One of seven windows destroyed in a house in Illiondale, Edenvale on Saturday afternoon after a hail storm hit the area. 201012 Picture: Handout/Supplied

Johannesburg - They were forged in an unusual weather system lurking deep in the super-cold stratosphere – golf ball-sized hailstones that shattered windows, dented cars and smashed windscreens.

In Gauteng, Ekurhuleni felt the brunt of the hailstorm on Saturday night. It was this same weather system, said forecasters, that was to blame for other adverse weather conditions across the country.

The system is called a cut-off low, which is made up of cold moist air riding high in the stratosphere, between 12km and 15km up.

“This phenomenon generates it own energy,” explained senior forecaster Jacqueline Riet of the SA Weather Service.

“When this cold air moves down, that is when we experience adverse weather.”

The adverse weather experienced over the eastern parts of Gauteng was high winds and large hailstones.

Ekurhuleni metro police were hit hard by the freak weather event.

Seventeen of their patrol vehicles were damaged in Boksburg, Germiston and Vosloorus. An Emergency Management Services vehicle was also damaged.

Some claimed the hail was the size of golf balls, while others said they were bigger – more like tennis balls.

“The hail lasted five minutes but it felt like a whole year, said Ekurhuleni metro police spokesman Inspector Kobeli Mokheseng.

No casualties were reported, he said.

The reason for the unusually large hailstones, said Riet, was because of the temperature in the stratosphere, which could fall to minus 50°C.

“When hailstones develop that high up, they grow that much larger.”

Usually, she explained, thunderstorms at lower altitudes were warmer, and by the time hail reached the ground, it had melted or reduced in size.

This system also caused the adverse weather conditions in the Western Cape, KwaZulu-Natal and Eastern Cape.

The Eastern Cape was the worst hit at the weekend, with severe flooding.

Yesterday, sections of the N2 were still closed to traffic after part of the highway collapsed, leaving a hole 25m wide and 50m deep between Port Elizabeth and Grahamstown.

Riet said Gauteng had a 30 percent chance of thundershowers developing on Monday.

The Star