Wrong Pressure in Cumulus 1.8.4?

[beteljuice]

Any Met reference will be Relative (Sea Level Adjusted)

I know it sounds Ars* about face, but if you think about the 'weight' of air above your head, that is absolute, what a barometer actually measures.

But ......... the amount of air above you on top of a mountain is much less than if you were at Sea Level (sometimes referred to as Mean Sea Level).

So that everybody is using the same 'yardstick', everybodies Absolute (Local) is translated to Relative (Sea Level).

As stated earlier, unless you live below sea level - relative will always be a higher figure than absolute !

[Shawn]

I would assume relative, as the I guess the absolute is the pressure at the sensor. So if most stations show sea level values the you will have to set the relative value to the 1029 or what ever it is at the time you set it.

You are just the other end of the railway line to me in Cheltenham.

http://www.richkb.pwp.blueyonder.co.uk/ ... /index.htm

Rich

I have set my station to 1029 hPa rel.....Yes i have worked in Shurdington a few times. I work for Wales and West Utilities (was Transco) so I'm the one digging up the road in and around Cheltenham


Shawn

[DanielF]

OK, thanks to you all for your comments. I've finally got it (worked out where I went wrong!)

Half the problem is my aging eyesight, which caused me to read 'Ref.' in EasyWeather when in fact it says 'Rel.'. So what I thought was some sort of 'reference' pressure used to calculate 'relative' pressure, wasn't! It is in fact the current 'normalised' pressure, and that's what Cumulus was (correctly) displaying (though the figure is wrong - I have to adjust my AWS now).

So as beteljuice has explained, all I need do is wait for a stable pressure regime, get the air pressure from my two nearest official stations (either side of me), average them and enter that as my current 'Rel.' reading, and the WH1081PC will thereafter report the adjusted (MSLP) pressure for my station. Simple!

Sorry to have wasted all this bandwidth due to my misunderstanding!

Daniel

[harrym1byt]

Go to-
http://freemeteo.com/

...and type in your city, select 'vicinity', then select pressure. It will show several local stations, the relative pressures they were recording and at what times it was recorded. Now look at Cumulus's graph for pressure at those times to work out what your error is and how much up or down it needs to be adjusted by. Make the adjustments in EasyWeather >System >Setup, which adjusts it in the LCD display itself - job done. They record pressures at 20 past and 50 past the hour, but often skip times and also take a while to arrive on the web page - hence the need to compare against your graphs.

Don't use yahoo's weather, as that only gives absolute pressure records.