Author Topic: Understanding wind speed with WU and the WS-1400-IP  (Read 3112 times)

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Offline Arktikos

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Understanding wind speed with WU and the WS-1400-IP
« on: February 28, 2015, 03:48:55 PM »
I am wondering if there are any answers and solutions as to why there is a discrepancy between the daily high wind speed/gust and the weather history graph/chart, and how to fix it to reflect a more accurate picture of wind conditions. Today my summary for Feb 28 says the high wind speed was 5.4 mph and gust was 7.4 mph. However when I look at the history chart the highest wind recorded is a mere .7 mph. This discrepancy has been fairly typical for this station. although on windier days the discrepancy is somewhat less.

My theory is that the daily history graph?chart, which appears to record an entry every 5 minutes simply takes whatever the station was reading at that moment whereas the daily high reading is the highest read the station saw, most likely at sometime between those 5 minute interval records. The station itself seems to update every 8 seconds so chances are, unless the unlikely event were to occur where the high wind speed just happened to coincide with the 5 minute interval then the true high speed will never be reflected in the daily history graph.

I think in my situation being a rather gusty place to begin with  makes it worse than someplace where there is a lot of sustained wind speeds. However, this for me makes the weather graph/chart paint a very incomplete picture of what the true wind conditions actually are, almost to the point of being worthless. I wish WU would use the actual highest wind speed that occurred within the 5 minute span between updates to the graph instead of whatever the station happened to be reporting at the 5 min interval. I know WU gets this information because I can see the speed being updated every few seconds on rapid fire mode and very often those speeds are far higher than what the graph will show.
 

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Offline billybob

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #1 on: March 07, 2015, 05:31:04 PM »
My theory is that the daily history graph?chart, which appears to record an entry every 5 minutes simply takes whatever the station was reading at that moment whereas the daily high reading is the highest read the station saw, most likely at sometime between those 5 minute interval records. The station itself seems to update every 8 seconds so chances are, unless the unlikely event were to occur where the high wind speed just happened to coincide with the 5 minute interval then the true high speed will never be reflected in the daily history graph.
Your theory seems pretty sound. I refreshed the webpage by holding the shift key on the keyboard and refreshing the webpage exactly at the five minute interval when the graph was supposed to update and got updated with the current wind/gust reading.
Not very accurate but logging updates every few seconds probably puts unnecessary load on the database considering the number of stations and the number of updates that are sent every second. Another problem is that every station sends data at different intervals so the calculated average wouldn't necessarily have the same accuracy across the board.

Offline CW2274

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #2 on: March 07, 2015, 07:06:50 PM »
Basically put, WU is pretty much worthless if you want your actual data, irregardless of station brand. Their updates on wind gust especially are almost never right.

Offline billybob

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #3 on: March 07, 2015, 07:46:13 PM »
Thanks for chiming in about the gust numbers. I was trying to understand the resolution comment in the thread http://www.wxforum.net/index.php?topic=25186.msg242313 and the 2.5 resolution.

I got my WS 1400-IP a week ago or so and the wind gust reading is what bugs me the most about the station. It wouldn't be that bad if the readings were rounded off and changed a bit but the same readings of 0, 2.5, 4.9, 7.4, 9.8, 12.3 etc over and over make the graphs look bad and the gust readings pointless.

They need to either report the top reading for a single 16 second interval or the average of the top couple of readings. The average of 16 gust readings is not working out obviously. I would rather take an erroneous reading here and there instead of the exact same estimated reading over and over.

I am going to email ambient on Monday to see if maybe I can help them beta test this feature because the way it is right now, makes an excellent product look bad even for an amateur like me.

Offline Arktikos

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #4 on: March 07, 2015, 08:10:32 PM »
Basically put, WU is pretty much worthless if you want your actual data, irregardless of station brand. Their updates on wind gust especially are almost never right.

Would this be true for all the online weather outfits? I can understand the need to limit the amount of data being uploaded, especially on a free service such as WU. Too bad the data retrieval system isn't more sophisticated. Seems like a 5 minute data buffer could be stored at the station location and when the upload occurs actual specific readings such as high, low, and average wind speed would be sent. This would at least reflect what occurs between the 5 minute interval.

