Rare clouds which have historically been blamed for a number of UFO sightings have been seen over northern skies in the UK.
The special cloud formation got its nickname from the smooth, symmetrical oval or round shapes it produces, which many have compared to the science fiction depiction of flying saucers.
Some also refer to them as pancake clouds, because they sometimes appear flat and stacked.
But they are formally called lenticular clouds, a name originating from a Latin word meaning “lens-like”.
The clouds, which are quite rare in the UK, were spotted in northern parts of the country earlier this week, over the likes of Gateshead, Newcastle, Cumbria and Scotland.
They form when the air is stable and winds blow across hills and mountains from the same or similar direction at different heights through the troposphere – the lowest layer of Earth’s atmosphere, according to the Met Office.
Pic: AP
Pic: AP
“When air blows across a mountain range, in certain circumstances, it can set up a train of large standing waves in the air downstream, rather like ripples forming in a river when water flows over an obstruction,” it explains.
“If there is enough moisture in the air, the rising motion of the wave will cause water vapour to condense, forming the unique appearance of lenticular clouds.”
Lenticular clouds spotted near El Chalten in Argentina. Pic: VWPics/AP
Do the clouds signify anything?
The UFO-shaped clouds may not beam anyone up into the sky – but they can cause very strong, gusty winds on the ground in a concentrated spot.
Pilots tend to avoid fling near them because they can cause quite a bit of turbulence, the Met Office says, while skilled glider pilots like them, because they act as a visual representation where air will be rising.