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Gandalf The White
10 January 2024 19:40:47

Given the in-depth Met Office analysis and all the model output available to us, including and especially the ensemble data, be very wary of reading too much into any individual operational run. Next week still looks really messy and uncertain with the potential for excitement, disappointment, rain, snow and some serious levels of cold all possible.

Originally Posted by: doctormog 



Exactly. When we see the ensemble suite we will have a slightly better idea whether ECM has picked up on a new trend or just found a milder solution this time.  We’re only talking about 100-200 miles a whole week from now, it’s barely even noise.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


fairweather
10 January 2024 19:43:38
In this run the GFS 12z ensembles are starting to deteriorate a bit now for the south compared with the last two days. Nevertheless the op is back at the top of the mild end after the 17th split. The first two days for the south have materialised (well not for real but in terms of a solid mean) at the cold end of the runs with the op being consistently wrong for these first two days up until now. Looking at the two distinct  clusters after the 17th the colder one is somewhat tighter together. It is highly possible that if the op regains the centre ground then themean will fall back to -7C as it has at last for the 15th -17th. Despite this disappointing run there is absolutely no reason why it won't fall back into place given the volatility after the 17th.
S.Essex, 42m ASL
Hippydave
10 January 2024 19:45:13
It's certainly a fun spell of model watching🙄

Cold, messy but cold, messy but mild IMBY/cold for most. LP tracks across southern england, LP tracks in to France, LP sits to the south west and waves. All in the space of a days model runs and often all options shown by the respective operationals, swapping around each run.

I'd guess there's another 48-72 hours of faffing around before we get some better agreement on how far north the LP gets and whether I should mentally prepare for reports showing heavy snow whilst it's 8c and raining over my house. I assume the disagreement is all due to how much energy ends up in the southern branch of the jet when it splits exiting the US, what angle it approaches us at and how it phases with 'that' LP, so not surprising there's a lot of different options at this range, irritating though it is given they have such a large impact on the weather for a chunk of us!

GFS ens aren't terrible I guess IMBY - there's support for the mild/wet interlude and also support for that to be colder and snowy. 
MOGREPS aren't wildly dissimilar, maybe a smidge less in the way of mild suggesting more south based LP options.
ECM - TBC.
GEM - CBA. (Fantastic looking Op though). 





 
Home: Tunbridge Wells
Work: Tonbridge
fairweather
10 January 2024 19:48:29

GEFS flipping quite wildly at the moment - goes to show the uncertainty. See what ECM throws out - no middle ground at the moment!

Originally Posted by: ballamar 


Only if you base that on the operational and control runs. The mean hasn't.
S.Essex, 42m ASL
Lionel Hutz
10 January 2024 20:07:04
Can I ask a question? We have an Op run and a control and then a range of other options. So are the control and Op runs somehow more to be relied on than the nameless runs? 
Lionel Hutz
Nr.Waterford , S E Ireland
68m ASL



doctormog
10 January 2024 20:13:10

Can I ask a question? We have an Op run and a control and then a range of other options. So are the control and Op runs somehow more to be relied on than the nameless runs? 

Originally Posted by: Lionel Hutz 



Someone can no doubt correct me if I am wrong and perhaps it changes between models but the operational run is the high resolution main run with no changes to the initial input data and the control uses the same data but at a lower resolution. All the ensemble members/perturbations have various tweaks made to their initial input data (and like the control are lower resolution).
Aberdeen
Current conditions (personal WS) 
The Beast from the East
10 January 2024 20:19:28

Is this the sort of run that Beast would call 'Pete Tong'? 

Originally Posted by: Chunky Pea 



LOL. First time checking the models today, and its certainly disappointing after looking like a long spell yesterday
 
"We have some alternative facts for you"
Kelly-Ann Conway - special adviser to the President
idot
  • idot
  • Advanced Member
10 January 2024 20:26:15
Confidence must remain high for the Channel Islands. 😎
https://twitter.com/JohnathanSizz 

 
Ally Pally Snowman
10 January 2024 20:26:31
Bit of a wobble from the ECM ensembles.  They do tend to follow the Op more than other models so hopefully will go colder tmrw.

