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Written by John Olszewski
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What happened?
The prospect for rain was, by and large, fulfilled. The intensity values included some very heavy falls. The Wednesday storm at Outjo with hail, generated a wind-squall which caused local but severe damage. Hail is not usually associated with situations when rain falls readily. But as some people have noted, the rain showers have a spasmodic nature to their occurrence. There is an occasional intrusion of a layer of westerly flow air.
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Written by John Olszewski
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What happened?
November should see the assemblage of a summer weather pattern gather and, from time to time, make its presence felt.
Springtime implies heat, some prospect of rain, but altogether showing the growing presence of a summer climate.
The Inter Tropical Convergence Zone (ITCZ) eludes computer models, but satellite images show a thickening cloud presence across equatorial Africa. The Indian ocean hosts, at the moment, two active disturbances just south the equator. Rainfall activity is building across Zambia while Katima’s data has 6 days out 7 with rain. A typical ITCZ fringe fall of 73.1mm indicates a wandering ITCZ.
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Written by John Olszewski
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Last weekend a cold front approached the Cape. It slowed down and the stagnation of the northern parts enabled a cut-off vortex to develop just west of the coastline. This was active by Monday and is only now beginning to drift eastward. Behind this development, semi-polar air was swept northward, on its western side and then the circulation performed a U-turn to sweep across Namibia providing breezes from westerly directions across some of the interior.
This air-mass arrival pushed east to meet and undercut the airflow circulating from points northerly across central Namibia. The resultant effect came in two phases. Where the air was moist enough, the undercutting by the colder air caused thunderstorm development and some heavy showers were registered.Closer to the cause of it all, the colder air of the cut-off vortex with clouds close to the surface brought low temperatures, day and night, to the southern parts.
The storm of some 103mm recorded on a part of the Mt Etjo Game Farm tops the rainfall charts for the week. Much further to the east, falls of up to 60mm were recorded in the Summerdown and Hochfeld areas.
The colder air did drive the moist band further away (eastward) by mid-week, so only the far northeast remained within the weather-active zone.
By Thursday, the rainfall potential was limited to those parts of the country where November rain is to be expected at this time of year. A more normal pattern is now visible on the weather charts.
The rainfall picture which appeared these last few days would seem to focus on the dividing line between the warm, moist flow around the anticyclone centered above Zimbabwe and the cooler flow brought northward and around the cut-off vortex. One can hesitate to call this a “front”, but it certainly does indicate an atmospheric divide. Frontal situations usually show the ability to displace the one by the other. The present pattern is giving more of a confluence of differing air flows as they end up in a joint northwest-to-southeast flow south of the Orange River.
Where the westerly flow met the northerly flow, there was the ability to undercut the warmer air. Where there are topographical obstructions, from quite small hills to mountains or mountain ranges, they influence this airflow rendezvous and the resultant storms can quickly assume cloudburst proportions. But the zone of these sudden and intense thunder storms is restricted to the parts where these two airflows are to be found close to each other.
Deeper into the moister air mass, showers of lesser intensity were to be found.
What’s coming
Present weather patterns across Namibia show little west or east momentum. The departure of the cut-off vortex lets the south warm up and return to normal temperature ranges. The moist circulation has little cause to move either way and this pattern should prevail until the mid-week after which a drift westward of the moist air is then more likely.
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Understanding Weather 
