North Wallowa Lenticulars, (lenticular >>> lens-shaped or bi-convex, from
lenticula, diminutive of lent >>> lentil), above the East Moraine, Wallowa Lake . ..

Lenticular clouds like the ones behind the smaller cumulus in
the foreground are the signature flowform of warm, dry, mountain
fallwinds. Examples are the notorious Föhn of the Alps, and here,
the Chinook winds north of the Wallowas. They are the product of
horrendously complex and difficult to predict orographic lifitng
processes. The mountains, basically, are such a powerful feature
of the landscape that they create their own weather, lifting frontal
movements approaching from the southwest over the Cascades
from the Pacific Ocean. The air cools with lifting, and because
colder air holds less water, the excess moisture falls as snow.
As the now drier air is pushed North, it then 'falls' and quickly rises
in temperature, making both people and animals feel uncomfortable,
and melting entire snowpacks in less than a day. As happened the
day after this photo was made, once the winds stop, which in a full-blown
Chinook storm can be fierce indeed, the rain or snow usually begins.

One other remarkable feature of lenticular clouds cannot be
conveyed in a still photograph. They are essentially standing waves,
which means that unlike most other clouds they do not move.
Instead, the air passes through and sustains the form, while
the cloud itself remains relatively constant.

On the road in the American Northwest.


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