The helm wind of corssfell, 1937‐1939

Author:
  • GMGordon Manley
    Gordon Manley
Open Access
Publisher website
Google Scholar
Abstract
Two years' study of the Helm Wind of the N. Pennines has led to certain conclusions, based on reconnaissance methods and direct observations, with which the somewhat contradictory features of earlier descriptions can be reconciled.The Helm Wind and its accompaniments form one example of a group of phenomena found in various parts of the world. In each case when a wind blows transverse to a range of mountains, a marked increase in the strength of the wind is noted by surface observers down the leeward slope and for a varying distance across the lowlands below, compared with that which prevails over the country as a whole.It is shown that this local increase in wind force arises inasmuch as the air descends the slopes to the lowlands with a velocity of the same order as that which would otherwise obtain in the free air at the summit level. Taking all the observations into account it appears that the circumstances necessary are (1) the existence of a sufficiently vigorous surface current with, by inference, a well‐developed inversion at a height which provisionally must be not more than three times that of the range from its base; (2) the crest of the range should be fairly even, and the leeward slope of the range must not be too steep or too broken‐up. The phenomena then resembles those which occur at a submerged weir with inclined faces; a “standing‐wave” is formed in the surface stream to leeward of the range. Vigorous downward and upward currents are found which may be dangerous to aircraft, but which may also be utilised. The conclusions reached are borne out by other authorities.Further study and investigation by more intensive methods on the ground, by the use of wind tunnels, and by gliders, would appear to be worth while. It is proposed to publish a further paper on certain aspects of the phenomenon.

This publication has 2 references indexed in Scilit: