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On a trip to Brighton, England on April 12th, 2015, I noticed this strange plume in the sky over the English Channel at about 13:00 hours. It looks like;

  1. Something that fell out of the sky - the news and other chatter over the following days revealed nothing which would support that.
  2. A tornado/wind vortex drawing water up from the surface?

Cloud Plume

Please note, I took this photo with my phone, with the window down and it is completely unedited. Is this a meteorological phenomenon, and if so, what is it?

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    $\begingroup$ Looks like a jet contrail to me. The jet didn't fall over the sky. It flew beyond the horizon. $\endgroup$
    – David Hammen
    Commented May 1, 2015 at 19:52
  • $\begingroup$ I agree with David. Most likely a jet plane that flew towards or away from you, and because of your vantage point it only seems that it was going up or down. $\endgroup$
    – Gimelist
    Commented May 3, 2015 at 2:01
  • $\begingroup$ @DavidHammen I appreciate the comment, but I don't see how that's possible. The vanishing point is about halfway down the image, where the base of the clouds is. The thin diagonal contrail down to the middle left is a jet crossing the sky. From this vantage point, an aircraft wouldn't disappear over the horizon like that. $\endgroup$
    – Jongosi
    Commented May 3, 2015 at 8:14
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    $\begingroup$ Is that a shadow it casts? If it were vertical, wouldn't the shadow look a lot different? $\endgroup$
    – Sergiu Paraschiv
    Commented May 4, 2015 at 9:10

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You are seeing an older jet contrail and its shadow. You can also see some newer contrails, and maybe even some older ones.

Contrails are not necessarily continuous. For example, the contrail that appears to be horizontal in the image below appears to magically appear near the left end of the image.

Image of a contrail that appears to suddenly start in the middle of the sky

That's what you are seeing in your image, but in this case the contrail in question appears to be vertical. The contrail stops about 1/3 the way up the picture. Given that the contrail gets thicker with increasing height up the picture, and becomes very diffuse near the top, I suspect that where the contrail stops is the youngest part of the contrail. That would mean the plane was flying away from your position (i.e., toward the horizon visible in the picture). The contrail stops at that point because the plane entered a region of dry, stable air. Contrails persist for seconds to several hours, depending on the local atmospheric conditions.

What about the dark band below the contrail? That's the contrail's volumetric shadow. You were in just the right place to see it. Notice that while the contrail is twisted and not quite straight, that dark band is straight. If you look closely, you can see that it doesn't end at the horizon. It appears to extend into the water. It's a shadow, a volumetric shadow to be precise.

The next two links are to images that show exactly this effect. These images appear to be copyrighted, so I'm going to leave them as links rather than embed them.

Link to image portraying a jet chasing it's volumetric shadow

Link to another image of a contrail and its volumetric shadow

Finally, this is a very striking example of the volumetric shadow from a contrail, in this case the launch of STS-98. This image is from Wikipedia, so it's fair use. In other images (you can search for them) taken from other angles, the shadow isn't nearly as striking, sometimes even non-existent.

Striking image of STS-98 launch, with volumetric shadow of the exhaust appearing to intersect the Moon

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    $\begingroup$ Your first image link is broken now. And the link to "yet another image" is also broken. $\endgroup$
    – Ruslan
    Commented Jun 8, 2018 at 20:38
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    $\begingroup$ @Ruslan - Thanks. I fixed the first image link, as well as links to two of images to which I linked via text links rather than embedded image links. (Note: I don't use copyrighted images directly in my answers, but linking to them is fair game.) $\endgroup$
    – David Hammen
    Commented Jun 8, 2018 at 21:51

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