'We couldn't predict storm'

CLOUDBURST: WEATHER EXPERTS 'CURRENTLY JUST DON'T HAVE THE TECHNOLOGY' TO WARN US

- Marizka Coetzer

The vicious thunderstorm which hit northern Johannesburg on Wednesday afternoon, causing widespread flooding, infrastructure damage and power outages, is classified officially as a cloudburst.

But predicting one of these with accuracy is almost impossible with current technology, says a weather expert.

Vox Weather meteorologist Michelle du Plessis said the storm that hit Johannesburg and surrounding areas was not a supercell, but a cloudburst.

“A cloudburst is defined as 10cm (100mm) or more of rainfall within one hour, leading to rapid water accumulation. This explains why areas such as Johannesburg, including Roodepoort, Krugersdorp, Sandton, and Kempton Park, recently experienced extreme rainfall,” she said.

The Witwatersrand escarpment played a key role in intensifying the event, as southwesterly winds forced moist air upwards, triggering a cloudburst that delivered over 100mm of rain in just an hour, Du Plessis said.

“Cloudbursts are difficult to predict because they develop quickly and affect limited areas. Unlike widespread thunderstorms, they depend on local wind patterns and topography, which can cause some storm warnings to seem exaggerated or, in other cases, underestimate severe conditions.”

Du Plessis said a cloudburst on a small scale was impossible to predict.

“Models are not that advanced yet. So, yes, we expected scattered storms in Mpumalanga and Limpopo yesterday, which were large-scale and the models showed, But this type of small-scale severe storms is unpredictable.”