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.
Ghostly 'UFO cloud' (lenticular cloud) hovering over mountains wows judges in weather photo contest
Photos by Harvey Carruth at The Dalles, Oregon - May 5, 2011
Taken by Photos by Kevin Lahey
Taken by Thedra
Taken by Stuart Anderson - August 3, 2006 - Saskatchewan, Canada
Alberta, Canada - June 21, 2005
Taken by Hanne Elmose - June 2004 - Sierra Nevada, Spain
November 26, 2003 - Space.com
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!"
These cloud formations could be interpreted as visitors in space ships in history.
UFOs in History
They may have been lenticular clouds
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