Downstream development in the Southern Hemisphere monsoon during FGGE/WMONEX

Abstract

Observationally it is seen as progressive cyclonic and anticyclonic vorticity increases that develop eastward in the monsoon trough at a speed of approximately 5 m s-1. The process results in many tropical cyclone and tropical depression formations over northern Australia and the South Pacific. It is shown that the downstream development process is generally consistent with linearized barotropic dynamics, and that the Southern Hemisphere monsoon, because of an intrinsic westerly basic state, is a particularly suitable region for downstream events. We suggest that the process has implications for other features of the monsoon circulation, namely onset and 40-50 day events. -from Authors