APOD: A Roll Cloud Over Uruguay (2013 Jun 02)

[APOD Robot]

A Roll Cloud Over Uruguay

Explanation: What kind of cloud is this? A roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud. When this happens uniformly along an extended front, a roll cloud may form. Roll clouds may actually have air circulating along the long horizontal axis of the cloud. A roll cloud is not thought to be able to morph into a tornado. Unlike a similar shelf cloud, a roll cloud, a type of Arcus cloud, is completely detached from their parent cumulonimbus cloud. Pictured above, a roll cloud extends far into the distance in 2009 January above Las Olas Beach in Maldonado, Uruguay.

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[stowaway]

A large asteroid with a moon of it's own just flew past Earth and we are looking at pictures of clouds. Why are our heads in the clouds? I don't get this

[Ann]

Sundays are often repeat days at APOD, so that the editors can get a day off.

If you want to read about the asteroid, check out this thread!

Ann

[ta152h0]

looks fake to me, like a Sunday April fool's gag between the astro guys when the boss is taking a break

[Beluga]

Google Morning glory cloud. Fascinating phenomenon !

[owlice]

looks fake to me, like a Sunday April fool's gag between the astro guys when the boss is taking a break

What looks "fake" to you?

[ta152h0]

looks like a photoshop in my humble opinion and you know , as well as I do, opinions can be incorrect. But I haven't seen in print any immediate denials. I have seen images of " rolling clouds " off wingtips, specially the B757 but nothing this big.

[geckzilla]

It's an unusual cloud formation and not one I've ever personally seen before but it is a known and documented phenomenon and this particular image doesn't bear any of the hallmarks of a typical digital manipulation job. There's no repeating patterns and there's an underlying complexity to the lighting you wouldn't expect a generated image to have. A clever individual could definitely create such an image without these telltale signs but why? There's also that color grain which is common with digital photography. Furthermore, there is EXIF metadata associated with the file. That's a lot of faked details. So many that it'd be easier to simply be in the right place at the right time and snap the photo. Occam's razor, anyone?

Anyway, it's also very impolite to accuse the creator of faking an image without any kind of detailed explanation about why you think it's fake. If you don't have the time to devote to such a claim then don't bother making it.

-Crafter of Mountains from Molehills

[owlice]

Anyway, it's also very impolite to accuse the creator of faking an image without any kind of detailed explanation about why you think it's fake. If you don't have the time to devote to such a claim then don't bother making it.

This, exactly.

Wolf, the universe is much bigger than your tiny experience in it. If you had bothered to google roll clouds before posting, you'd have seen other images of the same phenomenon that are "this big." Heck, if you'd just followed the links in the text, you'd have seen other images, and explanations, too! The links aren't decorative, you know.

[ta152h0]

I did not take long for RJN to retract a posting when evidence came to light an extremely deft poster had reported, supported with a very convincing video, of Betelgueuse exploding. It was a well crafted visual experience. Photographers should always open to scrutiny, even the robotic photographers.

[OzRob]

I have been viewing APOD's for many years and I don't get photos like this one. Sure it is a nice photo but it should be on Meteorological Picture of the Day! As far as I am aware Astronomy is the study of everything outside of the Earth's atmosphere.

[geckzilla]

I did not take long for RJN to retract a posting when evidence came to light an extremely deft poster had reported, supported with a very convincing video, of Betelgueuse exploding. It was a well crafted visual experience. Photographers should always open to scrutiny, even the robotic photographers.

Are you trying to say an APOD was once retracted? I don't think this is the case. I'm not sure what you are talking about.

[alter-ego]

looks like a photoshop in my humble opinion and you know , as well as I do, opinions can be incorrect. But I haven't seen in print any immediate denials. I have seen images of " rolling clouds " off wingtips, specially the B757 but nothing this big.

You should see these things from a hang glider. The 5-minute video is an interview interspersed with some great footage of big roll clouds viewed from above them, and without a fuselage

Click to play embedded YouTube video.

[ta152h0]

I have been schooled, and by experts in the field

[Beyond]

Here ya go, Wolf. A couple of nice cold ones.

[Looking Up]

Saw a roll cloud this week in Robinsonville, Mississippi; it was as long as the sky. It was an amazing sight, but very eerie!

[Cloudgazer]

Not having heard about roll clouds until the APOD crossed my way, I now know that I did have a sighting on 14th of May this year in South Africa, precisely from my garden in the George area/Southern Cape. Being an amateur photographer with a simple digital camera I still believe that the 3 photos I took could be interesting on the subject?

