Balanced Evolution of the Vertical Tilt of Simulated Tropical Cyclone Vortices in a Sheared Environment

The formation of a vertically aligned vortex is essential for the intensification of tropical cyclones (TCs), particularly under conditions of environmental vertical wind shear (VWS). This study investigates the physical mechanisms driving vortex tilt evolution in two simulated TCs subjected to environmental shears of 6 m s⁻¹ and 10 m s⁻¹. Our findings indicate that balanced dynamics play a pivotal role in governing vortex tilt. Specifically, the tilt-induced distortion of isentropic surfaces generates negative virtual potential temperature anomalies on the downtilt side and positive anomalies on the uptilt side of the vortex. As air parcels undergo cyclonic rotation along these distorted isentropic surfaces, they ascend on the right side of the tilt vector, resulting in increased relative humidity and eventual saturation. This leads to diabatic ascent and enhanced convection in the downtilt and downtilt-left quadrants, which amplifies the wavenumber-1 circulation through convectively coupled vortex Rossby waves, further modifying the vortex tilt. This study underscores the importance of balanced dynamics in understanding the interplay between vortex tilt, wavenumber-1 structures (Rossby waves), and convective asymmetries in the intensification of tropical cyclones under vertical wind shear.