November 2016

Cloud of the Month - November 2016

November 2016

A Mystery in the Clouds

Earlier this month, a peculiar ring appeared in the clouds over Warwickshire, England. James Tromans, who photographed the formation, asked what might have caused it. Clearly, this was time for some cloud detective work.

The ring was actually more of a curve, or a ‘U’, as there was no other half to it. It appeared to consist of regular lumps, or lobes, hanging down from the underside of a cloud layer. We wondered if this layer was an Altostratus, but off in the distance to the right of the image there appeared to be showers, like those produced by a storm cloud. This suggested that the cloud layer might in fact have been part of the huge canopy that spreads out at the top of a Cumulonimbus storm cloud.

Sometimes, to the rear of a storm, lobes of cloud known as mamma can be seen hanging from the underside of the canopy (see image 1). There certainly was a general appearance of mamma in the cloud layer. But could some of these mamma cloud lobes have arranged themselves into this strange, regular curved formation? It seemed unlikely.

There was something decidedly unnatural about the cloud’s appearance – as if it were man-made. Then it occurred to us that the photograph was looking towards Coventry Airport. Might this cloud effect have been in some way caused by an aircraft?

1. Could ‘mamma’ be involved? Spotted over Wilton, Wiltshire, UK, by William Saberton,
1. Could ‘mamma’ be involved? Spotted over Wilton, Wiltshire, UK, by William Saberton,

As planes fly through clouds made of ‘supercooled’ water droplets, they can encourage these extremely cold droplets to freeze and fall below, leaving behind a gap, known  as a dissipation trail, or ‘distrail’. Such formations are often seen in straight lines where planes ascend or descend through the cloud. But they can also appear in circular shapes when one is flying in a holding pattern as it waits to land (see image 2). James’s cloud wasn’t quite a distrail, but we felt we were getting close.

It was then that we recognised the regular spacing of the lobes. These sometimes appear below aircraft condensation trails (see image 3). They are caused by the interaction between the two swirling vortices produced by the wings. As these rotate in opposite directions in the wake of an aircraft, the two turbulent flows interact and combine to form a periodic pattern of turbulent downdrafts. In the right conditions, they appear as lobes hanging below the condensation trail.

2. Or was it to do with an aircraft ‘distrail’, like this spotted over Newcastle, Australia, by Jillian De Martin (Member 12801)?
2. Or was it to do with an aircraft ‘distrail’, like this spotted over Newcastle, Australia, by Jillian De Martin (Member 12801)?
3. The clue was in the turbulence lobes that can appear hanging from an aircraft contrail. You can see these in this strip of contrail spotted over the Smokey Mountains, US, by Gary Smith.
3. The clue was in the turbulence lobes that can appear hanging from an aircraft contrail. You can see these in this strip of contrail spotted over the Smokey Mountains, US, by Gary Smith.

This explained the formation. It was caused by an aircraft, which happened to be flying just above the base of the cloud layer as it turned in a holding patternabove the nearby airport. The plane’s condensation trail was hidden within the cloud layer, but the lobes of cloud descending below it, caused by the turbulence from its wings, appeared extending below the layer.

Phew! With that cleared up, we could finally relax once more.

Turbulence lobes beneath the contrail of an aircraft in holding pattern over Hampton Lucy, Warwickshire, UK, by James Tromans.

A Response from our Poet in Residence

kt-thumbnailKatharine Towers, poet in residence at the Cloud Appreciation Society, has written the third of her Cloud Studies inspired by our Clouds of the Month. Here is her commentary on it:

It was quite a challenge to write a poem about a condensation trail! I was keen to avoid getting involved with the technicalities of ice droplets and downdrafts, as such poems can easily be side-tracked into just showcasing unusual vocabulary.

What eventually seemed interesting was the idea that we can’t help trying to interpret natural phenomena – or seeing things we don’t understand in terms of things we can describe. The use of the word ‘U-turn’ in connection with the unusual circular contrail gave me a way into the poem.

Cloud Study III

Contrail

A long-drawn breath that won’t last
or an after-thought spelled out
in ice and heat and fall-streaks

or that hush that follows pain;
what’s left when everything has been said.

Hard to believe they mean nothing –
yes, even this one
shaped like a change of heart.

© Katharine Towers, September 2016

21 Comments
  • Hans

    November 11, 2016 at 8:56 am

    Congratulations James and detectives. Mystery solved. Great picture and great explanation. I now know the origin of the lobes you can often see under contrails.

  • Laurence Green

    November 11, 2016 at 5:19 pm

    Detective “Dick Barton” – Special Agent – has certainly been working overtime solving this intriguing mystery.

    Well done. I am sure other CAS members will be fascinated by the information provided.

    Glad to see it was chosen as “Cloud Of The Month”. So it should rightly be deemed thus.

    Laurence

  • Laurence Green

    November 11, 2016 at 6:29 pm

    I think the answer lies in the silhouette of the “aircraft” – it is a helicopter. The stubby sponsors on the craft are not the large slender wings as evinced on a passenger etc aircraft. Maybe if it were hovering over the same spot for some time the powerful downdraft of the helicopter’s rotor blades may have caused this peculiar cloud formation to occur.

