Cheers,

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.)

http://en.wikipedia.org/wiki/Morning_Glory_cloud

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!

http://www.youtube.com/watch?v=zPyfSd5LEKs

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.

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”!

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

Arizona also has gorgeous clouds/colored sunsets.

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

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.

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.)

Here are some more examples:

* Spectacular Mammatus Clouds over Hastings, Nebraska;

* Mammatus Clouds Over Mexico.

@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.

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!)

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.

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.

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.

Here’s a very good example: http://www.targetarea.net/2008/apr708sup3d.jpg