Physics Photo of the Week

October 4, 2013

"Niagra Falls" into Bee Tree Cove

This unusual cloud formation resembles a large water fall tumbling into Bee Tree Cove near Warren Wilson College on Sept. 18, 2013.  It did not cause any flooding because it was just a cloud.  The time-lapse animation (below) resembles a water fall, complete with "spray" rising from the base of the "falls".  A "cove" in the southern Appalachians is a narrow valley recessed into the mountains, similar to a "cove" along the ocean coast.  The photograph is looking across the Swannanoa Valley into Davidson cove (between Watch Knob on the left and Four Brothers on the right.  Bee Tree Cove lies just behind Davidson Cove, over the foreground ridge, where the cloud "falls" descends.  The animation plays at 333 times the original speed. 

Clouds (fog) descending over mountain gaps is a fairly common occurrence.  However this event occurred in the late afternoon around sunset, which is unusual.  The weather had recently cooled, there was a lot of fog in the area, but clear sky above the fog.  A chilly wind from the southeast brought cold, moist air from the lowlands into the Blue Ridge Mountains, forming fog as the winds were elevated to higher elevations while ascending the Blue Ridge.  As soon as the cold, foggy air mass reaches the ridge line of these mountains, it descends into the valley below, and even "splashes" or rebounds from its momentum crashing into the valley floor. 

The clear sky above, made pinkish by the setting Sun behind the camera, shows some very small high-level clouds moving the opposite direction from the fog bank.

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to

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