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=50893&model=ecm&var=2&run=12&lid=ENS&bw=1 
Bishop's Stortford 85m ASL.
DPower
10 January 2024 20:30:29
Forgetting verification stats for models ( northern hemisphere meaningless compared to our little island) the gfs has performed admirably this season so far. Ecm has been found wanting many, many times this winter and not just the det runs but ensembles as well. 
The gfs was the first to flag an obstruction if you like in the northerly flow coming down over the UK in the coming days ( cries of rubbish model from the same numbties on the other forum) and yet all models are now showing this low moving west to east across northern England, southern Scotland. How much it affect the cold air advection coming down from the north after this is still up for debate. I for one would like to think the 12z ecm det run has gone off on one ( horrible run). I am still of the mind that we will see more of a north to north easterly flow established with a stronger drive south of the colder air remodelled in future runs rather  than what the ecm has churned out tonight. The lower strat upper trop profile to me does not support what the ecm solution. 
A very cold and wintry outlook still very much on the menu.






























 
+2
The Dub Version
10 January 2024 20:30:32

Confidence must remain high for the Channel Islands. 😎

Originally Posted by: idot 



Gary????🤣
Berkshire
+1
Hippydave
10 January 2024 20:30:39
ECM ens rather 'meh' IMBY. More in the way of agreement for mild/wet interlude and more clustering of mild after that too. 
https://weather.us/forecast/2639022-royal-tunbridge-wells/ensemble/euro/temperature-850 

It's not a unanimous mild outlook and there's still some colder ones but diminished from earlier. 

Echoing Darren's comments, the Op has me down for a snow to rain event on the Wednesday with temps around 3c, which I think could be classed as 'unpleasant'! 

Only one run and all that but a somewhat depressing swing of the pendulum! Hopefully we'll see something of a nudge further South tomorrow, or GFS and it's Scandi HP musings will pick up strength and we can get another shot at an Easterly after others have played with the Northerly😛
Home: Tunbridge Wells
Work: Tonbridge
The Beast from the East
10 January 2024 20:30:40

Bit of a wobble from the ECM ensembles.  They do tend to follow the Op more than other models so hopefully will go colder tmrw.

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 



looking like collapse of the block nailed on and rain and flooding back on. Poor stuff
"We have some alternative facts for you"
Kelly-Ann Conway - special adviser to the President
Lionel Hutz
10 January 2024 20:38:29

Someone can no doubt correct me if I am wrong and perhaps it changes between models but the operational run is the high resolution main run with no changes to the initial input data and the control uses the same data but at a lower resolution. All the ensemble members/perturbations have various tweaks made to their initial input data (and like the control are lower resolution).

Originally Posted by: doctormog 



Thanks, Doc. So in theory, the Op is the best of the bunch?
Lionel Hutz
Nr.Waterford , S E Ireland
68m ASL



doctormog
10 January 2024 20:41:53

Thanks, Doc. So in theory, the Op is the best of the bunch?

Originally Posted by: Lionel Hutz 



In theory, yes. However I would say statistically it is still less reliable as a predictor than the ensembles, especially given inter-run inconsistency.
Aberdeen
Current conditions (personal WS) 
+1
The Dub Version
10 January 2024 20:42:24
Managed the first frost last night since beginning of December here. But now well above freezing during day and even now.Its clear its not cold enough. Poor first attempt.

2nd shot will have to be better for any hope Midlands southwards.
Berkshire
DPower
10 January 2024 21:03:41

Someone can no doubt correct me if I am wrong and perhaps it changes between models but the operational run is the high resolution main run with no changes to the initial input data and the control uses the same data but at a lower resolution. All the ensemble members/perturbations have various tweaks made to their initial input data (and like the control are lower resolution).

Originally Posted by: doctormog 


The ecm control along with the other 50 ensembles are all run at the same resolution but from a tweeked starting point. 
fairweather
10 January 2024 21:09:51

Managed the first frost last night since beginning of December here. But now well above freezing during day and even now.Its clear its not cold enough. Poor first attempt.

2nd shot will have to be better for any hope Midlands southwards.

