Photo of a front approaching Mmabatho , South Africa , showing clearly the sloping angle of the wedge of cooler, sandy air as it drives forward. I was hurriedly trying to get on the ground in my ASH25 before the front hit the airport. The front was I believe the Intertropical Convergence zone which regularly moves across the region and can be fairly scary, the wind changing from 20 kt headwind to strong tailwind in seconds as it transits.

Approaching Front - Mmabatho By Brian Bateson