Clouds have been captivating our imaginations for as long as we’ve walked on this planet.
The clouds in these lovely photos taken last Thursday evening are cirrus clouds. Cirrus clouds form very high in the atmosphere; they typically live between five and 13 km above sea level where the average temperature is -40 °C. They are unique among other cloud types in that they are made up of ice crystals rather than condensed liquid water. The formation of cirrus clouds is tied to the amount of metallic and mineral particles in the high troposphere, to which the ice crystals bind.
Cirrus clouds are generally characterised by thin, wispy strands, hence its name from the Latin word cirrus, meaning "a ringlet or curling lock of hair".
When cirrus clouds are carried horizontally by winds moving at different speeds, they take on a characteristic “hook shape”. These are known as cirrus uncinus - derived from Latin, meaning "curly hooks".
Cirrus clouds are usually white and predict fair weather. By watching the movement of cirrus clouds you can tell from which direction weather is approaching. When you see cirrus clouds, it usually indicates that a change in the weather will occur within 24 hours.
Grandma used to refer to these as mares' tails and was often overheard reciting this: “Mackerel scales and mares’ tails make lofty ships carry low sails." In the days of large sailing ships, this meant a storm would be approaching soon and the sails should be lowered to protect from the accompanying high winds.
Cirrus clouds can be beautiful, but they are by no means rare. These clouds can be present in up to 30 per cent of the Earth's atmosphere at any given moment.
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Cindy Day is the chief meteorologist for SaltWire Network
