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Joe Bloggs
07 January 2024 20:38:37

Nice  upgrade from the ECM ensembles  tonight. 

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=50893&model=ecm&var=2&run=12&lid=ENS&bw=1 

Originally Posted by: Ally Pally Snowman 



Thats brilliant news

Manchester City Centre, 31m ASL

fairweather
07 January 2024 21:30:05

With all the talk of dewpoints, I thought I'd give a link to this useful page which allows you to calculate the wet-bulb temperature from the "regular" temperature and the dewpoint:

Wet-bulb calculator 

Basically the wet-bulb temperature is the effective temperature that something moist - suck as a snowflake - will experience once you allow for evaporative cooling. It's useful as if the wet-bulb temperature is below zero all the way down to the surface then any falling precipitation will land as snow (though it may still melt on landing if the surface is too warm of course).

Originally Posted by: jhall 


I seem to remember about 55 years ago as a junior laboratory scientist using a thing called a "whirling hygrometer" which was basically like a football rattle with a wet bulb and dry bulb thermometer for measuring relative humidity. Those were the days with proper instruments, none of this new fangled electronic stuff 😀
S.Essex, 42m ASL
fairweather
07 January 2024 21:43:01
Nothing in the 18z op that I can see of any great deviation from the pattern of the last few days. Cold or very cold for most of us except for the predicted midway blip.
S.Essex, 42m ASL
Gandalf The White
07 January 2024 21:45:18

Looking at the Arctic pressure pattern that ECM run is technically about as zonal as you could get … just east to west. 😊

Originally Posted by: Rob K 



You have reminded me of a memorable chart from a very blocked pattern some years back (probably many years back) where the cold Arctic air from Scandinavia was adverted westwards all the way to Newfoundland.

One point I have been thinking of making is about the value of ensemble support and cross-model agreement.  We’ve all seen the ensembles flip and cross-model agreement evaporate: the point is that, to use the expression used by Donald Rumsfeld, there are known unknowns, which the ensembles are testing, and the unknown unknowns, which the models cannot test. 

As we have seen today, the ensembles will change as new data about the atmosphere is picked up.  The models will spring something expected, whether that’s to suggest a patttern change or backtrack on one.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


fairweather
07 January 2024 21:51:48
True and if you miss the odd one out here and there I have found little change in the pattern summary for several days now. i.e  Short cold snap now for 3-4 days followed by several days less cold (but not mild) followed by potential for a strong northerly plunge of cold air that may diffuse into something different but still cold. Obviously the second half is the most likely  to change a bit but most likely a below average type.
S.Essex, 42m ASL
White Meadows
07 January 2024 21:52:10
An easterly only 24hrs away. Not something you get to see often especially in January:

https://www.wetterzentrale.de/de/topkarten.php?map=1&model=gfs&var=1&time=0&run=18&lid=OP&h=0&tr=24&mv=0#mapref 
 
fairweather
07 January 2024 22:07:34
 I watched the '47 Big Snow on My 5. Not sure if it was a different version to before. Probably same footage, different commentators. As a 13 old in the '63 freeze I have changed my mind bout which was worse. In terms of sheer length, a lot of snow and possibly some lower minimums I feel '47 edges it. There was more relentless snow and it appeared to be much more windy. Apart from the actual blizzards'63 was quite benign for long spells. Throw in the hardships of fuel shortage, powercuts (there were some '63 I recall) and rationing and lower standard of living, no alternative heating sources to coal and wood (although that hadn't changed in '63 much )  there was better quality housing for many and transport infra-structure improved. I heard a fair bit first hand from my father as my brother was born in March '47 and he lived through both and said it was worse but he had vastly improved living standards by then, which I have mentioned before. Anybody lived through both - I think one or two are a bit older than me 😁 
Just to make it on topic I must check out the model output for '47. 😀
S.Essex, 42m ASL
White Meadows
07 January 2024 22:10:16

I watched the '47 Big Snow on My 5. Not sure if it was a different version to before. Probably same footage, different commentators. As a 13 old in the '63 freeze I have changed my mind bout which was worse. In terms of sheer length, a lot of snow and possibly some lower minimums I feel '47 edges it. There was more relentless snow and it appeared to be much more windy. Apart from the actual blizzards'63 was quite benign for long spells. Throw in the hardships of fuel shortage, powercuts (there were some '63 I recall) and rationing and lower standard of living, no alternative heating sources to coal and wood (although that hadn't changed in '63 much )  there was better quality housing for many and transport infra-structure improved. I heard a fair bit first hand from my father as my brother was born in March '47 and he lived through both and said it was worse but he had vastly improved living standards by then, which I have mentioned before. Anybody lived through both - I think one or two are a bit older than me 😁 
Just to make it on topic I must check out the model output for '47. 😀

Originally Posted by: fairweather 


Nice summary. 
check out Gavs weather vids on YouTube for full analysis of both, at least for 62-63

 
Gandalf The White
07 January 2024 22:16:06
Not much change out to T+150 on the 18z GFS; if anything the pattern is marginally further west v the 12z.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


doctormog
07 January 2024 22:19:52

Not much change out to T+150 on the 18z GFS; if anything the pattern is marginally further west v the 12z.

