Durham Sky

[IMG]http://i799.photobucket.com/albums/yy273/Davidtrout2/Durhamsky.jpg[/IMG]
This cloud formation was over Durham two or three weeks ago. Does anyone know what causes those crater-like shapes? K10+DA* 16-50mm lens

No idea, David. I've never seen anything like this. You can see how UFOs get reported...

They are called Hole Punch or Fallstreak clouds and are formed when an aircraft has passed through a thin layer of cloud (while climbing or descending), creating a dissipation hole. The holes occur when supercooled water droplets form into ice crystals and then fall as Virga. Ice crystals rob neighboring supercooled water droplets of vapor to further their own growth, working outward in a circle. The end result is a feathery Cirrus precipitation in the middle of a Altocumulus or Cirrocumulus layer.

This is the best example I have ever seen, and the Cloud Appreciation Society (Yes, seriously!) would bite your hand off to get you to put it on their website. It would probably be shortlisted for their annual callendar.

I have never seen two of them so close together: they must have been formed by different aircraft.

It looks like an alien face looking down!

Here's a link to a wikipedia article on them.

Thanks Jonathan. I'll send them an image when my e-mail gets fixed. Can't use it at the moment for technical reasons that are way beyond me.
David

Great! They'll love it. I have PM'ed you the address to send it to.

Rgds,
Jon

Lovely shot - well spotted

I was about to ring my pilot friend to ask what they were but aliengrove appears to have this explanation sorted

WOW Factor indeed !!! Must say we are always learning .

Well who better to explain an alien face in the clouds than aliengrove?

Great photo. I have ever seen clouds like that. I love clouds :

Now you've done it David, I cant get the damned X FIles theme tune out of my head

I believe these clouds can also be formed by the disturbance a meteorite causes as it fall to Earth, so if you find any funny rocks lying around, David, you may have an extraterrestrial souvenir of your alien cloud

At times like this I begin to worry about Aliengrove's AVATAR.
David

Wow I've never seen anything like it!