Wind direction when "calm"

[staze]

Curious about something. Weewx doesn't seem to submit wind direction to wunderground when things are "calm", but WC always submits wind direction, even when there's no measured wind. So you get lots of straight lines.

Any thoughts about which is better? Maybe wunderground should have an API policy about it and it's not for us to decide... but I thought I'd start a discussion. =)

See attachments. Note, these are from two separate stations about 5 miles apart (as the raven flies).

[staze]

I'm actually having a hard time finding what the "standard" should be for this type of thing. Some things indicate that if the wind is "calm" the direction should be 0 (not to be confused with 360). Section 2.1.2 of this: http://www.nws.noaa.gov/om/forms/resources/SFCTraining.pdf

That said, in the section it indicates that direction should be reported, if it can be calculated, even for winds below 6 knots. But they still indicate that for "calm" it should be 00 for direction.

Someone has to be a weather data expert on here! =)

[Randall75]

Hi Staze
 I looked at this also
 I do know that my wind vane will move when there is not enough wind to move it to detect how fast the wind is moving so you get direction but not wind speed so it is NNW but calm
cheers
 

[elagache]

Hi Staze, Randall, and WeatherCat fans,

I'm actually having a hard time finding what the "standard" should be for this type of thing.

. . . . . . .

Someone has to be a weather data expert on here! =)

I'm no expert, but I'll hazard a guess that you are complaining about something of a "non-problem."  Sure the graphs of wind-direction can look strange at times, but so what?

Remember, that for the vast majority of meteorology's history, graphs on demand were impossible.  So folks trying to make sense of the weather would have to recall the overall conditions and would be looking at all their instruments - not just one graph.  If the wind speed is less than some sort of intuitive criteria - they simply wouldn't look at the wind direction.  So the weird graph you are describing they would never "see."

Now as computer users and especially website owners, we don't like ugly graphs.  However, is that a reason to come up with an arbitrary convention?  I'm guessing it isn't enough of a issue for professionals.  If it isn't for them, perhaps we should just follow their lead.  As the old saying goes:

Mind over matter: "If you don't mind - then it don't matter!" . . . 

Cheers, Edouard 

[mcrossley]

As a non-WC user, my software is configured to use 360 for N and 0 for calm. Not that that means anything! 

[staze]

And according to the NOAA, that's how it's supposed to be.

I've emailed wunderground to see their take. Obviously this is probably, as said, a modern "problem", but it's more I was curious as to why WC did it one way (Stu?), and weewx another. Anyone use the Davis software and know what it does? I did find something that seemed to indicate weewx used to do it like WC does, but changed recently. Not sure why.

[WCDev]

I think it's 50/50 (and some services do not allow the wind direction to be omitted) - here's the Met-Offices take on it: http://www.metoffice.gov.uk/media/pdf/s/p/OH_Chapter51.pdf

[staze]

I think it's 50/50 (and some services do not allow the wind direction to be omitted) - here's the Met-Offices take on it: http://www.metoffice.gov.uk/media/pdf/s/p/OH_Chapter51.pdf

Interesting. So much like NOAA, they don't specifically say (that I can see), but it seems that WC treats the sensors like an anemograph (which from what I gather), no wind would still record the direction the wind last blew in. Maybe once our House of Representatives pull their heads out of their asses, and we have a funded federal government I'll shoot NOAA an email and ask. Because now, I'm just curious. =) But from what I gather, no wind is 0 degrees (as opposed to north which is 360). 

I do note that CWOP seems to have wind direction even when there is no wind from weewx... so for some reason, they're just not submitting it to wunderground when there's no wind. Could just be a bug on their part.