Weird clouds

By Phil Plait | March 5, 2009 3:26 pm

Share photos on twitter with TwitpicIf you follow me on Twitter (and you should, since I post stuff there that is not quite right for stuff here) then you may have seen my picture of a lone lenticular cloud over Boulder the other day. Those are fairly common around here, and fascinating to watch. I love odd clouds, and so I was happy to see a whole bunch of them on a website called Moolf (which I found via Reddit). Some are really incredible. I’ve seen the sky full of mammatus clouds, and it’s truly unearthly.

CATEGORIZED UNDER: Cool stuff, Pretty pictures

Comments (31)

  1. Viewer 3

    “I love odd clouds”

    I thought I’d only hear a statement like that from someone on drugs. …Actually no, that makes sense.

  2. Might I get a plug in for the Cloud Appreciation Society? Google for site.

  3. Terrestrial clouds are so boring. ūüėČ You want odd clouds, look at our gas giants. They is so pretty, but so deadly!

  4. Sarah

    Not boring clouds at all for glider pilots in Denver today.. surfs up!

    Winds aloft:
    9000 12000 18000 24000 30000 34000 39000
    DEN 2522+02 2433-06 2575-20 2592-30 741344 741651 239856

    decoded, thats 75 knots from 250 at 18000, 92 knots at 24000, 113kt@240 at 34000 and 230@98 at 39000

  5. justcorbly

    A long time ago (1974), I was about 10 miles west of Xenia, Ohio when an F5 tornado cut through the center of town. About 30 minutes after the storm hit, most of the sky was covered with clouds I’ve never seen explained. Imagine looking up at the bottoms of dozens and dozens of slightly overlapping saucers, each clearly rotating. I don’t recall any particular colors, but the central and lowest point of each saucer was darker The rest of the sky was a very dark grey, except for a large and bright orange spot to the southeast.

    The most frightening and freakiest sky I’ve ever seen.

  6. Helioprogenus

    There is something truly unsettling about mammatus clouds. I’ve never quite been able to put my finger on it, but their appearance is so foreboding. Meteorology dictates that their harbingers of bad weather, thunderstorms, etc. But beyond just the knowledge of that, the sheer experience of viewing them is of some kind of inherent discontent. It goes beyond the generalized malaise one feels when it’s overcast and dark.

  7. @justcorbly: I believe what you were seeing was the back end of the supercell that produced the tornado. They often have that sort of layer-cake, or “flying saucer” appearance.

    Here’s a very good example:

  8. @ justcorbly:

    They’re called “mammatus” and are the result of massive amounts of water being carried aloft in the supercell. The darker bottoms of the “saucers” are where the water droplets are densest, and hence dropping fastest and blocking the most light.

    They’re pretty cool, but yeah…a little freaky.

  9. Oops, sorry Helio…missed your post. Brainiac.

  10. With respect to the link:

    I always hear Kelvin-Helmholz clouds described as “rare”, but I’ve seen quite a few of them.

    I watched a Roll cloud once do its thing as I was driving to work. I kept thinking it was a soliton wave slicing across the sky. I’m not sure it wasn’t.

    I may have seen a Shelf cloud once. But I’m pretty sure if I ever saw anything like the one on the linked site, I would start whimpering while I dug a hole to hide in.

  11. justcorbly

    @drksky & @kuhniget:

    The clouds I remember bear a resemblance to mammatus, but each “saucer” was distinctly smaller than the images posted here (and elsewhere that I’ve seen).

    I don’t recall a layer cake effect, just looking at the bottom of a bunch of overlapping clouds. I also distinctly recall rotation in each cloud, but I’ll admit it’s been some time. Is rotation — real or apparent — associated with mammatus clouds?

    I was on a hill with unobstructed visibility and I’d guess those clouds covered about two-thirds of the sky. I remember the horizon to the east, where the storm was passing, was a solid black. Folks in Oklahoma are probably acclimated to that stuff, but I’d prefer not to have that opportunity.

  12. Timothy from Boulder

    The last photo, characterized as “clouds were rolled into long, distinctive ribbons after becoming trapped in air currents” is almost certainly wrong, or at least a horrible translation. After viewing a video of the the clouds (a quick Google of “Sapporo Meteorological Observatory” and “Strange-clouds-appear-over-Sea-of-Okhotsk” reveals a YouTube video of the clouds rather than just a single still) they are almost certainly clouds formed by gravity waves.

    Gravity waves (not to be confused with gravitational waves) occur when air at a different density than its surroundings bob up and down trying to achieve buoyancy equilibrium. The air velocity is actually perpendicular to the clouds shown, and will dip down and rise up at a frequency called the Brunt-Vaisala frequency (about 8-10 minutes in the troposphere). If the conditions (temperature and water vapor) are just right, as the air rises above the mean level, the temperature is slightly cooler and the air reaches saturation, forming clouds. As the air dips down to where the air is slightly warmer, the water vapor evaporates and the clouds disappear. The air can keep up this bobbing up and down (because there’s not a lot of friction or damping) for dozens of kilometers.

    Granted, for these to be so well formed and distinct, the conditions had to be just right, and this is the first time I’ve seen them photographed from a nearby aircraft. But clouds like this are frequently observed by satellite imagery.

    (There, that graduate class came in handy after all!)

  13. Kevin

    @Helioprogenus… in actuality, a harbinger is a sign of things to come. Mammatus clouds are usually – but not always – on the back side of a cumulonimbus cloud (thunderstorm) and are most easily seen after the storm is passed.

