Help identify unusual circular cloud type over Italy

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RJN
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Help identify unusual circular cloud type over Italy

Post by RJN » Fri Jul 01, 2011 5:46 pm

Can you help identify this cloud type? Obviously it is the circular cloud about the mountain I am referring to. Here is some background from an email send in to APOD:
mountaincloud_cossard_2816.jpg
...strange clouds on Becca di Viou (Aosta Valley, Italy)

The picture was taken today, the 1st of July 2011, in Aosta, at 11:50 a.m.
(local). If you need, I have got a few number of pictures in which you can observe the
cloud motion.
This is another candidate for APOD / Asterisk "Citizen Science". I bet alert readers can figure out this cloud type. (It might even be too easy.) Please -- have at it!

- RJN
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horseherb

Re: Help identify unusual circular cloud type over Italy

Post by horseherb » Fri Jul 01, 2011 5:58 pm

Circulonimbus . . or have I invented a new cloud type?
(head in the clouds)

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neufer
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Re: Help identify unusual circular cloud type over Italy

Post by neufer » Fri Jul 01, 2011 6:08 pm

A lenticular cloud whose center has precipitated out :?:
http://www.weathervortex.com/lenticular-clouds.htm
http://www.weathervortex.com/sky-holes.htm
http://en.wikipedia.org/wiki/Altocumulus_lenticularis wrote: <<Lenticular clouds (Altocumulus lenticularis) are stationary lens-shaped clouds that form at high altitudes, normally aligned perpendicular to the wind direction. Due to their shape, they are often mistaken for Unidentified Flying Objects (UFOs).

Where stable moist air flows over a mountain or a range of mountains, a series of large-scale standing waves may form on the downwind side. If the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds. As the moist air moves back down into the trough of the wave, the cloud may evaporate back into vapor. Under certain conditions, long strings of lenticular clouds can form near the crest of each successive wave, creating a formation known as a 'wave cloud.' The wave systems cause large vertical air movements and so enough water vapor may condense to produce precipitation. The clouds have been mistaken for UFOs (or "visual cover" for UFOs) because these clouds have a characteristic lens appearance and smooth saucer-like shape. Pilots of powered aircraft tend to avoid flying near lenticular clouds because of the turbulence of the rotor systems that accompany them, but glider pilots actively seek them out.>>
http://apod.nasa.gov/apod/ap030430.html
http://apod.nasa.gov/apod/ap050821.html
http://apod.nasa.gov/apod/ap080416.html
http://apod.nasa.gov/apod/ap090121.html
http://apod.nasa.gov/apod/ap090203.html
Last edited by neufer on Fri Jul 01, 2011 8:28 pm, edited 1 time in total.
Art Neuendorffer

fksr

Re: Help identify unusual circular cloud type over Italy

Post by fksr » Fri Jul 01, 2011 6:39 pm

Contrail from a plane making a U-turn?
Possibly a passenger flight that had an emergency (I've been on a flight where some of the hydraulics in the wings failed maybe 20 minutes after takeoff, and the plane did make a U-turn to return to the airport). Maybe a research or military plane?

Randy M

Re: Help identify unusual circular cloud type over Italy

Post by Randy M » Fri Jul 01, 2011 7:03 pm

See the information about cloud types, especially unusual "vortex" clouds at http://www.weathervortex.com/vortex.htm
Given the proximity of the cloud to the mountains, I would not be surprised to find it fit this category.

DosBoot

Re: Help identify unusual circular cloud type over Italy

Post by DosBoot » Fri Jul 01, 2011 7:13 pm

FKSR has my vote. I think it's a aircraft U-turn.
Not necessarily an emergency turn but a scenic turn over the mountains.

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jman
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Re: Help identify unusual circular cloud type over Italy

Post by jman » Fri Jul 01, 2011 7:24 pm

Smoke ring from a ground explosion?

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Chris Peterson
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Re: Help identify unusual circular cloud type over Italy

Post by Chris Peterson » Fri Jul 01, 2011 8:20 pm

I also agree a contrail is very likely. I definitely don't think it is related to a lenticular cloud, because the droplet dynamics are so different (and I've seen thousands of lenticular clouds, but never one with a missing center). I wouldn't expect lenticular clouds over Italy in July, either.
Chris

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owlice
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Re: Help identify unusual circular cloud type over Italy

Post by owlice » Fri Jul 01, 2011 8:34 pm

This may be a type of cloud referred to as a "Dorset doughnut."
A closed mouth gathers no foot.

