Numerical study on the vertical tilt of a typhoon vortex

The relationship between the vertical tilt of a typhoon vortex and the asymmetric components of its thermodynamic fields was investigated in a quantitative manner based on the numerical simulation data obtained for Typhoon Chaba in 2004. In order to understand the mechanism by which the tilt occurs, a Lagrangian trajectory analysis as well as a two-dimensional theoretical formulation were developed and applied to the numerical model data. The results suggest that the robust features of the vortex tilt observed in the simulated data are strongly linked to the asymmetries of the thermodynamic fields caused by the environmental vertical wind shear. The results also suggest that the same mechanism as for the vortex tilt leads to a down-shear to downshear-left preference for rainfall in the typhoon inner core regions.