Wind Direction when winds are calm should not be zero

I have noticed that when winds are calm, the firmware snaps to North until the wind picks up again. This causes a problem with wind charts in 3rd party software and creates inaccurate wind charts showing a substantial amount of North wind when there was none. Any thoughts if there are any solutions?

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This has been debated some in the past. Go to NULL position or leave the latest till …

The decision was made to set to 0° after quite some back and forth between the two options.

Now I can imagine this causes some weird behaviour but could you explain a little more where and the data coming in via ?? Local UDP, from WF servers ??? For sure there are solutions without reverting back to more radical solutions


I would prefer it stay at the former direction with a speed of zero.


Data coming from UDP in to Weather Display

I can imagine that some official rule is that when there is no wind, the direction is set to north. Great for official reports, not so practical for real time measurements.

Also setting it to north doesn’t add any useful information. Anyone with a bit of common sense would realize that wind direction is irrelevant when the speed is zero. So the wind direction can in principle be anything.

With that in mind, it would be more useful to show the direction of the last measurement when there was wind. That is also more inline with mechanical devices, they don’t rotate to the north when there is no wind, they stay in the same direction when windspeed drops to zero.

just my two cents.


it would be more useful to show the direction of the last measurement when there was wind. That is also more inline with mechanical devices, they don’t rotate to the north when there is no wind, they stay in the same direction when windspeed drops to zero.

I agree completely. I don’t like it constantly returning to North in variable, very light winds.

Lots of software reports direction=0 with speed=0, FWIW.


What I have noticed about the Null value is that with slight gust from non North directions on the average wind speed and direction it gets reported as wind out of the N, NW, NE when in fact the slight gust are from the S , SW, SE . This is what i have noticed ? Has any one else noticed this ?


Here’s a comparison between the Davis VP2 and WeatherFlow. Mounted on the same pole, same time period selected, etc. WeatherFlow just reports 0 degrees (or 360) when the wind speed is calm.WindDirPieCompare

Like you I see a major difference in wind distribution measurement. I live where the main direction of the air flow is from the SW, and yet looking at the wind distribution on my Weather Display chart for the SKY unit it says N, and that really blows things away from a local conditions perspective. As commented, I would expect the unit to display the last direction wind was sensed in as forcing it back to N and expecting TP sw to determine is the wind from the N @ 0mph i.e. calm or is it just going back to it’s home position, is quite a challenge. Certainly weather display is taking the data and logging it as the wind direction rather than null data.

I’m with you. This just doesn’t look right to mewind

Cumulus software has this as an option, which I use for my Davis VP2.

Use zero for current bearing if speed is zero

I prefer to use it that way, myself. However, having ‘options’ is always best for the end user.


Zero wind speed being North is not really what I am talking about. When I have my sky set for 3 sec updates and I have several mild gust and zero speed north indications in a minute it reads north when a lot of the gust in that minute were from the south , east or west but the north averages with the wind gust in the 1 minute and I end up with a north wind value in that minute
when in fact the wind I received in that minute was never from the north NW , NE , … ?

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Watching the wind this afternoon I am seeing what you describe, where the wind is from the SW/S with 3 second updates, the wind drops it goes back north. I think it’s sorta tied in with what folks are saying that driving the reading N doesn’t provide a true reflection of the conditions.

I did a little more research last night and found old references online saying the US and UK government weather bureaus have had differing suggestions over the years of what should be reported. Sometimes you read ‘show the last’ sometimes you read ‘show zero degrees’, sometimes you read “…if the wind is below NNN mph for XYZ seconds…” or the like.

Wondering if the issue of why it can’t show the last registered direction for when wind ‘was’ greater than zero is more of an issue of not wanting the Sky or Hub to have to save previous state and have that programming logic in there. It’s far simpler to just report what you see with a default=0 setting I guess.

Some even show 0 (zero) for no wind and 360 for north wind.

If WeatherFlow adopted this third parties could use it.

As it is we use wind speed of zero.

Yes I realize that when there is no wind that north is default But I am saying that when there are spurts of wind from south , west , east and variants of that the averaged minute value that are shown are averaged with that of null north value in the 3 second intervals and it shows a false reading in the minute average when wind values are light. Like it would show that wind is from the NW for minute average and actually only wind we got was from the WEST

I think you will find that zero wind does not affect the 1 minute average.

This is how WeatherFlow calculates (did the last time I checked) the average.

It will probably be the end of the week before I can verify that, just got 6" of rain cold front moved through . I am basing my thoughts from observations that I made when it was 95 + degrees last week and the wind was very light and definitely out of South SW and I would have NW / NE wind readings on the minute average . My other weather station never read any north wind readings.
I hope you are right though

You need to remember that ultrasonic anemometers and mechanical ones are apples and oranges. Ultrasonics can measure winds so minuscule that they wouldn’t even spin mechanical cups. Short of putting the ultrasonic in a sealed chamber, it will find even a draft and report the speed/direction if left unfiltered.

Having used an unfiltered ultrasonic, I have seen first hand how they will report random wind directions even on an apparently calm day. (You should see the weewx wind direction graph when the virtual wind vane is spinning around in circles on a calm day!) There’s a reason why the weather services (who have been using ultrasonics way longer than WF has been making them) have set standards for “variable” wind direction reporting under certain speeds, and I for one applaud WF for filtering the wind data to actually make it useful…