1. Marin B

    Marin B Active Member

    Did you see this thread? It has the explanation.
  2. Dan Page

    Dan Page Active Member

    Most likely variations in the wind speed at the contrail altitude.
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  3. Trailspotter

    Trailspotter Senior Member

    What a difference 8 minutes made
    Actually, it is not about the time interval but a difference between atmospheric conditions in two locations separated by the distance that a passenger jet flies in this time interval :cool:
    This is a photo of Air Tahiti Airbus 340 (F-OJTN) near Cambridge that I took today at about 11:32 UTC:
    Screen Shot 2016-03-25 at 21.40.10.

    And this is the photo of the same plane taken 8 minutes later, over Grantham:
    [​IMG]F-OJTN Airbus A340-300 by Rich Bamford, on Flickr

    Note how the gap between the engines and contrails shortened between the two locations. As it was a level flight with nearly a constant speed, this difference is likely to be due to a difference in relative humidity at the cruise altitude (higher in the latter location).
    Last edited: Mar 25, 2016
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  4. Marin B

    Marin B Active Member

    Korean Air flight KE18 flew over my house today. And within a minute or two one of the trails started dissipating in an unusual pattern while the other trail persisted. At least I don't recall having seen this particular pattern before. Any explanations?

    KE18. KE18 26Mar16 006.JPG KE18 26Mar16 007.JPG KE18 26Mar16 008.JPG KE18 26Mar16 010.JPG KE18 26Mar16 012.JPG
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  5. Mick West

    Mick West Administrator Staff Member

    It's a hybrid contrail pair, and the the regular contrail. Hybrid contrails are part of the regular contrail that is then altered by the wake vortices, which break up via the crow instability. The different trails have different crystal sizes, plus the vortices are moving so they separate out.




    This video shows the full process
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  6. Trailspotter

    Trailspotter Senior Member

    Transition between aerodynamic and exhaust contrails
    Emirates flight UAE40 Airbus A380-861 A6-EOR on approach to my location initially made an aerodynamic contrail that changed to an ordinary exhaust contrail without interruption. I've caught the moment of transition - just four seconds elapsed between the two following photos:
    It looks like the exhaust contrail was already mixed up with the aerodynamic contrail by the time when I took the first shot :(

    The aircraft was still ascending and the transition happened at the altitude of 25,000 ft or less.
    Screen Shot 2016-03-27 at 15.14.36.

    The aerodynamic contrail segment persisted the longest. It got separated from the rest of the trail and developed a cumulus appearance:

    In the exhaust contrail segment, a pair of hybrid contrails formed (see the above post) that dissipated via the Crow instability nearly simultaneously with the rest of the exhaust contrail:
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  7. Trailblazer

    Trailblazer Moderator Staff Member

    After a couple of largely contrail-free days they're back this morning. Nice shadow and sundog from the train window. Not 100% sure of the flight but I think it was a private Dassault Falcon at FL410.


    And, not the best picture, but this trail started almost right in line with the edge of the cloud. Watching the plane before taking this photo it was definitely above the cloud layer but the contrail is clearly visible through it.

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  8. Trailblazer

    Trailblazer Moderator Staff Member

  9. Brendan

    Brendan New Member

    Looks like a hybrid contrail, just about to break apart. Plane was flying from the East over Berlin on 28 March at 10:23.

    The second shot was taken four seconds later, with the camera pointing a bit lower down.

    The difference in those few seconds can be seen in a comparison of close ups taken from the two Raw files. Zooming in shows where the condensation tubes get narrower and, in a couple of places, burst apart.

    Hy0Div3. Hy4SecDiv3. CompareHy4s1000x800.
    Last edited: Apr 1, 2016
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  10. Marin B

    Marin B Active Member

    Very blue sky for the most part in the San Francisco Bay Area today, but as I stepped outside for lunch I noticed a single, fairly wide trail, which I believe was formed by two jets both at 38,000 feet on the same flight path to Seattle. So apparently pilot #2 isn't very fearful of what's coming out the back of jet #1 ;) It spread and faded pretty quickly, so it's not a very spectacular shot. I saw on FlightRadar24 that both flights made a big bend in their flight paths over Salinas, so if the trails persisted at all over Salinas we might see more reports about it on the chemtrail sites like a few weeks ago.


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  11. Trailblazer

    Trailblazer Moderator Staff Member

    Lots of contrails out to the north and west of my location in Hampshire this morning.


    But looking round to the south at the same time the sky is much clearer:


    And indeed a patch of drier air is moving up from the south (these photos were taken just before 10am UTC)


    In another couple of hours I would expect the trails to largely fade away (my location is marked with the red dot).

