Sinusoidal Thin Contrails Explained [Meandering Solitary Hybrid Contrails; the 'Rook' Instability]

Trailspotter

Senior Member.
This is a follow up to the thread https://www.metabunk.org/threads/squiggly-sinusoidal-thin-contrails-over-europe.3194/ that I think merits its own thread.

In the above thread there are seven in total different occurrences of these highly unusual contrails captured on photo or video. I have trawled Google Images, flickr and youtube to find more reported occurrences and raised the total to more than 60 cases spanning over the past 15 years. One example has already made to the Wikipedia article on Contrail (English and Polish versions).

d157fc7863450de25178cae880d1d100._.jpg
Sinuous vapor trail over south-east Poland.

Here is a selection of observed thin contrails (in three galleries):




These numerous examples show that sinusoidal thin contrails are not a freak event but a recurrent albeit rare phenomenon. They are exactly what they look like - solitary hybrid contrails. Hybrid contrails are (parts of) exhaust contrails entrained in the wing tip vortices: http://contrailscience.com/hybrid-contrails-a-new-classification/. Normally, hybrid contrails come in pairs, like the vortices themselves. They are formed in a narrow range of RH and usually observed behind large planes that create stronger wake vortices, e.g., Boeing 747. The lifetime of a hybrid contrail pair is limited by the Crow instability (http://en.wikipedia.org/wiki/Crow_instability) that breaks down a pair of counter rotating vortices. Formation of solitary hybrid contrails apparently occurs in the same range of RH but additionally requires some form of atmospheric turbulence capable of decoupling the vortex pair. Solitary vortices can have a longer lifetime, therefore solitary hybrid contrails can persist, unlike a hybrid contrail pair.

There are instabilities in solitary vortices causing vortex meandering, a phenomenon which has been observed in experimental studies of airfoil tip vortices in wind tunnels.
Screen shot 2014-09-21 at 10.43.13.png

Solitary hybrid contrails display similar behaviour: in the beginning they form fairly straight lines and then transform into meandering shapes of gradually increasing amplitude. This phenomenon yet awaits its researcher, but the underlying causes are likely to be the same or similar to the causes of the Crow instability: an ambient turbulence and self induction of a vortex with itself. Playing on the name of its discoverer, I propose the name for the solitary vortex instability: the 'Rook' instability. Rook is a bird of the corvid family; the juvenile rook is similar to carrion crow, whereas their adults are readily distinguishable.

Alternative explanation of the sinusoidal shape, as suggested in several discussions of individual occurrences of solitary thin contrails, is their perturbation by atmospheric waves. This explanation however can be ruled out by the observations of a sinusoidal thin contrail coexisting with an ordinary exhaust contrail from the same plane which is not perturbed (see the last gallery above).

Below is a published account of one of the observation (from onlinelibrary.wiley.com/doi/10.1256/wea.266.05/pdf)

More pictures of the above contrail are available at this link:

http://www.forteantimes.com/forum/viewtopic.php?t=24312


Below are a few examples of 'newborn' solitary hybrid contrails:

right behind the plane (like in the above description):


at the end of a typical double stranded hybrid contrail:

Full Size: https://www.metabunk.org/data/MetaMirrorCache/39a379cd272be87788ddb6b0248b297e._.jpg

and (taken by some guy from Santa Monica);)

http://contrailscience.com/contrail-of-the-day/

detached from the rest of contrail:

followed by evolution of the detached segment:

Solitary hybrid contrails compared to ordinary hybrid and exhaust contrails of similar ages:
Rook contrail gallery 4.png

Solitary hybrid contrails in 3D

In at least two cases, the solitary hybrid contrails have been observed from different locations and photographed at about the same time. Using these photographs I have reconstructed the contrails' shapes in the form of pseudo stereo images:

thin contrail 6 stereo.png
Rotterdam, February 18, 2013

thin contrail 7(G).png
Göttingen, January 22, 2014


Neither of these two contrails lays in one plane. Both consist of a number of irregular helical turns, the shapes of which resemble a stretched paperclip rather than a coil spring. Viewed at some angles, such irregular helical shapes may look very different from a sine curve, like, for example:


and


Appeal to the readers:

A solitary hybrid contrail is a very rare phenomenon. Therefore, if you happen to see one, please observe it thoroughly. Please note the time and place of observation and report it here asap. This would help the identification of atmospheric conditions as well as the types of planes and would facilitate further research of this phenomenon.
 
