Cloud street

Cumulus clouds lining up to form a classic thermal cloud street.

Cloud streets aligned by a strong westerly over England and Wales after passage of cold front.

Cloud streets over the open water (lower left portion of the image) in the Bering Sea.

Cloud streets are rows of cumulus or cumulus-type clouds aligned parallel to the low-level wind.

The most favorable conditions for their formation occur when the lowermost layer of air is unstable, but is capped by an inversion-by a stable layer of air. This often occurs when upper air is subsiding, such as under anticyclonic conditions, and is also frequently found when radiation fog has formed overnight. Convection occurs below the inversion, with air rising in thermals below the clouds and sinking in the air between the streets. Cloud streets provide glider pilots with lines of rising air, enabling them to fly straight for long distances while still climbing.

Cloud streets are usually more or less straight, but rarely cloud streets assume paisley patterns when the wind driving the clouds encounters an obstacle. Those cloud formations are known as von Kármán vortex streets. Although conventional cloud streets are clearly visible from the ground, large scale patterns such as these are seen best on satellite photographs.

See also

• Gravity wave
• Marine stratocumulus

References

• Dunlop, Storm (2002) The Weather Identification Handbook Guilford, Connecticut: The Lyons Press. ISBN 1-58574-857-9
• Scorer, Verkaik (1989) Spacious Skies David & Charles ISBN 0-7153-9139-9
• "Cloud Streets Pave Hudson Bay". NASA Earth Observatory. http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17108. Retrieved 2006-05-01. 
• "Cloud Streets Photographed over Gulf of Mexico: Gallery of Cloud Streets Images". http://www.meteorologynews.com/2009/10/29/cloud-streets-photographed-over-gulf-of-mexico/. Retrieved 2009-10-29. 

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