Big feather in the sky........

[Jonny]

Can anyone explain what this is all about, there was a couple of these feather like clouds in the sky at the time........

[Tormentil]

Que ??

[Alan]

Originally Posted by Tormentil

Que ??

Na if it was Que he'd put two eyes above it!

Maybe an aeroplane vapourtrail as it hit a very cold air stream?

[eeyore]

I would have said that that was a dispersing contrail from a jet - but i could be wrong.

[henrya]

Looks like a fallstreak to me - a bit complicated to explain but it's all to do with supercooling and ice crystals, I think the feather is composed of ice crystals formed from the supercooled cirrus vapour that surrounds it. Note the clear space round the feather where the vapour has aggregated. See the weather Gallery for a photo of a much more pronounced example where the hole is much more obvious and well defined. (I might be wrong about this as I stlll don't fully understand the process!).

henrya

[smartie]

This looked interesting, so I thought I'd look up fallstreak and see if I could understand what it was. I found out that "A precipitation fallstreak is a manifestation of an inhomogeneity in the mycrophysical structure of the storm." So that clears that up nicely, then! Excuse me, I'm off for a lie down now...

[smartie]

Afraid I can't - all Greek to me. And you'll have noticed I can't even spell it in English - should of course say "microphysical".

Thanks for the welcome. I'm learning a lot - though not about fallstreaks

[jennyb]

Originally Posted by smartie

This looked interesting, so I thought I'd look up fallstreak and see if I could understand what it was. I found out that "A precipitation fallstreak is a manifestation of an inhomogeneity in the mycrophysical structure of the storm." So that clears that up nicely, then! Excuse me, I'm off for a lie down now...

I preferred Henrya's explanation

Jenny

[Jonny]

Originally Posted by henrya

Looks like a fallstreak to me - a bit complicated to explain but it's all to do with supercooling and ice crystals, I think the feather is composed of ice crystals formed from the supercooled cirrus vapour that surrounds it. Note the clear space round the feather where the vapour has aggregated. See the weather Gallery for a photo of a much more pronounced example where the hole is much more obvious and well defined. (I might be wrong about this as I stlll don't fully understand the process!).

henrya

Well done Henrya........I asked a weatherman friend what it was and he confirmed what you said.......


That sir is a Fallstreak Hole in cirrocumulus and is common.

The cirrus cloud under the center of the hole gives us a clue to what is happening. Cirrocumulus cloud is made up of super cooled water droplets if they freeze they drop out of the bottom.

If there had been virga forming under the hole or the hole was clear of cloud it would have suggested ice crystals are falling through the cirrocumulus from higher up


I am still none the wiser, but I now have a name for it. Cheers for all the replys..........

[henrya]

Quote
That sir is a Fallstreak Hole in cirrocumulus and is common
Endquote

But I've been looking for one for the last three months and haven't seen one - maybe I 'll have to spend less time in front of this computer thing!

Anybody want an explanation of supercooling?

henrya