The Helm Wind is a named
wind in
Cumbria,
England, a strong north-easterly wind which blows down the south-west slope of the
Cross Fell escarpment. It is the only named wind in the
British Isles, although many other mountain regions in Britain exhibit the same phenomenon when the weather conditions are favourable. It may take its name from the
helmet or
cap of
cloud which forms above Cross Fell, known as the Helm Bar, since a
line of clouds over the fells can predict and accompany a Helm. Research into the helm wind was carried out by
Gordon Manley in the 1930s. He interpreted the phenomenon in hydrodynamic terms as a "
standing wave
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect ...
" and "rotor", a model confirmed in 1939 by glider flights.
The
dale
Dale or dales may refer to:
Locations
* Dale (landform), an open valley
* Dale (place name element)
Geography
;Australia
* The Dales (Christmas Island), in the Indian Ocean
;Canada
* Dale, Ontario
;Ethiopia
*Dale (woreda), district
;Norway
*D ...
at the head of the Eden Valley has its own Helm Wind, which sweeps over
Mallerstang Edge, particularly affecting the central part of the dale.
This can be similarly fierce and can blow for two days or more, sometimes sounding like an express train. As with the wind at Cross Fell, its arrival is accompanied by the formation of a dense cap of cloud (a "Helm Bar") which, in this case, forms along the high ground on the eastern side of the dale.
References
{{Reflist
External links
Example of a Helm Bar taken from near Appleby in Westmorland on April 3rd 2007on a website that specialises in "wind of the world".
Climate of England
Föhn effect
Geography of Cumbria
Winds
Pennines
pl:Wiatr#Lokalne wiatry nazwane