Dark Vertical Lines in Folkestone, Kent — Contrail Volumetric Edge Shadow

[Mick West]

Article:

Strange Black Line Photographed In Folkestone, Kent on May 10, 2023 at 8:05am.
The witness stated. "The building at the bottom of the black line is eurotunnel and when I saw it, it lasted about 4 mins."

Source: https://twitter.com/Underbelly2_0/status/1656370048166948868

This looks like a contrail shadow to me. An "edge shadow" where the viewer is in-line with the contrail and the sun, both of which are likely behind the camera. Discussed in more detail here:

https://contrailscience.com/contrails-dark-lines-chemtrails/

Local Weathermen also thought a shadow, but seemed unfamiliar with this type:

Article:

Mike Clay, chief meteorologist at the local station Bay News 9, was also left stumped by the unusual black line shooting down from a cloud.

The weatherman shared the pictures with some of his colleagues, one of whom came up with a possible explanation, suggesting that the dark line could be the shadow of a contrail.

Contrail is the condensation trail left behind jet aircraft. Contrails form when hot humid air from jet exhaust mixes with environmental air of low vapour pressure and low temperature.

For a contrail shadow to be seen, atmospheric conditions must be just right, with the sun hanging low on the horizon.

Source: https://www.kentonline.co.uk/folkestone/news/residents-and-experts-baffled-by-strange-black-line-in-the-s-286739/

That not entirely true, as the sun can be quite high. You can get contrail shadows any time of the day.

We can geolocate the viewpoint:
https://www.google.com/maps/@51.094...4!1sICYwR5zuELDEAcXzPIw81g!2e0!7i16384!8i8192

Giving us a line of sight to Chunnel building:

Almost due west, consistent with the morning sun?

Date is May 10, 2023 at 8:05am (BST) 0705 UTC (0005 PDT, my timezone for Suncalc)
http://suncalc.net/#/51.0933,1.1903,13/2023.05.10/00:05

A perfect match for the line of sight.

Finding the plane needs only one that leaves a portion of its contrail aliged with the sun. The straight line of the shadow is not the exact shadow the contrail, but rather a "ray" of shadow viewed edge on. Given the time, it is likely a US to Europe plane, of which there are several. The track of the plane is not the same as the trace of the contrail, which. usua gets blown off by up to 10°, so a possible plane is Eurowings 69, which did go directly over Folkstone

Reported wind from 218, SSW, which is consistent with the difference in contrail and ground track

 

[Mick West]

A similar case from 2015:
https://www.metabunk.org/threads/dark-beam-in-front-of-a-contrail-massa-italy-edge-shadow.6708/

It that case I was also able to track down likely plane.

 

[Mick West]

I took this video a few years ago. It shows a relatively high sun behind the camera causing a near-vertical shadow.

 

[Trailblazer]

That's quite a striking effect. I've taken a few contrail shadow photos over the years but not seen one as vertical as that. When they are at an angle they are more obviously a shadow - especially if the sun is visible too. This is one I took last year.

 

[Edward Current]

It's counterintuitive that these shadows appear against a clear sky. I feel like, in addition to the angle of the Sun, contrail, etc., there must be conditions at play here, such as a certain amount of haze in otherwise clear air. Or perhaps in an industrial world, there are always enough particulates to cause a discernible shadow?

I went looking for a similar effect from clouds and found this photo taken from orbit by the NASA Earth Observatory. Taken over India.

 

[JMartJr]

I went looking for a similar effect from clouds and found this photo taken from orbit by the NASA Earth Observatory. Taken over India.

I suspect the visible dark shadows there are being cast on the surface of the ocean rather than being atmospheric.

 

[Mick West]

It's counterintuitive that these shadows appear against a clear sky. I feel like, in addition to the angle of the Sun, contrail, etc., there must be conditions at play here, such as a certain amount of haze in otherwise clear air. Or perhaps in an industrial world, there are always enough particulates to cause a discernible shadow?

They are not really "against" a clear sky. They are *in* the sky. Consider that the sky looks darker blue at higher altitudes. If you've got a contrail that 5-6 miles up then the volume of air it's shadowing is a lot. Even with zero particulates, the change in Rayleigh scattering by air molecules will give the dark line. Water vapor haze, or particulates, will make it more apparent.

 

[tonyj154]

100% agree, shadow from a contrail. I live in Lincolnshire and see these shadows all the time. We have a very flat landscape and it's rural. You can go out on to the marshes where there is nothing around you and a lot of open sky.