Absolutely spectacular shot of lenticular clouds over the Sandwich islands.
Also known as altocumulus standing lenticularis, these are stationary, lens-shaped clouds that form at high altitudes. They are included in the middle layer cloud family because the bases of the clouds are stationed between about 2,000 and 7,000 meters. These clouds form when moist air is forced to flow up around mountains and large hills. The water is super cooled and condensed from air below the dew point temperature.
Pilots avidly try to avoid these clouds which cause extreme turbulence. The turbulence is caused by a rotor circulation. This circulation forms within the lee of the barriers (mountains or hills) or within a valley. The rotor is a type of lee eddy. The surface wind of the cloud is an opposite direction to the gradient wind. However, because of the large vertical air movements, sailplane and glider pilots favor these clouds which can give great vertical lift and climb to extreme altitudes for gliding.