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Banner Cloud (November 07)

Banner Cloud (November 07)

November 07 Cloud of the Month
(Click image to enlarge) Photographed over the North Face of the Eiger in Switzerland
© Bob Peterson (see it in the gallery)

November 07 Wiro

Flying the Flag for Clouds

‘Orographic clouds’ are ones that form when wind has to rise to pass over mountains. As it does so, it can sometimes cool enough for its moisture to condense into droplets that appear as cloud. Orographic clouds are called ‘lenticular’ when they hover some distance from the peak and look like flying saucers. They are called ‘cap clouds’ when they sit right over the mountain. But the orographic cloud shown above, trailing elegantly from the North Face of the Eiger in Switzerland, is known as a ‘banner cloud’.

Most banner clouds have a more even appearance but this one seems composed of fluttering ribbons with gaps in between. It is an effect you sometime see when there is a lot of turbulence in the airstream.

Could the mighty mountain and the ephemeral cloud possibly have less in common? And yet they are faithful companions, who proclaim their friendship whenever they unfurl their glorious banner to the world.

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