Storm-Scale Dynamical Changes of Extratropical Transition Events in Present-Day and Future High-Resolution Global Simulations

Abstract Tropical cyclones (TCs) propagating into baroclinic midlatitude environments can transform extratropical cyclones, in some cases resulting high-impact weather conditions far from the tropics. This study extends analysis of transition (ET) changes multiseasonal global simulations using Model for Prediction Across Scales–Atmosphere (MPAS-A) under present-day and projected future conditions. High resolution (15 km) covers Northern Hemisphere; TCs ET events are tracked based on sea level pressure minima accompanied by a warm core use cyclone phase space method. Previous these showed large over North Atlantic (NATL) basin, with exhibiting 4°–5° northward latitudinal shift ~6-hPa strengthening post-transition cyclone. Storm-relative composites, primarily representing post-transformation cold-core events, indicate that this increase storm intensity is associated an intensification neighboring upper-level trough downstream ridge, poleward center, conducive to enhanced trough–TC interactions after completion. Additionally, composite event located right-jet entrance outflow jet strengthened relative its counterpart. Localized impacts such as heavy precipitation strong near-surface winds, significantly future-climate simulations; 6-hourly NATL increases at super-Clausius–Clapeyron rate area-average increasing 30%. Furthermore, intensified contributes lower-tropospheric potential vorticity stronger upper-tropospheric outflow, implying more extreme climate scenario.