Taken from the same place in McKinnon Reserve at sunset.
The 10 March 2008 was a day of interesting weather. It started fine and calm, the sky clear blue with nary a cloud. By midday lenticular clouds* had appeared as shown in the first photo above. These lenticular clouds or "lennies" as they are sometimes called, stayed through the day. The shape and number of clouds in the pancake like stack changed as new lennies formed and the older clouds at the top of the stack disappeared. Since lenticular clouds are formed by strong wind we knew that although the air was calm where we were that wind was coming. By late afternoon, the wind appeared at the far end of Lake Ohau, moved toward us and about 20 minutes later, reached Ohau Village at gale strength. The second photo above shows these clouds at sunset. (If you are interested, note the horizontal rotation about a vertical axis of the clouds in the middle of the left stack. I think it fascinating that the clouds in the middle of the stack have rotated relative to the clouds above and below, apparently due to the shear force of a westerly wind, while maintaining their vertical position in the stack.)
These clouds are named "lenticular" because they are lens shaped. Strong wind passing over a high mountain produces standing waves in the air above and somewhat downwind of the mountain. If the air is moist, changing pressure (compression followed by decompression) in these waves results in condensation making the shape of these standing waves visible. Their formal name is: "altocumulus standing lenticularis" meaning a high heap of lens shaped clouds formed by a standing wave. Pilots of powered planes and pilots of sail planes (gliders) are particularly interested in "lennies" as they are not only associated with high wind but also vertical wind. They are usually avoided by power plane pilots because of the turbulence but are sought by glider pilots for the rapid vertical lift they give. Some physicists, including the author, think that standing waves are the basic building block of matter and thus the universe. Hence my fascination with lenticular clouds as they give me a visual demonstration of how matter is formed.