Dry thunderstorms
They occur usually in the interior - speaking mainly of conditions in South Africa - often during early summer. Normal thunderstorm conditions are found except that the air is very dry (low relative humidity) and condensation takes place at quite a high altitude. Precipitation occurs but as the air is very dry, it is reabsorbed back into the air as water vapour before it reaches the ground.
A study of the climatic maps will reveal that most of South Africa's rain comes from thunderstorms. The one exception which experiences less than 10 days of thunder per annum is the South Western Cape.
Most thunderstorms, over 100 days per annum, are experienced in the Drakensberg Mountains in the east. This is due to the moist air flowing in from the Indian Ocean is forced to rise to cross the mountains. If it is unstable it will continue to rise and thunderstorms will occur - OROGRAPHIC RAIN.
Thunderstorm activity diminishes from east to west across South Africa. The air along the west coast is dry and stable in comparison to the east and therefore seldom experiences thunder.
Thunderstorms do cause extensive environmental damage. Hailstorms can obliterate whole crops of maize, fruit and sunflowers etc. within a couple of hours. It also causes stock losses and human deaths from time to time. Strong winds also contribute to the chaos sometimes evident in built-up areas as the storm water drains cannot cope with the high volumes of water. Lightning also sometimes kills people and can also quite often cause veld-fires as well which then also result in destruction of ecosystems and loss of animal grazing. On badly managed farms where vegetation has been removed by overgrazing or untimely ploughing, and other bad farming methods, the large volume of water and lack of vegetation is responsible for soil erosion.
Oh why is it that something so attractive and impressive so often belies it's true strength and intent?
Tornadoes are also interesting and impressive and we'll take a more in depth look at them soon as well.