Synoptic flow perturbations over West Africa

Abstract

Utilising wind data for the significant levels: 2 000 feet, 850, 700, 500, and 300 mbs, detailed analyses of West African upper-air charts reveal distinct features of the atmospheric flow, especially in connection with mid-tropospheric easterly wave activity over the area.

The history of a semi-vortical perturbation whose motion was in rhythm with the propagation of a 700 mb easterly wave is described.

It is concluded that an easterly wave model incorporating the 700 mb trough (and ridge) as integral feature(s) of the flow describes best the majority of significant weather zones and puts on a firmer basis the existence of westwards moving semi-vortical lines of thunderstorms frequently traversing the heart of West Africa during the rainy seasons.