Lenticular cloud

Lenticular cloud
Lenticular cloud above northern Presidential Range, New Hampshire, United States
Genus	Alto- (Latin for high) -cumulus (Latin: heap)
Species	lenticularis (Latin: lens-shaped)
Altitude	6,000-12,000 m (20,000-40,000 ft)
Classification	Family A (High-level)
Appearance	lens-like
Precipitation cloud?	Sometimes
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Altocumulus lenticularis often forms in the lee of mountains.

Lenticular clouds are stationary lens-shaped clouds that form at high altitudes, normally aligned perpendicular to the wind direction. Lenticular clouds can be separated into altocumulus standing lenticularis (ACSL), stratocumulus standing lenticular (SCSL), and cirrocumulus standing lenticular (CCSL).

Formation

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. If the temperature at the crest of the wave drops to or below the dew point, moisture in the air may condense to form lenticular clouds. As the moist air moves back down into the trough of the wave, the cloud may evaporate back into vapor. Under certain conditions, long strings of lenticular clouds can form near the crest of each successive wave, creating a formation known as a 'wave cloud'. The wave systems cause large vertical air movements and so enough water vapor may condense to produce precipitation. The clouds have been mistaken for UFOs (or "visual cover" for UFOs) because these clouds have a characteristic lens appearance and smooth saucer-like shape. Bright colors (called Irisation) are sometimes seen along the edge of lenticular clouds.^[1]

Flight

Pilots of powered aircraft tend to avoid flying near lenticular clouds because of the turbulence of the rotor systems that accompany them, but glider pilots actively seek them out. 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 3,000 km; 1,864 mi) and altitude (15,460 m; 50,721 ft) were set using such lift^[2].

Gallery

Lenticular Cloud Rings covering Mt. Jefferson, near Detroit Lake, Oregon, United States

Lenticular cloud hovering over Mt. Psiloritis, Crete, Greece

Very low-altitude Lenticular clouds near Homer, Alaska, United States

A colourful lenticular cloud appears on the sky above Kuantan, Malaysia.

See also

• Cap Cloud
• Helm Wind

References

External links

Wikimedia Commons has media related to: Lenticular cloud

• [1] - Lenticular Cloud descending upon palm trees in desert.
• kcocco.com - Altocumulus Lenticular Clouds, Wastach Mountains, Utah
• pixdaus.com/single.php?id=6528#read_c - lenticular cloud above Mt Fuji.
• [2] - Picture of the Day 2009-01-21: A Lenticular Cloud over New Zealand
• Sistek, Scott. "Mt. Rainier puts on a show!". KOMONews.com. http://www.komonews.com/weather/blog/35631614.html. Retrieved 2008-12-11. 
• [3] - APOD: Lenticular Clouds near Mt. Ranier, Washington, USA
• [4] - San Francisco's Richmond District 2007: "Lennies" attacking the Richmond