Comparing Pressure with Met Office Observations

[CandlemanUK]

Hello Everyone,

This is a first post, so please be understanding of my lack of knowledge!

I've just got what I now understand to be a Fine Offset weather station from Maplin. I've downloaded this fine Cumulus software and am having fun setting it all up. Most things are very well documented, but I can't get my head around the pressure. I have set my recorder up for HPa and absolute pressure, and cumulus indicates a different reading, which I think I have sussed as the same as the Relative reading on the recorder unit, presumably this is adjusted for altitude? Ok fine so far, but why are both these readings here substantially different from those that are shown on the weather charts on the Met office, or BBC sites? The units seem to be the same (HPa).

What settings should I use on Cumulus and the Recorder unit, am I missing something, or is the Barometer faulty?

Many apologies if this has been covered elsewhere, and any help or advise would be greatfully accepted.

Thanks in advance,


Pete.

[Repairman77]

Hi Pete; this had me fooled as well when I first got my station.

Cumulus reads the Relative pressure data and displays that.
You can alter the relative reading on the console (ignore the absolute).
See the instruction book for how to alter Relative Pressure.
That should then display the correct reading on Cumulus.

However the sensors in these units are not that accurate so you will have to set the Relative pressure value to the Met office or other accurate websites.

Here's a good one...
http://www.xcweather.co.uk/
I've found that site to be one of the most accurate.

Hope that helps,

Mike.

P.S. Can you fill in the Location in your profile so that we know what part of the UK or World you are in; County or State will do.

[callum91]

Weather stations should always be set to Mean Sea Level pressure.

Any website such as the one mentioned previously which uses METAR reports (airport weather reports) would be fine - just a case of finding the nearest Airport and perhaps waiting for a day when there is high pressure and not much wind about to set it.

However, the Air traffic controllers round down the pressure readings in METAR reports for safety, so an even better source of pressure readings is SYNOP reports (automated weather station reports) which will give you the pressure to the nearest 10th of a millibar (e.g. 1018.9).

In the UK you can locate your nearest SYNOP station here http://www.metoffice.gov.uk/climate/uk/networks/
and then fetch the latest SYNOP report, already decoded, from here http://www.mundomanz.com/meteo_p/byind? ... y_coun&l=1

[Reentrant]

Here's a good one...
http://www.xcweather.co.uk/
I've found that site to be one of the most accurate.

Is "altimeter" on that site the same as "relative pressure"?

[steve]

Is "altimeter" on that site the same as "relative pressure"?

Not quite. Altimeter pressure only takes altitude into account, but "relative pressure" is normally MSLP and takes other factors (e.g. temperature) into account. For setting a barometer for meteorological purposes, you should use MSLP.