Cumulus Support

Hello,

I have noticed that my wind speed graph looks different than neighbouring stations a few miles away. Both using the same weather station.

This is my wind chart...



...and this is a neighbouring station's



I am trying to understand why my wind chart has 'long' periods of the same wind speed and the neighbour's does not. I have looked back at the date and sure enough the identical numbers appear in groups from the VP Console. I am a new VP user and wondered if other forumites may have an understanding if this is simply a setting in the console of the ISS itself.

Any suggestions welcomed.

Andrew

Wind speeds vary enormously even when located reasonably close to each other. Topography, tree lines & siting of the anemometer in relation to the ground as well as how close it may be to the roof line etc. etc. etc..
Comparing wind speeds is probably a futile exercise unless both anemometers are virtually next to each other & using readings in the same format, IE both using Kts or Mps so they can be compared like for like.

Hello Touchtone,

Thanks for the advice. I did wonder whether it was simply as you mention, local conditions or was it a setting somewhere.

Regards

Andrew

It looks like you are plotting the instantaneous gust, and the other station is plotting the 10 minute high gust?

Hello mrcrossley,

I am looking at the wind speed (yellow) line not the wind gust (green) line.

As an example, the data from the console, when extracted from Cumulus' July13log.txt shows periods of wind speed (yellow) line similar to...

17/07/2013 00:23 0.9kts
17/07/2013 00:24 0.9kts
17/07/2013 00:25 0.9kts
17/07/2013 00:26 0.9kts
17/07/2013 00:27 0.9kts
17/07/2013 00:28 0.9kts
17/07/2013 00:29 0.9kts
17/07/2013 00:30 0.9kts
17/07/2013 00:31 0.9kts
17/07/2013 00:32 0.9kts
17/07/2013 00:33 0.9kts
17/07/2013 00:34 0.9kts

The question I am asking myself is "Were the conditions really a constant 0.9kts wind for the 11 minutes between 00:23 and 00:34 on 17th July?" There are multiple examples of the same in the log file. Seems strange to me...

Regards

Andrew

So the yellow speed line is your average wind speed. What is plotted depends on the Cumulus settings. For instance do you have integer wind speeds enabled (the VP2 works in mph natively, so not sure what effect this setting has if you are using knots) this will round the figure to the nearest mph which can make it appear to 'stick'. Also the averaging period will affect the plot. Unless you know the other stations settings it will be difficult to make comparisons with yours.

I think the comparison between sites comment is valid, there are too many unknown variables. Your comment regarding the rounding made me think, I did change it recently to see whether I liked it and then changed it back again where is has stayed sicne then. I went back to the data before during and after the change. It makes interesting reading...

Before, rather what I would expect...
11/07/2013 16:00 4.8
11/07/2013 16:10 3.9
11/07/2013 16:20 4.4
11/07/2013 16:30 4.8
11/07/2013 16:40 5.4
11/07/2013 16:50 5.1
11/07/2013 17:00 4.7
11/07/2013 17:10 4.6
11/07/2013 17:20 4.5
11/07/2013 17:30 4.7
11/07/2013 17:40 4.4
11/07/2013 17:50 4.1
11/07/2013 18:00 4.4
11/07/2013 18:10 4.8

During, again makes sense...
13/07/2013 08:15 0
13/07/2013 08:20 1
13/07/2013 08:25 1
13/07/2013 08:30 1
13/07/2013 08:35 1
13/07/2013 08:40 2
13/07/2013 08:45 1
13/07/2013 08:50 1
13/07/2013 08:55 1
13/07/2013 09:00 2
13/07/2013 09:10 2
13/07/2013 09:15 1

After, I expected to see data 'similar' in nature to the 'before' set
14/07/2013 11:35 2.6
14/07/2013 11:40 2.6
14/07/2013 11:45 3.5
14/07/2013 11:50 3.5
14/07/2013 11:55 3.5
14/07/2013 12:00 3.5
14/07/2013 12:05 3.5
14/07/2013 12:10 3.5
14/07/2013 12:15 3.5
14/07/2013 12:20 3.5
14/07/2013 12:25 4.3
14/07/2013 12:30 3.5
14/07/2013 12:35 3.5
14/07/2013 12:40 4.3
14/07/2013 12:45 4.3
14/07/2013 12:50 4.3
14/07/2013 12:55 4.3
14/07/2013 13:00 4.3

Here I see blocks of similar data which makes me suspicious since generally the conditions hadn't changed, same high pressure over UK, same high temperature locally...

Andrew

Are you using the average wind speed from the console, or have you set Cumulus to calculate it? What other wind speed settings have you selected?

Yes, I am using the average wind speed delivered from the console and not set for Cumulus to calculate it. The remaining settings are as per the screen shot below:

I'm not sure I understand what you think the problem is, in that case. You have very low wind speeds, so it seems to me that it's quite reasonable that the 10-minute average could show the same value for several minutes. Note that 0.9 kts is 1 mph, and the station has a resolution of 1 mph. At low speeds, it can only show zero, 0.9, 1.7 etc. For the average value, you might expect other values to be shown, as you apparently saw in your 'before' data. But Cumulus is just reading whatever value the console is supplying. Note that it's the Davis DLL which does the conversion from mph to kts.

You could check to see if the anemometer wind cups do spin easily & are not being restricted by cob webs or something else. Cob webs can & do slow down the wind cups & they can build up very quickly. I was surprised to have that problem within a few weeks of installing my new station.
I now have a dog flee collar around the pole & that has been working well since. My anemometer is mounted about 7 feet above my roof ridge & about 25 feet above the ground, so it is surprising that spiders get that far up, but they do.

Hi,

Let me do some more checks and try and present the perceived problem a little more articulately. I have only had my VP2 up for a week so am getting used to it and the differences between this AWS and my old Fine Offset.

Andrew