Mean motion field in East Africa at the level of the East African low level jet core

Abstract

The mean flow over East Africa at the 1.5 km level during May through September is presented. All available daily wind vectors from 1952–1973 for 22 pilot balloon stations were used.

The southeast-southwest monsoon current is a dominant feature. It is highly diffluent between 38 °E and 40 °E. There is little penetration inland as the current is blocked by the meridionally-oriented highlands. Vertical directional changes show general veering with height. The flow has maximum intensity in July–August with mean peak speeds of 15–17 m/s at 0600 GMT. The layer of strong winds lies between 0.3–2.5 km. Vertical wind shears increase from May, reach a maximum in June–July and decrease thereafter.