Update (Thurs 28th). The model runs have converged nicely (though
Cape Town got an unexpected dose of thunderstorm activity on the 21 May 2009, when a trough which was situated along the West Coast seemed to close into a coastal low pressure around Cape Town. This caused some upper air instability which coupled with the moisture present was enough to produce some unforecast thundershowers. Activity began around 06:30am and continued till around noon, with the strongest storms occuring earlier- around 7am. The thunderstorms brought very little rain but gave a great lightning display as it passed over False Bay. Below are some images I managed to get of the storm in Somerset West, credits to the South African Weather Service for the radar image.