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Trailspotter

Senior Member.
Appendix 1.
Distribution of known occurrences of solitary hybrid contrails by country.

*
occurrences from the previous thread https://www.metabunk.org/threads/squiggly-sinusoidal-thin-contrails-over-europe.3194/

EDIT: I did not intend to embed the youtube links, it happened automatically.


UK (10):


*London Heathrow, September 1, 2001

https://www.flickr.com/photos/brew/64779243/
https://www.flickr.com/photos/brew/64779248
http://www.forteantimes.com/forum/viewtopic.php?t=24312
http://img.photobucket.com/albums/v212/phoenixinferno/DSC00052.jpg
http://img.photobucket.com/albums/v212/phoenixinferno/DSC00053.jpg
http://img.photobucket.com/albums/v212/phoenixinferno/DSC00054.jpg
*Berkshire (Reading and London Heathrow), November 19, 2005

https://www.flickr.com/photos/davidrvetter/2246916624/
Wales, February 6, 2008

https://www.flickr.com/photos/jalpics/2261910142/
Scotland, February 13, 2008

Kent, March 7, 2008

https://www.flickr.com/photos/f3liney/5542862082
Norfolk, March 19, 2011

https://www.flickr.com/photos/smr61/6431807915
Oxford, November 30, 2011

Cheshire, November 6, 2012

https://www.flickr.com/photos/moggers/8490499048
Wiltshire, February 19, 2013

http://www.dailystar.co.uk/news/latest-news/379425/Was-this-pilot-DRUNK-Plane-bemuses-onlookers-with-crazy-vapour-trail
Cornwall, May 15, 2014

Netherlands (8)

http://epod.usra.edu/blog/2007/04/contrail-votices.html
http://i57.photobucket.com/albums/g207/Jurgen01/clouds/Image5.jpg
December 18, 2006

February 9, 2008

https://www.flickr.com/photos/compumess/4000525593
https://www.flickr.com/photos/compumess/4001290332
October 9, 2009

https://www.flickr.com/photos/pupparado/5642272619/
https://www.flickr.com/photos/pupparado/5642272671/
March 22, 2011

https://www.nufoto.nl/fotos/329227/condenssporen-boven-den-haag.html
https://www.flickr.com/photos/redratz/8487855262/ (34 MP)
http://www.ufomeldpunt.nl/melding/2201-sporen-in-de-lucht
http://i.imgur.com/eP1gRCM.jpg
*February 18, 2013

http://www.ufomeldpunt.nl/melding/2313-vliegtuigspoor-met-daarachter-witte-lijnen-letters
*March 4, 2013

https://www.flickr.com/photos/johandecocq/8652390875
April 15, 2013

https://www.metabunk.org/threads/squiggly-sinusoidal-thin-contrails-over-europe.3194/ #1
*January 12, 2014

Germany (8)

https://www.flickr.com/photos/offshore/117381786
Berlin, March 24, 2006

https://www.flickr.com/photos/entity999/484492409
Göttingen, October 2006

https://www.flickr.com/photos/reneroman75/2168752468
Braunschweig, Germany, January 5, 2008 (?)

https://www.flickr.com/photos/fabianfranke-fotos/5435702363
February 11, 2011

https://www.flickr.com/photos/62915046@N03/6217821455
Bavaria, October 5, 2011

http://wetter.fkg-goettingen.de/Diverses/Wellenspur/Wellenspur/Wellenspur.html
Göttingen, January 12, 2014

http://www.goettinger-tageblatt.de/Nachrichten/Goettingen/Uebersicht/UFO-oder-Drohne-Kondensstreifen-westlich-von-Goettingen-gibt-Raetsel-auf
http://zeit-zum-aufwachen.blogspot.co.uk/2014/01/kondensstreifen-westlich-von-gottingen.html
Göttingen, January 22, 2014

http://web.pregocms.de/geo-rg/page.php?p=16645&n=16645
Place and time unknown

USA (6)

http://www.rense.com/general/chemsnake.htm
California, May 12, 2000

https://www.flickr.com/photos/michael_walters/2099378541
Iowa, December 7, 2002

http://geekswithblogs.net/jjulian/archive/2007/12/17/117790.aspx
*Kansas, December 17, 2007

https://www.flickr.com/photos/58709123@N05/5495956552
Pennsylvania, March 3, 2011

