On May 28, 6:52*pm, wrote:
On 28 May, 14:38, Tudor Hughes wrote:

* * It sounds as if it was thunderstorm-related but extremely rapid
falls can be caused by gravity waves. * One of these affected west
London (Sunbury) on about 19 Jan 1977. * We had a mercury barometer in
the laboratory and you could actually just about see the mercury
surface falling. *I cannot remember the exact figures (it has been
written about, probably in "Weather") but 8 mb in 5 minutes seems to
ring a bell. *There were gusts to 30 kn but nothing more in an
otherwise breezy cloudy SW'ly. *The expected End Of The World did not
happen.

Tudor Hughes, Warlingham, Surrey

Well-remembered, Tudor. (It was actually the 25th of January, but
what's six days in 31 years ... !) Heathrow had a fall of 7 mbar in 5
min and I can recall first-hand accounts of the duty observers
thinking either all their barometers had broken at the same time, or
the world/their career/their life was ending, or quite possibly all
four. Must have been hairy on final approach I'm sure. Reference in
Weather for those who want to look it up:

Harvey, I. G. and Warren, D. E. (1978) Observations of rapid pressure
variations: 25 January 1977. Weather, 33, pp. 11-17.

That reminds me: I haven't seen a really good 'jiggly' barograph trace
from a series of thunderstorms for a long time now. Must be overdue.

No sign of the Northern England rapid drop this morning down this way
(fairly steady 8 mbar fall 22-04z, then fairly steady 1001-1002 mbar
until a rise set in 13z), so there must have been a significant
additional gradient somewhere for a while ...

--
Stephen Burt
Stratfield Mortimer, Berkshire

I can still visualise the barometer at its place in the
laboratory. I was working for BP at the time, and being what they are
no expense was spared with apparatus. Its nominal use was to check
the pressure for distillations but frankly that was a bit precious and
I used to read purely it out of meteorological interest. Like the
forecasters I literally thought it had sprung a leak and said so
(" ..... there's something wrong with this....") but it bottomed out
and later started rising slowly. BP Sunbury is just south of Heathrow
and you could watch the planes taking off and landing. We
occasionally did a bit of work on oil additives to justify our rather
generous salaries.

Tudor Hughes, Warlingham, Surrey.