June 2015

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Unidentified Flying Cloud

[/vc_column_text][/vc_column][/vc_row][vc_row row_type=”row” use_row_as_full_screen_section=”no” type=”full_width” text_align=”left” css_animation=””][vc_column width=”2/3″][vc_column_text]The Altocumulus lenticularis cloud is an ‘orographic’ cloud formation, which means that it tends to form as winds are forced upwards to pass over mountains. The name lenticularis comes from the Latin for a lentil, but these clouds often look more like flying saucers.

When the atmosphere is stable, the wind flowing over the mountain can follow a rising and dipping path downwind of the peak. This is an invisible ‘standing wave’ of air, and when the wind contains enough moisture it can lead to a lenticularis cloud forming at the crest, like this wonderful example spotted by Pilar Quijada over Madrid, Spain.

In a steady wind, the position of the standing wave remains fixed and so the lenticularis cloud also stays in place. Its droplets form at the upwind side of the cloud where the air cools as it rises towards the wave’s crest. They race through the cloud with the wind, only to evaporate away again on the downwind side as the air sinks and warms once more. Although the droplets are zipping along, the points where they form and evaporate are fixed. So this UFO-shaped cloud just hovers in place in the lee of the peak.

Photograph © Pilar Quijada.[/vc_column_text][/vc_column][vc_column width=”1/3″][vc_single_image image=”79927″ img_size=”large” add_caption=”yes” qode_css_animation=””][/vc_column][/vc_row]

2 thoughts on “June 2015”

  1. Laurence Green avatar Laurence Green says:

    Congratulations, Pilar!

    There were quite a number of really wonderful photos submitted by members last month.

    I think Ian Loxley, Photo Editor, must have had more than a fair share of rather sleepless nights wondering which of the many, many lovely photos to choose for the Cloud Of The Month award.

    Ian, you have my sympathies!

    Thanks to everyone, as ever.


  2. Pia Severin and Steven Valentine avatar Pia Severin and Steven says:

    Make excellent conditions for soaring in sailplanes.

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