The mechanical influence of continental topography on the trajectories of tropical cyclones near the west coast of México

L. ZAVALA SANSÓN

Abstract

The evolution of tropical cyclonic vortices on the eastern North Pacific is examined by means of a barotropic model with an idealized continental topography. The aim of the study is to investigate the trajectories of cyclones in this area affected by both the topographic and the planetary β effects. The topographic β effect is mainly due to the ascending slope of the orography, and induces the vortex to drift towards local “northwest” direction, which coincides with the geographical northwest (because of the topography orientation). As a result, the vortex drift is clearly enhanced when both effects are considered. The precise direction of the trajectory depends on the initial geographical position with respect to the continent. Vortices initialized at southeastern areas (around 12º N, 95º W) are deflected by the Sierra Madre del Sur more to the west, following a trajectory almost parallel to the continent. For vortices initialized at 15º N or more, their drift is mainly due to the planetary β effect, although eventually they are attracted towards the Sierra Madre Occidental at higher latitudes. These conclusions suggest the possible influence of orography on the trajectories of real tropical cyclones in this area.

Keywords

Tropical cyclones; Northeast Pacific; continental topography; hurricanes

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