Weather Conditions in Southern Africa for Long Distance and High Speed Soaring Flights or The "Magic" of the Trough Line
by Helmuth Fisher
Introduction
Extraordinary soaring flights, such as Klaus Holighaus' world record over a 1400 km triangular course and Helmuth Fischer's speed world record over a 1000 km triangular course of 169,7 km/h, have put the spotlight on South Africa as one of the prime "hunting grounds" for world records.
Due to the lack of understanding of Southern Africa's weather mechanism, the potential of this area has not been fully explored. Record attempts were mainly undertaken during relatively short periods and launch points were not systematically chosen. This is not surprising as to date no in-depth analysis exists of the South African weather conditions in respect of soaring flights.
With this paper the author attempts to shed some light on the subject.
The Weather Pattern of the South African Summer
Most of the interior of South Africa is situated at an elevation of between 3.000 and 5.000 ft MSL. Therefore, only atmospheric conditions above 950 - 850 mb are of interest for the soaring areas under discussion. During the summer months, the interior is screened off from the effect of frontal systems by coastal mountain ranges, in particular to the South of the country.
Two oceans surround the "Southern Cape" of Africa. The Atlantic Ocean to the West and the Indian Ocean to the East and South East. Two currents determine the temperature of the two oceans. Originating from the Antarctic region, the cold Benguela current brushes the Western cost of the country. In contrast a warm current emanating from an area South of Madagascar affects the Indian Ocean to the East and the South East of the country.
The major weather engine for the Southern African region is a strong high pressure system over the Atlantic Ocean, which periodically sweeps around the country to link up with a high pressure system over the Indian Ocean. The outstanding and, for soaring, most important feature in this "concert of air masses" is the formation of a heat low over the interior of Southern Africa during the summer months. Due to its elongated shape this is frequently referred to as the "trough line".
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