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Brian Gaze
01 December 2023 11:42:36
GFS 5 day 500hPa bias stats are shown on this chart:

https://www.emc.ncep.noaa.gov/users/verification/global/gfs/ops/grid2grid_gfs_4cycles/images/bias_HGT_P500_fhr120_G002NHX.png 

At a quick glance, there is no obvious pattern apparent to me. Perhaps analysis of the data would show otherwise.
Brian Gaze
Berkhamsted
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"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
doctormog
01 December 2023 11:52:21
Withe details observed regionally compared with on a global scale I doubt it would show any statistically significant difference.
Timmytour
01 December 2023 12:01:11
When we've come into a cold period in winter I have basically three default positions on viewing the modelling of the following two weeks...

1)  I don't think the breakdown is going to happen quite like the models are telling us. They would have shown it breaking down like that in December 1962 if they'd been around to view.

2) The way the models are showing that breakdown happen is eerily reminiscent of what took place in early January 1947

3)  This is going to be a long winter of searching for opportunities of mini-cold spells,

I've currently moved away from default position number one and am at the moment clinging on to default position no. 2 😀
Broxbourne, Herts 133ft ASL
Saint Snow
01 December 2023 12:04:21
The GFS 6z Op at least is terrible for northern blocking. Although the PV in general is pretty scattered, it shows a few lobes of the scattered PV coalescing over Canada & Greenland to form a partial PV, which begins to oscillate around itself (which will spin-off lows across the Atlantic towards the UK).

That is doom for the chances of a Greenland High, or even retrogression of any Scandinavian high that may still form.

The 0z had a not totally dissimilar formationing of the PV with low heights over N Canada and Greenland. The 18z, FWIW, kept the PV well-scattered.

The fact it's well into FI, and there's not been a consistent signal for it is a straw to cling to. But if GFS is onto something with the PV organising over Canada/Greenland, then we can kiss goodbye to the chances of a Yuletide cold and snowy spell for the UK.





 

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
ballamar
01 December 2023 12:11:26
A lot of scatter in the ENS no default zonal setup guarantee yet. Hopefully a Scandi high potential causing the uncertainty. Anyway seen snow on the first day of winter - more than last year!
squish
01 December 2023 13:23:40
The fact this thread dropped from the front page says it all really !

but ( just for fun)…06z NAVGEM

https://modeles3.meteociel.fr/modeles/navgem/runs/2023120106/navgemnh-0-168.png?06 
D.E.W on Dartmoor. 300m asl
Quantum
01 December 2023 13:39:36

The fact this thread dropped from the front page says it all really !

but ( just for fun)…06z NAVGEM

https://modeles3.meteociel.fr/modeles/navgem/runs/2023120106/navgemnh-0-168.png?06 

Originally Posted by: squish 



GEM0z keeps it going too.
 
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.
squish
01 December 2023 15:27:15
ICON 12z classic 80s winter battle ground.
batten down the hatches at least for a few days … 
D.E.W on Dartmoor. 300m asl
Retron
01 December 2023 15:38:05

ICON 12z classic 80s winter battle ground.
batten down the hatches at least for a few days … 

Originally Posted by: squish 


Yes, a fascinating run - all the classic ingredients for a proper easterly blast.

It makes a change (and this includes all the models) to see a proper upper high trapped to the north of the jet - it's over Greenland at the moment and will migrate to Svalbard in the next few days. It's after that when things could turn interesting, depending on where it ends up next!

It's worth mentioning that all the models show a marked pressure rise over Finland next week as the result of that upper high, and it's no surprise that ICON has the highest readings. The higher the better from the point of view of coldies, or at least those coldies who favour an easterly...

 
Leysdown, north Kent
Quantum
01 December 2023 15:58:24
Negitive tilt on the ARPEGE12Z and substantially different to the ICON12Z.

UserPostedImage
This is still not close to being resolved yet.
 
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.
Saint Snow
01 December 2023 15:58:58

Yes, a fascinating run - all the classic ingredients for a proper easterly blast.

It makes a change (and this includes all the models) to see a proper upper high trapped to the north of the jet - it's over Greenland at the moment and will migrate to Svalbard in the next few days. It's after that when things could turn interesting, depending on where it ends up next!

It's worth mentioning that all the models show a marked pressure rise over Finland next week as the result of that upper high, and it's no surprise that ICON has the highest readings. The higher the better from the point of view of coldies, or at least those coldies who favour an easterly...

 

Originally Posted by: Retron 



That low over Iceland at t+180 looks like it begins to disrupt against the strengthening block to its east.

How do you rate the chances of the low disrupting fully and throwing energy SSE'wards over the UK? And would I be right in thinking that, in such a scenario, the low would drag cold southwards along with a trailing front of snow?

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
The Beast from the East
01 December 2023 16:22:51
GFS almost gives us a backdoor easterly. Just seems too much energy going north and not under. Shame
 
"We have some alternative facts for you"
Kelly-Ann Conway - special adviser to the President
Retron
01 December 2023 16:26:52

That low over Iceland at t+180 looks like it begins to disrupt against the strengthening block to its east.

How do you rate the chances of the low disrupting fully and throwing energy SSE'wards over the UK? And would I be right in thinking that, in such a scenario, the low would drag cold southwards along with a trailing front of snow?

