lenticular clouds are usually formed near mountains, as air, which flows over and down the side of the mountain, will overshoot and spring back up (much like how a car will continue to bounce a bit after going over a speed bump). the air oscillates like this for a while, with clouds forming on the upward part of the wave as the moist rising air cools.
lenticular clouds are a bundle of movement, yet look stationary, as the flow of air up one side of the mountain replenishes the cloud on the windward side, while the dry air flowing down the other side dries the cloud out on the leeward side. these clouds can appear to hover for hours or even days until weather conditions change, and are even occasionally confused for ufos.
photos by (click pic) rolland hartstrom, carlye calvin, david h collier, john terry, cyda101, jason hill, alpsdale and marc veraart. see also: circumhorizontal arcs, asperatus clouds, mammatus clouds, polar stratospheric clouds, noctilucent clouds and cloud iridescence.
