Most winds in general are horizontal with lower levels of the wind in
contact with the ground, trees, and other drag inducing objects which
slow the lower level wind through friction and turbulence. Slopes more
or less facing broadside to the oncoming wind can accelerate the wind as
more wind is passing through the same cross section. Often a ridge more
or less at right angles to the wind will act similar to an airplane wing
where the wind over the top is accelerated and moves faster than the air
before feeling the effect of the ridge.
Patrick NJ5G
On 5/16/2017 11:42 AM, Bill via TowerTalk wrote:
My place out in KH6 is an example of how much stronger the wind is up top.
I live on a very steep slope facing the tradewinds, which normally blow at an
average of 12-15 MPH. When it is blowing this hard it is impossible to raise
or lower antennas. So any raising or lowering must be done at lower speed
levels.
Why, when the wind is only 5-6 MPH it is usually closer to 15 MPH at the top of
a 90 foot tower. It is amazing how at the base you feel almost no wind but it
quickly picks up once you get about 20 feet or so. I've had many 200 ft towers
on the mainland but have never experienced such a big difference in surface and
top of the tower speeds.
Being on a steep upslope is the reason, I'm sure.
73 Bill KH7XS
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