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  12. Trailblazer

    Trailblazer Moderator Staff Member

    Follow-up, two hours later and there are just a few persistent trails left in the distance to the NW.

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  13. Spectrar Ghost

    Spectrar Ghost Senior Member


    C-17 landing at O'Hare, I believe on runway 9L. Though I know it's designed for STOL performance, it's still impressive that it lands on the same 7,500' runway as the A319s and regional jets.
  14. Spectrar Ghost

    Spectrar Ghost Senior Member

    Notably, Obama comes to town in three days, so I'm guessing motorcade or possibly choppers.
  15. Spectrar Ghost

    Spectrar Ghost Senior Member

    Probably motorcade.
    Somewhat later three Ospreys also landed. I think, though the lighting made it uncertain, that they were in the dark freen of HMX-1, the squadron that flies Marine One.
  16. Gridlock

    Gridlock Active Member

    Numerous pictures of the Beast inside C-17s so that does seem to be how it travels. I'm idly wondering whether that improves its gas mileage or not.

    EG from Wikipedia

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  17. Trailblazer

    Trailblazer Moderator Staff Member

    A layer of thin cloud is making some quite dramatic contrail shadows this morning. This one just now was Air Canada 881 from Paris to Toronto, a Boeing 777 at 32,000ft. (Plus a bonus BA flight heading in to land at LHR.)

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  18. Trailspotter

    Trailspotter Senior Member

    A Tale of Two Trails

    The first contrail that I've spotted during my vacation in Sicily:
    The Emirates UAE186 Airbus A-380-800 leaves trail above steam plume from a side vent of Etna.

    Screen Shot 2016-04-10 at 22.29.05.
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  19. Conspiracyman

    Conspiracyman New Member

    [​IMG] Screenshot from a video I took of an Airbus a340 leaving some contrails.

    Attached Files:

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  20. M Bornong

    M Bornong Senior Member

    My wife and I flew from KCI to LAX aboard Spirit #785, yesterday evening. We flew over this contrail, it looked like it was almost close enough to touch.


    It looks like Southwest #4286, flying from Dallas to Denver is the most likely plane to leave this, it was flying nearly 7000 ft lower than us.


    I'm still working on the identification of this "smoker" (;)) that passed behind our plane at 1:23 UTC, April 11. (sorry about the quality, I only got one shot and I was in a really awkward position)

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  21. M Bornong

    M Bornong Senior Member

    It looks like it was Virgin America #236 LAX to ORD. I was looking for something that was crossing our path, I guess I missed him when he passed us on our port side 1000 ft. above us.

  22. Balance

    Balance Senior Member

    Spoilt for choice today so vidoe'd a few that were contrailing. Appx 25miles away, cheapo camera and not-so-steady tracking. (vid zipped and attached if that's ok?).

    Not only spoilt for commercial aircraft, I saw two Cobham Falcon FA20's, an A400 doing circuits around Hurn airport (about 15miles away) and a Chinook clapping around the locale.



    Attached Files:

    Last edited: Apr 12, 2016
  23. Trailblazer

    Trailblazer Moderator Staff Member

    I posted this shot before. This was probably about 2,000ft below the contrail (crossing flight was at FL380, we had recently started descending from the same level).


    Later we actually passed right through an older dispersed trail. These are grabs from a video, it's quite hard to make out until we emerged from it (second and third grabs, unfortunately with a finger over the lens!)




    Certainly not as well-defined as this example from YouTube!

    Last edited: Apr 12, 2016
  24. Trailspotter

    Trailspotter Senior Member

    Here is another interesting contrail that I saw in Sicily near Agrigento on April 5, 2016. It definitely originated from a military jet:
    IMG_1585.JPG 10:09:02 UTC
    I'm certain about its military origin not just because the aircraft turned around the Sun and did not appear on FR24. I heard it, but could not see it even at the full zoom of my camera that readily picks up a private jet flying overhead at 40000 ft. Only after some enhancement of the photo, a small triangular shape appeared ahead of the trail, consistent with a fighter jet:
    IMG_1588.JPG 10:09:27
    I followed the trail a bit before returning to the admiration of ancient temples:
    IMG_1591.JPG 10:13:13
    Twenty minutes later I've noticed an odd shape of the contrail remnants, which persisted for twenty more minutes:
    IMG_1602.JPG 10:33:24
    IMG_1603.JPG 10:39:25
    IMG_1608.JPG 10:48:49
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  25. Spectrar Ghost

    Spectrar Ghost Senior Member

    Looks like a Dassault Mirage, either III or 2000. Probably French or Spanish; the Italians use AMXs.
  26. Trailblazer

    Trailblazer Moderator Staff Member

    A classic "tic tac toe" pattern this morning:


    The trails in both directions were quite short and perfectly placed to cross from my vantage point. Looking at FR24, it was clear that they were also very low.

