photo #4417183

Kathleen Janick (Cloud Appreciation Society Member 49,856) spotted these rows of Stratocumulus lenticularis clouds at sunrise over the Gulf of Maine from Cape Elizabeth, Maine, US. The smooth bands of cloud reveal undulating air currents that can develop in our lower atmosphere downwind of mountainous terrain. Such rising and dipping in the flow is visible when the air cools enough at the peaks for its moisture to form droplets or ice crystals of cloud and warms enough at the troughs to form cloud-free gaps. In stable atmospheric conditions, such wavelike air flows can extend huge distances downwind of the hills or mountains that caused them. We can’t say for sure what terrain would have caused Kathleen’s wavelike rows of Stratocumulus lenticularis, but it’s possible they were caused by the Appalachian mountains some 125 miles (200 km) to the north east