Durban - While there was high speculation that the explosion at the Klaarwater major substation was the cause of the sudden wave of hot wind and dry temperatures on Tuesday night - described by many online as “freaky and scary” - the South African Weather Services (SAWS) has rushed to allay fears.
According to SAWS Tuesday night’s weather system that blew over Durban and pushed temperatures in some parts of the city to up to 40 degrees Celsius at 9.30pm was nothing more than a “berg wind”.
SAWS Durban-based forecaster, Julius Mahlangu, spoke to IOL on Wednesday to explain what actually happened on Tuesday night.
“What happened was that there was a cold front approaching and met with dry winds from the inland area and this resulted in what we call Berg Wind,” Mahlangu said.
Another weather organisation, STM Weather, described Tuesday evening’s events as a heat burst.
It said heat bursts are associated with thunderstorms.
“For a heat burst to occur there needs to be both a dissipating thunderstorm and a hot, dry environment in the mid-levels of the atmosphere, combined with a shallow surface inversion.
“Thunderstorms develop when moist, unstable air is lifted upwards; the moisture in the cloud eventually condenses and later falls as precipitation. Once the thunderstorm loses its updraft, the thunderstorm is said to be downdraft dominated.
“When this happens with a hot and dry atmospheric midlevel in place, the moisture associated with the downdraft evaporates and initially cools this layer, increasing its rate of descent toward the surface.
“The cooling ends once all the moisture has evaporated, thus causing warming and mixing of the warm (inversion) layer. The heat burst occurs once the warm and dry air descends to the surface (see schematic below),” STM said.
According to STM, the phenomenon which was first observed in 1963, occurs towards the end of spring and summer.
Last night, temperatures in Durban rose as high as 31 degrees Celsius with an air humidity of around 37%, according to hygrometers around my home.
IOL
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