What do other people use to record accurate wind conditions? I am very new to all of this!
Alaska Data Portal:
http://tinyurl.com/q9rp3sw

Earth: a visualization of global weather conditions
forecast by supercomputers.
http://tinyurl.com/nbrgnnr

Offline Arktikos

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #5 on: March 07, 2015, 08:31:26 PM »
Thanks for chiming in about the gust numbers. I was trying to understand the resolution comment in the thread http://www.wxforum.net/index.php?topic=25186.msg242313 and the 2.5 resolution.

I got my WS 1400-IP a week ago or so and the wind gust reading is what bugs me the most about the station. It wouldn't be that bad if the readings were rounded off and changed a bit but the same readings of 0, 2.5, 4.9, 7.4, 9.8, 12.3 etc over and over make the graphs look bad and the gust readings pointless.

They need to either report the top reading for a single 16 second interval or the average of the top couple of readings. The average of 16 gust readings is not working out obviously. I would rather take an erroneous reading here and there instead of the exact same estimated reading over and over.

I don't think it is estimated so much as it is rounded off maybe.

So I wonder how wind gust speed is calculated at gov weather stations?  It must be a peak speed recorded within some time frame. I guess then that what is defined as wind speed is an average speed in that given time frame. My Ambient Weather also reports the gust speeds in multiples of around 2.45 but the actual wind speed isn't like that, there is no 2.45 pattern to it.   
I am going to email ambient on Monday to see if maybe I can help them beta test this feature because the way it is right now, makes an excellent product look bad even for an amateur like me.

Let us know what they say!
Alaska Data Portal:
http://tinyurl.com/q9rp3sw

Earth: a visualization of global weather conditions
forecast by supercomputers.
http://tinyurl.com/nbrgnnr

Offline CW2274

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #6 on: March 07, 2015, 09:01:54 PM »
Basically put, WU is pretty much worthless if you want your actual data, irregardless of station brand. Their updates on wind gust especially are almost never right.

Would this be true for all the online weather outfits? I can understand the need to limit the amount of data being uploaded, especially on a free service such as WU. Too bad the data retrieval system isn't more sophisticated. Seems like a 5 minute data buffer could be stored at the station location and when the upload occurs actual specific readings such as high, low, and average wind speed would be sent. This would at least reflect what occurs between the 5 minute interval.

What do other people use to record accurate wind conditions? I am very new to all of this!
All I know is that the hi/low and in between data I send to the NWS is always an accurate representation of my actual conditions, WU, practically never.

Offline floodcaster

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #7 on: March 08, 2015, 09:38:24 AM »
Thanks for chiming in about the gust numbers. I was trying to understand the resolution comment in the thread http://www.wxforum.net/index.php?topic=25186.msg242313 and the 2.5 resolution.

I got my WS 1400-IP a week ago or so and the wind gust reading is what bugs me the most about the station. It wouldn't be that bad if the readings were rounded off and changed a bit but the same readings of 0, 2.5, 4.9, 7.4, 9.8, 12.3 etc over and over make the graphs look bad and the gust readings pointless.

They need to either report the top reading for a single 16 second interval or the average of the top couple of readings. The average of 16 gust readings is not working out obviously. I would rather take an erroneous reading here and there instead of the exact same estimated reading over and over.

I don't think it is estimated so much as it is rounded off maybe.

So I wonder how wind gust speed is calculated at gov weather stations?  It must be a peak speed recorded within some time frame. I guess then that what is defined as wind speed is an average speed in that given time frame. My Ambient Weather also reports the gust speeds in multiples of around 2.45 but the actual wind speed isn't like that, there is no 2.45 pattern to it.   
I am going to email ambient on Monday to see if maybe I can help them beta test this feature because the way it is right now, makes an excellent product look bad even for an amateur like me.

Let us know what they say!

fyi
Wind Speed
The wind speed shall be determined by averaging the speed over a 2-minute period. At designated stations, Table 5-1 shall be used to estimate wind speeds when instruments are out of service or the wind speed is below the starting speed of the anemometer in use.

Wind Gust
The wind speed data for the most recent 10 minutes shall be examined to evaluate the occurrence of gusts. Gusts are indicated by rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls. The speed of a gust shall be the maximum instantaneous wind speed
Bill


Offline btcompute

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #8 on: March 08, 2015, 11:54:14 AM »
Quote
Wind Speed
The wind speed shall be determined by averaging the speed over a 2-minute period. At designated stations, Table 5-1 shall be used to estimate wind speeds when instruments are out of service or the wind speed is below the starting speed of the anemometer in use.

