Effects of topography on the evolution of Typhoon Saomai (2006)

Topographic effects on the evolution of Typhoon Saomai (2006) are investegated by conducting a series of numerical simulations with 100% (CTL), 75% (H75), 50% (H50), and 25% (H25) terrain height of Taiwan using the Weather Research and Forecasting (WRF) model. Compared with the Japan Meteorological Agency (JMA) best track, it is shown that the CTL simulation reproduces track and intensity similar to the observation. In sensitivity experiments, the typhoon generally moves more southward and its intensity increases with increasing terrain height. These effects become significant as the typhoon approaches to Taiwan. The Central Mountain Range (CMR) in Taiwan plays the role of weakening of easterly flow in the lower troposphere and suppressing a generation of the northerly flow in the upper troposphere. The CMR also prevents the development of the tropical storm, and makes the tropical storm to go around Taiwan by blocking effect. The undeveloped tropical storm causes more southern track of the typhoon and induces weak vertical wind shear. The weak vertical wind shear keeps the warm region near the typhoon center in the upper troposphere, and helps the development of the typhoon.