Montana, January 5, 2013

https://www.flickr.com/photos/timloco/8659954201
Utah, April 14, 2013

Poland (4)

http://projectavalon.net/forum4/showthread.php?45677-interesting-contrail
*April 21, 2009

http://lotnictwo.net.pl/3-tematy_ogolne/14-samoloty_na_wysokosciach_przelotowych/1927-smugi_kondensacyjne-15.html
August 19, 2009

http://upload.wikimedia.org/wikipedia/commons/0/00/Sinuous_vapour_trail_over_south-east_Poland.JPG
March 2, 2011

http://wszechocean.blogspot.co.uk/2014/03/meteor-samolot-czy-ufo.html
March 21, 2014

Czech Republic (4)

http://forum.pegase.tv/viewtopic.php?t=3447
December 14, 2006

http://www.ceskatelevize.cz/porady/10315081586-turbulence/211411058140046/
November 21(?), 2011

http://ditaf.rajce.idnes.cz/bizardni_kondenzacni_stopa
February 16, 2012

http://ditaf.rajce.idnes.cz/Bizardni_kondenzacni_stopa_II./
April 14, 2012

Belgium (3)

http://weerfoto.buienradar.nl/s/tr/c4/38508.html
http://weerfoto.buienradar.nl/p/2011/05/38508.jpg
May 24, 2011

http://spaceweathergallery.com/indiv_upload.php?upload_id=97888
May 31, 2014 (observation of two thin trails with a 30 min interval)

Sweden (3)

https://www.flickr.com/photos/cobrakarin/4348900871
Lund, February 11, 2010

https://www.flickr.com/photos/x-finity/6931622585
Stockholm, April 25, 2011

http://www.alltomvetenskap.se/nyheter/vita-linjer-i-skyn-kan-paverka-vader-och-klimat
Place and date unknown

France (2)

https://www.flickr.com/photos/76384935@N00/5512827055
https://www.flickr.com/photos/76384935@N00/7217702770/
Rhone-Alpes, March 1, 2011

https://www.flickr.com/photos/ti-toulousain/6796239704
Toulouse Blagnac Airport, February 29, 2012

Russia (2)

http://www.starlab.ru/showthread.php?t=4072
http://www.starlab.ru/attachment.php?s=4f2ecf0e7b3f90426efbded863233458&attachmentid=466&d=1116257631
Tatarstan, May 15, 2005

St Petersburg, October 6, 2010

Denmark (1)

http://vejret.tv2.dk/artikel/id-44971611:sjovt-fænomen-er-piloten-forvirret.html
October 23, 2011

Finland (1)

https://www.flickr.com/photos/dration/6172835446
September 5, 2011

Bulgaria (1)

https://www.metabunk.org/threads/squiggly-sinusoidal-thin-contrails-over-europe.3194/ #27
*March 18, 2010

Romania (1)

June 6, 2009

Hungary (1)

https://www.flickr.com/photos/zsuzsmo/8222798651
November 20, 2012

Canada (1)

https://www.flickr.com/photos/terrio/3383550809
Ottawa, March 24, 2009

Japan (1)

http://4travel.jp/travelogue/10745794
http://4travel.jp/photo?trvlgphoto=27973197
January 28, 2013

Australia (1)

https://www.flickr.com/photos/phunnyfotos/6065505622
Victoria, August 20, 2011

Unlocated (3)

https://www.flickr.com/photos/ltce/3393262710/
European airspace, March 28, 2009

https://www.flickr.com/photos/pervspics/3471941700/
in the air, April 21 2009

http://i.imgur.com/zeoIw.jpg
unknown location, at least two years ago



The leading position of UK is likely due to a bias of my searches toward English compared to other languages that I've searched with. However, the European dominance over the rest of the world is significant. The reasons for this is yet unknown. It could be due to an increased occurrence of clear air turbulence that correlates with the position of jet stream and/or a higher density of large aircraft routes over central Europe.
 
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Mick West

Administrator
Staff member
Excellent work!

This seems like a very good explanation for all the observed squiggly contrails. Particularly compelling is this image:


Which shows a trail almost exactly like those observed, and the entire evolution from plane to squiggle.

