Starship Asterisk*

Mammatus Clouds over Mount Rushmore

Explanation: What's that below those strange clouds? Presidents. If you look closely, you may recognize the heads of four former US Presidents carved into famous Mount Rushmore in South Dakota, USA. More obvious in the featured image are the unusual mammatus clouds that passed briefly overhead. Both were captured together by a surprised tourist with a quick camera in early September. Unlike normal flat-bottomed clouds which form when moist and calm air plateaus rise and cool, bumpy mammatus clouds form as icy and turbulent air pockets sink and heat up. Such turbulent air is frequently accompanied by a thunderstorm. Each mammatus lobe spans about one kilometer. The greater mountain is known to native Lakota Sioux as Six Grandfathers, deities responsible for the directions north, south, east, west, up, and down.

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Nice weather photo of the day.

XgeoX wrote: ↑Mon Dec 07, 2020 10:39 am Nice weather photo of the day.

Nice third-planet-from-the-Sun photo of the day!

Santa’s beard.

Not sure what this has to do with astronomy. Nice pic but not really astro related.

Mammatus clouds are usually quite interesting to me; very nice photo!
What is the structure below the presidents?

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https://apod.nasa.gov/apod/ap191215.html
https://apod.nasa.gov/apod/ap180819.html
https://apod.nasa.gov/apod/ap151018.html
https://apod.nasa.gov/apod/ap130828.html
https://apod.nasa.gov/apod/ap110220.html
https://apod.nasa.gov/apod/ap071230.html

I liked it better before the 3D graffiti...
Rob

So that's what theyr'e called! I saw a tremendous example once, on the plain to the South of Kilimanjaro; from horizon to horizon, the cloud seemed to be boiling in cells - seen from beneath. It was quite scary, in fact, as I doubt that anyone who saw it would have known what was going on (except perhaps the meteorologists at Kilimanjaro Airport).