UAE citizens were left baffled after a mysterious ‘whirlpool hole’ suddenly appeared in the sky above the city of Al Ain this weekend.
The large circular patch of clear sky emerged inside the otherwise heavy cloud near the border with Oman, as if somebody had punched a hole in the atmosphere.
Astronomer and meteorologist Ebrahim Al Jarwan posted a short video clip of the hole on Twitter, adding that the ‘rare and beautiful’ sight was referred to as a ‘Fallstreak hole’ or ‘hole punch cloud’.
One user replied that it looked as as if ‘God has thrown a stone into a lake’, while others pondered whether the strange phenomenon had been caused by an extra terrestrial UFO.
But meteorologists quickly cleared up the mystery with a scientific explanation for the mystifying hole.
They usually form in mid- to -high level clouds made up of supercooled water droplets – water below 0°C but not yet frozen.
Aircraft punching through this cloud layer can cause air to expand and cool as it passes over the wings or propeller.
This change in temperature can be enough to encourage the supercooled droplets to freeze and form ice crystals which are large enough to fall from the cloud layer in this distinctive pattern.
This is the ‘fallstreak’ that occurs in the middle of the cloud – which is essentially snow.
The freezing crystals disturb the cloud layer and cause more freezing around them.
Sometimes the holes in fallstreak formations can expand up to 30 miles (50 km) across within an hour of appearing as neighboring droplets start to freeze.
Although scientists have a clear explanation for the origins of the photogenic phenomenon, fallstreak holes are not widely known about because of their rarity.
As a result they are often blamed on UFOs.