Newbie query

[glassman]

Hi Steve

Kids gave me a Fine Offset station for Christmas but I soon realised that the supplied Easy Weather software
was more trouble than it was worth so found Cumulus with a Google search.

Congratulations on an EXCELLENT piece of software !

All has been fine until this morning when I switched on the computer and downloaded the data to Cumulus -
I am running 1.8.4 build 605. There was no wind gust data plotted on the graph for the period the computer
was powered down. The graph plotting was normal while the computer was powered up and data was being
sent direct to Cumulus - IE gust data was shown on the graph.

The computer was powered down for a few hours during the day and the same thing happened - IE no gust
data is shown on the graph for the time the computer is powered down.

Here is a relevant section data from the Jan09log file

15/01/09,14:25,7.4,80,4.2,9.2,9.2,181,0.0,0.0,1010.6,12.9,21.0,40,9.2
15/01/09,14:55,7.0,82,4.1,4.5,4.5,90,0.0,0.0,1010.8,12.9,20.8,39,4.5
15/01/09,15:25,6.8,83,4.1,3.8,3.8,181,0.0,0.0,1011.0,12.9,20.5,39,3.8
15/01/09,15:55,6.6,83,3.9,3.8,3.8,135,0.0,0.0,1010.9,12.9,20.3,40,3.8
15/01/09,16:25,6.1,83,3.4,4.5,4.5,45,0.0,0.0,1011.1,12.9,20.1,40,4.5
15/01/09,16:55,5.8,81,2.8,4.5,4.5,135,0.0,0.0,1011.3,12.9,20.0,40,4.5
15/01/09,17:25,5.6,79,2.2,5.4,5.4,135,0.0,0.0,1011.4,12.9,20.2,41,5.4
15/01/09,17:30,5.5,79,2.1,3.1,5.4,55,0.0,0.0,1011.2,12.9,20.2,41,2.2
15/01/09,17:40,5.5,79,2.1,4.6,6.9,122,0.0,0.0,1011.4,12.9,20.4,42,4.5

The figures in blue are when the station was sending data directly to the computer
and the gusts were being plotted - any suggestions??? I can supply any other data
that might help pinpoint the problem

Best regards

Glassman

[steve]

The station only logs one wind value, so for the periods when Cumulus isn't running only one wind value will be logged and plotted (twice).

Steve

[glassman]

Hi Steve

Thanks for your instant reply ............

that was a stupid question I wont ask again !!!

Best regards

Glassman

[steve]

No - not stupid at all; my answer was completely wrong. I was thinking of wind direction.

Have you got Cumulus calculating a 10-minute average? Your station is logging at 30-minute intervals, and Cumulus uses the gust value to calculate the 10-minute average, so they're going to come out the same. You may be better off not using the Cumulus 10-minute average.

Now, whether Cumulus should be using the gust value to calculate the wind average for these stations is another question. For some types of station, this is definitely the right thing to do. For Fine Offset stations, I'm not so sure. But I'm loathe to change it until someone can tell me definitively how the gust value is defined.

Steve

[Frank02]

Hi Steve,

I just wish to say that I am using the Cumulus calculate 10-min average and it works very well. With the calibration I am using, I am always very close to the official Wind gusts and Wind speed reported.

However, I run Cumulus 24/7 so therefore I don't encounter the above situation since the wind 10min average is calulated from the gusts received from the station every 48 seconds all the time.

I don't really like the fine offset average as it is too often ups and downs (will go from 30kmh to 0kmh, back to 32kmh, etc. every 48secs) and that kinds of screw up the wind chill calculation.

The Cumulus calculation, I think, gives a more realistic figure of the wind average overtime.

Thanks.

[Frank02]

Glassman,

When you use the Cumulus 'Calculate 10min average', the 'Gust' figure gets plotted on the graph which corresponds to the highest gust reported by the station within the last 10 minutes. If you close Cumulus, that figures doesn't get calculated and therefore doesn't get plot on the graph when you restart Cumulus (I think).

You may, if you wish, change Cumulus so that the station reported gust (called 'Latest' in Cumulus) gets plotted on the graph. You would do so by selecting the Display option from the Configuration menu and check the 'Plot Latest Gust'. However, if you do so, be aware that you may end up with Gusts which are lower than the average when Cumulus is running and you are using the Cumulus 'Calculate 10min average'.

I hope I got it right.

[Frank02]

Also glassman,

You may wish to set your station to log (record) the data every 10 minutes (instead of every 30 minutes) if you also log the data every 10 minutes in Cumulus.

[Frank02]

Me again

I guess I didn't confuse only glassman but also myself

Steve,

When Cumulus isn't running, what 'Wind Speed' do you plot on the graph? The average wind value logged in the station or a '10 min running' average calculated from the gusts value recorded in the station log?

Thanks.

[steve]

When Cumulus isn't running, what 'Wind Speed' do you plot on the graph? The average wind value logged in the station or a '10 min running' average calculated from the gusts value recorded in the station log?

If you have Cumulus set to calculate the 10-minute average, it's the latter (which is why it comes out to the same as the gust if your logger is set to 10 minutes or more), but otherwise it's just the average read from the logger.

It's interesting that you find that the calculated 10-minute average is good, when it's using the gust value. I was thinking I should switch to calculating it from the station 48-second average instead, but from what you say maybe I should leave it alone.

Steve

[Frank02]

Hi Steve,

Right now I am using a calibration multiplication factor of 1.7 for both the wind gust and wind speed. But since I use the Cumulus calculate 10min average, I am not even sure that I need a calibration value for wind speed. If you were to use the station reported wind average to calculate the Cumulus 10min average, my guess is that I would need to use different calibration values for both wind gust and wind speed in order to match the official weather reports in my area.

[Frank02]

Ok, I think I got it now. When the wind speed and wind gust are the same than you see only one line on the graph.

Thanks.

[glassman]

Hi all

Wow that sparked off some discussion!

Thanks Steve and Frank02 for the suggestions.

Having read through the string and got fairly confused!
I have now set the station to log every 10 minutes using
the Easy weather software thats about all its useful for!

Cumulus was already set to plot "latest gust"

I will see what happens now !

Best regards

Glassman