On Wednesday12 November, the heavens opened and Grahamstown was hammered by a deluge.
The Port Elizabeth Weather Office's Garth Samson, client liaison officer, and Quinton Jacobs, senior forecaster, walk us through the science behind yesterday's weather.
On Wednesday12 November, the heavens opened and Grahamstown was hammered by a deluge.
The Port Elizabeth Weather Office's Garth Samson, client liaison officer, and Quinton Jacobs, senior forecaster, walk us through the science behind yesterday's weather.
The weather yesterday was characterized by convective (thunderstorm) activity. This type of activity can spawn some amazing and sometimes eerie cloud formations.
A typical thundercloud (known as a cumulonimbus cloud) can reach heights in excess of 10km. This in itself is impressive, however when these storms are particularly severe they can display some wonderful shapes and ominous shades.
This can be from the mammatus (udder shapes) under a thundercloud to a funnel cloud (which in essence forms a tornado) Yesterday Port Elizabeth’s weather was characterised by cloudy conditions which were relatively low.
The real serious weather was above this, so we did not see the splendour of the event.
East London, however had less cloud which was higher and they got a glimpse of these clouds.
The large ominous looking clouds over East London were what is termed Wall Clouds. A wall cloud (or pedestal cloud) is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which sometimes forms tornadoes.
It is typically beneath the rain-free base (RFB) portion of a thunderstorm, and indicates the area of the strongest updraft within a storm.
Rotating wall clouds are an indication of a mesocyclone in a thunderstorm; most strong tornadoes form from these. Many wall clouds do not rotate, however. This is simply the outflow boundary of the thunderstorm.
Rotating wall clouds often lead to tornadoes, which could have occurred yesterday, but no reports thereof.
As it was an indication of a gust front, it is possible that there were strong straight line winds in places, which could have caused damage.
Below is the explanation, with satellite pics.
See gallery for reader pics of the storm.
