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

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.

Stephen ,wasn't my 5mb drop in an hour very significant ?,we can only be
about 40 miles from you.......


RonB
wrote in message
...
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

"ronaldbutton" wrote in message
...
Stephen ,wasn't my 5mb drop in an hour very significant ?,we can only be
about 40 miles from you.......


wrote in message
...

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


4.6mb drop in an hour (on the AWS) just up the road from Ron. Barograph
shows a nice jiggly trace as well.

All the best

--
George in Epping, West Essex (107m asl)
www.eppingweather.co.uk
www.winter1947.co.uk
COL 36055

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.


I was at Wattisham at the time and was drawing up a chart when I glanced at
the anemograph next to me. I asked the assistant, who was sending the
hourly ob to Air Traffic, to read the the pressure again. He asked why but
I just asked him to humour me. He read it, looked at the 2309 copy and the
register, then read it again. The pressure drop was 7mb. He called the info
to ATC and whilst he was sending the hard copy to them I suggested he read
it again - it had bounced up again by 5mb. During this, the wind rose by
about 10kt and we went into fog. A bit of a shock when you're in a warm
sector and expecting a nice boring day!


--
Graham P Davis, Bracknell, Berks., UK. E-mail: newsman, not newsboy.
"What use is happiness? It can't buy you money." [Chic Murray, 1919-85]