Originally Posted by: Saint Snow 


I'd rate it a bit higher now the 12z GFS is coming out! 😄

In all seriousness, I'd say that's a low chance at the moment (the full disruption thing), but at the moment 24 hours is a long time in model-watching. It's clear that even small changes upstream make a massive difference in our neck of the woods, and I doubt anyone could confidently predict the situation on say Monday. At the moment I'd say a ridge following on (as per MetO and GFS) is more likely, pushing the low SE'wards over us, rather than the low being shoved away by heights to the east, but again - you can't be confident in either of those really.

As for a disrupting low moving close to the UK with snow on the boundary... as ever it depends on how cold the air is ahead of the front, whether it's just a thin boundary layer of cold air or whether it's deeper, the exact angle of attack (we always want to see fronts running more east-west than north-south in a battleground)... all sorts of things. It's something that the models will struggle with even 12 hours out.

Heck, just look at Sunday's potential snow "up north" to see how hard it all is - could be rain, could be a bit of wet snow for Wales and the NW of England, could all be a bit further south and stay dry up there.

It's at times like this you realise just how hard it is for the models to, well, model the situation!
Leysdown, north Kent
doctormog
01 December 2023 19:26:18
Again the 12z ECM is less progressive than the 00z at day 10. 

https://www.wetterzentrale.de/maps/ECMOPEU12_240_1.png  
Ally Pally Snowman
01 December 2023 19:29:03

Again the 12z ECM is less progressive than the 00z at day 10. 

https://www.wetterzentrale.de/maps/ECMOPEU12_240_1.png  

Originally Posted by: doctormog 



Yep another  day 10 ECM 12z easterly lol.
One day!
Bishop's Stortford 85m ASL.
CField
01 December 2023 20:03:55
As said before those reds to the south west need to do one...Still too close for comfort
Favourite snowstorm
Famous channel low
Dec 31st 1978
Hastings East Sussex
Foot of level snow severe drifting
Next day max temp -4 degrees Celsius
White Meadows
01 December 2023 20:17:46
Met office offers a little intrigue for late December:

”…colder interludes, but these likely to be short lived at first. Perhaps a greater chance of a longer cold spell late in the period.”
Ally Pally Snowman
01 December 2023 20:50:02

Met office offers a little intrigue for late December:

”…colder interludes, but these likely to be short lived at first. Perhaps a greater chance of a longer cold spell late in the period.”

Originally Posted by: White Meadows 



That's an unusual eyebrow raiser from the the Met Office there. 
 
Bishop's Stortford 85m ASL.
Quantum
01 December 2023 21:25:15
There it is on the ICON 18Z.
UserPostedImage
You might need to view it bigger to see: https://modeles12.meteociel.fr/modeles/icon/archives/2023120118/iconeuw-1-108.png?18
The double band of low uppers is evaporational cooling. Whenever you see that think snow! 

 
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.
Quantum
01 December 2023 21:57:42
The behaviour of the interactions between all these low level LPs is clearly befuddling the models; things like wind speed, wind direction, temperature, precip intensity minute differences can be the difference between loads of snow and nothing. No wonder the metoffice are refusing to commit to anything saturday night onwards.

Everything is on the table; we are literally 2 days out from potential snowmagedon or potential dissapointment with everything in between. And we do this all again on Monday and Tuesday and who knows how long.

 
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.
squish
01 December 2023 21:58:49
Regardless of cold prospects there is quite a high chance of another named storm next week ( probably Thursday)

https://modeles14.meteociel.fr/modeles/ukmo/archives/2023120112/ukmonh-0-144.png?12 

 
D.E.W on Dartmoor. 300m asl
White Meadows
01 December 2023 22:00:27

The behaviour of the interactions between all these low level LPs is clearly befuddling the models; things like wind speed, wind direction, temperature, precip intensity minute differences can be the difference between loads of snow and nothing. No wonder the metoffice are refusing to commit to anything saturday night onwards.

Everything is on the table; we are literally 2 days out from potential snowmagedon or potential dissapointment with everything in between. And we do this all again on Monday and Tuesday and who knows how long.

 

Originally Posted by: Quantum 

Sorry Q but that is hyperbole if ever I saw it.
Theres clearly no chance of ‘Snowmageddon’ anywhere in the UK over the next 10 days. 
squish
01 December 2023 22:10:47
I agree with Quantum....look at the snow accumulation charts on ICON and even GFS for the next 5 days. Scotland at least and quite a lot of Wales are at continued high risk.

Meanwhile here is the 18z GFS take on the potential Thursday storm

https://modeles16.meteociel.fr/modeles/gfs/runs/2023120118/gfsnh-0-138.png?18 
D.E.W on Dartmoor. 300m asl
Gandalf The White
01 December 2023 22:41:33

Sorry Q but that is hyperbole if ever I saw it.
Theres clearly no chance of ‘Snowmageddon’ anywhere in the UK over the next 10 days. 

Originally Posted by: White Meadows 



Why do you feel the need to keep doing this?
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


Rob K
01 December 2023 22:55:45

Yep another  day 10 ECM 12z easterly lol.
One day!

Originally Posted by: Ally Pally Snowman 


Just imagine if the actual winter weather in the UK was created by Day 10 charts, every day. 
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

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