Clear air turbulence over South Africa

Abstract

Clear air turbulence (CAT) at high altitude remains a hazard to aviation which can result in passenger injury and aircraft damage. Two limited surveys of CAT events over South Africa, 1993-1995 (inclusive) and 1998 are used to illustrate the most likely synoptic conditions under which CAT can be expected. A case study of CAT associated with an upper-air trough and a mountain wave is presented. The study also evaluates the effectiveness of the Ellrod Turbulence Index (ETI) derived from model data provided by the UK Met. Office. A forecast of ETI derived from the Global Spectral Model of the United States National Center for Environmental Prediction (NCEP) is also reviewed.