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

The development of a vertically aligned vortex is crucial for tropical cyclone (TC) intensification, especially in the presence of environmental vertical wind shear (VWS). Comparing with previous studies, this study provides more rigorous evidence on the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity (PV) inversion method. Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s-1 and 10 m s-1, we show that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component, which is characterized by vortex Rossby waves. Furthermore, the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core. As an air parcel undergoes cyclonic rotation, it ascends on the right side of the tilt vector, which increases relative humidity, leads to saturation, and drives the development of convective asymmetries, with maximum upward motion aligned with the tilt direction. This study suggests that the response of TC vortices to environmental VWS involves complex interactions between vortex tilt, asymmetries in TC structure, and convection, all of which can largely be understood within the framework of balanced dynamics.