What happened?
First of all, some more rain and second, a pattern departure (but not disappearance) eastward.
The only source (out of 5) to offer the possibility of thunderstorms last Thursday was the South African aviation prognosis. The Windhoek area lay on the fringe of the moist air advection. The storm development was rapid. It took less than 60 minutes for cumulus cloud to erupt into a cumulonimbus and set the weather ball rolling. Within another 30 minutes some 15 thunderheads were visible across the visible range: a radius of 100km or more.
The edge of an air mass, where it clashes with another, different type of air mass can provide such rapid developments. In the current range of weather patterns, tropical air (warm, moist and unstable) and Atlantic (cool but undercutting) lying next door to each other such occasions can readily occur. In climates classed as dry, it augurs well when such occasions loom and come to rainy fruition.

It is becoming clear that the influence of climate change and a latent level of resistance by a perceived normal pattern provides a scenario witnessing a struggle for a measure of control across our skies. A not dissimilar range of activity can be seen across the rest of the southern hemisphere.
The prime focus must start with the equatorial Pacific which shows an El Nino presence in mid-ocean but with more-or-less normal conditions where El Nino should be most pronounced in the far eastern Pacific. Anticyclonic cores remain in a La Nina-latitude range: 35oS to 45oS across the southern Pacific.
Over Africa the Intertropical Convergence Zone (ITCZ) is located in the middle of the sub-continent more or less over Zambia.
Only in the South Atlantic is a reversal to be seen with the anticyclonic core now residing around 30oS.
Mobile cells do move around the sub-continent but weaken as they pass the Marion Island area and thus moist inflows across Mozambique and into the continental interior are limited.
All-in-all, the El Nino Southern Oscillation (ENSO) is very poorly defined. Its influence can only be very limited, but there does seem to be some sort of disturbance which may well have other distinct and separate causes.
Yet, as the thundery interludes in the Windhoek area showed just a week ago, tropical air does not need much impetus to arrive and build. Resultant storms match tropical air mass expectations.
What’s coming?
The South African forecast notes heat low pressure troughs forming over the western interior by the weekend and remaining for the forecast period.
Upper air predictions keep a confused (light and variable zone) picture across Africa north of 30oS, but there appears to be only limited access to the Congo air-mass present above central Angola and eastwards.
In fact, while the ITCZ remains active, there is not much drive to divert its moisture to the south. But the longer term outlook indicates a drift of the Zambian section westward toward central and south-eastern Angola. Once the ITCZ has shifted to Angola, rain prospects over Namibia will revert to normal but that is not expected during the next few days.