Hi, with a little luck I can share with you these 3 images of the roll cloud I sighted mid-May in South Africa.
The sunset lighting was not conducive to great photos with a small digi cam, the reduction in size to upload even takes more away from them, but anyway: I hope someone enjoys looking at them ...
Cloudgazer

[neufer]

Hi, with a little luck I can share with you these 3 images of the roll cloud I sighted mid-May in South Africa.
The sunset lighting was not conducive to great photos with a small digi cam, the reduction in size to upload even takes more away from them, but anyway: I hope someone enjoys looking at them ...

Very pretty, Cloudgazer. But this seem to be Kelvin–Helmholtz instability due to velocity shear and/or lee waves:

<<The Kelvin–Helmholtz instability (after Lord Kelvin and Hermann von Helmholtz) can occur when there is velocity shear in a single continuous fluid, or where there is a velocity difference across the interface between two fluids. An example is wind blowing over water: The instability manifests in waves on the water surface. More generally, clouds, the ocean, Saturn's bands, Jupiter's Red Spot, and the sun's corona show this instability.>>

<<In meteorology, lee waves are atmospheric standing waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above the Krkonoše. They are periodic changes of atmospheric pressure, temperature and orthometric height in a current of air caused by vertical displacement, for example orographic lift when the wind blows over a mountain or mountain range. They can also be caused by the surface wind blowing over an escarpment or plateau, or even by upper winds deflected over a thermal updraft or cloud street.>>

An arcus cloud is a low, horizontal cloud formation. Roll clouds and shelf clouds are the two types of arcus clouds. A shelf cloud is usually associated with the leading edge of thunderstorm outflow; roll clouds are usually formed by outflows of cold air from sea breezes or cold fronts in the absence of thunderstorms.

A roll cloud is a low, horizontal, tube-shaped, and relatively rare type of arcus cloud. They differ from shelf clouds by being completely detached from other cloud features. Roll clouds usually appear to be "rolling" about a horizontal axis.

They are a solitary wave called a soliton, which is a wave that has a single crest and moves without changing speed or shape. One of the most famous frequent occurrences is the Morning Glory cloud in Queensland, Australia. One of the main causes of the Morning Glory cloud is the mesoscale circulation associated with sea breezes that develop over the Cape York Peninsula and the Gulf of Carpentaria. However, similar features can be created by downdrafts from thunderstorms and are not exclusively associated with coastal regions.

Coastal roll clouds have been seen over California, the English Channel, Shetland Islands, Lithuania, Eastern Russia, other maritime regions of Australia, off the Mexican coast in the Sea of Cortez, Uruguay, in the Canadian provinces of Nova Scotia and Ontario, and Campos dos Goytacazes and Coronel Vivida bay in Brazil.>>

[Cloudgazer]

Thanks a lot, Neufer, for clarifying - just when I thought I had caught something really rare and spectacular.
Just tell me how frequent these Kelvin-Helmholtzes are and whether I am likely to see some of these again. This was the very first time and I've been cloud-gazing for many years ...
Cloudgazer

[neufer]

Thanks a lot, Neufer, for clarifying - just when I thought I had caught something really rare and spectacular.
Just tell me how frequent these Kelvin-Helmholtzes are and whether I am likely to see some of these again. This was the very first time and I've been cloud-gazing for many years ...

Those as pretty as your red ones could be fairly rare.

Why not continue cloud-gazing and see if you can answer to question for us.

[Cloudgazer]

Hi! Of course I'll continue pursuing my obsession with clouds ... meanwhile found a few interesting articles on the K-Hs now that my interest is roused. Don't quite get your comment re 'answer to question'.

[neufer]

Hi! Of course I'll continue pursuing my obsession with clouds ... meanwhile found a few interesting articles on the K-Hs now that my interest is roused. Don't quite get your comment re 'answer to question'.

Start to get concerned when you actually DO get my comments.

Until then, keep your eye out for foosball shaped clouds.

[geckzilla]

I think "to" was supposed to be "the" in that last sentence. Too bad you can't get paid for confusing people, Art. (Or can you?)

[Beyond]

Start to get concerned when you actually DO get my comments.

What? Me worry get concerned? Nah! Even IF i should be able to digest some of the indigestible... I'm beyond it all. Muhahahahahaha(burp)hahahahahaha.

[bystander]

For sake of brevity and getting this thread back on track, many Cloudgazer and
associated posts have been split and merged with the original Question by a novice.