Hail frequency in the Pretoria — Witwatersrand area during 1962 to 1972

Summary Hail observations were made in the Transvaal, South Africa, during the decade 1962 to 1972. The hail-reporting network covered an area of 2800 km² with Pretoria in the northeast and the also densely-populated Witwatersrand in the south. A panel of about 800 voluntary observers contributed 10 560 hail reports during this period. Isopleths of hail frequency within the network were plotted. The pattern was strikingly similar to the isohyetal map. More rain and hail occurred in the urban areas than elsewhere and there was a relationship to topography. Pretoria received less hail than the Witwatersrand, a ridge about 300 m higher than Pretoria.