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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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#1
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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 ! |
#2
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![]() 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. |
#3
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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 |
#4
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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 |
#5
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#6
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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 |
#7
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![]() "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 |
#8
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![]() 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. |
#9
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![]() 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 |
#10
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![]() 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. |
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