Photo by Mark J. Madigan - Walsenburg, Colorado - May 20, 2003

Lenticular clouds, technically known as altocumulus standing lenticularis, are stationary lens-shaped clouds that form at high altitudes, normally aligned at right-angles to the wind direction.

Where stable moist air flows over a mountain or a range of mountains, a series of large-scale standing waves may form on the downwind side. Lenticular clouds sometimes form at the crests of these waves. Under certain conditions, long strings of lenticular clouds can form, creating a formation known as a wave cloud.

Power pilots tend to avoid flying near lenticular clouds because of the turbulence of the rotor systems that accompany them, but sailplane pilots actively seek them out. This is because the systems of atmospheric standing waves that cause "lennies" (as they are sometimes familiarly called) also involve large vertical air movements, and the precise location of the rising air mass is fairly easy to predict from the orientation of the clouds.

"Wave lift" of this kind is often very smooth and strong, and enables gliders to soar to remarkable altitudes and great distances. The current gliding world records for both distance (over 3,000km) and altitude (14,938m) were set using such lift.

Lenticular clouds have been mistaken for UFOs (or "visual cover" for UFOs) because these clouds have a characteristic lens appearance and smooth saucer-like shape.

There is also a fascinating print medium called Lenticular Printing.

Cheryl Cost sent these pics of lenticular clouds taken in Muizenberg a beach-side suburb
of Cape Town, South Africa on April 2, 2017 in the afternoon while walking her dogs.

Valentine's Day: A Heart Shaped Lenticular Cloud   APOD - February 14, 2016

Can a cloud love a mountain? Perhaps not, but on a Valentine's Day like today, one might be prone to seeing heart-shaped symbols where they don't actually exist. A fleeting pareidolia, the featured heart was really a lenticular cloud that appeared one morning last July above Mount Cook National Park in New Zealand. A companion video shows the lenticular cloud was mostly stationary in the sky but shifted and vibrated with surrounding winds. The cloud's red color was caused by the Sun rising off the frame to the right. Lenticular clouds are somewhat rare but can form in air that passes over a mountain. Then, vertical eddies may form where rising air cools past the dew point causing water carried by the air to condense into droplets. Unfortunately, this amazing sight made the fascinated videographer late for breakfast.

Cap Cloud over the Sierra Nevadas   NASA - November 26, 2013

One might say this was a bell weather day for the Sierra Nevada mountains. In January, just as the Sun was setting above the district of Albayz’n in Grenada, Spain, a huge cloud appeared as a bell capping the Veleta peak. Such a Cap cloud is formed by air forced upwards by a mountain peak, with the air then cooling, saturating with moisture, and finally having its molecular water condense into cloud droplets. Such a bell-shaped cloud structure is unusual as air typically moves horizontally, making most clouds nearly flat across at the bottom. Vertical waves can also give additional lenticular cloud layers, as also seen above. Given the fleeting extent of the great cloud coupled with momentarily excellent sunset coloring, one might considered this also a bellwether day for an accomplished photographer.

Mt. Hood and a Lenticular Cloud   NASA - April 17, 2013

What kind of cloud is next to that mountain? A lenticular. This type of cloud forms in air that passes over a mountain, rises up again, and cools past the dew point -- so what molecular water carried in the air condenses into droplets. The layered nature of some lenticular clouds may make them appear, to some, as large alien spaceships. In this case, the mountain pictured is Mt. Hood located in Oregon, USA. Lenticular clouds can only form when conditions are right -- for example this is first time this astrophotographer has seen a lenticular cloud at night near Mt. Hood. The above image was taken in mid-March about two hours before dawn.

National Geographic

The summit of Washington's Mount Rainier lies hidden beneath a stack of horizontally layered lenticular clouds. These clouds are formed by high winds blowing over rough terrain and are sometimes described as a "stack of pancakes."

Photo by Dahlia Rudolph at Mt. Rainer - October 5, 2011

View form the International Space Station

Photos by Harvey Carruth at The Dalles, Oregon - May 5, 2011

Photo by Elizabeth Duffy at Bishop, California - October 24, 2010

Photo by Rasa at Mount Shasta - August 12, 2009

Photo by Bettina Fischer at Mt. Etna - March 11, 2009 - after doing energy work

Lenticular Clouds Above Mt. Rainier in Washington State
NASA - February 3, 2009

A Lenticular Cloud Over New Zealand
NASA - January 21, 2009

Lenticular Clouds Over Mount Shasta

Taken by Photos by Kevin Lahey

Taken by Thedra

Taken by Peter K. - April 8, 2008 - Palm Desert, California

Taken by Stuart Anderson - August 3, 2006 - Saskatchewan, Canada

Taken by Joan Smith - Dec. 26, 2006 - in Sedona, Arizona

Alberta, Canada - June 21, 2005

Spain 2004

Taken by Hanne Elmose - June 2004 - Sierra Nevada, Spain

Lenticular Cloud Over Hawaii

November 26, 2003 -

Astronomers are always looking up. Sometimes they see interesting things that aren't as far up as we normally think they're looking. Peter Michaud, a public information officer for the Gemini Observatory in Hawaii, took this picture yesterday of an unusual cloud formation above the islands. It is called a lenticular cloud, due to its lens-shaped appearance. These clouds are formed by so-called mountain waves of air created by strong winds forced over high mountains.

In this case, the mountain is Mauna Kea, a 13,796-foot peak (4,260 meters) where one of the two Gemini telescopes sits, along with several other observatories. (A twin to the Hawaiian Gemini scope is situated in Chile.) "At the high points in the wave, moisture in the air condenses out to form a cloud," Michaud explained. "In the photo you can see that the wave established this morning displayed two peaks. Actually there were four -- two more were downstream from Mauna Loa, but the other two were not as impressive as Mauna Kea's!"

Mount Baker - Washington State 202

Taken by Scott Hunziker - 2002 - Mount Rainier Washington State

Taken by Jim Griggs - Sunrise Rocky Mountain National Park in Colorado 2002

Lenticular Clouds in Art

These cloud formations could be interpreted as visitors in space ships in history.

Painted in 1420

This fresco is located in the San Francesco Church in Arezzo, Italy.

UFOs in History
They may have been lenticular clouds