On May 28, 8:20 am, "Rob Brooks"

At about 0645 BST this morning the pressure fell by 5.5mb inside the
hour.
This is shown on my barograph and also on my AWS Vantage pro, so
there is no
instrument failure. The pressure has now recovered, but the change
on my
barograph looks like some major feature has passed through. I have
not seen
a pressure change of this magnitude in such a short time scale- I
can only
assume it was a storm cell that was very close by.

Rob
Farsley
near Leeds

.... I can't now remember the criterion or exact details of the
warnings structure, but I *do* remember that in the days when this
country had a vibrant coal mining industry, such events had to be
'warned' to the NCB (as was) by the various MMOs and/or Weather
Centres around the UK. Very difficult to predict of course -
essentially monitoring the observations (actually quite easy to do in
the days when we had hand-plotted hourly charts) and being alert &
quick! (The mines would actually have barometers at the pit head, so
we were actually a second-line of defence really).

I believe that it was a rapid *fall* of pressure that was critical:
such would unbalance the atmospheric pressure 'environment' in deep
mines, allowing potentially explosive gases from old workings
(nominally sealed off - but always slightly porous) to mix with the
air in the operational part of the mine. The problem was diagnosed as
far back as the end of the 18th century according to one search I've
just done.

Another area that caused problems with such events was the issue of
the Regional Pressure Settings (FOQNH/minimum pressure setting for
safe operation of aircraft altimeters) - a rapid, unexpected fall in
such could cause panic in CFO!
[ I'm sure it's much better now ;-) ]

Martin.

--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023