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nsrobins
19 December 2022 10:56:45
Offcially I don't have a scooby anymore what's going to happen over Christmas and towards the New Year.
If (a huge if with knobs on) GFS 06Z OP is correct, we have a few days of snow showers before the Arctic unleashes the hounds from hell over the New Year period. Exciting to see - yes. Chances of verfication - virtually zero.
Neil
Fareham, Hampshire 28m ASL (near estuary)
Stormchaser, Member TORRO
Downpour
19 December 2022 10:57:53

It just proves the point that just because there’s a large temperature contrast across North America, it doesn’t mean that LP systems will always drive eastwards across the Atlantic and bring us mild, changeable weather.  It’s all about the jet stream.

Originally Posted by: Gandalf The White 



GFS not without interest on the edge of the semi-reliable. 

Looks mild in the reliable (including Christmas Day) for all but the north of Scotland / highest ground. 

However, a change to a colder outcome is hinted even in the South come Boxing Day. Not much point looking much beyond that at this stage. 

Will be interesting to see if it commands any support. 
Chingford
London E4
147ft
Ally Pally Snowman
19 December 2022 11:00:25
Ridiculous GFS 6z 🥶🥶🥶🥶🥶🥶
Bishop's Stortford 85m ASL.
Saint Snow
19 December 2022 11:04:23
Lovely 6z.

At 12pm on Xmas Day, -5c 850hpa air is into Northern England with the 528dam line just below the border. Come 6pm, that cold air is down to a line running approx South Wales to the Wash - and it continues its path southwards.

With winds from NNW'ly to a WNW'ly and some unstable air, by Xmas evening, we'd be looking at snow showers into the western half of the UK, possible feeding through the Cheshire Gap into the Midlands.

I'd prefer it all to happen 24 hours earlier (I think snow on the evening of Xmas Eve is the pot of gold), but an actual white Xmas would be beautiful.


Pity it's just one famously fickle model at t+150 🤣🤣🤣 But we can dream...

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
+1
squish
19 December 2022 11:09:26
Quite a degree of support for this emerging theme on the 06z. Heres the mean +180

https://modeles16.meteociel.fr/modeles/gens/run/gensnh-31-1-180.png?6 

There are some equally stunning runs to the op in there eg no.5
D.E.W on Dartmoor. 300m asl
Gusty
19 December 2022 11:11:50
Oh what Fun ! 😂
Steve - Folkestone, Kent
Current conditions from my Davis Vantage Vue
https://www.wunderground.com/dashboard/pws/IFOLKE11 
Join Kent Weather on Facebook.
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squish
19 December 2022 11:23:19
The NASA run ( for what its worth), was showing heights remaining stable over Greenland and the US low going up the west side on its 00z run yesterday giving a similar scenario to todays 06z with the edition of  a deep low pushing up from the Azores towards the UK at day 10.  Todays run is trickling out and shows similar thus far....
D.E.W on Dartmoor. 300m asl
Saint Snow
19 December 2022 11:36:20
You'd expect the US/Canadian models to have a better grasp of how such a low would behave, than European/RoW models.

Both GFS and GEM have the low running northwards. GFS keeps it more intact, though, so more WAA, whereas GEM fills it, making the North Atlantic all rather messy. ECM does actually begin to also run the storm northwards, but then has it dissipating - but also sending a lobe of energy eastwards into the Atlantic, which heads our way and flattens any southwards ridging from the GH (which, though lack of WAA, is too flabby to have much influence anyway)

 

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
Joe Bloggs
19 December 2022 11:40:48
Just looked at the 06z GFS op. Gosh. :o

If anything the 06z GEFS are a minor downgrade to last nights 18z, or more specifically, the cold air is slower to move south compared to last night’s ensemble set. 

The -5C isotherm is straddling the far north of England whereas previously it was aligned over the M62 on 12z Christmas Day. 

https://www.wetterzentrale.de/maps/GFSAVGEU06_150_2.png 

The mean on latter frames is very much a north/south split. 

