Helm Bar
Richard Bailey
its effect on flying a glider. I had never heard of this cloud formation
before and found it interesting. During a short holiday in the North
Pennines, I saw the Helm Bar yesterday, quite briefly, over Dufton Pike and
stretching towards, but not as far as, Cross Fell. It seemed to form and
reform quite quickly. Can anyone explain what causes this very local
phenomenon?
Richard Bailey
Holbeach Marsh, Lincs.
Ken Cook
news:40b78f12$1...@mk-nntp-1.news.uk.worldonline.com...
Hi, Richard,
Briefly, as there are people on this ng with far more expertise than I
have, requirements for the Helm - the only named wind in the UK - are
(according to local hero, Professor Gordon Manley,
Temperature inversion below 6 000ft.
Moderate to fresh NE wind (Tynemouth should be experiencing NE 15mph
minimum).
As the wind was S or SE yesterday here, it probably wasn't The Helm you
saw as the wind has to blow at 90 degrees to the range of hills (ie
NE'ly). Could it have been a lenticular cloud or orographic cloud formed
as the wind was forced upwards? They are very common in this area (see
Copley web page).
The Helm is caused by the escarpment lying transversely to the surface
wind acting like a submerged weir in a stream of water. A standing wave
is set up just below the weir. As well as the Helm cloud above the fell,
there is also a Bar cloud between 3 and 8 miles downwind. Between them
the wind roars fiercely down the fell from the NE followed by a calm
area as the air rises again to form the bar.
HTH (all courtesy of the late, great Prof. Gordon Manley)
Try a google search for more info.
ATB,
--
Ken Cook, Copley (5miles north of Barnard Castle), County Durham.
830ft
http://mysite.freeserve.com/copley
(MO climat. site updated before 10Z and 19Z daily)
kencookATcopleydurham.freeserve.co.uk
All times GMT
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Jack Harrison
Ken is quite right - you almost certainly observed wave clouds in a SW wind.
The Helm Bar occurs only in a NE'ly.
Anyway, why is the 'Helm Wind' (as Ken points out) the only named wind in
Britain?
I would certainly be prepared to 'invent' names for some of those tedious
winds (winter and spring mainly) off the North Sea that bring persistent low
cloud to much of E and SE England. Mind you, a 'moderator' (of terminology)
might be a good idea!
Jack
Richard Bailey
copy it back to the ng in the hope that I might see it?
BTW what I saw was a faint bar-shaped cloud, almost no more than a mist,
which formed and re-formed several times, over a period of about 15 minutes,
over the top of the fells, as seen from the A66.
Richard.
"Jack Harrison" <jack.h...@virgin.net> wrote in message
news:40ba2328$0$6321$65c6...@mercury.nildram.net...
Martin Rowley
> Unfortunately my server failed to pick up Ken's post. Would someone
kindly
> copy it back to the ng in the hope that I might see it?