On Oct 10, 12:44*pm, "Roger Smith" wrote:
"Stephen Davenport" wrote in message

...
On Oct 10, 10:34 am, "Roger Smith" wrote:





"Richard Dixon" wrote in message

....
There will be no pressure in the UK on Thursday - repeat - NO
pressu

http://expertcharts.weatheronline.co...ts/en/ecmwf/20....

Richard

Now updated it seems! But, as the TV people sometimes say, a good time to
check your barometer.

Out of interest, what is the significance of the 1013hPa line? Is that
figure a generally accepted delineation between high and low pressure or
is
it just a facet of this particular forecaster?

Roger

1013.25 hPA is average sea-level pressure.

Stephen.

Thank you, Stephen- Hide quoted text -

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In the good old days of mercury- in- glass barometers, Torrecelli
found the atmosphere supported a 76 cm long column of mercury.
A nice round figure which converts to a not so round 1013.25 mb.

How they decided 76 cm of mercury was an average sea level pressure I
do not know.

Was it the average pressure in Rome in a year around 1643? What about
adjusting to sea level?
Were they that clever?

Len Wood
Wembury

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