Dear All,

Does anybody know the most rapid recorded pressure rise during the
passage of an extratropical system? I just tried googling with little
success, I'm sure we've talked about it before on here.

"Lothar" in France had rises of 27mb/3hr - but this appears to be
surpassed by the "Greenhouse Low" - an extraordinary low that hit
Iceland in 1991 with sustained winds of 57m/s recorded and pressure
rises of 30.4mb/3hrs. I'd doubt the validity of those gusts!!

Anyhow - does anybody know of 3-hour pressure rises bigger than these?

Cheers,
Richard

p.s. If anyone wants to read more about this:

http://cat.inist.fr/?aModele=afficheN&cpsidt=2917156 - abstract but no
content
http://folk.uio.no/jegill/publications.html - "Potential
vorticity-based interpretation of the evolution of 'The Greenhouse
Low', 2-3 February 1991" - probably a bit more technical !

On Oct 26, 12:03 am, "Richard Dixon" wrote:
Dear All,

Does anybody know the most rapid recorded pressure rise during the
passage of an extratropical system? I just tried googling with little
success, I'm sure we've talked about it before on here.

"Lothar" in France had rises of 27mb/3hr - but this appears to be
surpassed by the "Greenhouse Low" - an extraordinary low that hit
Iceland in 1991 with sustained winds of 57m/s recorded and pressure
rises of 30.4mb/3hrs. I'd doubt the validity of those gusts!!

Anyhow - does anybody know of 3-hour pressure rises bigger than these?

Cheers,
Richard

p.s. If anyone wants to read more about this:

http://cat.inist.fr/?aModele=afficheN&cpsidt=2917156- abstract but no
contenthttp://folk.uio.no/jegill/publications.html - "Potential
vorticity-based interpretation of the evolution of 'The Greenhouse
Low', 2-3 February 1991" - probably a bit more technical !

In "Weather", March 1975, there is a short article (M W Stubbs)
on an unusually deep Low that passed more or less directly over OWS "D"
(44N, 41W) at 2025Z on 29 Jan 1972. The lowest pressure recorded was
947.5 mb. At 2000Z the pressure was 955.3, 3-hr tendency -35.0 mb.
From various other figures quoted one can deduce that the 3-hr tendency
at 2025Z was -41 mb. At 2025Z the pressure then rose 22.6 mb in 35
minutes(!), and the 2100Z ob shows 340°/85 kn, sky obscured, heavy
showers, pressure 970.1 mb. At 2300Z, the last ob quoted, the
pressure was 987.8 mb, tendency +32.5 in 3 hrs. Extrapolating to
2325Z, the 3-hr tendency would be +40 to +41 mb.

Tudor Hughes, Warlingham, Surrey.

On 25 Oct 2006 16:03:22 -0700, "Richard Dixon"
wrote:

Dear All,

Does anybody know the most rapid recorded pressure rise during the
passage of an extratropical system? I just tried googling with little
success, I'm sure we've talked about it before on here.

"Lothar" in France had rises of 27mb/3hr - but this appears to be
surpassed by the "Greenhouse Low" - an extraordinary low that hit
Iceland in 1991 with sustained winds of 57m/s recorded and pressure
rises of 30.4mb/3hrs. I'd doubt the validity of those gusts!!

Anyhow - does anybody know of 3-hour pressure rises bigger than these?

No... but the biggest UK and british Isles pressure rise in 3 hours
was during the Great Storm of October 1987, was it not? I quote from
the Met Office website's analysis
http://www.meto.gov.uk/education/sec...ents/1987.html

"The greatest rise over three hours occurred at the Portland Royal
Naval Air Station in Dorset, where, between 0300 and 0600 UTC, the
rise was 25.5 mb. This was, by some margin, the greatest change in
pressure - either upwards or downwards - ever recorded in three hours
anywhere in the British Isles. At many places in southern England, the
pressure rose more than 20 mb in three hours. The return period for
such an occurrence is, again, roughly once in 200 years."

--
Dave

On Thu, 26 Oct 2006 02:20:06 +0100, Dave Ludlow
wrote:


"The greatest rise over three hours occurred at the Portland Royal
Naval Air Station in Dorset, where, between 0300 and 0600 UTC, the
rise was 25.5 mb.

That does not surprise me: I have my Open Scale trace of this event at
work and I think from memory mine was about 20-I will look again. I
recorded at Ryde,Isle of Wight

I am pretty sure the 'Weather' journal did a review of that event and
at the end of it there were quite a few figures given of the sort you
would like to hear about.

My colleagues sail from what was HMS OSPREY- some of the Olympics 2012
are being held there. It is going to be 'fun' as a relief road to the
area is unlikely to be ready by that time.

I went down to Portland Bill last week during a good gale and it was a
fantasically refreshing experience watching the Race below the
point.What is quite surprising is how close to sea level the point is-
no cliffs- and Portland seems to tilt downwards towards the sea. A
tour of the lighthouse at £2 seems to be a good bargain..and I was
amused at the Health and Safety notice warning people at the point
that the fog horn might go off without warning

R

On a tatty piece of sub-ether Robin Nicholson at
said...
On Thu, 26 Oct 2006 02:20:06 +0100, Dave Ludlow
wrote:


"The greatest rise over three hours occurred at the Portland Royal
Naval Air Station in Dorset, where, between 0300 and 0600 UTC, the
rise was 25.5 mb.

snipped

I am pretty sure the 'Weather' journal did a review of that event and
at the end of it there were quite a few figures given of the sort you
would like to hear about.

snipped

They did do a review of 1987 storm in Weather and plus the old Metmag.
Anyone remember that publication?

