Topic: Anemometer Siting Question

[LIWeather]

I always try to get my data as acurate as possible. For no other reason then I want to be as close as possible.

So, the proper siting recommendations call for the anemometer to be at a height of 33 feet (10 meters but more specifically, 32.8 feet) above the ground. I had mine at 31-32 feet on a 10 foot mast attached to my chimney.

What I started to realize is that my wind readings seemed to be lower than what appeared to be stronger gusts. I checked against other nearby stations and realized some higher gusts recorded nearby but not from my station. Now, I realize that terrain, structures, different heights of the anemometer, etc. influence readings.

The next windy day, I observed that my mast was shaking, thus, throwing off my wind readings. I am not able to place guy wires so the other day, I decided to lower the mast to about 3-4 feet above the chimney. I'm not a huge fan of it being so close to the opening but I wanted to do my best of eliminate the shaking.

Luckily, I didn't have to wait long for another wind event. I haven't checked many nearby stations but I did notice I was still recording lower gusts.

My questions are, am I obsessing over something that I won't ever be able to validate because no 2 stations being the same in terms of siting? Being as though guy wires are not an option, I have considered a metal chain link fence post as a mast. I don't know exact specs yet, but they are typically about 6 feet tall and maybe 3 inches wide in diameter? My thought is it won't flex as much due to the larger diameter. Would this also incur a heavier wind load on the chimney? I certainly don't want my chimney to come down because of a strong wind event. It may be worth mentioning that I have the mast attached with kendorf to the chimney.

General thoughts on the mast idea? Should I just get over it? Lol Thank you!

[Aardvark]

I would check to be sure all your set screws on the wind cups are tight enough to make sure that there is no slippage.

It is possible that the wind from the other stations you speak of are getting different wind speeds because of their location compared to yours.  The official weather here is out at the Des Moines Airport. The NOAA is out at Johnston at the other end of town.  Neither agree on windspeed and none agree with me.   

How close to your location is the other closest other station?

I have a 33 foot mast and even with guy wires, I get sway.  I don't think it is bothering the readings.     I wouldn't  worry about it. the readings you have are at your house.   definitely I would not put a heavy pipe up to your chimney and risk a gust loosening the cement so you would have to  deal with that.

[LIWeather]

Thank you for the thought out reply. The cups are tight. I am surprised i even though of that lol Thanks for pointing it out though. Im using a Radio Shack mast that doesn't have a very large diameter. Ive observed less of a sway and more of a shake in higher winds. I cannot see how this doesn't throw off the equilibrium if you will, for lack of a better term. I'm having difficulty determining if the shake is impacting readings or the wind patterns aren't as strong where my anemometer is located.

My thought with the metal fence post is that it's larger diameter which would provide a more sturdy mast. Typically, they are not super heavy but again, I'd have to put one in my hands to get a feel for the weight. I was also trying to get a feel from the group if you all thought it would create more of a wind load due to the larger diameter. I would guess it's lighter than the current Radio Shack mast.

I don't expect to get the same wind readings as an open area such as an airport or on the water. Perhaps it's just that the wind gusts at my location don't get as high as forecasted. I would love to rule out the mast as being a cause for not clocking those higher wind gusts. Plus, I know the higher the mast, the less effect structures and the roofline will have. After adusting the height, I'm closer to the roofline then I've ever had it.

I may just chalk it up to my specific location and be happy with what I get. I'd love to hear of other viable mast options attached to a chimney that won't shake or sway as much. As well as not carry a greater wind load. Guy wires would probably be a solution but it's not an option with my setup.

[Aardvark]

I am also using a RadioShack Mast.   They are a sturdy item. I've had mine now since 1993.     Can you drive over to the closest location that is giving you a speed you believe to be correct?  Give it a lookie.

Just like rain,which falls differently over an area, wind is the same.   We are in microclimates.

I am assuming you have a chimney mount for the mast from radioshack?   




