"Foehn" Clouds Over The Franklin's

Weather Talk

POSTED: Sunday, December 8, 2013 - 6:46pm

UPDATED: Monday, December 9, 2013 - 1:20pm

What Causes This Veil Of Cascading Clouds Over Our Mountains?

This photo of clouds cascading down the western slopes of the Franklin Mountains is an excellent example of “Foehn Clouds” and “The Foehn Effect". Steve Green took this shot from west El Paso on November 25th this year.

The original Foehn, or Föhn Cloud in German, was the name of a warm southerly wind coming up and over the Swiss Alps. Now this term is used to describe similar meteorological effects on all mountains all over the world.

This wind encounters a mountain range on its way and is forced up, rising in order go over the mountains and get to the other side. While rising along the mountain slopes, in contact with the ground and by the cooling effect, it gets colder. As cold air cannot contain the same quantity of humidity than warm air, some heavy rains or snowfall occur on the humid mountainside and these rains or snowfall gets stronger and stronger as the mass of air gains altitude. As the air rises up the wind ward side of the mountain the rain or snow condenses and releases latent heat, this helps dry out the air mass.

When the air reaches the top of the mountain it is quite dry. When all the humidity has gone on this side of the mountain range; the air is warm and the weather is very nice.

There is an amazing visible effect of a barrier or bank of clouds blocked on top of the ridge, obscuring the mountain tops this is known as a “Foehn Wall”, which marks the highest point where the precipitation ends on the windward slopes. The clouds suddenly vanish on the down slope side,, occasionally into a spectacular "waterfall of clouds".

By an effect of "rebound", the clouds reappear slowly much further from the range, while already over the lowlands.. This is called the “Foehn Effect”.Just as a funny side note, years ago, a German company AEG, used “"Fön" “as a name for their electrical hair driers. The brand name eventually became the generic word and "Fön” is now used in German for all electrical hair driers.

Chuck DeBroder, Chief Meteorologist
KTSM, NewsChannel 9, NBC, El Paso, TX
twitter: Chuck DeBroder NC9 @wxchuckNC9

(Photo: Steve Green sgreeneptx@gmail.com http://www.stevengreenphotography.com)


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