Who doesn’t love lying on your back on a summer’s day looking up at the clouds and
seeing shapes in those fluffy lumps of cotton wool that are drifting overhead.
Look, there’s a rabbit, there’s a dragon, there’s a space invader!
It’s a perfectly normal hobby for a grown man, and don’t let anyone tell you different,
ok?
Good, now.
Not all clouds are created equal, and amongst the everyday nimbostratus and cirrocumulus,
there are some real weirdos out there – owing their existence to nothing more than a bit
of wind and water vapour.
So here are some of my favourites
Quick cloud making 101.
Warm air rises and cools, the water vapour that it contains then condenses out into tiny
droplets, and that, essentially, is a cloud.
Under the right conditions these droplets can coalesce and fall as rain,
Plus, that combination of hot updrafts and cooler downdrafts can make the inside of a
cloud a writhing turbulent jumble of water, ice, and electric charge, which can give rise
to torrential rain, or hail, or lightning and thunder.
Normal storm clouds like this are called cumulonimbus, and even the average Joe is a force to be
reckoned with - towering to heights of up to 14 kilometers, fed by the convection of
warm, moist air up high into the troposphere.
When it comes to aerial displays of strength, nobody does it better than a cumulonimbus.
And when it comes to cumulonimbus, you don’t get anything more impressive than a supercell.
These giant storm clouds are formed when several cumulonimbus organise into a single structure.
And they’re unbelievably immense, stretching over hundreds of miles from side to side,
and with the power to generate golf-ball-sized hailstones and devastating tornadoes.
While a normal storm cloud will dissipate within an hour or so, the terrifyingly efficient
organisation of wind within a supercell means that they’re self-sustaining, and they can
last for several days.
If anything deserves the title King of Clouds, it’s the supercell.
Next, from the sublimely huge to the ridiculously weird.
These are MAMMATUS, actually what’s known as an “accessory cloud” – they form
attached onto other larger scale structures.
They’re called ‘mamma’ after the Latin word for udders, or breasts, because meteorologists
thought that they looked like boobs.
Yeah, I’m guessing there were no female meteorologists around to help set the matter
straight…
If you’re lucky, you might see mamma on the underside of a cumulonimbus’s incus,
the part that spreads out like an anvil at the top.
And that’s because they form from a kind of ‘reverse convection’.
At the top of a warm cumulonimbus cloud, it loses heat up into the stratosphere, and the
cooler air drops down, condensing into smooth, pendulous lobes.
And because they owe their existence to the vapour in the main cloud, it follows that
the more powerful the thundercloud, the more buxom the mamma will be!
Number three is a type of lens-shaped cloud that’s often mistaken for flying saucers.
In fact, the first ever photo of a supposed UFO turned out to be one of these lenticular
clouds.
You’ll find these eerily smooth and stationary clouds loitering around near mountains and
hills, which is a clue to how they’re formed.
When wind blows near the ground and encounters a sudden rise in the topography, it’s deflected
up and over it, forming a standing wave.
At the crest of that wave, just above and a little downwind from the top of the mountain,
the air is at its coolest and the water vapour condenses forming a cloud that’s stretched
out in the direction of the wind.
Interestingly, although lenticular clouds stay still in one place, the wind is rushing
through them at a rate of knots, and with comes the water vapour that keeps condensing
and evaporating again and again at this fixed point.
Clouds that are formed by wind flowing over the earth’s lumps and bumps are called oro-graphic
clouds, and our next weird one is formed in a similar way.
Nacrous clouds are sometimes known as mother of pearl clouds, because of their astonishing
array of colours - shining pink, blue and yellow in the dusky sky.
Gorgeous
They’re unique among clouds, in that they don’t form in the troposphere where the
rest of their vaporous brethren lie.
Instead, they can be found in the stratosphere, over 32 kilometers up above the polar regions
of the Earth.
Under particularly still atmospheric conditions, winds can loft water vapour p through the
tropopause – that’s the invisible layer between troposphere and stratosphere, the
normal ceiling to most clouds where temperature stops decreasing with altitude.
And once in the stratosphere, tiny ice crystals just a few thousandths of a millimetre across
form at around minus 85 degrees Celsius.
When the sun shines through these crystals at a shallow angle, their interference creates
glorious rainbow colours.
Unfortunately, this spectacularly beautiful cloud is also one of the most destructive,
as its ice particles act as catalysts for the breakdown of ozone by CFCs.
And now for my number one favourite weird-ass cloud, which - I’d like to start by saying
- has absolutely nothing to do with its name.
It’s the Morning Glory.
It rolls over the Gulf Savannah of northern Australia during September and October.
This annual spectacle got its name from its tendency to appear in the morning, and the
sense of wonder it evokes in all who see it.
It’s a type of ROLL CLOUD, formed when air masses flowing in opposite directions meet,
to create long tubular clouds that seem to roll back on themselves as they move forwards.
But, the Morning Glory is even better than that, its a special case.
Thanks to the unique geography and climate in northern Australia, these roll clouds can
be nearly a thousand kilometres long, and speed across the landscape at up to 35 miles
an hour.
They’re so vast – and most importantly, predictable - that gliders can literally surf
the cloud like a breaking wave, reaching blistering speeds of up to 160 miles per hour and performing
daring tricks in its strong airflow.
I really really really want to do that.
Can anyone make that happen, please?
So, there you go, five weird and wonderful clouds to impress your fellow cloud-spotting
mates with.
There are so many more out there, I’d love to hear about your faves.
Let me know in the comments below, and of course, don’t forget to like and subscribe.
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