Not quite as good is the photo I took on dec 21, Santa Monica, looking west from Santa Monica. I dug up the original for a higher resolution image taken 4:13:22 (camera time)


and the two planes in a wider context at 4:12:31, 51 seconds earlier
 

Mick West

Administrator
Staff member
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WeedWhacker

Senior Member
so did the vortices do this to the clouds? or is that something else?
I think it's a combination of factors....but you're on the right track.....

The "sinusoidal" element that causes "some" persistent contrails to develop in that visible way is likely due to atmospheric processes....partly as a result of the way the airplane can affect the air "currents" as it passes (**)....and also how the existing atmospheric forces, PRIOR to when the airplane entered, are going to interact.

(**) The wingtip vortices, that are produced....for example....

The airplane can be a "trigger" in this interpretation. Of course, "Mother Nature" uses other "triggers", long before airplanes were invented by Humans.

Also....since clear air is (virtually) transparent to Human eyes. When clouds form it tends to "draw attention". But the currents....whether horizontal, vertical or a combination? Of "clear" air are invisible...we only see the effects of such currents ON the clouds, which are "visible"...this includes contrails, of course.
 

skephu

Senior Member.
So is it in reality more helical rather than sinusoidal? Sinusoidal imples that the contrail lies in a plane.
 

Mick West

Administrator
Staff member
So is it in reality more helical rather than sinusoidal? Sinusoidal imples that the contrail lies in a plane.
A helix is sinusoidal, just in three dimensions. The point is more that it's a 3D squiggle, not a 2D squiggle.
 

skephu

Senior Member.
A helix is sinusoidal, just in three dimensions. The point is more that it's a 3D squiggle, not a 2D squiggle.
A helix is not sinusoidal. The projection of a helix may be sinusoidal. The word sinusoidal imples a 2D curve lying in a plane.
The point of my question was whether this contrail lies in a plane or is a 3D helix.
 

Trailspotter

Senior Member.
So is it in reality more helical rather than sinusoidal? Sinusoidal imples that the contrail lies in a plane.
In reality, or more accurately, in my 3D reconstructions, the helical turns are rather flat. A good approximation of the contrail shape is a wire loosely wrapped around school ruler:P1210506.JPG

viewed from a flat side it is sinusoidal.
 

Mick West

Administrator
Staff member
A helix is not sinusoidal. The projection of a helix may be sinusoidal. The word sinusoidal imples a 2D curve lying in a plane.
The point of my question was whether this contrail lies in a plane or is a 3D helix.
Getting into semantics here.
http://www.merriam-webster.com/dictionary/sinusoidal
So a helix is definitely sinusoidal by the dictionary. People's personal usage of the word might vary.

But I think I answered your questions with:
The point is more that it's a 3D squiggle, not a 2D squiggle.
However looking at all the examples above, they seem (as Trailspotter noted) rather flat. Just not always entirely flat - and this variation can give some trails that look odd from some angles, especially this example:


With that one you have to think how it could be laid out on a flat surface with none of the "loops" actually crossing. Then perspective and some vertical displacement gives the illusion of loops.
 

skephu

Senior Member.
In reality, or more accurately, in my 3D reconstructions, the helical turns are rather flat. A good approximation of the contrail shape is a wire loosely wrapped around school ruler:
viewed from a flat side it is sinusoidal.
What makes it flat?
I also wonder what determines the direction of the flat side. Is it usually vertical, horizontal, or random direction?

BTW does anyone know a meaningful explanation of the Crow instability? The Wikipedia description is obscure to me.
 

Mick West

Administrator
Staff member
BTW does anyone know a meaningful explanation of the Crow instability? The Wikipedia description is obscure to me.
The simplest explanation is that two parallel vortices that rotate in opposite directions in a fluid are inherently unstable, and will interact with each other - magnifying existing irregularities in each other.

All planes have these two wake vortices, regardless of if you can see them. So they all have these squiggles in the air behind them. You just only see them when a hybrid contrail forms in them.
 

Trailspotter

Senior Member.
What makes it flat?
I also wonder what determines the direction of the flat side. Is it usually vertical, horizontal, or random direction?
This is a good question, to which I know no answer. Finding it would require more observational data and a professional research. You can get some idea about these from the Crow's original article (a free copy of which is available at http://flair.monash.edu.au/seminars/2007/Crow_1970.pdf).
 