Originally Posted by: The Dub Version 


Same here. Like pulling hens' teeth here trying to get temp to drop. There's just that nagging breath of wind that's keeping it around 2C. 
S.Essex, 42m ASL
jhall
10 January 2024 21:10:23

Someone can no doubt correct me if I am wrong and perhaps it changes between models but the operational run is the high resolution main run with no changes to the initial input data and the control uses the same data but at a lower resolution. All the ensemble members/perturbations have various tweaks made to their initial input data (and like the control are lower resolution).

Originally Posted by: doctormog 



That's as I understand it too. But unless it's changed fairly recently, the increased OP resolution only applies up to T+240, which no doubt is why the successive charts start appearing much more quickly after that point. That's for the GFS. It looks from the diagrams as though the ECM simply doesn't run the OP beyond T+240, as the bold green line simply terminates.
Cranleigh, Surrey
+1
White Meadows
10 January 2024 21:18:32
Looks like temps rising to 9-10c by Tuesday with 6 consecutive wet days down in Sussex. 
A fair reflection of overall output from this evening as shown in the main online forecasts.

 
Joe Bloggs
10 January 2024 21:20:35

You double-dosed on the prozac this morning?

😁

The way I see the GFS 6z is:

Tuesday - snow-bearing front moving south over Scotland into northern England but fizzling out as it does so, as pressure builds from the west. Very fragmented by the time it reaches the Gtr Manchester/Merseyside/Cheshire area, giving just very patchy, light snizzle.

Wednesday - pressure too high over western England for showers, but plenty of snow showers over Scotland. Further south, a Channel low gives snow to southern areas.


Some of the charts yesterday - excluding GFS - were amazingly snowy for a band between the south Midlands up to around the Ribble-Tees line.

I want those back!!!  😊😆😊

Originally Posted by: Saint Snow 



So 12z GFS is probably more your cup of tea. 

The low pushes further north, as a result the cold convective feed NW’ly feed is cut off before it has really got going, and we rely on the precipitation from the south delivering frontal snow. 

The worst case scenario for us both is the low is so far north that it cuts off convection off the Irish Sea, but not quite far north enough, delivering a snow storm to the Midlands up to Staffs and we stay dry. 💀

 

Manchester City Centre, 31m ASL
Gandalf The White
10 January 2024 21:23:34

Thanks, Doc. So in theory, the Op is the best of the bunch?

Originally Posted by: Lionel Hutz 



A key point to bear in mind is that even the Operational run includes estimates, since there are more grid points than there is actual data. If you start with a degree of uncertainty that can only grow over time: the ensemble suite attempts to rest the stability of the evolution by tweaking some of the opening estimates.

The higher resolution should be better at picking out smaller changes that can evolve to influence the bigger picture: eg the sudden appearance of that small feature which delayed the plunge south of the Arctic air mass.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


+1
Brian Gaze
10 January 2024 21:29:46
Big spread on the ECM ENS tonight.

UserPostedImage
Brian Gaze
Berkhamsted
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doctormog
10 January 2024 21:29:58

A key point to bear in mind is that even the Operational run includes estimates, since there are more grid points than there is actual data. If you start with a degree of uncertainty that can only grow over time: the ensemble suite attempts to rest the stability of the evolution by tweaking some of the opening estimates.

The higher resolution should be better at picking out smaller changes that can evolve to influence the bigger picture: eg the sudden appearance of that small feature which delayed the plunge south of the Arctic air mass.

Originally Posted by: Gandalf The White 



👍 All very good points.

 
Aberdeen
Current conditions (personal WS) 
Gandalf The White
10 January 2024 21:45:07

Big spread on the ECM ENS tonight.

UserPostedImage

Originally Posted by: Brian Gaze 



If you look closely at the scatter what is happening is that a few of the ensemble suite show a brief milder push happening early on 18th, for a few hours before dipping back down. Then on 19th-20th the Control picks up the second mild push and that’s supported by a cluster, whilst another cluster keeps London in the cold air.  After that there is the usual spaghetti but we’re out at Day 9-10 and beyond.

Don’t get me wrong, it’s not a clear picture, but it seems to be confirming what we’ve seen in recent runs concerning the ebbing and flowing of the cold-mild boundary.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


+1

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