Victor Mugabe, Stellenbosch University, Earth Science, Matieland, South Africa, Susanne Fietz, Stellenbosch University, Department of Earth Sciences, Faculty of Science, Stellenbosch, South Africa, Lynwill G. Martin, South African Weather Service, c/o CSIR Environmentek, Stellenbosch, South Africa and Helene Angot, University Grenoble Alpes, Grenoble, France