Originally Posted by: Gandalf The White 



Yes good consistency again so far. I wonder how the later stages will evolve this time.
Gandalf The White
07 January 2024 22:26:22

Yes good consistency again so far. I wonder how the later stages will evolve this time.

Originally Posted by: doctormog 



Into the second half of the run now, at T+198, and there are more pronounced upper heights in the Greenland area, with a stronger ridge.

 
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


Joe Bloggs
07 January 2024 22:27:48
It’s gonna be a nippy one this run. 👀

Manchester City Centre, 31m ASL

doctormog
07 January 2024 22:30:23

It’s gonna be a nippy one this run. 👀

Originally Posted by: Joe Bloggs 



Just a little:
https://www.wetterzentrale.de/maps/GFSOPEU18_216_1.png
UserPostedImage 
Rob K
07 January 2024 22:32:41
Some quite cold air coming down from the north on the 18Z GFS run by the 17th. 
Yateley, NE Hampshire, 73m asl
"But who wants to be foretold the weather? It is bad enough when it comes, without our having the misery of knowing about it beforehand." — Jerome K. Jerome
doctormog
07 January 2024 22:36:40

Some quite cold air coming down from the north on the 18Z GFS run by the 17th. 

Originally Posted by: Rob K 



Actually as has been the case for days, the cold air comes down from the north from the 14th. The details are changing with each run beyond that and in the last couple of runs the trend has been towards a more wintry scenario.
Gandalf The White
07 January 2024 22:36:55
Not a bad Day 10 chart if it’s a blocked pattern and cold air you want….

https://www.meteociel.fr/modeles/gfse_cartes.php?ech=222&code=code&mode=0&mode3h=0&runpara=0&carte=1 
 
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


squish
07 January 2024 22:37:09
Pressure starts building again around Greenland at +240 rather than collapsing SE
D.E.W on Dartmoor. 300m asl
Saint Snow
07 January 2024 22:39:19
A particularly snowy 18z 😍

Martin
Home: St Helens (26m asl) Work: Manchester (75m asl)
A TWO addict since 14/12/01
"How can wealth persuade poverty to use its political freedom to keep wealth in power? Here lies the whole art of Conservative politics."
Aneurin Bevan
Downpour
07 January 2024 22:40:02
A colder, drier picture in the short run, which will come as welcome respite to the saturated ground. Medium term a rise towards something less cold but the dry theme continues. 
Chingford
London E4
147ft
Polar Low
07 January 2024 22:41:48

Some quite cold air coming down from the north on the 18Z GFS run by the 17th. 

Originally Posted by: Rob K 



close to lake effect at that time for Scotland

https://www.meteociel.fr/modeles/gfse_cartes.php?&ech=222&mode=2&carte=1 
Joe Bloggs
07 January 2024 22:43:50

A particularly snowy 18z 😍

Originally Posted by: Saint Snow 



A “wow” run for NW England there. 

The best charts still remain in the unreliable though so not counting my chickens. 

Manchester City Centre, 31m ASL

Polar Low
07 January 2024 22:47:12
About 6cm a hour for Scotland  that’s going
 
doctormog
07 January 2024 22:47:32
In terms of timescales, it is now below the one week mark when the first -10°C t850s reach the north coast so despite being almost a week out it’s not really classic “FI” territory. The building blocks are of course in place before then.
Joe Bloggs
07 January 2024 22:50:54

In terms of timescales, it is now below the one week mark when the first -10°C t850s reach the north coast so despite being almost a week out it’s not really classic “FI” territory. The building blocks are of course in place before then.

Originally Posted by: doctormog 



I’m becoming more and more confident that this  will happen , but not quite so confident (yet) that this  will happen.

Yes the overall pattern looks very promising but the actual weather on the ground is still very much up for grabs. 

Manchester City Centre, 31m ASL

Downpour
07 January 2024 22:51:58

Not a bad Day 10 chart if it’s a blocked pattern and cold air you want….

https://www.meteociel.fr/modeles/gfse_cartes.php?ech=222&code=code&mode=0&mode3h=0&runpara=0&carte=1 
 

Originally Posted by: Gandalf The White 



An eternity away in forecasting terms, Gandalf. In the reliable drier is the watchword. And I assume all TWOers will welcome that. 
Chingford
London E4
147ft

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