On Sat, 5 Feb 2005 17:02:50 -0000, Trevor Appleton wrote in


OK who can work out what the circular feature is over Holland? (log in
required - free reg)

http://www.sat.dundee.ac.uk/abin/pro...roject.ch2.jpg

I'd go with the Von Karman vortex idea suggested by Karl Cooper. There is
certainly a suggestion of a similar, but less obvious, feature upwind and
to the SSW.

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 05/02/2005 20:53:57 UTC

Note on the Modis image there appears to be
another similar pattern developing in the cloud to the south south west.

No evidence of vorticity at the surface on these hourly plots:

Karl, Orkney, Scotland
Processing the image shows the second vortrex well and the extensive gravity
wave activity in the area.

I would suggest this is the expression of a PV streamer and vortex (-ices)
seen in the 12Z WV image-

http://www.sat.dundee.ac.uk/pdus/BW/...51200BW1_g.jpg

Soundings at both Trappes and Merignac show the dry air aloft due to the PV
intrusion-

http://weather.uwyo.edu/cgi-bin/soun...512&STNM=07145

http://weather.uwyo.edu/cgi-bin/soun...512&STNM=07510

PV streamers have been called 'tropospause shear lines' which suggests how
vortex spin up can occur along them.Unusual appearance in this case
though.Is the central white area caused by convection or convective
overturning (?),

regards,
David

Sorry,

vortrex=vortex
tropospause=tropopause

David

These two images show the features quite well. They look like Von Karman
vortices, but I have also seen ones similar to these develop over the open
ocean. In that case, if they were downwind of any land it was more than 500
km away.
http://www.btinternet.com/~wokingham...1410-b-uk.html
http://www.btinternet.com/~wokingham...1410-d-fr.html
--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.btinternet.com/~wokingham.weather/wwp.html
"Trevor Appleton" wrote in message
...

OK who can work out what the circular feature is over Holland? (log in
required - free reg)


http://www.sat.dundee.ac.uk/abin/pro...5/1412/project.
ch2.jpg

These two images show the features quite well. They look like Von Karman
vortices, but I have also seen ones similar to these develop over the open
ocean. In that case, if they were downwind of any land it was more than 500
km away.
http://www.btinternet.com/~wokingham...1410-b-uk.html
http://www.btinternet.com/~wokingham...1410-d-fr.html

and also
http://www.btinternet.com/~wokingham...1533-c-uk.html
--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.btinternet.com/~wokingham.weather/wwp.html
"Trevor Appleton" wrote in message
...

OK who can work out what the circular feature is over Holland? (log in
required - free reg)



http://www.sat.dundee.ac.uk/abin/pro...5/1412/project.
ch2.jpg

"Bernard Burton" wrote in message
...
These two images show the features quite well. They look like Von Karman
vortices, but I have also seen ones similar to these develop over the open
ocean. In that case, if they were downwind of any land it was more than
500
km away.
Processing Bernard's images reveals at least 3 vortices.I can't buy the von
Karman vortex idea as one wld expect to see evidence of pairs of
vortices.IMO the better the better analogy is with Kelvin Helmholtz
instability along a shear line -in this case a steep potential vorticity
gradient.
See eg-
A. van Delden and R. Neggers, 2003: A case study of tropopause
cyclogenesis. Meteorological Applications, 10, 197-209.
http://www.phys.uu.nl/~nvdelden/Trop.Cyclogenesis.pdf
but note the synoptic situation and resulting scale of vortex is
different.In principle the physics is similar,
regards,
David

"Waghorn" wrote in message...

I would suggest this is the expression of a PV streamer and vortex (-ices)
PV streamers have been called 'tropospause shear lines' which suggests
how vortex spin up can occur along them.Unusual appearance in this case
though.Is the central white area caused by convection or convective
overturning (?),

regards,
David

Thanks David. On reflection, any similarity to a Von K vortex is superficial
+ the feature is larger and the cloudless area is quite small.

Karl, Orkney