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Pic of the week: Flying saucer clouds baffle onlookers in Cape Town

Lenticular clouds hover over Cape Town, South Africa on Sunday. (Kyle Mijlof)

Sunday looked like a scene from Independence Day over Cape Town, South Africa. Social media blew up with photos like this one along with captions like, “what the heck are these?” or “there are UFOs over Cape Town!” or my personal favorite, “pancakes in the sky. Who’s hungry?”

I’m happy to report that they were neither spaceships nor pancakes, but lenticular clouds, or altocumulus standing lenticularis, which is latin for “lens-shaped.”

Lenticular clouds form in stable environments with strong winds aloft, where moist but stable air flows over a mountain creating standing gravity waves on the downwind (or lee) side. Generally, the mountain range must be oriented perpendicular to the prevailing winds in order for this clouds to form. If the air temperature cools enough to condense the water vapor in it, a lenticular cloud may appear.

[Flying saucer clouds float over the Blue Ridge Mountains]

Lenticulars are most common in the spring or winter when winds aloft are strongest, and for this reason they are known as “New Mexico’s winter cloud.”

Since these types of clouds do not typically form over flat terrain, a vast majority of people have never seen them. Thus it can be rather elusive and a shocking sight when seen for the first time.

Pilots actually use lenticulars as a sign of where NOT to fly. Since lenticular clouds are formed by strong winds and eddies or gravity waves near mountains, they indicate a turbulent atmosphere.

But while pilots avoid a lenticular-filled sky, gliders seek them out. The turbulent “wave lift” associated with these clouds can allow gliders to reach remarkable heights and distances. The world records for gliding height (50,721+ feet) and distance (1, 864 miles) were set in these types of environments!

Back to last Sunday. There were so many pictures shared from Cape Town this weekend, I couldn’t share just one. Here’s an honorable mention by Diane Pritchard who simply said, “funky clouds over Cape Town.”

Yup — pancakes! #PassTheSyrup

Finally, a quick check on NASA’s hi-resolution MODIS imagery from Sunday reveals what could be the row of lenticular clouds lined up over the mountains just west of the city of Cape Town.

And just in case you haven’t had enough cloud geekery today, Google “Mt. Rainier lenticular clouds.” You’re welcome.

Weather is awesome. #cwgpicoftheweek