Clouds tell stories and when it’s time to batten down the hatches
Clouds, wolke, ilifu … in any language they are fascinating atmospheric phenomena.
More importantly, clouds tell stories about approaching weather and weather that has already passed – they are up there for a reason, not just accidentally.
Ndlambe residents are very fortunate to have a plethora of cloud-spotting opportunities – from the humble fair-weather cumulus to the ominous cumulonimbus storm cloud.
In their simplest form, clouds are composed of water vapour, forming and re-forming as the surface and upper winds, and convection currents move them both vertically and horizontally.
Clouds are named according to an international classification scheme, which is based on low, middle and high-level clouds. Latin names are given to the various types of clouds occurring at these three levels (altitudes).
Clouds which warn of approaching inclement weather from the west along our coastal belt include cirrus, altocumulus and stratus.
As a cold front approaches from the west, high level cirrus clouds start assembling in the western skyline. Often these clouds resemble mares’ tails, hooks and feathers.
Within a day or so, they lower and thicken into what is known as cirrostratus, which can cover the whole sky, sometimes forming a halo effect around the sun.
With the passage of time, cirrus clouds are then replaced by middle level altocumulus and altostratus clouds.
If you are fortunate, you may spot lens or almondshaped clouds (altocumulus lenticularis) or cirrocumulus, which may exhibit the colours of the spectrum, caused by ice crystals in the cloud at very high altitudes.
Sailors often refer to this as a “mackerel sky” and quickly find shelter in the nearest bay or harbour.
Scud clouds (fractostratus) announce the arrival of the leading edge of a cold front, as the wind switches from north-easterly to south-westerly. These clouds race off the sea at very low altitudes of 100m above sea level. This is a clear signal to “batten down the hatches” before the arrival of heavy rain squalls coming off the sea.
Summer clouds are very different from winter but are perhaps less complicated and easier to read.
Thunderheads build during a hot and humid day to the north of Makhanda, clearly visible from the coast, some 60km away.
If conditions are ideal, a cumulonimbus cell may develop vertically to such an extent that it punches through the tropopause into the stratosphere, some 1215km high.
A tell-tale cap or anvil shows the movement of the storm, termed a cumulonimbus capillatus cloud.
Often these storms slide tantalisingly to the southeast of Makhanda and reach the coast where all hell breaks loose, with lightning, thunder, flash-flooding and hail.
Lightning is often the deadliest hazard of all, where seeking immediate shelter becomes paramount.
It is a common misconception that once the rain and thunder has stopped that it is safe to venture outside.
To the contrary, lightning can travel enormous distances of up to 30km from the storm centre and strike unwary victims who may think the danger is over.
Interestingly, many lightning fatalities are recorded on golf courses and open recreational areas which have elevated points such as trees where lightning is most likely to strike.
Golfers playing with graphite clubs are even more at risk.
There are a few other spectacular atmospheric phenomena which keen weather observers may see occasionally. During winter, huge cumulonimbus clouds sometimes form out to sea over the Agulhas Stream, about 35km offshore.
This occurs when colder air moves across the warmer Agulhas stream. Coastal residents are then treated to fantastic fireworks displays at night, which can continue for up to 12 hours.
Perhaps the rarest of sightings in winter are stratospheric clouds which occur at very high altitudes of 25,000m. They are composed of water and nitric acid in temperatures of -78°C and are best seen at morning and evening twilight, very low above the horizon. They are brightlycoloured, showing the different hues of the rainbow.
The next time you’re feeling down in the dumps and a bowed over by life’s cares and worries, look up towards the sky and you may be pleasantly surprised by what nature has to offer, free of charge!
Summer clouds are very different from winter but are perhaps less complicated and easier to read.