17 January 2014
Despite a freak storm over Windhoek’s southern suburbs on Tuesday, general rainfall conditions have only improved marginally over the past week but are still far from ideal.
This week’s synoptic charts were dominated by an anti-cyclonic circulation which persisted with its core over the Karas region for most of the week.
This lead to extremely high day temperatures in Karas and Hardap, still very much in place by Thursday afternoon.
What the anti-cyclonic circulation does is to create a huge spinning wheel of air covering basically the entire country. For this wheel to advect moisture from Angola, its core needs to shift east and slightly north.
Usually this time of the season, this core sits over northern Botswana or western Zimbabwe from where, Namibia being on the western slope of this sub-continental rotation, it receives moist air from Angola which leads to widespread rains.
This is not yet the case and the jury is still debating developments for next week.
When the anti-cyclonic core sits over Namibia, either to the south or the north, it dumps huge amounts of moisture over the north-western corner of the country, i.e. the Kunene region. Indications of thundery weather for Kunene grew stronger as the week progressed. Unfortunately, it also tends to halt the Inter-tropical Convergence Zone, the so-called ITCZ, at the border with Angola leading to copious rains over that country, but relatively drier conditions over Namibia. This outcome is clearly reflected by the recorded rainfall figures.
Although rains fell over almost the entire northern half of the country, except for a few very isolated showers, the totals are rather disappointing. This is after all the main rain month, and for January to reach or exceed its average rainfall, improved precipitation will have to happen before the end of the month.
Daily rainfall over Namibia from 10 to 16 January 2014:
Katima Mulilo drops; Mpacha 4.2; Bagani 11.5; Rundu 6.6; Oshikango 0.2; Ondangwa Airport 15.8; Elunda Agricultural College 32; Okahao 3.8; Omaruru 8.2; Outapi 15.7; Ruacana 21; Tsumeb 30.5; Grootfontein Airport 2.9; Otjiwarongo 12.8; Windhoek city 42.2; Rehoboth 2.5; Gobabis 11; Aranos 0.8; Keetmanshoop Airport 10.2 and Karasburg 0.2mm. (Daily rainfall data provided by the Namibia Meteorological Service)
Two forecasts expect rainy conditions to subside in general although some moisture is indicated for at least the next four days from Windhoek northward but predominantly to the western half. Widespread rains should occur from the Kunene river southward across the Kunene region as far south as the Khomas Hochland but do not expect too much from the individual showers. Chances for another freak storm are rather slim.
As the core of the anti-cyclonic circulation is expected to shift to the east, it will bring some respite to the Karas Region in terms of temperature, but hot, cloudy days with only isolated showers will remain at the order of the day.