A Numerical Study on the Typhoon Cyclonic Deflection Tracks near the Terrain

The study is focusing on the mechanisms of typhoon cyclonic deflection tracks (CDT) near eastern coast of Taiwan. We analyzed 49 CDT typhoon cases from 1960 to 2010 and most of the cyclonic deflections (74%) are occurred northern than 23 °N. The Weather Research and Forecasting (WRF) Model was used to do the numerical experiments with potential vorticity (PV) tendencies diagnosis, which interpreted the observational results. The deep layer averaged wave number one component of the PV with horizontal advection (HA), vertical advection (VA) and diabatic heating (DH) tendencies are diagnosed for storm movements. The northern landfall storms have significant vorticity stretching and subsidence warming, which occurred in the leeside to the south part of the typhoon. The subsidence warming suppresses convection and produces heating asymmetry for the typhoon structure. The vorticity stretching (VA tendency) and diabatic heating asymmetry (DH tendency) contributes to CDT. The HA tendencies in general do not contribute to the CDT. Our results highlight the effects of vorticity stretching and asymmetric convective heating in producing the CDT to north of 23 °N near the Taiwan east coast.