/ 5 August 2006

Snow, floods and a tornado — all in one week

This week South Africa experienced weather extremes starting with a berg wind and a tornado, and ending with snow and floods.

A report by South African Weather Service meteorologists Luis Fernandes and Lee-Ann Clark — from the National Forecast Centre in Pretoria — detailed the week’s strange weather.

On Monday, said the meteorologists, a cold front moved over the southern and south-western parts of the country, resulting in very cold, wet and windy conditions over the south-western high ground of the Northern Cape.

At the same time, there were berg-wind conditions over the KwaZulu-Natal north coast and lowveld.

Winds over the central and eastern interior were between 20kph and 30kph.

The central and southern interior had below-zero minimum temperatures, due to earlier dry conditions.

The Cape south coast and parts of the Little Karoo received ”significant rainfall”.

On Tuesday, ”the cold front continued its eastward trek across the central parts of the country, resulting in very cold conditions over the western interior”. It snowed on the high ground of the Northern and Western Cape.

”A deep upper-air trough was developing in association with the front, and this caused a band of showers and thundershowers to develop.” This band gradually moved east.

Just before 7pm on Tuesday, a confirmed tornado passed through Dullstroom on the Mpumalanga escarpment.

Maseru in Lesotho had heavy snow and there was ”very heavy rainfall” on the Cape south coast and heavy falls on the KwaZulu-Natal north coast.

That day, George and Knysna in the southern Cape recorded 230mm and 169mm of rain respectively, and Cape St Lucia in KwaZulu-Natal nearly 95mm.

”By Wednesday morning, almost every station in South Africa had reported rainfall during the previous 24 hours, with very significant falls being measured on the Cape south coast,” said the meteorologists. There were floods along the Western Cape south coast.

”Minimum temperatures stayed close to or above zero in most places, due to cloudy and windy conditions over the interior. Winds exceeded 50kph in many places.

”Snowfalls were reported in the Northern Cape, Eastern Cape, Free State, KwaZulu-Natal Drakensberg and even as far north as Ottosdal in the North West province and Johannesburg.”

”The low-pressure system associated with the cold front was still just south of the Eastern Cape coast, with cold air still pouring into the interior, while an intense upper-air low was centred over the northern Free State.”

There were gales and very rough seas along the coast, and very heavy rainfall moving from the Western Cape to the Eastern Cape. In 24 hours, Humansdorp recorded 300mm and Kareedouw 269mm.

On Thursday, ”the system began moving away to the south-east”. The interior cleared but snow continued over Lesotho and the north-eastern mountains of the Eastern Cape.

Rain cleared in most places but continued over the Eastern Cape, which had ”significant falls” and strong to gale-force winds. ”It remained very cold and windy over the interior of the country where temperatures struggled to reach 10 degrees Celsius in many places.”

By Friday, Weather SA predicted that the weekend would bring very cold conditions for Mpumalanga’s southern highveld, eastern and north-eastern Free State, Lesotho, the northern high ground of the Eastern Cape and the south-western high ground of KwaZulu-Natal.

Gale-force winds and rough seas with waves in excess of 5m were expected on Saturday along the coast from Algoa Bay to Richards Bay. — Sapa