Wind Gust
The wind speed data for the most recent 10 minutes shall be examined to evaluate the occurrence of gusts. Gusts are indicated by rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls. The speed of a gust shall be the maximum instantaneous wind speed

Floodcaster,
What is the source of this info? Ambient, WU, other?
Thanks

Offline Arktikos

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #9 on: March 08, 2015, 12:26:51 PM »
The other day I ordered a small hand held wind speed meter, made by Ambient Weather http://www.amazon.com/gp/product/B005DF9VUC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 and it came in yesterday. My plan was to try to figure out these readings that are being posted on WU but I realize that the best way to do that will be indoors with a fan in order to get a set speed. I have a large 3 speed fan that should do the trick. I would like to understand more about what the 1400 sees as a gust by playing with the fan speed and watching the results on LiveData. Once I determine that the actual wind speed is not just some calculated formula then I can at least calibrate the 1400 and then put it back on the pole. If it turns out that the speed it reads is actual speed of the wind and not something rounded off like gusts are then I think the next thing I'd like to do is get a Meteobridge and try the 1400 out with other weather data sites and possibly even my own site someday.
Alaska Data Portal:
http://tinyurl.com/q9rp3sw

Earth: a visualization of global weather conditions
forecast by supercomputers.
http://tinyurl.com/nbrgnnr

Offline floodcaster

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #10 on: March 08, 2015, 01:20:27 PM »
Quote
Wind Speed
The wind speed shall be determined by averaging the speed over a 2-minute period. At designated stations, Table 5-1 shall be used to estimate wind speeds when instruments are out of service or the wind speed is below the starting speed of the anemometer in use.

Wind Gust
The wind speed data for the most recent 10 minutes shall be examined to evaluate the occurrence of gusts. Gusts are indicated by rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls. The speed of a gust shall be the maximum instantaneous wind speed



Floodcaster,
What is the source of this info? Ambient, WU, other?
Thanks

Federal Meteorological Handbook 1.  See chapter 5.
http://www.ofcm.gov/fmh-1/fmh1.htm

Bill


Offline btcompute

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #11 on: March 08, 2015, 01:36:48 PM »
Quote
Federal Meteorological Handbook 1.  See chapter 5.
http://www.ofcm.gov/fmh-1/fmh1.htm

Thanks!

Offline billybob

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #12 on: March 08, 2015, 08:29:15 PM »
@floodcaster : Thanks for the information.

@ Arktikos : I think the wind readings are fairly good, maybe a little under reported but my sensor is only 10 feet from the ground and not that far from my house. The anemometer may not turn at really low wind speeds but that's a hardware limitation (Wind Speed Accuracy: ± 2.2 mph). The wind gust readings however are using some weird logic ( Wind Gust Calculation: Peak wind speed in 16 second update period) and generate graphs like the one below.

They seem to be taking m/s readings and converting them to mph. That would generate numbers like the ones we see. However, we need some better rounding options.


Looking forward to your fan test results as they should be very interesting and informative.

Edit: Looks like they are changing the gusts readings in m/s to 1.1, 2.2, 3.3, 4.4 and so on to get the numbers on the graph. I don't really understand why they would do that  :shock: They shouldn't be padding the m/s readings like that and probably should round off the mph readings . That would give slight variations in the gust calcuations and make the graphs look much nicer. Of course this is assuming that the sensor can report in smaller increments than the padded m/s speeds. I don't see why not though since the wind readings themselves are measured down to 0.1 :? On the other hand the supposed accuracy is ± 2.2 mph which equals to surprise surprise 1 m/s  ](*,)
 


« Last Edit: March 08, 2015, 09:26:39 PM by billybob »

Offline Arktikos

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Re: Understanding wind speed with WU and the WS-1400-IP
« Reply #13 on: March 10, 2015, 01:16:01 AM »


Looking forward to your fan test results as they should be very interesting and informative.



Probably wont be happening real soon as I'm heading out of town for several weeks.
Alaska Data Portal:
http://tinyurl.com/q9rp3sw

Earth: a visualization of global weather conditions
forecast by supercomputers.
http://tinyurl.com/nbrgnnr