FrankN

New Member
Above The Hague (Netherlands) (very near the royal stables) looking due west on 18-02-2015 around 16:00
There was a contrail like the ones in this forum. Very sharp, and curvy. It reminded me of a rocked fail.
I did not take a picture and the trail disappeared quickly in about 10 minutes after I had first seen it the trail was almost gone. Looking at google maps I figure this contrail must have been above sea near Hoek van Holland
Hope this helps.
 

Mick West

Administrator
Staff member
Above The Hague (Netherlands) (very near the royal stables) looking due west on 18-02-2015 around 16:00
There was a contrail like the ones in this forum. Very sharp, and curvy. It reminded me of a rocked fail.
I did not take a picture and the trail disappeared quickly in about 10 minutes after I had first seen it the trail was almost gone. Looking at google maps I figure this contrail must have been above sea near Hoek van Holland
Hope this helps.
Also spotted by Willem, who emailed me this, with pics
CET is UTC+1, so 16:00 CET is 15:00 UTC
Location is 52.0094494,4.3354893

photo (13).JPG photo (16).JPG photo (15).JPG photo (12).JPG photo (14).JPG
 
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Trailspotter

Senior Member.
Thanks to @FrankN and Wilem for this observation. I will look into it this weekend, after I return home from traveling. I've checked FR24, there were a few planes above the area at the time. My favourite candidate is SIA308 Airbus A380 that flew over it ten minutes earlier, at about 14:50 UTC.
 
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Mick West

Administrator
Staff member
My favourite candidate is SIA308 Airbus A380 that flew over it ten minutes earlier, at about 14:50 UTC.
That certainly matches Willem's viewpoint in the park (note I copied the wrong coordinates, which should have been 52.0094494,4.3354893, just a few hundred feet away though), and is looking towards the Hook of Holland, as @FrankN reported.
 

Attachments

Mick West

Administrator
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Of possible interest, the plane had just started to descend at that point and going from 40,000 ft through 30,000 feet as it approached the horizon


The trail in the photos though would likely only be a portion of this, as it seems to be nearly overhead down to the tops of the trees, still at a fairly high angle.
 

Mick West

Administrator
Staff member
Another photo has emerged from the same day, but nearly two hours later.

Ghent-squiggly contrail-IMG_20150218_174800.jpg
Photo: Tim BAETENS, (c) CAELESTIA/Belgisch UFO-meldpunt



In this case, the location and direction can be more accurately determined, as around 51° 2'28.14"N, 3°43'36.20"E, about at the intersection of Kantienberg and Kramersplein, taken from inside a car.

A likely candidate is RBA98, a 787 from London to Dubai (kml attached)


In this case it was climbing out of London, not descending towards it, but would still have been at around 34,000 feet over the coast, and then 35000 when overhead. The apparent angle above the building puts it between the coast and Bruges. So would have been quite visible in this region:


The drift of the trail from the radar track matches the wind direction from the earth.nullschool.net images above.
 

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Trailspotter

Senior Member.
I found a series of photos by A380spotter depicting an interesting case of contrail evolution. Two Cargolux B747s, LX-VCA and LX-SCV, crossed their paths over Heathrow on April 6, 2015 at about 16:00 BST (15:00 UTC):
Each plane left a pair of hybrid contrails:
However, the evolutions of these pairs were different. In one pair the trails dissipated simultaneously through the Crow instability, whereas in the other pair one of the trails dissipated quicker than the other:
Unfortunately, there are no further pictures featuring evolution of the remaining solitary thin trail, that I believe would have got squiggly. Also, unfortunately, I found this series too late to check on FR24 which plane was which and what were their courses, altitudes, etc.
 
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Trailspotter

Senior Member.
I found a series of photos by A380spotter depicting an interesting case of contrail evolution. Two Cargolux B747s, LX-VCA and LX-SCV, crossed their paths over Heathrow on April 6, 2015 at about 16:00 BST (15:00 UTC):
I have found these flights on Planefinder.net. I have never used this server before, and I will have to explore it more, as it allows playback of earlier flights than provided by free version of FR24.
Cargolux cross.png
The solitary hybrid contrail came from CV436 (CLX436) LX-VCA. Interestingly, this plane was higher at 39,000 ft, but appeared to produce a wider gap between its initially two hybrid contrails, than LX-SCV at 37,000 ft.
 

