A Perfect Circle In The Clouds?

[Snowkissed]

If this video has not been tampered with and what we are seeing is real, what scientific explanation do you have for this hole in the clouds?

http://www.youtube.c...d&v=z91AZnGX338

[Beasterly]

Wow, as many said, HAARP. This has happened before in Russia and some other places.

[Andy Bown]

Absolutely nothing to do with UFOs despite the linking videos to the right of that one!

I think something similar has been photographed in the UK in the last few years and was posted on Net Weather, the reason was

to do with aircraft but I can't exactly remember how/why!

[Snowkissed]

Thanks Andy, I thought I remembered the same post, but have also forgotten the explanation. It certainly is interesting though!

[Evening thunder]

Wow, as many said, HAARP. This has happened before in Russia and some other places.

These HAARP conspiracy theories and others do tend to get on my nerves sometimes, but I usually ignore them.

Basically these theories are a load of nonsense. The formation is I believe called a 'fall streak hole' where the moisture in that part of the cloud has precipitated out. I have seem pictures of these before.

I will leave it to the more knowledgeable about these to explain how/why they form. I think one thing I've heard was that particles from the exhaust of a place 'seeds' the cloud in that particular spot in the sky as the plane passes through?

[Chris K]

A fallstreak hole (also: hole punch cloud) is a large circular gap that can appear in cirrocumulus or altocumulus clouds. Such holes are formed when the water temperature in the clouds is below freezing but the water has not frozen yet due to the lack of ice nucleation particles. When a portion of the water does start to freeze it will set off a domino effect causing the water vapor around it to freeze and fall to the earth as well, spreading outward from center to produce a "hole"...

http://en.wikipedia.org/wiki/Fallstreak_hole

[Snowkissed]

Thats geat! Thank you so much - mystery solved

[Nick L]

Yes it is definitely nothing sinister! They are commonly caused by aircraft going through the cloud, causing it to "fall out" as ice crystals. Cloud physics did teach me something I'll do a proper post on it shortly.

Ok, this process occurs with supercooled clouds consisting of just water (no ice, initially at least). When an aircraft passes through it, the exhaust introduces aerosols to the cloud which initiates ice crystal growth as the water drops have something to freeze onto. This causes a chain reaction, as the surrounding water freezes and causes the ice crystals to grow and become greater in number. Not all water droplets will freeze however, the ice crystal formation will cause a reduction in something called the vapour pressure, meaning some droplets will simply evaporate.

The ice crystals continue to grow at the expense of the remaining water droplets, and will eventually grow to such a size that they drop out of the cloud, causing the big hole you can see in the video! More examples:

[max011293]

yes, as mentioned it is indeed a fallstreak hole, caused by super-cooled droplets finding a suitable freezing nuclei, such as that expelled in aircraft exhaust fumes. It has a chain effect in that surrounding super-cooled droplets also start to freeze and fall, creating the observed circular hole

[knocker]

Absolutely nothing to do with UFOs despite the linking videos to the right of that one!

I think something similar has been photographed in the UK in the last few years and was posted on Net Weather, the reason was

to do with aircraft but I can't exactly remember how/why!

Yes it was fairly recent because I replied. If I remember the photo was taken near Prestwick airport.

[Snowkissed]

Thank you Nick L for such a detailed reply.

[Flipflop]

I took this last year in Hull, its the first time iv seen anything like it just glad i had the camera handy.

[Chris K]

I would love to see one 'in person', bet it's impressive to watch.

[Nick L]

Thank you Nick L for such a detailed reply.

No worries, it keeps me on my toes

[Sprites]

Woudnt it be funny if all cloud physics books were wrong, and we had to learn everything from scratch... Just a thought : -)

[Nick L]

Woudnt it be funny if all cloud physics books were wrong, and we had to learn everything from scratch... Just a thought : -)

No...because that's a whole term of learning out of the window for me!!

[Aaron]

Look at all those people shouting HAARP..