swirling through the air in mesmerising saucer like shapes, these exceptionally rare lenticular clouds are the most common explanation for ufo sightings the remarkable looking disc shapes were spotted by amateur photographer glenn spencer, 42, in the sky above chester in cheshire the formations, also known as wave clouds, were scattered over miles, producing a stunning spectacle rarely seen in the uk, lenticular clouds are formed when a tall geographic feature, such as the the top of a mountain, obstructs a strong wind the interruption in airflow creates a wind wave pattern in the atmosphere on one side of the mountain and at the top of these waves, moisture in the air condenses and forms a cloud as air moves down into the trough of these waves the water evaporates again, leaving behind clouds in a characteristic lenticular shape mr spencer noticed them while driving to the shops and was so amazed that he stopped the car to retrieve his camera from the boot he said: 'i tried to follow them to higher ground to get a good view they were just so mesmerising and i thought they looked amazing it is easy to see why people mistake them for ufos they are brilliant i've never seen anything like it' scroll down for video  rare spectacle: these lenticular clouds, also known as altocumulus standing lenticularis, are hardly ever seen in british skies  stunning: they form when wind blows over high ground and then undulates down in a stream of waves creating a rippled effect as the air cools  commonly mistaken for ufos: the clouds are sometimes reported as ufos, particularly the flying saucer, because of their lens shape  how they form: they occur when the air meets obstructions such as mountains and the clouds' thickness creates incredible contrasts of light  mesmerising: amateur photographer glenn spencer, 42, noticed the flying saucer shaped clouds as he was driving to the shops in cheshire  pilots of powered aircraft tend to avoid flying near lenticular clouds because of the turbulence of the rotor systems that accompany them 
uk cheshire
extraordinary lens shapes are exceptionally rare lenticular clouds and are also known as wave clouds . they are hardly ever seen in the uk but were spotted by an amateur photographer in the sky above cheshire . the rippling effect is created by cooling air and the clouds are the most common explanation for ufo sightings 