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Quantum
15 January 2025 10:55:32

In simple terms and as others have said, if you don’t have low heights underneath the high it simply collapses SE and you’re left wallowing in nothingness whilst if snows in Athens. A jet on steroids screaming out of the US doesn’t necessarily mean curtains for a potential Scandy block but it doesn’t help.

Originally Posted by: nsrobins 


Yes this seems to be right. And the upper trop cold pool which achives this on the 0Z is really small. If its making that much of a difference then I clearly need to rethink my criteria for whether or not a run is good.
2024/2025 Snow days (approx 850hpa temp): Total: 6 days with snow/sleet falling
18/11 (-6), 19/11 (-6), 23/11 (-2), 22/12 (-5), 04/01 (-5), 05/01 (0)
2023/2024 Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Total: 12 days with snow/sleet falling.
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)
Quantum
15 January 2025 10:59:33

In simple terms and as others have said, if you don’t have low heights underneath the high it simply collapses SE and you’re left wallowing in nothingness whilst if snows in Athens. A jet on steroids screaming out of the US doesn’t necessarily mean curtains for a potential Scandy block but it doesn’t help.

Originally Posted by: nsrobins 


The blob of cold core that undercuts isn't even from that US surge! Its from the icelandic low at T+120h or its from the low currently near newfoundland. On the 0Z the deep low was slightly stronger and the end result was it lowered heights over Europe at the right time.

It really is a tiny difference and I'm shocked it matters far more than the other stuff which was all better on the 6Z. But I guess it really is absolutely essential to get those low heights into Europe.
2024/2025 Snow days (approx 850hpa temp): Total: 6 days with snow/sleet falling
18/11 (-6), 19/11 (-6), 23/11 (-2), 22/12 (-5), 04/01 (-5), 05/01 (0)
2023/2024 Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Total: 12 days with snow/sleet falling.
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)
tallyho_83
15 January 2025 11:01:02
Surely this is a prime prime Example of how our cold spell or a Scandinavia high with easterly as per models over past few days were showing can go wrong:
We have high pressure trying to build over to our north over Iceland and Scandinavia @ +156hrs but quickly get's flattened and why? Look what's happening over NE States of USA and Canada:
Brutal cold there and uppers of -20c and daytime maxes of -10c over Washington DC, - could be the coldest Inauguration day in History. See below on the 06z GFS Op run and run the synoptics charts from 20th - You'll see what I mean and wouldn't you agree this is partly to blame for why our HLB fails? Otherwise it's ironic how the cold airmass in NE America and Canada deepens then our HLB and Scandinavian suddenly goes from models as per below.
UserPostedImage
Yet the irony is all models predicted a very mild January for NE America and Canada and so far it;s been brutally cold there and set to get colder YET again.
Home Location - Kellands Lane, Okehampton, Devon (200m ASL)
---------------------------------------
Sean Moon
Magical Moon
www.magical-moon.com


Rob K
15 January 2025 11:18:59


Yet the irony is all models predicted a very mild January for NE America and Canada and so far it;s been brutally cold there and set to get colder YET again.

Originally Posted by: tallyho_83 


It's easy to see why there is so much scepticism about global warming in the US: they always seem to get brutal cold outbreaks in recent years as the rest of the planet misses out.

On the model front, it's certainly an interesting battle setting up between a big block and a powerful jet. Currently I think we are a bit too far west to be in the battleground but that could change.
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
+2
Russwirral
15 January 2025 11:25:09
The 6z GFS run just shows how fickle these BFTE setups can be.  A consistent hint that something easterly will happen around the 20-25th Jan... however if the HP be slightly  in the wrong place and you just get southerly winds.


Weather station:
https://www.wunderground.com/personal-weather-station/dashboard?ID=IWIRRAL24#history 
Saint Snow
15 January 2025 11:42:18
Is it worth a reminder that the general consensus on here is that the 6z is one of the less reliable runs on GFS 😉

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
Ally Pally Snowman
15 January 2025 12:13:30
Ensembles look poor for deep cold so far today.  A chilly waft rather than a Beast but it wouldn't take much of a shift to see a much more exciting easterly. 🤞
Bishop's Stortford 85m ASL.
Arbroath 1320
15 January 2025 12:15:37

Is it worth a reminder that the general consensus on here is that the 6z is one of the less reliable runs on GFS 😉

Originally Posted by: Saint Snow 


It has always been suggested that the 6z and 18z are the less reliable runs. Not sure what the evidence is though?
Kenmore, Highland Perthshire, GGTTH
Gandalf The White
15 January 2025 12:58:56

It has always been suggested that the 6z and 18z are the less reliable runs. Not sure what the evidence is though?

