Flood-producing cloud bands over the Kalahari Desert

The characteristics of flood-producing cloud bands over the Kalahari Desert (15-30°S, 15-22°E) are described using daily time-scale observations, reanalysis and satellite data. The cloud band extends southward from Angola, producing short periods of intense rainfall over Namibia. Their frequency of occurrence is ～8% according to singular value decomposition of gridded 1° daily GPCP rainfall 1996-2008. The environmental features evident from case study and composite analysis include: (1) cut-off low over the Namibian coast and deep anticyclonic ridge south of Africa, (2) inflow of air from vegetated surfaces to the northeast (Q?>?300 W m^?2) into a 300 km wide meridional axis, (3) a large-scale sea breeze that enhances afternoon convection, and in the background, (4) warming of the southeast Atlantic Ocean off Angola. Short-range GFS forecasts appear accurate for the devastating 5 February 2009 event 5 days in advance.