Wayne
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Re: Help identify unusual circular cloud type over Italy

Post by Wayne » Fri Jul 01, 2011 9:04 pm

It appears to be a slightly distorted contrail from a plane in circular holding pattern.

It's much larger than naturally formed annular clouds and the kicker is that it's far beyond the foreground mountain, but below the cloud deck, and so is quite low but also very large, just what you'd expect from a plane holding at something like FL3000.

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Re: Help identify unusual circular cloud type over Italy

Post by luigi » Fri Jul 01, 2011 10:40 pm

I don't think this is a contrail.
The texture doesn't look like one, looks natural and different at different parts. The curve is too steep to be logical for an airplane, it's more than 180 degrees and the position above the mountains makes little sense to be a holding point for aircrafts.
With the mountains below I'd say it is some kind of natural vortex formation.

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owlice
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Re: Help identify unusual circular cloud type over Italy

Post by owlice » Sat Jul 02, 2011 1:17 am

Here are two additional images of this cloud. These are a larger size than I usually post, and I apologize for that, but even so, I've cut them down a good bit from their original size and feel bad about that, too!

[attachment=1]P6060295.jpg[/attachment]

[attachment=0]P6060297.jpg[/attachment]

The top one was taken before the bottom one; the cloud was expanding.
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A closed mouth gathers no foot.

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neufer
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Re: Help identify unusual circular cloud type over Italy

Post by neufer » Sat Jul 02, 2011 2:12 am

owlice wrote:
The top one was taken before the bottom one; the cloud was expanding.
The cloud is moving left to right.
Why do you say it is expanding?
Art Neuendorffer

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owlice
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Re: Help identify unusual circular cloud type over Italy

Post by owlice » Sat Jul 02, 2011 2:53 am

The wine I had with dinner, perhaps? :oops:
A closed mouth gathers no foot.

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neufer
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Hooked on cirrus

Post by neufer » Sat Jul 02, 2011 11:22 am

http://www.theairlinepilots.com/met/cirrusuncinus.htm wrote: ImageImage
Cirrus Uncinus

Distribution: Worldwide.

Height: Above 16,500 feet.

Cause: Saturation of air mass at upper levels, combined with strong wind immediately below cloud level.

Associated Weather:
May indicate an approaching frontal system.

<<This often spectacular variation of cirrus cloud is also known as hooked cirrus (uncinus is the Latin for hook), or cirrus mares' tails, a reference to the cloud's resemblance to a horse's tail.

Cirrus uncinus forms in much the same way as other cirrus formations. However, its distinctive pattern of filaments is the result of a high-speed wind below the level at which the ice crystals form. As the crystals descend under the influence of gravity, this wind rapidly smears them across the sky, forming the distinctive, elongated, hooked shapes.

Like other cirrus clouds, uncinus is a result of high-level moisture, and is therefore often associated with the approach of a frontal system. Since it is also evidence of a high-speed, high-level wind, it may indicate the presence of a jet stream.

Normally, cirrus uncinus produces no significant weather on the ground, although snow showers may be visible immediately below cloud level. These usually evaporate well before reaching the ground and are therefore classified as virga.

As cirrus uncinus generally indicates the presence of high- speed winds, pilots often associate this cloud with turbulence. In most cases, however, the turbulence would cause little discomfort to pilots or passengers.

Excerpt from The Book " Weather "
Acknowledgement due: John W. Zillman, William J. Burroughs,
Bob Crowder, Ted Robertson, Eleanor Vallier-Talbot and Richard Whitaker.>>
Art Neuendorffer

Dario Seglie, Italy

Re: Help identify unusual circular cloud type over Italy

Post by Dario Seglie, Italy » Sat Jul 02, 2011 4:05 pm

Question to Guido Cossard, Italy:
Dear Guido,
what is the duration of this phenomenon (minutes, hours, etc.) in the Aosta Valley ? and this circular cloud was the first appeared ?
Ciao,
Dario Seglie, Pinerolo, Italy
IFRAO-UNESCO Liaison Officer

Guido Cossard

Re: Help identify unusual circular cloud type over Italy

Post by Guido Cossard » Sun Jul 03, 2011 9:34 am

The duration of the phenomenon was 5 minutes. This appearance is the first documented. I've received a few number of other similar appearance, but I didn't personally check.