June 24, 2003
Lenticular clouds can form when moist air is cooled to the dewpoint as it's forced up over mountain tops. As the air sinks back into the valleys on the leeward side of the mountains, adiabatic warming triggers the evaporation of the cloud. I snapped this photograph late one morning in North Elba, New York, looking east toward the Great Range of the Adirondacks. The cloud appears to be more than 2 miles long (3.2 km), and its long axis parallels the long axis of the Great Range. Several of my students and I had just finished a late September backpacking weekend, and whereas the temperatures in the valleys had been moderate, the High Peak temperatures were extremely cold -- setting the stage for the creation of this gigantic lenticular cloud. It was sufficiently cold, in fact, that water in canteens actually froze during the short time we were on Algonquin Peak.