.... using this site:-

http://www.sat24.com/

choose VIS imagery for Europe and you can see (now the sun is
illuminating the cloud tops) a near-perfect arc of line convection with
(I think) just one break. Seems to be coming forward associated with
cyclonically-sheared development associated with the
slow-moving/warming-out vortex seen here ...

http://www.wetterzentrale.de/pics/Rtavn001.png

Martin.


--
West Moors / East Dorset
Lat: 50deg 49.25'N, Long: 01deg 53.05'W
Height (amsl): 17 m (56 feet)
COL category: C1 overall

On 15/11/2012 09:29, Martin Rowley wrote:

... using this site:-

http://www.sat24.com/

choose VIS imagery for Europe and you can see (now the sun is
illuminating the cloud tops) a near-perfect arc of line convection with
(I think) just one break. Seems to be coming forward associated with
cyclonically-sheared development associated with the
slow-moving/warming-out vortex seen here ...

http://www.wetterzentrale.de/pics/Rtavn001.png


.... just correcting myself somewhat; undoubtedly a convective element,
but cross-referring to IR image, obviously NOT a classic line-convection
event - the cloud tops aren't nearly cold enough and the 'line' doesn't
show up to match the VIS picture. So more like a boundary-layer feature
- perhaps propagating outward from the deeper convection further west ...??

Martin.


--
West Moors / East Dorset
Lat: 50deg 49.25'N, Long: 01deg 53.05'W
Height (amsl): 17 m (56 feet)
COL category: C1 overall

"Martin Rowley" wrote in message
...
On 15/11/2012 09:29, Martin Rowley wrote:

... using this site:-

http://www.sat24.com/

choose VIS imagery for Europe and you can see (now the sun is
illuminating the cloud tops) a near-perfect arc of line convection with
(I think) just one break. Seems to be coming forward associated with
cyclonically-sheared development associated with the
slow-moving/warming-out vortex seen here ...

http://www.wetterzentrale.de/pics/Rtavn001.png


... just correcting myself somewhat; undoubtedly a convective element, but
cross-referring to IR image, obviously NOT a classic line-convection
event - the cloud tops aren't nearly cold enough and the 'line' doesn't
show up to match the VIS picture. So more like a boundary-layer feature -
perhaps propagating outward from the deeper convection further west ...??

Martin.


--
West Moors / East Dorset
Lat: 50deg 49.25'N, Long: 01deg 53.05'W
Height (amsl): 17 m (56 feet)
COL category: C1 overall

Re my (and your) earlier posts Martin, I was referring to the line of IR
activity. I agree that the narrow line of convection on the vis image is a
boundary layer feature, and is probably tied to a change from southerly to
westerly flow across it. The boundary layer air ahead of the line has been
over the cooler water off the NW African coast, and could act as a trigger
to lift the slightly warmer air circulating the vortex at lower levels,
initiating the line of convection.

--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
http://www.woksat.info/wwp.html

"Martin Rowley" wrote in message
...

... using this site:-

http://www.sat24.com/

choose VIS imagery for Europe and you can see (now the sun is illuminating
the cloud tops) a near-perfect arc of line convection with (I think) just
one break. Seems to be coming forward associated with cyclonically-sheared
development associated with the slow-moving/warming-out vortex seen here
...

http://www.wetterzentrale.de/pics/Rtavn001.png

Martin.


--
West Moors / East Dorset
Lat: 50deg 49.25'N, Long: 01deg 53.05'W
Height (amsl): 17 m (56 feet)
COL category: C1 overall

The band of activity also seems to be linked to the region of strong
diffluence near the axis of the jet on the southern side of the upper
vortex, also linked to a short-wave trough rotating the vortex.
http://www.wetterzentrale.de/pics/Rtavn0015.png


--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
http://www.woksat.info/wwp.html

On 15/11/2012 10:23, Bernard Burton wrote:
"Martin Rowley" wrote in message
...

... using this site:-

http://www.sat24.com/

choose VIS imagery for Europe and you can see (now the sun is illuminating
the cloud tops) a near-perfect arc of line convection with (I think) just
one break. Seems to be coming forward associated with cyclonically-sheared
development associated with the slow-moving/warming-out vortex seen here
...

http://www.wetterzentrale.de/pics/Rtavn001.png

Martin.


--
West Moors / East Dorset
Lat: 50deg 49.25'N, Long: 01deg 53.05'W
Height (amsl): 17 m (56 feet)
COL category: C1 overall

The band of activity also seems to be linked to the region of strong
diffluence near the axis of the jet on the southern side of the upper
vortex, also linked to a short-wave trough rotating the vortex.
http://www.wetterzentrale.de/pics/Rtavn0015.png


.... thanks for that Bernard: a fascinating feature and demonstrates once
again the beauty of the atmosphere!

And we've even had a single sferic out of it - which I have to admit I
hadn't expected after my *second* post on the subject - but I would have
done after the first!

Collapse of stout party :-)

Martin.


--
West Moors / East Dorset
Lat: 50deg 49.25'N, Long: 01deg 53.05'W
Height (amsl): 17 m (56 feet)
COL category: C1 overall

Martin Rowley wrote:

On 15/11/2012 10:23, Bernard Burton wrote:
"Martin Rowley" wrote in message
...

... using this site:-

http://www.sat24.com/

choose VIS imagery for Europe and you can see (now the sun is illuminating
the cloud tops) a near-perfect arc of line convection with (I think) just
one break. Seems to be coming forward associated with cyclonically-sheared
development associated with the slow-moving/warming-out vortex seen here
...

http://www.wetterzentrale.de/pics/Rtavn001.png

Martin.


--
West Moors / East Dorset
Lat: 50deg 49.25'N, Long: 01deg 53.05'W
Height (amsl): 17 m (56 feet)
COL category: C1 overall

The band of activity also seems to be linked to the region of strong
diffluence near the axis of the jet on the southern side of the upper
vortex, also linked to a short-wave trough rotating the vortex.
http://www.wetterzentrale.de/pics/Rtavn0015.png


... thanks for that Bernard: a fascinating feature and demonstrates once
again the beauty of the atmosphere!

And we've even had a single sferic out of it - which I have to admit I hadn't
expected after my second post on the subject - but I would have done after
the first!

Collapse of stout party :-)

Martin.

I had occasion to investigate this sort of feature in some detail a while ago -
Bernard may remember the event, which I discussed with him. I located a few
papers (including a couple in 'Weather') dealing with these very distinct and
persistent lines of vigorous but relatively shallow convection. They sometimes
produce rainfall intensity and squalls out of proportion to their vertical
development. Radar imagery and sometimes visible wavelength satellite imagery
give a completely different impression to that gained from IR satellite
imagery. If reliance is placed solely on radar imagery it is very easy to be
misled into thinking that the imagery is the result of a line of Cb.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.