Environment Planet Earth How Lenticular Clouds Are Formed By Jaymi Heimbuch Writer California Polytechnic State University, San Luis Obispo Jaymi Heimbuch is a writer and photographer specializing in wildlife conservation. She is the author of The Ethiopian Wolf: Hope at the Edge of Extinction. our editorial process Twitter Twitter Jaymi Heimbuch Updated May 31, 2017 Share Twitter Pinterest Email Planet Earth Weather Outdoors Conservation Is that a UFO? cyda101/iStock. A lenticular cloud, or by the more scientific name Altocumulus lenticularis, is a fascinating cloud formation, if simply for its strangeness. Want to know how to spot one of these saucer-like clouds? Click through to find out where, when and how these clouds form to boost your odds. (Text: Jaymi Heimbuch) She'll be comin' round the mountain AlterYourReality/iStock. You’re most likely to spot a lenticular cloud near hills or mountains. They need a certain air current to form, and just the right conditions tend to happen around the topographical formations that encourage the right air currents. The air up there Christopher Michel/Flickr CC. So how do they happen? First, they need a current of moist air forced upward, as happens when air travels up the side and over the top of a mountain. The moisture condenses to form a cloud. But to make a lenticular cloud, versus any other type, there’s an extra step needed. Riding the waves Yurio1978/Shutterstock. When the moist air reaches the crest of the mountain, a wave pattern, or atmospheric standing wave, is created in the air flow. As the air hits the crest of the wave and moves downward, the cloud formed at the crest may evaporate, forming the cloud which sits at the very crest of the wave. Sometimes strings of lenticular clouds form at each crest of each successive wave in the wind pattern. In constant motion Marc Veraart/Flickr CC. Lenticular clouds are a bundle of movement, yet they look stationary. That’s because the flow of moist air up one side of the mountain replenishes the cloud on the windward side while the dry air flowing down the other side dries the cloud out on the leeward side. When formed above a mountain, it can seem to hover for hours or even days until weather conditions change. Rare circumstances Yurio1978/Shutterstock. Though they typically form near hill or mountain ranges, there are instances when they form over flat or low terrain. In this instance, it is fluctuating wind speeds that cause their formation, rather than atmospheric standing waves. On a different level lfstewart/Shutterstock. There are actually three types of lenticular clouds: altocumulus standing lenticularis (ACSL), stratocumulus standing lenticular (SCSL), and cirrocumulus standing lenticular (CCSL). The category into which a lenticular cloud falls depends on the height at which it forms above the Earth’s surface. Saucers and waves sierrarat/iStock. Some can look like flying saucers while others look just like the choppy waves of the sea. Lenticular clouds have been used to explain away some UFO sightings. Picture perfect Steve Ryan/Flickr CC. A real treat for landscape photographers and cloud enthusiasts (aren’t we all cloud enthusiasts, really?), lenticular clouds can form at any time of day. But it’s at sunset that they really show off that strange, smooth, and seemingly unmoving shape. A pilot's friend or foe Melanie Metz/Shutterstock. Though they're beautiful, pilots flying powered airplanes avoid getting too close since the clouds indicate the air movement that causes severe turbulence. But pilots flying glider planes seek them out since they indicate rising air which helps the pilot gain height. Pretty as a painting Semmick Photo/Shutterstock. In the right place, at the right time of day, these clouds can make a landscape look like a water color painting! Keep an eye to the sky Angel DiBilio/Shutterstock. So if you want to see lenticular clouds for yourself, hang out around hills or mountains during winter and spring. With luck and the right weather conditions, you’ll see them!