    @Harold… Shelf clouds are cool. For some reason, we had an abundance of them last year during storm season, and I got some crazy shots of them.

    @Phil… I saw your lenticular cloud image on yoru Tweet. I photographed some of them a few years ago, and was shocked when I saw them – because I life in the Great Lakes area, and we don’t have a lot of mountains. :)

  14. IVAN3MAN

    Extract from Wikipedia: Mammatus (also known as mammatocumulus, meaning “bumpy clouds”) is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud. The name “mammatus” is derived from the Latin mamma (breast), due to the resemblance between the shape of these clouds and human female breasts. (Cloud pareidolia, eh? :-) )

    Here are some more examples:

    * Spectacular Mammatus Clouds over Hastings, Nebraska;

    * Mammatus Clouds Over Mexico.

  15. @Phil– As you probably know, the National Center for Atmospheric Research is here and Boulder, and we host an amazing Digital Image Library ( that contains hundreds of amazing images of atmospheric phenomena gathered by our staff and scientists over the past 49 years.

  16. Phil,

    Do different regions of the country have significantly different cloud formations depending on the local weather, atmospheric conditions, etc.? I’ve lived in a few different states and I’ve noticed substantial differences in the type of cloudcover. I always left open the possibility that it was my imagination, but I think Oregon clouds look different than Wisconsin clouds, which look different from New Mexico clouds. (Altitude plays a role in this too, I’m sure.)

  17. IVAN3MAN

    Here’s some more weird clouds: Lenticular Clouds Gallery

  18. Here in Edmonton, Alberta, I had the priviledge of seeing noctilucent clouds first hand. It was in the middle of the night (around 1 or 2am), smack in the middle of summer (when it never actually gets completely dark around here), and at first I thought I was seeing the northern lights, except the colour was all wrong (pale light blue), and they were far too stable. Truly beautiful and unearthly.

  19. @ justcorbly:

    I don’t believe mamma clouds rotate, other than the usual movement you’d get from what is essentially an upside down (and reversed…as it’s cold air) convection bubble. The really dramatic formations don’t feature big huge “boobs”, but rather a whole sky filled with modest, handy-sized mammaries. They can change shape, growing and shrinking, rather quickly. That, combined with the overall movement of the storm itself might have caused the effect you remember. Or not.

  20. MadScientist

    I like irridescent clouds – they’re awesome. :) I’ve only noticed 1 so far though. I have a few friends (including some crazies that go to Antarctica) who get to see polar stratospheric clouds – go check out photos of them.

    Arizona also has gorgeous clouds/colored sunsets.

    Don’t you envy the English? They get to see clouds most days of the year.

  21. Martin Watts

    The cloud Appreciation Society is at (for a nice lenticular). I love lenticular clouds. Never seen a decent one here in the UK but they were magnificent up in the highlands of Iceland. I believe APOD has also also feqatured some – from over Mount Hood if I remember correctly.

  22. Charles Boyer

    If you like that sort of stuff, has galleries of all kinds of strange clouds. Check it out sometime.

  23. Todd W.


    After seeing some of those pics of lenticular clouds, I can see how they might be mistaken for flying saucers.

  24. IVAN3MAN

    @ Todd W.

    Indeed, Todd! I remember seeing such photographs of lenticular clouds in a school library book (I forgot the title), back in the 1970s, debunking UFOs.

    P.S. Before some grammar-Nazi points it out to me, I should have written in my previous post: Here are some more weird clouds:…; not “Here’s some more weird clouds:…”

    Man, when are we gonna get a preview/edit facility here? It’s getting to be like waiting for the “Second Coming”!

  25. justcorbly

    … a whole sky filled with modest, handy-sized mammaries.

    That’s in accord with what I recall, Kuhnigget. I’ve been near several other tornado-producing storms, but this was the only time I was effectively directly under one. None of the others looked anything like this. The Xenia tornado was, I believe, the largest storm produced during the large tornado breakout of 3-4 April in 1974.

  26. Chris

    The roll cloud looks like a Morning Glory. They form in the Gulf of Carpentaria in northern Australia and glider pilots love them.

    The one labeled shelf cloud looks to me more like a mesocyclone, a rotating wall cloud beneath a supercell that sometimes drops a tornado. Check out this amazing time-lapse video of one!

  27. Great clips, Chris! One of these days I want to go on a stormchaser trip. Maybe when a mesocyclone drops a safe full of loot in my backyard.

    As to the comment (way) above regarding different clouds in different parts of the country, that to me me is one of the joys of travel. Here in Southern California we have the most boring skies imaginable, cloudwise, that is. This time of year we get the occasional poofy blobs, but for 9-10 months it’s either blue-grey vault o’ heaven or grey-brown vault o’ fog.

    Although yesterday there were some spiffy stratus clouds racing across the sky. Of course, those were caused by space aliens from another dimension. (Seriously, according to the woo-woos.)

  28. In my astrophotos album I made room for nice atmospheric phenomena. I also love strange clouds. See this fantastic arrangement of lenticulars from my balcony (descriptions in Spanish…):


  29. Nice shots, Guillermo!

  30. Levi in NY

    If you click “next” on that page, you’ll see some pretty cool tree pareidolia. The last tree on that page resembles the Virgin Mary more than any window stain or sandwich I’ve ever seen.


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