Where Angels Dance
May 11, 2004
The photo above showing interesting cloud formations stacked atop the Omataco Mountains in Namibia, Africa was taken in mid March of 2004. When stable, stratified air is forced over a mountain, like water flowing over rocks in a shallow stream, it expands and cools below the dewpoint. As water vapor in this air condenses, clouds will form. On the lee side of the mountain, as the air moves downward, it's compressed and warms above the dewpoint. The warming allows the cloud droplets to evaporate, thus dissipating the cloud.
The shape of the mountain governs the shape of the cloud. If it's a conical mountain top, a lens-shaped or lenticular cloud often results. However, if the moist layer has a fine structure (very thin moist and dry strata), the cloud may look something like a stack of tortillas, as shown above.
Although these clouds are stationary, fixed above the mountain, wind may be blowing through the clouds rather rapidly. Fluctuations in wind speed, direction and moisture content can lead to noticeable changes in the cloud's shape. These changes, though random, may create the illusion that the cloud is spinning.