Originally Posted by: Arbroath 1320 


I made a similar comment a couple of weeks ago and Brian put up the stats, which showed no real difference.  I must admit I thought the same as you.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


Brian Gaze
15 January 2025 13:20:29
The other point is the differences in accuracy between the various models is reducing as you would expect. Improvements are increasingly incremental, so the tortoise is now catching up with the hare.

https://emc.ncep.noaa.gov/users/verification/global/gfs/prod/atmos/headline/images/evs.global_det.all_models.acc.hgt_p500.allyears_yearly.timeseries_valid00z_f120.g004_nhem.png 

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
Lionel Hutz
15 January 2025 14:11:09

It's easy to see why there is so much scepticism about global warming in the US: they always seem to get brutal cold outbreaks in recent years as the rest of the planet misses out.

On the model front, it's certainly an interesting battle setting up between a big block and a powerful jet. Currently I think we are a bit too far west to be in the battleground but that could change.

Originally Posted by: Rob K 


That's always at the back of my mind whenever I hear talk of a Scandi block. If the block is just a bit too far East, we can get stuck in very mild Southerlies or Southeasterlies(admittedly that risk is higher for me being that bit further West). However, as you say, we'll see what happens, a bit to go before this is set in stone.
Lionel Hutz
Nr.Waterford , S E Ireland
68m ASL



Quantum
15 January 2025 15:29:59
OK so ICON12Z is fine.
So really there are three crucial factors not two.
1) CONUS cold core (Ideally further south and west)
2) Atlantic blocking (Ideally further north and west)
3) Early atlantic low (As strong and as far south as possible)

Here you can see the low heights asociated with 3) moving south ready to support the block. This is ICON12Z T+165. You can see both an upper level trough with asociated cold air. Without this the block collapses south.

UserPostedImage
https://modeles12.meteociel.fr/modeles/icon/archives/2025011512/icon-6-165.png?12 
2024/2025 Snow days (approx 850hpa temp): Total: 6 days with snow/sleet falling
18/11 (-6), 19/11 (-6), 23/11 (-2), 22/12 (-5), 04/01 (-5), 05/01 (0)
2023/2024 Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Total: 12 days with snow/sleet falling.
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)
Quantum
15 January 2025 16:04:32
The initial trough is further south on the GFS12Z compared to GFS6Z. That's a good sign.
Seems to be merging with the Iberian trough. That's interesting. Presumably its a good thing?
2024/2025 Snow days (approx 850hpa temp): Total: 6 days with snow/sleet falling
18/11 (-6), 19/11 (-6), 23/11 (-2), 22/12 (-5), 04/01 (-5), 05/01 (0)
2023/2024 Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Total: 12 days with snow/sleet falling.
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)
ballamar
15 January 2025 16:31:32
GFS op could be a classic of front pushing back west rain to snow events
Quantum
15 January 2025 16:49:10
ICON,GFS,UKMO, GEM all completely different.
Apparantely tiny details are having alot of impact. I swear for GH type scenarios its just 'amount of amplification' and more or less just that. I think I'll give up trying to reduce this to 2 or 3 important factors; its clearly not working.
2024/2025 Snow days (approx 850hpa temp): Total: 6 days with snow/sleet falling
18/11 (-6), 19/11 (-6), 23/11 (-2), 22/12 (-5), 04/01 (-5), 05/01 (0)
2023/2024 Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Total: 12 days with snow/sleet falling.
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)
squish
15 January 2025 17:06:12
I would say ICON, UKMO and GEM are roughly along the same lines around +168.
The 12z gfs has reverted to its ‘burns day’storm scenario again , although previously has been showing much more along the lines of the 12z GEM .
I agree is very fine margins and fascinating to watch how it all unfolds 
D.E.W on Dartmoor. 300m asl
Retron
15 January 2025 17:10:49
Hopefully the GFS won't be right when it comes to the 12z run and its descent into more gales... it's already been the windiest few months here for several years and I've really enjoyed the recent quiet weather! All good things have to come to an end, I suppose.

The GFS has had a knack of picking these sort of things up at a 10-day range and, unlike the easterlies, they seem to come off more often than not! It's quite a change from recent runs.