Ambient Weather has some different mounting that you should give a lookie at. they ship out promptly.    http://www.ambientweather.com/amwemoso.html

[LIWeather]

I have 2 pieced of kendorf about 2.5 feet apart on the chimney to provide as much support as possible. The stuff is super strong, better than any metal strapping sold at RS.

I chose the RS mast b/c it was sturdy, or so I thought. I had it as high as I could go to get as close ton proper siting as possible. I'm afraid lowering it is bringing ithe oops close to the roofline and potentially cutting of wind flow or creating an updraft creating a crosswind.

What is crazy is I have seen a few local setups and most are using Rain wise gear, below the top of the chimney.

I'm likely agonizing over this...lol I just want to clock those bigger winds accurately. Thanks for he feedback!

P.S. nice setup

[ocala]

Anemometer sighting is the number one issue with any personal weather station.
Most of us do not have the luxury of having an open field with no obstructions.
The best you can do is safely install it at the most optimum place you can and live with it.
Sorry I don't have any better advice but that's the reality.

[LIWeather]

Yeah, I suppose you are correct Ocala. I guess I'll try to experiment with heights a little more as well. Unfortunately, I was not able to observe the latest adjustments I made to the height to see if it was more stable. Think a perpendicular mast off of the side about 6-12 inches long with another small upward piece would prevent shaking?

I will drive around and check out some of the local stations as well as look over some of their data this week to compare.

Thank you again gentleman.

[Aardvark]

I can say for sure, that it was interesting for me to get that mast in that tripod. I did it myself and I believe I took it down . A dead lift, then lower it to the ground not to break anything.  then the reverse up.  Since then I haven't moved it in 10 years and have no desire to do that. When the top unit goes, it will make a nice bird perch.

[Scalphunter]

I wouldn't worry about a little shake  on that mast.  If you even been to see and see what thost cups go thru in an storm you wonder how they manage to stay in  place.  Most are anywhere from 30 to 100 feet up. out on an yardarm  where the snap from rolling is magnified. like the last skater in an group doing the whip, plus the  pitching and slamming that is transmitted  up there everytime  the vessel plows into the sea..

John

[LIWeather]

Thanks for the ambient link. My overall thought on it was that the mast diameter was not large enough, thus, allowing it to shake in higher winds. The mast I looked at on the ambient site was 1" in diameter where my mast is 1 1/4" in diameter. I'm sure others are available but I only looked at 1 mast.

I'm struggling to see how this shaking doesn't throw off spinning of the cups. Clearly, I'm not an expert and am seeking others experiences with shaking. I apologize for my ignorance and redundancy. I'm just trying to wrap my head around this more.

It is coming dwn to just dealing with what I have. I'm a bit concerned about using a larger diameter mast as it will increase the wind load on an aging chimney so I'll experiment a little with heights to find my happy medium.

[ValentineWeather]

I'm struggling to see how this shaking doesn't throw off spinning of the cups.

The cups are free spinning so it would take a tremendous amount of shaking to have much effect. I've recorded 66 mph wind speeds with lots of vibration on the 30' Tele-pole. #1 influence is Location, #2 height of anemometer. I wouldn't worry much about vibration or even swaying but having a good location is priority and nearly impossible for 90% of us.
I have the height 30' but being surrounded by old growth trees makes my wind speeds in town less than my 2nd weather station outside of town with anemometer mounted only 16' high. This location is premium with little wind drag no obstructions.

[Aardvark]

Thanks for the ambient link. My overall thought on it was that the mast diameter was not large enough, thus, allowing it to shake in higher winds. The mast I looked at on the ambient site was 1" in diameter where my mast is 1 1/4" in diameter. I'm sure others are available but I only looked at 1 mast.

I'm struggling to see how this shaking doesn't throw off spinning of the cups. Clearly, I'm not an expert and am seeking others experiences with shaking. I apologize for my ignorance and redundancy. I'm just trying to wrap my head around this more.

It is coming dwn to just dealing with what I have. I'm a bit concerned about using a larger diameter mast as it will increase the wind load on an aging chimney so I'll experiment a little with heights to find my happy medium.

there is a little shaking in the wind, but it won't throw off your values.