 

Manchester City Centre, 31m ASL
Hippydave
19 December 2022 11:42:22
Doesn't look like there's anymore agreement for the period 26th onwards IMBY than there was a couple of days ago. It looks likely the cold air that Scotland will be under from the 23rd will at least temporarily make it over the whole country around the 26th December but thereafter all options remain on the table.

The occasionaly entertaining op run is nice to look at but given last few days by this evening it's just as likely to pick a mild solution and have deep fetch south westerlies over the whole UK instead. 

In terms of looking at the detail a bit more it does look potentially very snow for some 24th and maybe 25th - Scotland favoured but could be some snow over higher ground in Northern England on Christmas day too, possibly a few showers around North Wales later in the day over higher ground too. Down here the 25th just looks damp and miserable on the 6z op but would be happy enough with that if the rest of it verified, unlikely though that is.

A few more days needed I think!
Home: Tunbridge Wells
Work: Tonbridge
+2
Brian Gaze
19 December 2022 11:52:58
I've added in a new option on the GEFS graph plotter which enables you to set an above or below parameter and plot only the runs which meet it. For example, display only the runs for the London grid point which dip below -10C at the 850hPa level.

https://www.theweatheroutlook.com/premium/gefs-graphs.aspx 



UserPostedImage
Brian Gaze
Berkhamsted
TWO Buzz - get the latest news and views 
"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
+5
Downpour
19 December 2022 11:56:12

Doesn't look like there's anymore agreement for the period 26th onwards IMBY than there was a couple of days ago. It looks likely the cold air that Scotland will be under from the 23rd will at least temporarily make it over the whole country around the 26th December but thereafter all options remain on the table.

The occasionaly entertaining op run is nice to look at but given last few days by this evening it's just as likely to pick a mild solution and have deep fetch south westerlies over the whole UK instead. 

In terms of looking at the detail a bit more it does look potentially very snow for some 24th and maybe 25th - Scotland favoured but could be some snow over higher ground in Northern England on Christmas day too, possibly a few showers around North Wales later in the day over higher ground too. Down here the 25th just looks damp and miserable on the 6z op but would be happy enough with that if the rest of it verified, unlikely though that is.

A few more days needed I think!

Originally Posted by: Hippydave 



An excellent summary. I concur. Lots to play for again. Will be interesting to see this afternoon’s GFS run. 
Chingford
London E4
147ft
Downpour
19 December 2022 11:57:48

I've added in a new option on the GEFS graph plotter which enables you to set an above or below parameter and plot only the runs which meet it. For example, display only the runs for the London grid point which dip below -10C at the 850hPa level.

https://www.theweatheroutlook.com/premium/gefs-graphs.aspx 



UserPostedImage

Originally Posted by: Brian Gaze 



a great feature - allows us to ignore all the horrible mild permutations! 
Chingford
London E4
147ft
scillydave
19 December 2022 12:45:27

I've added in a new option on the GEFS graph plotter which enables you to set an above or below parameter and plot only the runs which meet it. For example, display only the runs for the London grid point which dip below -10C at the 850hPa level. https://www.theweatheroutlook.com/premium/gefs-graphs.aspx   

Originally Posted by: Brian Gaze 

 I'm loving the consistency of the graph above Brian. Cold spell nailed on! 🤣Who needs the other 25 perturbations!   
Currently living at roughly 65m asl North of Cowbridge in the Vale of Glamorgan.

Formerly of, Birdlip, highest village in the Cotswolds and snow heaven in winter; Hawkinge in Kent - roof of the South downs and Isles of Scilly, paradise in the UK.
+2
Jiries
19 December 2022 13:05:05

a great feature - allows us to ignore all the horrible mild permutations! 