Ian Jacobs

New Member
Very well done! I especially like the first stereo pair. To my eye that shows the trail confined to a plane as a first approximation. If we define the principle displacements to an x,y plane then displacements in the orthogonal z direction amount to 10 % or less if the x,y displacements. I think it may be misleading to describe the path as a helix. Displacements in the z direction seem to me to be a small and possibly somewhat irregular secondary effect.

Thank you for the explanation, which makes complete sense to me. (I had wondered if the thin trails were perhaps the result of wingtip trails only of which I have one example, but your explanation discounts that. I also agree that KH instability in the atmosphere cannot be the mechanism. I have one example of a trail that I think is disturbed by a kH instability and it looks nothing like the tails above.) Those images are not relevant here, but if you would like to examine them for interest I can put them somewhere.

Best regards

Ian
 

Trailspotter

Senior Member.
New photos of solitary hybrid contrails from Germany. The top one appears to be very recent (the last week?)


Dieses Foto unseres Users Ferdinand Kröger, aufgenommen am Donnerstagnachmittag südlich von Reit im Winkl, sorgte für einiges Rätselraten bei Experten und unseren Usern.
© Ferdinand Kröger


Eine Userin hat diese Linien im März in Nordhessen fotografiert.
© Cordula Bernert

Sources:
http://www.chiemgau24.de/chiemgau/a...chiemgau-koennte-dahinterstecken-5887505.html
http://www.chiemgau24.de/chiemgau/a...au-video-zeigt-moegliche-ursache-5890751.html
 
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Trailspotter

Senior Member.
From https://diary4dan.wordpress.com/2015/12/15/crazy-contrail-contortions/
This seems to be a busy path in both directions. By the time it could be one of the three A380 that went along it in easterly direction shortly before 15:00 UTC (16:00 CET). The latest one was UAE16:
Screen Shot 2015-12-15 at 20.15.30.png

The camera actually was facing South West, there the Sun was at the time. Its position can be derived from the convergence point of the shadow lines.
 
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Trailblazer

Moderator
Staff member
This seems to be a busy path in both directions. By the time it could be one of the three A380 that went along it in easterly direction shortly before 15:00 UTC (16:00 CET).
Could the fact that it is a busy path be significant? A380s are big aircraft and must produce a lot of vortex turbulence. Perhaps the timing just happened to be right for the contrail from one aircraft to get caught up in the turbulence from a preceding one?
 

Trailspotter

Senior Member.
I have copied here a part of my recent post in related thread:

More interestingly, this or, possibly, another sinusoidal contrail was captured on a time lapse video:

http://video.ilgazzettino.it/index....il-mistero-delle-strane-scie-nei-cieli-veneti

The video shot in the mountains of Belluno fortuitously captured the evolution of a sinusoidal thin trail. It begins with a typical two-stranded hybrid contrail, then one strand dissipates, followed by the amplification of squiggles in the remaining strand, like in several previous cases:
https://www.metabunk.org/sinusoidal...-hybrid-contrails-the-rook-instability.t4539/

The identification of the flight in the time lapse video seems possible, but finding the exact viewpoint in Google Earth to determine the heading of the plane and timing from the sun position may be tricky. Alternatively, a few potential candidate flights could be used as guides in searching for the camera location and viewing directions. My favourite, based on the relative headings and timings of three other contrails in the video is QTR40 A380:
View attachment 16886
I have found an approximate viewpoint of the above video. Like another recent video by the same author, it probably was "timelapsed with GoPro Hero3 Black", FOV of which is wider than the ground level view in Google Earth. The QTR40 track downloaded from FlightAware and the Sun position at 15:14 UTC give a nearly perfect match to ground landmarks and other features:
Screen Shot 2015-12-29 at 18.46.33.png
QTR40 GE.jpg

Thus this trail indeed was left by a A380 plane flying a level flight at 39,000 ft. The earth.nullschool.net forecast at 250 hPa suggests there was a 30 km/h tailwind at a slightly lower altitude, but the wind direction was changing from westerly to northerly in this general area.