--
Rob C. Overfield
Hull

Felly sgrifennodd Dave Ludlow :
The return period for
such an occurrence is, again, roughly once in 200 years."

For any one given place (or specifically for this one location), or for
the whole of the UK? It makes a big difference! If for any one given
place, that's not so amazing.

Adrian
--
Adrian Shaw ais@
Adran Cyfrifiadureg, Prifysgol Cymru, aber.
Aberystwyth, Ceredigion, Cymru ac.
http://users.aber.ac.uk/ais/weather/ uk

"Tudor Hughes" wrote :
On Oct 26, 12:03 am, "Richard Dixon" wrote:
Dear All,

Does anybody know the most rapid recorded pressure rise during the
passage of an extratropical system? I just tried googling with little
success, I'm sure we've talked about it before on here.

In "Weather", March 1975, there is a short article (M W Stubbs)
on an unusually deep Low that passed more or less directly over OWS "D"
(44N, 41W) at 2025Z on 29 Jan 1972. The lowest pressure recorded was
947.5 mb. At 2000Z the pressure was 955.3, 3-hr tendency -35.0 mb.
From various other figures quoted one can deduce that the 3-hr tendency
at 2025Z was -41 mb. At 2025Z the pressure then rose 22.6 mb in 35
minutes(!), and the 2100Z ob shows 340°/85 kn, sky obscured, heavy
showers, pressure 970.1 mb. At 2300Z, the last ob quoted, the
pressure was 987.8 mb, tendency +32.5 in 3 hrs. Extrapolating to
2325Z, the 3-hr tendency would be +40 to +41 mb.

That's the one I remember reading about ... I'm pretty sure that's
the North Atlantic record, but I've no idea whether the North Pacific
- or indeed the Southern Ocean -- has done better (or worse!)

Philip

On Oct 26, 9:53 am, (Adrian D. Shaw) wrote:
Felly sgrifennodd Dave Ludlow :

The return period for
such an occurrence is, again, roughly once in 200 years."For any one given place (or specifically for this one location), or for
the whole of the UK? It makes a big difference! If for any one given
place, that's not so amazing.

Adrian
--
Adrian Shaw ais@
Adran Cyfrifiadureg, Prifysgol Cymru, aber.
Aberystwyth, Ceredigion, Cymru ac.http://users.aber.ac.uk/ais/weather/ uk

You seem to be confusing a large pressure change with a
localised phenomenon like heavy rainfall. A once-in-200 yr deluge at
any one place could be found *somewhere* in the country almost every
year but a large pressure change affects a much larger area than a
violent downpour. There was a rapid rise in pressure over thousands of
square miles and each station that recorded it would have its own "once
in 200 yr" record.

Tudor Hughes, Warlingham, Surrey.

Tudor Hughes wrote:

In "Weather", March 1975, there is a short article (M W Stubbs)
on an unusually deep Low that passed more or less directly over OWS "D"
(44N, 41W) at 2025Z on 29 Jan 1972. The lowest pressure recorded was
947.5 mb. At 2000Z the pressure was 955.3, 3-hr tendency -35.0 mb.
From various other figures quoted one can deduce that the 3-hr tendency
at 2025Z was -41 mb. At 2025Z the pressure then rose 22.6 mb in 35
minutes(!), and the 2100Z ob shows 340°/85 kn, sky obscured, heavy
showers, pressure 970.1 mb. At 2300Z, the last ob quoted, the
pressure was 987.8 mb, tendency +32.5 in 3 hrs. Extrapolating to
2325Z, the 3-hr tendency would be +40 to +41 mb.

Thanks Tudor - pretty extraordinary figures. I'm wondering if the
Icelandic report is the biggest pressure rise over land. I struggle to
believe the 59m/s sustained wind report however (109kts, if I'm not
wrong?) !

Cheers
Richard

Richard Dixon wrote:
Tudor Hughes wrote:

In "Weather", March 1975, there is a short article (M W Stubbs)
on an unusually deep Low that passed more or less directly over OWS "D"
(44N, 41W) at 2025Z on 29 Jan 1972. The lowest pressure recorded was
947.5 mb. At 2000Z the pressure was 955.3, 3-hr tendency -35.0 mb.
From various other figures quoted one can deduce that the 3-hr tendency
at 2025Z was -41 mb. At 2025Z the pressure then rose 22.6 mb in 35
minutes(!), and the 2100Z ob shows 340°/85 kn, sky obscured, heavy
showers, pressure 970.1 mb. At 2300Z, the last ob quoted, the
pressure was 987.8 mb, tendency +32.5 in 3 hrs. Extrapolating to
2325Z, the 3-hr tendency would be +40 to +41 mb.

Thanks Tudor - pretty extraordinary figures. I'm wondering if the
Icelandic report is the biggest pressure rise over land. I struggle to
believe the 59m/s sustained wind report however (109kts, if I'm not
wrong?) !

Cheers
Richard


Thanks for that. I was on duty that day (or night, I cant remember but
34 years ago, I now feel very old). We found a blank barograph chart in
the store room, and plotted the trace for the 36 hour period. It was
very difficult to get the detail right, as the pressure had risen and
fallen by 20mb or more in about the width of the pen we were using. But
it was an amazing trace and for a time I did have a written copy of the
observations we received, but that seems to have been lost. We tried to
imagine what life must have been like on the ship that day - rather
them than me.