper-level trough and ensemble diagnostics for improved forecasting.

Contribution

It introduces a large-scale dynamical analysis framework using ensemble forecasts and reanalysis data to identify early triggers of rapid intensification in hurricanes.

Findings

Upper-level trough enhances ascent and divergence during RI

Stronger Trenberth forcing precedes RI onset

Dynamical forcing influences storm environment and shear

Abstract

This study examines Hurricane Lidia rapid intensification (RI) in the understudied northeastern Pacific, focusing on its interaction with an upper-level trough. Using IFS-ECMWF ensemble forecasts and ERA5 reanalysis, we analyze the large-scale dynamical mechanisms driving Lidias intensification. Results show that the trough played a crucial role in promoting RI by enhancing synoptic-scale ascent, upper-level divergence, and eddy flux convergence. In the higher-intensification ensemble group, stronger Trenberth forcing emerged prior to RI onset, suggesting a causative role in preconditioning the storm environment. This dynamical forcing likely triggered latent heat release, which in turn modified the upper-level potential vorticity structure and contributed to a subsequent reduction in vertical wind shear. In contrast, the lower-intensification group exhibited weaker forcing, higher shear, and a lack of sustained ventilation. These findings highlight the importance of diagnosing early dynamical triggers for RI, particularly in regions where operational access to high-resolution models is limited. This approach provides a cost-effective framework for anticipating RI using ensemble-based diagnostics and could serve as a valuable forecasting tool in data-sparse areas such as the Pacific coast of Mexico. Future studies should combine this large-scale methodology with high-resolution simulations to better capture storm-scale processes and validate multi-scale interactions in RI events.