wrote:
On 30 Sep 2006 15:35:11 -0700, "Weatherlawyer" wrote:
Gary Edstrom wrote:
What kind of cloud formation is this?

http://gbe.dynip.com/weather/R3442A.JPG

I have been scanning some of my old 35mm slides and came across this one
I took out in Westlake Village, California back in November 1983. The
feathery appearance really made it look different. I know little about
weather and wanted to ask someone what it was. But, it was forgotten
about until this morning when I happened to scan it. So, can someone
tell me 23 years after the fact what it was?

A contrail. Plenty of discussion about them on usenet.

I'm not entirely sure about that. Looks equally well as wispy,
feathery sort cirrus (mare's tale), especially because of the hooked
nature at the fore. If it is this sort cloud, they are not uncommon
in blue skies half a day or less ahead of a thunderstorm cell with
anvil tops. The material which is blown off the cumulonimbus to
create that flat anvil top has to go somewhere, afterall, and it
proceeds ahead of the storm cell at a considerably greater speed. The
isolation of the cloud, however, brings that somewhat into doubt as
you usually see several of these together under that circumstance.

But mares tails are plural for a reason. This is the mark of one
passing liner or maybe a fighter or some other large fuel burner.

Note the directions of the dissipation where the whisps take the
direction of the vortices of a vehicle kept aloft by a pair of wings.
The turn-over is in different directions for each line of condensation.

The cloud stayed a long while because there was little side wind. With
mares tails, the effect is produced by a side wind where the layer
enters a layer of still air and the water threshold allows the
formation of visible vapour at the interface.

But the striations all leave the line in the same direction -or at
least, with the wind.