    Laurence

  • Michael

    November 12, 2016 at 2:15 pm

    Fascinating! I will post in the forum a recent photo of an unaware recording of such an occurrence . I wonder, Boeing has developed and installed a new wing tip ” wing” that is supposed to get a bit more fuel efficiency for the aircraft. Are these vortexes produced by the new wing tip or are they a sign of the unimproved ?

  • Gavin Pretor-Pinney

    November 12, 2016 at 6:45 pm

    Laurence, do you mean that little black shape near the top, to the left of centre? I’m pretty sure it’s a crow!
    Michael, that’s a great follow-up with your post in the Forum. As you suggest, it does indeed look just like a crowd watching a bonfire:
    https://cloudappreciationsociety.org/forums/topic/novembers-cloud/

  • Laurence Green

    November 14, 2016 at 5:55 pm

    Hi Gavin

    As an ornithologist I can certainly vouch for the silhouette as definitely not being a crow. The “wings”, in relation to the elongated heavy body, are far too short. The silhouette, given its size in relation to the cloud and ground ,would translate to a really huge, huge bird of Condor size.

    Crows have large “flappy” wings and short bodies. They are big heavy birds (highly intelligent at that) so they maximise their precious energy when flying by proceeding dead straight with no wavering on their onward path. That is why the old English saying comes about:- “To fly straight as a crow”. Also, crows do not fly that high up – to do so would serve no purpose and cost them dearly for energy spent. They are not a bird of prey, they are carrion feeders and that means easy food pickings, especially where human beings are about and discarding easy-to-get food etc.

    I am an aviation enthusiast of some 5o years plus. I know aircraft and helicopters like the back of my hand. This is definitely a helicopter. The silhouette is really high up in the sky. At that height, as said, the “crow” or any other bird would be of huge size.

    Fascinating the correspondence this marvellous photo has provoked. Love it!

    Laurence

  • Dick

    November 15, 2016 at 11:33 am

    Is James Tromans in the forum? I’d like to know if he saw a helicopter or a bird. I think it’s a corvid, perhaps a rook or a crow, and it has three companions in the background, unless James’ lens was mucky. :)
    Superb photo, definitely worthy of being Photo of the Month.

  • Laurence Green

    November 15, 2016 at 6:02 pm

    The two birds in the lower part of the picture are minute compared to the big heavy “object” way, way above which would be even smaller given the vast height difference. Two birds cannot generate themselves generate enough energy to work onto the cloud, either from above or from below.

    Laurence

  • Christine von Allwoerden

    November 15, 2016 at 7:47 pm

    Most fascinating pic and explanation by Gavin and others. Not sure if I can make out a helicopter..

  • Elizabeth Berlangieri

    November 16, 2016 at 7:12 am

    Well if it’s not a bird or a plane…maybe it’s Superman?

  • Laurence Green

    November 16, 2016 at 5:44 pm

    Most helicopters have a tell-tale”tadpole” shape to them. The object in the topmost part of the photo has all the hallmarks of a “tadpole” shape.

    Fascinating the way this intriguing photo has provoked welcome discussion. Keep it coming.

    As an aside, I think maybe the famous Belgian detective, Hercules Poirot, (author – Agatha Christie) might be called in to investigate further. Hmmm….!

    Laurence

  • Photo Editor

    November 17, 2016 at 4:37 pm

    Have added an image to Mikes forum post, may solve another mystery…IanL..

  • Laurence Green

    November 23, 2016 at 5:31 pm

    “Fait accompli”

    Laurence

  • Mary J

    November 24, 2016 at 3:04 am

    Now that you all have the formation of the clouds and birds sorted out, let’s hear it for a very fine poem by Katherine – kudos to you, dear! Nicely phrased! 👏🏼

  • Nigel Cook

    November 24, 2016 at 4:19 am

    I thought the new wingtips on modern aircraft reduced this turbulance, aka as in bird flight where is was taken from.

  • Nicholas Ireland

    November 24, 2016 at 9:08 am

    Writing as a pilot I can confirm that the “Winglets” fitted to many modern aircraft are designed to reduce wingtip vortices and thus reduce drag and improve fuel efficiency. However, aircraft flying at that height do not generate condensation trails and a holding pattern is flown a a racetrack pattern with two parallel straight legs of one minute duration and two 180 degree turns, also each timed to take one minute, giving a for minute pattern

  • Mr Peter Roper

    November 24, 2016 at 11:06 am

    In my humble opinion the three smaller “objects’ are nothing more than specks of dirt/dust on the camera sensor. The larger black object is certainly a bird flying at no more than 150ft. unless James’s camera is very dirty!

  • Peter Evans

    November 24, 2016 at 1:31 pm

    The cloud and it’s detection is fascinating but well done to Katherine for a super poem!

  • Anne Stevenson

    November 24, 2016 at 4:49 pm

    I didn’t realize we have a Poet in Residence!

    And what a lovely poem, thank you, Katherine.

  • Gavin Pretor-Pinney

    November 24, 2016 at 10:08 pm

    Yes, Anne.
    Katharine has been our new poet in residence for a few months now. She has been writing wonderful poems, which we plan to publish at the end of the year of her residency. You can see her two previous poems for the recent Cloud of the Months here:
    https://cloudappreciationsociety.org/october-2016/
    https://cloudappreciationsociety.org/september-2016/
    We are very lucky to have her contributing!

  • Alyson

    November 26, 2016 at 7:30 pm

    Great detective work, I really enjoyed the trail. Thanks guys. Alyson

Post a Comment