Update:
Using FR24 and FlightAware, I have identified flights for other contrails in the time lapse video, OK725 at 00:00 (corresponds to 14:48 UTC) and AZ404 at 00:17 (15:22 UTC). Thus the time acceleration factor is about 2 minutes of real time per second of the video and the lifetime of the solitary hybrid contrail was about six minutes.

Attached is a KMZ file with the QTR40 track, the camera viewpoint and the location of a local landmark La Vedetta at the top of the mountain on the left.
 

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Trailspotter

Senior Member.
Today, March 25, 2016, I have observed the formation of a solitary hybrid contrail, but, regrettably, it's dissipated without developing a clear sinusoidal shape.

A Cargolux Boeing 747 passed southwest of my location around 12:50 UTC:
IMG_0092.JPG
Screen Shot 2016-03-25 at 12.56.14.png

Initially, it left a typical hybrid contrail, in one segment of which the contrail strands were separated notably wider than usual:
IMG_0096.JPG
One of the strands in this segment dissipated rather quickly, whilst the other strand remained for longer and developed a wavy shape before dissipating itself. However, the wave amplitude (in the direction perpendicular to the line of view) was rather weak:
IMG_0097.JPG
IMG_0099.JPG
IMG_0103.JPG

The elapsed time from the formation of this contrail segment to the dissipation of its last strand was about 5 minutes. The last solitary strand outlived a later (younger) segment of the same hybrid contrail, which dissipated in a 'normal' way (through the Crow instability):
IMG_0100.JPG
 
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Trailspotter

Senior Member.
In flickr, there are recent photos of a new occurrence of a sinusoidal thin trail on March 24, 2016:
Solitary hybrid contrails; the 'Rook' instability by Mila Zinkova, on Flickr

The photographer Mila Zinkova lives in San Francisco. Her name has already been mentioned here in another thread on unusual multiple halos over SF:
https://www.metabunk.org/unusual-mu...-crystals-odd-radius-halos.t7334/#post-176511

We have quite a few members from the SF area. I wonder if any of them seen or heard about more observations of this trail?
 

Trailspotter

Senior Member.
Update on the previous post.

The photographer confirmed the location and time of the photo and added that the camera was facing west, or north west. This gives the most likely culprit being the Korean Air Airbus A-380-800 KAL11 from Seoul to Los Angeles that passed over San Fransisco from northwest at about 20:55 UTC (13:55 PDT):
Screen Shot 2016-04-10 at 09.05.13.png

The plane heading almost perfectly was aligned with the wind direction at 250 hPa, but the wind speed was gradually decreasing along the flight track.
Unfortunately, despite it occurred over a big city (San Francisco), I was not able to find more records of the observation of this sinusoidal thin trail, with the exception of the Patrick Roddie's time lapse video:
Screen Shot 2016-04-10 at 21.59.06.png
As his camera's exact location is known, the sun position in the sky can be used to determine the moment (1:15) corresponding the time of the solitary trail observation (21:00 UTC = 14:00 PDT). The Roddie's camera pointing to the South, i.e., in a perpendicular direction, captured a different segment of the KAL11 trail, that might or might not have evolved a sinusoidal shape. At the highest resolution (1440p60 HD) on a big screen, the western end of the trail does look squiggly, but a wide camera angle does not allow to see fine details.
 

Trailspotter

Senior Member.
I noticed in the comments section that someone had linked it up to a Qantas A380.

According to the comment, the author of this collage has also observed and photographed the trail. I agree with this identification, as the positions of the sun and two nascent trail are consistent with the time on FR24 screenshot, but I'd prefer the time of observation being confirmed independently. Regrettably, the photos in the link are stripped off metadata.
 

Trailspotter

Senior Member.
A new sighting of this rare contrail from Oxfordshire, UK on November 2, 2016 at about 08:42 UTC. Below is a cropped photo, full version of which can be seen on flickr: https://flic.kr/p/NMeANp
Screen Shot 2016-11-10 at 14.01.12.png
The time and location have been verified by the photo's author.

Once again, the most likely culprit was Airbus A380 (UEA206 A6-EDB) that passed over at FL370 about six minutes earlier.
Screen Shot 2016-11-10 at 14.09.01.png
The ordinary contrail the most likely belongs to EasyJet A319 that passed over at the time of the photo along the same track at FL320.
 
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