    What was happening was that planes departing Stansted and flying south (right to left in the photo) and planes departing Bristol and flying east (roughly towards the camera) were both ascending through a region just above 25,000 feet where contrails were forming. Once they reached about 28,000 feet the trails stopped.

    Here is the next crossbar being drawn - the plane is hidden behind the FR24 label in the screenshot.


    The next flight from Bristol (vertical trail) apparently climbed a bit faster and was out of alignment!


    The reason for the low contrails appears to be some unusually cold upper air above the UK at the moment. At 300mb (roughly 30,000ft) it is close to -55°C across southern England.

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  27. Trailblazer

    Trailblazer Moderator Staff Member

    Just looking at this in a bit more detail. The Relative Humidity map at 300mb for the time in question would normally suggest that persistent contrails would be rather unlikely, with RH on the low side (my location marked with the red dot).


    However, here is the sounding for Herstmonceux, on the south coast of England about 60 miles away to the southeast, for 1am BST that morning (00Z UTC).


    There is a narrow band with RH around 60-70% (actually maybe rather higher, given the dry bias of sounding instruments), at an altitude of 7,000-7,750 metres. That equates to about 23,000ft to 25,500ft. Above 300mb (8,900 metres, or 29,200ft), the RH rapidly drops to zero, which explains why higher-altitude planes were leaving no trails at all.

    12 hours later, at 1200Z, the band of higher RH has moved upwards slightly, to about 7,700 to 8,150 metres (25,000 to 26,800ft) although the air is slightly drier overall.


    The actual altitude I observed contrails (at about 0700Z) was more like 25,000 to 27,500ft, which is reasonably good agreement.

    Incidentally, the very cold air over the UK at the moment means that the tropopause is also very low, and most cruising aircraft will be flying in the stratosphere. This is the skew-T chart for Herstmonceux last night. I have arrowed the tropopause, which is just below the 300mb level, at around 29,000 feet:

    Last edited: Apr 14, 2016
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  28. Trigger Hippie

    Trigger Hippie Senior Member


    Brought my truck in for repairs this morning. On my walk home I saw this. The picture doesn't do it justice, but the contrails were a brilliant white one a beautiful deep blue.



    Great day for persistent spreading contrails in Toronto. I should get out more often.


    Later in the afternoon, when I went to pick up my vehicle, I caught three contrails in the same shot. (Too bad the buildings are in the way)


    Same patch of sky, a few minutes later, from a slightly different angle.
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  29. Spectrar Ghost

    Spectrar Ghost Senior Member

    It's anarchy I tell you!

    Nice photos.
  30. Trigger Hippie

    Trigger Hippie Senior Member

    Thank you.

    I noticed the "A", LOL. The other photos contain an H, X, Z
  31. M Bornong

    M Bornong Senior Member

    NASA had a DC-8 flying over the San Joaquin Valley today, testing the air quality. I got it as it made it's last pass by Bakersfield.

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  32. Gridlock

    Gridlock Active Member

    My inner child is laughing quite a lot at that flight path...
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  33. JRBids

    JRBids Senior Member

    OK my camera's not as good as some here, but there were some big fat contrails last night. DSCN9283.JPG DSCN9284.JPG
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  34. JRBids

    JRBids Senior Member

    And video.

    Attached Files:

  35. tinkertailor

    tinkertailor Senior Member

    Evidently our chemtrail overlords are Freudians...
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  36. Trailspotter

    Trailspotter Senior Member

    The Raytheon Sentinel R1 (modified Bombardier Global Express) flying north of Cambridge, UK today (10 am UTC, not on FR24):
    This time lighting was right for outlining the radar pod underneath the fuselage.
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  37. Dan Page

    Dan Page Active Member

    Bright, deep, blue sky day today, the air above is fairly dry, so the contrails are short lived. Took a few pics of this China Airlines Cargo B747-400 en-route from Anchorage to Chicago at 37,000'. Hard to see the aircraft as I'm on the shadow side, and due to the angle of my position to the engines on the right side, it looks like there are only 3 trails, but there are most definitely 4. The trail dissipated within 10 minutes.
    CAL5236Apr19-2016. P1070849.JPG
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  38. cloudspotter

    cloudspotter Senior Member

    Over the Northumberland coast in northern England yesterday evening around 19:00 BST

    IMG_8563.JPG IMG_8576.JPG

    Managed to get a decent shot of one of them

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  39. Trailspotter

    Trailspotter Senior Member

    Butterfly with contrails?;)
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  40. Gridlock

    Gridlock Active Member

    That's an F-22 by the looks of it - rare beast.

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