Interesting Clouds

[Spongebob]

Hi everyone,

I saw this weird cloud pattern and wondered what process is at play here?

It was taken from this image:

Original Image

Thanks in advance

KjF

[opplevelse]

Ohh this is a fantasic example of a Karman vortex street

It occurs in the wake of an island or other protrusion on a flat surface, like the sea. there are dzens of examples, but you can have a read of them here ...

http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street

a fascinating example of fluid mechanics at work!

Edited June 24, 2008 by opplevelse

[Spongebob]

Cool Thanks for that . . .. impressive wiki !

[Gibli]

Another good example here, off the west coast of Mexico. This island often produces von Karmen vortices. Hit 1km or 500m for a closer look if your computer can cope - the 'previous' button also useful for a look back over the last few days or weeks.

http://rapidfire.sci.gsfc.nasa.gov/subsets...08183.terra.2km

Gibli

[opplevelse]

Can anyone help, I saw a cloud last year and it looked like a huge ring doughnut, or something out of Independence Day. It was an almost perfect round shape very large and very dark in colour, but in the middle was what looked like a hole or the middle was being sucked upwards. I never had my camera with me so didn't get a picture, I have never seen anything like it before.

probably a "hole punch" cloud ... i'll post some example photos later, but basically what you saw was probably not being sucked up but actually falling down. Ice crystals precipitating out of the cloud often form a funny kind of tail that can look like the cloud being sucked up.

At a friends house now but will come bck to this later for you!

[opplevelse]

Ok did it look something like this?

What could create a huge hole in the clouds? Such a hole, likely hundreds of meters across, was photographed last month from a driveway near Mobile, Alabama, USA. Very unusual to see, hole-punch clouds like this are still the topic of meteorological speculation. A leading hypothesis holds that the hole-punch cloud is caused by falling ice-crystals. The ice-crystals could originate in a higher cloud or be facilitated by a passing airplane exhaust. If the air has just the right temperature and moisture content, the falling crystals will absorb water from the air and grow. For this to happen, the water must be so cold that all it needs is a surface to freeze on. The moisture lost from the air increases the evaporation rate from the cloud water droplets so they dissipate to form the hole. The now heavier ice crystals continue to fall and form the more tenuous wispy cloud-like virga seen inside and just below the hole. Water and ice from the virga evaporates before they reach the ground.

http://apod.nasa.gov/apod/ap040112.html

There are literally hundreds of photos of them. I have only seen them 3 times myself

http://images.google.com.au/images?sourcei...sa=N&tab=wi

[opplevelse]

Can you draw what you mean3 because I am a little lost I am afarid!

[opplevelse]

hmmm odd, was it oriented vertically (i.e. was the donut sitting perpendicular to the ground) or was it horizontal?