Mechanisms of Topographic Steering and Track Morphology of Typhoon-like Vortices over Complex Terrain: A Dynamic Model Approach

This study investigates the mechanisms of topographic steering and the resultant track morphology of typhoon-like vortices over complex terrain. Leveraging a dynamic model based on potential vorticity (PV) conservation, we conducted a comprehensive sensitivity analysis over both an idealized bell-shaped mountain and the realistic topography of Taiwan. Results indicate that a triad of controls governs track evolution: vortex intensity (α), terrain geometry (dhB*/dt*), and interaction time (impinging angle γ). To quantify predictability, we introduce the Track Divergence Percentage (td), which partitions the phase space into distinct Track Diverging (TDZ) and Converging (TCZ) Zones. While idealized simulations established this fundamental structure, realistic experiments incorporating vortex decay revealed that orographic complexity and shallow approach angles (<145°) lead to regimes of hyper-sensitivity and "terrain capture." These findings establish a unified quantitative framework for understanding track bifurcation and looping, offering crucial insights for assessing forecast uncertainty in mountainous regions.