Dynamical processes controlling the evolution of early-summer cut-off lows in Northeast Asia

Abstract Cut-off lows are crucial extratropical circulation systems that can bring weather extremes over large areas, but the mechanism responsible for life cycle of cut-off remains elusive. From a perspective regional eddy-mean flow interaction, this study investigates dynamical processes controlling evolution early-summer Northeast Asia using 6-hourly reanalysis data. Through diagnostic local wave activity (LWA) budget, we show low is initialized by Rossby train originated from subpolar North Atlantic, and then reinforced rapidly zonal LWA flux convergence baroclinic eddy generation, eventually decayed through energy dispersion advection. Furthermore, evolutions above strongly modulated changes background flow. In early summer, located at eastern exit midlatitude jet to north subtropical exhibits weak meridional gradient potential vorticity, which favors frequent formation cyclonic anomaly accumulation. Prior onset several days, propagates along Eurasian jet, initializes Asia. With aid mean advection anomalous momentum, winds decelerated accelerated center. The former obstructs packet proceeding downstream latter stronger generation below jet. two together maintain strengthen in rapidly.