Wind Direction Strongly Biased in Tempest to North?

Noticing an extreme northern direction bias on the Tempest. I still have had my Davis station up so I can see wind direction. My winds are mostly from the west in general and I RARELY get winds from the north. I’ve noticed that when winds aren’t steady that the Tempest likes to report northern (or mostly northern) winds. I can see winds being from the south on the Davis (and the wind vane stays solidly south) and the Tempest will report the wind as being from the north. If we have stronger or steadier winds, it seems to register direction correctly.

Just a suspicion (based on my previous life as a programmer)… Does the tempest register no wind as coming from 0 (or 360) rather than null? For a simple scenario, it seems like if winds are like 3mph on one “tick” from 180 degrees then it has two “ticks” with no wind it registers it as coming from 0 degrees. Then the 3 tick average would be 1mph from the north east (60 degrees) instead of 1 mph from the south (180 degrees). (180 + 0 + 0)/3 = 60 degrees, instead of (180 + null + null)/1 = 180 degrees.

Not sure if this is a bug or a hardware issue or what.

https://tempestwx.com/station/19062/graph/65146/wind/2

I have reported many bugs with averaging, most have been fixed. I also reported the one with averaging while zooming out. Yours is just another example of it.
I took your data, zoomed in the the most detailed level. Look at the data at 12.20 and the 5 minutes before it on the left in this image. The average, including the 2 null measurements should be NE, but when you look at the zoomed out level in the right of this image, the data point at 12.20 shows more NNNE. I might have been spamming them with too many bugs so this one was ignored. Let’s hope your observation helps in strengthening support in fixing this. @dsj
Post from august 2019:

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I agree with Matt4. Wind does seem biased to the North. I have a line of tall trees about 20’ to the North of my tempest so wind can’t easily come from that direction. Southwest is most common. My readings are mostly from the North though.

@jimyouse, just to make sure… you are 100% sure the Tempest is facing the correct direction? With the WF logo pointing due North?
–Sam

I used my iPhone set to True North and Google Maps and handheld compass for comparison. There was very little difference in True North and Magnetic North.

I’m not convinced there is a problem but I do feel the wind direction seems to be from the North a little too much for where the Tempest is sitting. I wouldn’t have mentioned it if I hadn’t seen his post.

We had some storms yesterday and the direction of the higher winds and gusts look correct to me in the charts. Maybe I’m wrong about the direction of the regular background breeze.

I don’t have a known accurate device for comparison like he does though.

Thanks.

Understood, just wanted to make sure that there was not an error due to the Tempest not being pointed in the correct direction.

Siting can be difficult for the home user… most of us do not have a perfect wind fetch in all directions (as you say you have a stand of trees about 20’ north of your Tempest), which will cause some difference in wind speed and direction.

As a sailor, being out on the water quite a bit, we begin to realize that there are many, many factors in our environment the affect the wind… and we realize how little is require to change the wind.

Can you verify that what you actually feel standing next to your Tempest is no what it’s reporting when you see this happening?
–Sam

just to make it perfectly clear, at least the webinterface has a bug that averages towards the north when there are periods of no wind at all. It doesn’t have anything to do with the exact north orientation of the unit at all.

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Just to verify, on my siting I’ve verified the direction of the tempest is correct (WF logo pointing north). I’d be a little less convinced that it was a reporting issue if I wouldn’t have kept the Davis analog vane there.

Totally realize wind is one of those oddball things where it can be affected easily (especially at slow speeds), but never saw this with my Davis station, and having an analog wind vane to use as current reference makes it look a bit more like a potential issue. I can stand next to the installation and confirm observations as well. When I go to check what’s going on when it is happening, it seems to be only when the wind has calm moments. Only other thing I can think is if the wind is too low to be felt or move the analog vane but is truly pushing from north ever so slightly… not sure sensitivity of Tempest vs an analog device, just seems odd that most winds are predominantly SW in this location but super low winds would be northerly (but as has already been said, wind is an odd thing)

I’m wanting to move it to a rooftop install, but wanted to make sure everything was good before doing so.

The sonic sensor on the Tempest is way more sensitive than the analog Davis device… so, yeah… the Tempest will show wind before the Davis does.

It does seem that what you are seeing is the anomaly of super light to calm winds being reported as N.

I just got a little wet using the hose and stood by the tempest for a few minutes. It appears to be correct. I can feel the slight breeze from N and NW.

Thanks.

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Hi Matt and welcome to the community! Wind is tricky! We’ve taken a look at a sample of your data and everything looks good in terms of data integrity - your hardware is functioning properly. We need a little more info to help troubleshoot the apparent northern bias. These issues are often due to siting and/or the subtle differences between an ultrasonic anemometer and a spinning cup & vane anemometer.

The most helpful thing would be to point out a more specific time range where you are seeing this phenomenon. And if you can share your Davis station’s data for the same time range, that would help a ton with troubleshooting. Also, if you can provide photos and describe how you have your Tempest installed (as it relates to potential obstructions on your property as well as how it relates to your Davis), that will help.

Hmm. There’s nothing built in to the way the tempest samples wind that would cause it to have a northern bias. The one-minute observations you see at the deepest zoom level are an average of 20 samples (one every 3 seconds). And it’s true that if the direction is highly variable during any particular one-minute period then the “average direction” may not be very meaningful - but it still shouldn’t have a northern bias. To answer your question about the math side of things: when the wind speed is 0 the direction is null (not 0 or 360), and therefore does not affect the average.

Assuming this is during light wind events, is it possible the Davis vane is simply “settling” into facing south? As you probably know, one of the drawbacks to a physical wind vane is that inertia & gravity can prevent it from aligning to the true direction of the wind, especially when the wind is unsteady or very light. A slight tilt from perfectly horizontal can create a position that the vane will literally gravitate toward.

Yes! There is still a bug in the apps in terms of the way direction is averaged as you zoom out (the one-minute 0 speeds are being counted in the direction average as a direction of 0). Thanks for the reminder, @sunny - I will make sure that gets moved up the priority list. That may be part of the confusion here @matt4 - to eliminate that, be sure you are zooming all the way in to the one-minute graph before you compare the data.

Much of the same discussion may apply to your situation, Jim, but I’m glad to hear the Tempest seems to be agreeing with your physical observations now!

PS: I’m quite impressed by your improvement upon the old “wet your finger” technique… :slight_smile:
finger

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I’ll have to do the wet the finger technique for sure!!!

Based on what is being said, I’m wondering if it is just some sort of local phenomenon from siting or whatever. As pointed out, it takes a bit of wind to get an analog wind vane to move and if the sonic sensor is much more sensitive, I wouldn’t be able to rely on the analog vane for an accurate direction reading. Given that this happens in very light winds, maybe I’ve got some sort of micro-pattern that’s driving very light northerly winds with the current siting.

I’m planning on siting the station up on the roof this weekend (I have a scary high roof but the weather will be perfect this weekend), which may change things up since there are less obstructions up there (although of course the roof pitch might give me other issues, but that’s a bridge to cross later, lol).

Appreciate the input.

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