Here's the day 9-and-a-bit wind chart, showing gusts in the 60s and 70s down here. Beyond that there would be strong winds for all, but there are no gust charts that far out (and it's academic anyway, of course!)
UserPostedImage
Leysdown, north Kent
idj20
15 January 2025 17:18:53

Hopefully the GFS won't be right when it comes to the 12z run and its descent into more gales... it's already been the windiest few months here for several years and I've really enjoyed the recent quiet weather! All good things have to come to an end, I suppose.

The GFS has had a knack of picking these sort of things up at a 10-day range and, unlike the easterlies, they seem to come off more often than not! It's quite a change from recent runs.

Here's the day 9-and-a-bit wind chart, showing gusts in the 60s and 70s down here. Beyond that there would be strong winds for all, but there are no gust charts that far out (and it's academic anyway, of course!)
UserPostedImage

Originally Posted by: Retron 


Welp, a repeat of Burns Day 1990. Oh well, it was nice while those easterly outputs lasted. Still very subject to changes but this type of output doesn't surprise me. When North America go deep cold, the UK has the fall out with cyclogenesis crap. Happens every time.

Folkestone Harbour. 
+1
tierradelfuego
15 January 2025 17:42:39

Here's the day 9-and-a-bit wind chart, showing gusts in the 60s and 70s down here. Beyond that there would be strong winds for all, but there are no gust charts that far out (and it's academic anyway, of course!)
UserPostedImage

Originally Posted by: Retron 


Even more academic obviously is the 27th with gusts showing at 90+s along the Dorset to IOW coast. Fingers crossed the 12z Op is disproving the "belief" that the pub and hangover runs are less accurate...
Bucklebury
West Berkshire Downs AONB
135m ASL

VP2 with daytime FARS
Rainfall collector separated at ground level
Anemometer separated above roof level
WeatherLink Live (Byles Green Weather)
nsrobins
15 January 2025 17:54:09

Even more academic obviously is the 27th with gusts showing at 90+s along the Dorset to IOW coast. Fingers crossed the 12z Op is disproving the "belief" that the pub and hangover runs are less accurate...

Originally Posted by: tierradelfuego 


To be fair the probability of a high-end storm is the same as a screaming easterly at that range.
Neil
Fareham, Hampshire 28m ASL (near estuary)
Stormchaser, Member TORRO
ballamar
15 January 2025 17:56:51
Given the consistency of the GFS at the moment I think it’s safe to say any option is possible - easterlies do seem to be notoriously difficult to model. Am sure it will be back in subsequent runs in one form or another. Certainly not boring
Retron
15 January 2025 17:57:47

Even more academic obviously is the 27th with gusts showing at 90+s along the Dorset to IOW coast. Fingers crossed the 12z Op is disproving the "belief" that the pub and hangover runs are less accurate...

Originally Posted by: tierradelfuego 


Ah, yes - looks like wxcharts has gust maps that far out, unlike MC. As you say, hopefully it's just GFS going off on one, those gusts look horrendous!

https://wxcharts.com/?panel=default&model=gfs,gfs,gfs,gfs®ion=uk&chart=max_gustsmph,850temp,wind10mmph,snowdepth&run=12&step=300&plottype=10&lat=51.398&lon=0.922&skewtstep=0 
Leysdown, north Kent
doctormog
15 January 2025 18:08:38

To be fair the probability of a high-end storm is the same as a screaming easterly at that range.

Originally Posted by: nsrobins 


I think that is a perfect summary for the output at that time point!
Aberdeen
Current conditions (personal WS) 
Brian Gaze
15 January 2025 18:10:16

Ah, yes - looks like wxcharts has gust maps that far out, unlike MC. As you say, hopefully it's just GFS going off on one, those gusts look horrendous!

https://wxcharts.com/?panel=default&model=gfs,gfs,gfs,gfs®ion=uk&chart=max_gustsmph,850temp,wind10mmph,snowdepth&run=12&step=300&plottype=10&lat=51.398&lon=0.922&skewtstep=0 

Originally Posted by: Retron 



GEFS wind gusts only go to t+240 IIRC. GFS all the way out.

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
Snow Hoper
15 January 2025 18:57:01
Unfortunately the Met Office favour a low in the NW Atlantic with not much of an E influence. The models are beginning to show this outcome, probably in part, due to the intense cold across the pond.
Going to war over religion is like killing each other to see who has the better imaginary friend.


Home : Thorndon, Suffolk.

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