Originally Posted by: Downpour 



Retron used to do the graph updates and now one showing -15C uppers.  I see lot of very cold uppers just tad north of Scotland, surely it have to go somewhere? Whcih should go to UK direction.
Quantum
19 December 2022 13:10:18
UserPostedImage

Something we are starting to see for the xmas cold spell that we did not see in the MO output for the last cold spell was the 'extraordinary cold uppers' which I'd define as <-15C somewhere in the UK. We are seeing this for the xmas cold spell. Every run now has a handful of <-15s. In terms of 'deep cold' the xmas cold spell actually has more potential than the last cold spell, though its worth pointing out, that 2 days of deep cold produces less cold at the surface than 2 weeks of shallow cold.
 
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)

Total: 8 days with snow/sleet falling.

2022/2023 Snow days (approx 850hpa temp):

18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)

Total: 7 days with snow/sleet falling.

2021/2022 Snow days (approx 850hpa temp):

26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.
+1
Gusty
19 December 2022 13:13:45
Its encouraging to see the uncertainty post 26th December. Far better than staring at tightly packed ensembles well above the norm marching out to the end of the suite.

Lots of options now on the table as the models figure out what happens next.
 
Steve - Folkestone, Kent
Current conditions from my Davis Vantage Vue
https://www.wunderground.com/dashboard/pws/IFOLKE11 
Join Kent Weather on Facebook.
https://www.facebook.com/stevewall69/ 



Jiries
19 December 2022 13:15:22

UserPostedImage

Something we are starting to see for the xmas cold spell that we did not see in the MO output for the last cold spell was the 'extraordinary cold uppers' which I'd define as <-15C somewhere in the UK. We are seeing this for the xmas cold spell. Every run now has a handful of <-15s. In terms of 'deep cold' the xmas cold spell actually has more potential than the last cold spell, though its worth pointing out, that 2 days of deep cold produces less cold at the surface than 2 weeks of shallow cold.
 

Originally Posted by: Quantum 


Could give us more snow events on shorter deep cold than 2 weeks of bone dry cold spell?  Widespread very low uppers from NW to NE so surely it have to hit UK directly. nothing should stop on the path.  
Brian Gaze
19 December 2022 13:32:23

I'm loving the consistency of the graph above Brian. Cold spell nailed on! 🤣Who needs the other 25 perturbations!   

Originally Posted by: scillydave 



Here we go.

https://www.theweatheroutlook.com/premium/gefs-graphs.aspx?run=06&fv=tmp850&loc=london&lat=51.5&lon=0&p=p1_p2_p3_p4_p5_p6_p7_p8_p9_p10_p11_p12_p13_p14_p15_p16_p17_p18_p19_p20_p21_p22_p23_p24_p25_p26_p27_p28_p29_p30_p31_&cty=line&pv=-15&pd=min 



UserPostedImage
Brian Gaze
Berkhamsted
TWO Buzz - get the latest news and views 
"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
+1
fairweather
19 December 2022 15:30:23

Ridiculous GFS 6z 🥶🥶🥶🥶🥶🥶

Originally Posted by: Ally Pally Snowman 


Yes, a bit of an outlier to say the least. It does briefly find one friend between the 29th and 1st. A fair few around the more likely -5C  (London) though but that won't be cold enough.
S.Essex, 42m ASL
squish
19 December 2022 15:44:06
If you're watching the 12z gfs come out see how the low over the continental US develops ( as it doesn't even exist yet at +12hrs) and how it influences us down the line. Its fascinating stuff.
 
D.E.W on Dartmoor. 300m asl
squish
19 December 2022 15:54:44
The jet profile is quite 'subtly' different across the US at +72, which will likely lead to a very different outcome post Christmas...but we will see....
D.E.W on Dartmoor. 300m asl
Saint Snow
19 December 2022 16:03:58

The jet profile is quite 'subtly' different across the US at +72, which will likely lead to a very different outcome post Christmas...but we will see....

Originally Posted by: squish 




Got everything crossed that it just firms up on the 6z evolution (and that other models fall into line 😀)

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
Brian Gaze
19 December 2022 16:06:03
Out to t+114.

UserPostedImage
Brian Gaze
Berkhamsted
TWO Buzz - get the latest news and views 
"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan

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