Mt St Helen pic
from Marcia Muonio
Picture by Brent and Jan LeBaron
MT. St. Helens, which sits about 30 miles from our house as the crow flies, continues to spew ash, while it is forming a lava dome in the crater and still having minor tremors. Here, in this sunrise shot, she appears to be blowing smoke rings (and anything so benign is welcomed, given recent history.)
What forms the "smoke rings" is the air flowing over the mountain getting pushed up higher as it goes up and over the top. The moisture content and initial temperature are just right so that the moisture condenses from a vapor to small particles at the higher altitude. When the moving air moves past the peak and comes down again, the particles evaporate back to an invisible vapor. The two "pancakes" describe that there are two layers of air for which this is happening, thus making this awesome picture possible. It's called a lenticular wave in the aviation industry.
