"Bernard Burton" wrote in message
...
"George Booth" wrote in message
...
On 22/04/2013 11:25, Bertie Doe wrote:
Is there a rule of thumb for wind veering or backing with height? Reason
I ask: I often see actual wind say, bonfire smoke to differ by 60
degrees, with cloud-over-ground movement? TIA.



In general wind veers and increases with height. Memories of fretting
over this on airfield layout for glider winching.

UKMO F214 spot wind forecast E.Anglia pm today gives 1000' 230/25knots,
2000' 240/30knots all the way up to 18000' 310/45knots.

Another useful source
http://rasp.inn.leedsmet.ac.uk/RASPt...SPtableGM.html where you'll
have to select 'soundings' from LH window, select the one you want and
see the wind speed and directions displayed on right of graph.

--
George in Epping, west Essex, 350'asl
www.eppingweather.co.uk
www.winter1947.co.uk

Not quite the whole story George.

Your statement is only true in the boundary layer, below about 1km
altitude. This veering and increasing with height is caused by the
frictional drag of the surface. The degree of coupling between the surface
air and that at 1 km is an essential ingredient in maintaining the surface
wind. If the coupling is reduced, for example due to the establishment of
a strong surface temperature inversion (radiational night-time cooling),
the surface wind soon decreases to near calm, due to frictional drag.
During the daytime, coupling is at a maximum in an unstable boundary layer
temperature profile, and the surface wind speed and direction will be
closest to that at 1 km altitude.
As has been pointed out elsewhere, wind in the free atmosphere, that is,
above the surface boundary layer, veers with height in the presence of
warm advection, and backs in the presence of cold advection. The magnitude
of the vector change with height is directly related to the magnitude of
the thermal gradient. It is this type of effect you are seeing in the F214
winds you quote.
And of course it is all specific to the hemisphere that you are observing
in. In the southern hemisphere, frictional retardation causes backing of
the flow with height in the lower boundary layer; and in the southern
hemisphere winds veering with height indicate cold advection, and winds
backing with height indicate warm advection.

I bet it's as clear as mud now! ;-)
--
Freddie
Bayston Hill
Shropshire
102m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/#!/BaystonHillWx for hourly reports