The NOAA/NWS standard for an anemometer is at the top of a 33 foot tower.
Winds going over or around hills, buildings, trees, whatever, will be
stronger than if not disturbed by upstream objects. Also, winds usually
increase with elevation. The affect an obstruction would have on wind speed
would depend on the size of the obstruction and the speed of the wind. Best
to avoid any obstruction if possible. NOAA/NWS sees wind reports from non
NWS locations that can be 100's of feet in the air on towers or bridges.
Their feeling is that as long as they know the elevation above the ground,
the data is useful to them. To get wind reports that are most accurate, NWS
suggests you should stick to a 33 foot tower if possible, anemometer on the
top. As we all know this height is not common or practical for most home
weather stations.
So, placement on a regular old ham tower where the beams are on top could
mean that the anemometer could be at the top of the mast (bit difficult to
service if the need arises) or side mounted out 3 feet or so at some level).
In my case, the anemometer is mounted above the temp, rain and humidity
sensors (the latter 3 in a solar shield) on a mast in one of the standard
tripod mounts at the very west end of my roof (approximately 35 feet above
ground) with the anemometer 7 feet above the roof. There may be some
up-effects now and then but from various measurements at other places and at
the tower (some 150 from the anemometer) the differences in wind speed seem
to be negligible.
Always keep in mind the ability to get at the wx equipment if something
happens (a condx I run into about once a year).
In summary, from experience and from input from discussions with NOAA/NWS
expects on siting, the difference in any wind speed relative to your concern
would not be worth worrying about as long as the anemometer location is in
free air space.
By the way, mine is a Peet station, hard-wired, but nothing wrong with
wireless. Stay away from Oregon Scientific, experience by many people down
here in the Central OR coast area has been they don't hold up well (read as
corrode fast and fail). Their indoor stuff seems to be fine. Davis has a
good reputation.
See my reporting under Yachats at
http://www.ocrg.org/telemetry_feed/ocrgwx.html, used by MesoWest and NWS.
Don W7WLL
-----Original Message-----
From: ag6v@whidbey.com
Sent: Monday, August 31, 2015 2:49 PM
To: towertalk@contesting.com
Subject: [TowerTalk] weather station on tower?
Hi All -- I'm thinking of putting up a weather station at my QTH, and
connecting it with WUnderground.com (as in "W"eather Underground).
I want to know wind speed and direction at or near my tower and _ON_
the tower will give the most accurate data, it seems.
Questions:
* anyone notice interaction/RFI issues of a USB-connected weather
station on a tower or close to it?
* what experiences do you all have?
* the WUnderground.com site has a number of suggested weather station
packages -- any others you like?
73,
----
Donna Hinshaw
AG6V
ARRL Life Member
SKCC 6933T
CWOPS 911
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