Wind direction interval
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Should the reported Wind Direction be the instantaneous direction at the moment the data is sent, or the average direction for the last minute or 5 minutes? Same for Wind Speed, should it be instantaneous speed, or the average of the last couple minutes?
I'm asking because the only documentation I can find is a forum post that doesn't specify the time interval of any of the measurements, and some wind vanes might be a bit loose and easily influenced by tiny variations in wind, which would be negligible if using the average of a couple minutes (say 5 minutes).
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I would use an average (using vectors)
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@lightmastertech
WMO standards indicate the wind speed will be determined from the average over the 10 minutes preceding the observation.According to https://library.wmo.int/doc_num.php?explnum_id=3425
"The wind reported should be the mean over the 10 min preceding the observation.
If during this period there has been a marked discontinuity lasting at least 2 min,
the mean values should be assessed over the period after the discontinuity.
A marked discontinuity occurs when there is a wind direction
change of 30° or more with a wind speed of 10 kt (5 m/s) or more,
before or after the change, or a wind speed change of 10 kt (5 m/s) or more.The averaging period for measuring variations from the mean wind speed (gusts)
should be 3 sec."
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@lightmastertech plus one for using the average, a single instantaneous reading every five minutes minutes is a bit meaningless.
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@lightmastertech For now, we will adopt the rules from Citizen Weather Observer Program (CWOP).
Temperature
To reduce small variations in second to second measurements that are attributed to sensor sampling “noise” and not representative of ambient temperature, the following time sampling intervals for measurements are suggested:
- Temperature: latest 5 minute average
- Dew Point: latest 1 minute average
Wind
Mean Wind Speed and Direction: 2-minute mean of speed and direction sampled before the observation valid time sampled from high-resolution data (minimum: 5 second instrument polling).
Gust: Maximum instantaneous wind value observed in the 10 minutes before the observation valid time sampled from full resolution data (minimum: 5 second instrument polling).Pressure
Reporting frequency: 1-minute updates derived from the minimum reported pressure value observed in the past minute. Typically, basis for the 1-minute minimum pressure reports are from a series of ten 6-second interval instantaneous pressure measurements.
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@TomSlavkovsky said in Wind direction interval:
@lightmastertech For now, we will adopt the rules from Citizen Weather Observer Program (CWOP).
Temperature
To reduce small variations in second to second measurements that are attributed to sensor sampling “noise” and not representative of ambient temperature, the following time sampling intervals for measurements are suggested:
- Temperature: latest 5 minute average
- Dew Point: latest 1 minute average
Wind
Mean Wind Speed and Direction: 2-minute mean of speed and direction sampled before the observation valid time sampled from high-resolution data (minimum: 5 second instrument polling).
Gust: Maximum instantaneous wind value observed in the 10 minutes before the observation valid time sampled from full resolution data (minimum: 5 second instrument polling).Pressure
Reporting frequency: 1-minute updates derived from the minimum reported pressure value observed in the past minute. Typically, basis for the 1-minute minimum pressure reports are from a series of ten 6-second interval instantaneous pressure measurements.
Okay, I'll update my Meteobridge to use those averages. Thanks.
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Dear Windy Team, what about forecasts? Do you post instantaneous values for GFS/ECMF or do you guys post-process and use average values like 2min or 10 min averages?
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@bloah hi we don't post-process weather models in any way. This post was regarding weather stations.
