This spectacular photo of clouds rolling over condos on Panama City Beach has gone viral after being posted by Panhandle Helicopter on its Facebook page. The weird cloud formation is the result of moist air flowing inland and condensing as it rises into cooler air. Meteorologist Dan Satterfield, of the American Geophysical Union, describes the process on Dan’s Wild Wild Science Journal blog:
“Cool air offshore was very nearly at the saturation point, with a temperature near 20ºC and a dew point of about 19.5 degrees C. The air at this temperature can only hold a certain amount of water vapor, and how much it can hold depends heavily on the temperature. Drop the temperature, and it can no long hold as much water vapor, so some of it will condense out and a cloud will form.
“In this case, the air was cooled by lifting it about 50 meters over the top of the condos,” Satterfield continues. “A parcel of unsaturated air will cool when lifted at a rate of 1 degree C per 100 meters. In this case, it probably cooled about 0.5 degrees C, but that was all it took! On the back side of the condos, the air slowly sinks back down and warms at the same rate. As it warms the air can hold more water vapor and the cloud evaporates and disappears!”
The video below includes a visual explanation of the phenomenon from the Weather Channel: