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Christmas Update

PostPosted: 2013 Dec 20, 16:57
by Richard_Griffith
Interesting video from the Met Office on this weekend's storm situaton - watch out for updates ... -christmas

Merry Christmas to all

Re: Christmas Update

PostPosted: 2013 Dec 21, 20:49
by Eddy Graham
Hello Richard,
I am watching the development of this next low very closely from here in Stornoway, as various forecasts have it as deep as 936hPa or lower on Christmas Eve, close to land here. If I am correct, this would be the first sub-940hPa low to cross a part of land of the British Isles for at least the past 60 years, if not longer... (?)... but I will need to check Stephen Burt's Weather article on "the lowest of the lows" from a few years ago (Stephen, if you are reading this, I'd be delighted if you could confirm this statement of mine or not!). I recall the absolute longest MSLP is about ~922hPa from Scotland in late 19th century.
Meanwhile, I will be calibrating my barograph and have it wound fully in anticipation on Monday!
Kind regards and merry Christmas to all
Eddie Graham

Re: Christmas Update

PostPosted: 2013 Dec 21, 22:27
by Stephen Burt
Eddie and all -

The situation for the Christmas Eve low does indeed look interesting. This evening's Met O 72 h forecast chart deepens it to below 936 mbar (i.e. a closed 936 mbar isobar) not far off Lewis at 12z Tuesday. Meanwhile, the ECMWF forecast for the same time has a closed 924 mbar isobar slightly further off NW Scotland, and GFS a closed 928 mbar isobar in a similar position to ECMWF.

All three would imply that the barometer could fall to around 936 mbar in the northern Hebrides and the far north-west of Scotland, and quite possibly a bit below this at Sule Skerry, where there is a currently-operational AWS (IIiii 03010).

The lowest MSL pressure recorded at a land station within the British Isles back to 1886 has been 937.6 mbar recorded at Stornoway at 0020 GMT on 20 December 1982: at Sule Skerry it may have dropped as low as 936 mbar on this occasion. I wrote this event up in Weather (Burt SD. 1983. New UK 20th century low pressure extreme. Weather, 38: 208–213, and Burt SD. 1983. The lowest of the Lows ... Extremes of barometric pressure in the British Isles, Part 1 – the deepest depressions. Weather, 62: pp 4-14). Since 1949 and in the UK and Republic of Ireland, only the extreme north-west of Scotland has experienced barometric pressures below 940 mbar, and then only once, in December 1982.

On the morning of 8 December 1886, the barometer may have fallen as low as 924 mbar over northern Ireland, although the lowest authenticated value was 927.2 mbar at Belfast at 1330h, close to the centre of the depression. The British Isles record stands at 925.6 mbar, recorded at 2145h on 26 January 1884 at Ochtertyre, near Crieff (56° 23’ N, 3°53’W, 101m AMSL). This remains the lowest unchallenged
MSL pressure reading yet recorded in the British Isles. Corroborative evidence is afforded by the (MSL) readings of 927.2 mbar at Aberdeen at 2330h, 927.3 mbar at Dundee at 2230h, 927.4 mbar at Culloden, near Inverness, at 2300h, 927.5 mbar at Oban at 2100h, 928.8 mbar at Glasgow and 929.6 mbar in Edinburgh. Contemporary sources agree that these were the lowest pressures recorded in Scotland for at least the previous 120 years.

The all-time North Atlantic record stands at 912–915 mbar between Iceland and Scotland near 62°N 15°W on 10 January 1993.

Unless the track and depth of the storm are seriously amiss - and these 'bomb' events are difficult to get exactly right 72 h in advance - I think it very unlikely that the all-time British Isles record will be approached, but we could well see the 1982 Stornoway extreme surpassed, giving the lowest MSL pressure in these islands since 1886.

Eddie, if you are going to check your barograph, don't forget to notch it up by at least 20 mbar, on the assumption that the scale only goes down to 950 mbar! I'll look forward to your updates during the storm. The wind should be 'interesting' too - so keep safe!


Re: Christmas Update

PostPosted: 2013 Dec 22, 17:25
by Eddy Graham
Dear Stephen

Thanks very much for your detailed reply... and yes that was my next question! (whether to notch it up 20hPa or so, as the Casella barogram paper that I use only goes down to 950hPa). Actually, I normally keep the barograph in the office (as our Maritime dept at the college owns it), but I think I will bring it home for the festive period from tomorrow onwards and reset it here in Stornoway town, about 1km east of the college (as my office will be closed from Christmas until the New Year). We are at an altitude of about ~25m in the town.

This month has been truly extraordinary in terms of the volatility of the weather, and certainly ranks high on my list of lifetime "memorable weather experiences" (though it has been exhausting to keep up with it at times too!). I know the met station could change significantly yet for T+48hrs, but I am ready in anticipation of historic meteorological event as well.

A merry Christmas & best wishes to all
p.s. I was of course referring incorrectly to the Ochtertyre 1884 record in my last message. As you say, the value was 925.6 mbar (not ~922hPa, as I guessed in my previous message).