Model Output Discussion - Colder but how cold and for how long?

[bluearmy]

Just now, Chrisover93 said:

Would this be south of the M4 event 

Depends how the low evolves from there 

looks like it’s deepening but disrupting a little at the same time 

at day six not worth over analysis 

[Tamara]

18 minutes ago, Cold Winter Night said:

Thank you for your very insightful posts as always.
I can imagine it must be refreshing for you for once not to be forced by the diagnostic to go against the cold preference in here...

What I do wonder about is why apparently the NWP in the extended is so rudderless, as it seems to generally ignore that retention and renewed push of +AAM. With your explanation of the wind flow budget in mind I would expect a very large spread later on, but this morning's EPS had only a handful of members that retain heights in more Northerly latitudes, the ensemble even seems to converge on that +NAO outcome that is the polar opposite (quite literally) of a +AAM response. EPS even more so than GEFS, I must say.

Considering all this, it seems like we might have to brace ourselves for some model output surprises over the coming week. A highly interesting battle between GSDM and NWP.

Based on the modelling of the huge gyre of vortex across NE Europe and that part of the arctic to retrograde in tandem with the Greenland amplification it makes sense that height anomalies will respond accordingly to a more cyclonic regime. But is is within that regime with embedded upper and increasing surface cold across N/NW Europe and remaining pockets of -ve zonal mean -ve zonal winds at high latitudes that considerable resistance must surely make it difficult for flat westerly inertia to cleanly navigate the road blocks. Additionally, it will not be long before a further push comes from momentum transport from the tropics into the extra tropics to replenish the sub tropical jet stream and equally further poleward amplification. Putting that together, disruption of vorticity is more intuitive to expect than positively tilted wholesale displacement of -ve higher latitude inertia & its associated dense cold air.

NWP is not ignoring the tropospheric diagnostic and not battling it. NWP doesn't lead the diagnostic. It is rather led by it, but trying to decode a lot of complex factors that do not align with the traditional westerly gyre of a +ve AO and NAO. 

Lastly and finally on this, the term "rudderless" refers much more to collective smoothed ensemble means. It is of course possible to look at individual clusters of ensemble solutions to see which are maybe in the ascendancy or vice versa. But even here, if the overall modelling is blindsided by a false signal or jet stream bias calculation at a given distance, then members within the clusters will also reflect that inaccuracy. They are best looked at as a snapshot in time of progress (or otherwise!), and not any definitive prediction at that given distance.

[bluearmy]

1 minute ago, Nick123 said:

Is that where the winds meet to create a fun zone? Wish I was better at terminology lol

Would probably be shown as a trough with those arrows on it 

very much a snow maker but not worth pinning your hopes at this range 

[Nick123]

Just now, bluearmy said:

Would probably be shown as a trough with those arrows on it 

very much a snow maker but not worth pinning your hopes at this range 

Yes just nice to look at, couldn't have been drawn better for me If I'd done it myself lol

[Harsh Climate]

Huge 12z runs to come out soon, obviously won't be definitive but should shed some light on 2 possible snow scenarios next week. 

a. The possible slider/disturbance from the NW Tuesday.

b. The potential snowmageddon from the Southwest on Wednesday.

.

Let's see if these scenarios are still on the table.

But I see some subtle hints: 

a. That the feature from the NW not making it past Southern Scotland/Northern most parts of England, whilst

b. The feature from the SW barely makes it into Southern England, or blows up and heads way north into Northern England. Each scenario obviously having huge ramifications on whatever your locality.

Not even that bothered what the charts say after Wednesday now, as is way beyond FI in this setup, any track of Wednesday's low if it happens at all won't be decided until <T24 .

[Nick123]

Just now, Nick123 said:

Yes just nice to look at, couldn't have been drawn better for me If I'd done it myself lol

And thank you for taking the time to respond by the way

[BLAST FROM THE PAST]

For me GFS is on a wobble, there’s a whole lot of winter weather to get through over the next 7+ days….indeed it’s 3c here now….bloody cold.  
Excellent consistency from Tamara, I really am focussed on 20/1….I fly to Austria for ski trip to Kaprun…..snow is good in the Alps….I don’t want an issue at Gatwick….but I’m on ‘watch mode’

 

BFTP

[Ghost of winters past]

6 minutes ago, Catacol said:

Do my eyes - and my refresh button - deceive me? Has the MetO just put out an updated medium forecast for next week and then retracted it back to yesterday's within an hour? Hmm. Maybe my computer is broke. I'm off for an MRI shortly - my knee is definitely broke unfortunately...

Meanwhile if you do nothing else today please read Tamara's surfing post and avoid being a slave to NWP output in the unusual pattern that is beginning to unfold. NWP doesn't deal with blocking patterns very well and tends to default too quickly to default westerlies when the blocks get hard to read. That's not to say that week 2 isnt going to get less cold - I think it looks likely that it will - but such phrases are relative and folk should keep in mind that Glosea Feb forecast from yesterday.

I just had a team meeting and we discussed the potential impact of snowfall next week. First time I've done that since 2018. Gave me a warm, fuzzy feeling. What is it about snow that is so alluring? 

Best post a chart to keep the ModPolice happy. @Scott Inghamday as start of the proper cold feed now looks a nailed on certainty. Scott - early creme eggs are yours....

Indeed you are correct..they have ...your eyes are fine

 

[bluearmy]

5 minutes ago, Catacol said:

Do my eyes - and my refresh button - deceive me? Has the MetO just put out an updated medium forecast for next week and then retracted it back to yesterday's within an hour? Hmm. Maybe my computer is broke. I'm off for an MRI shortly - my knee is definitely broke unfortunately...

Meanwhile if you do nothing else today please read Tamara's surfing post and avoid being a slave to NWP output in the unusual pattern that is beginning to unfold. NWP doesn't deal with blocking patterns very well and tends to default too quickly to default westerlies when the blocks get hard to read. That's not to say that week 2 isnt going to get less cold - I think it looks likely that it will - but such phrases are relative and folk should keep in mind that Glosea Feb forecast from yesterday.

I just had a team meeting and we discussed the potential impact of snowfall next week. First time I've done that since 2018. Gave me a warm, fuzzy feeling. What is it about snow that is so alluring? 

Best post a chart to keep the ModPolice happy. @Scott Inghamday as start of the proper cold feed now looks a nailed on certainty. Scott - early creme eggs are yours....

Don’t think so catcol but wrong thread to ask !

the mist is now clearing for next week (the envelope shrinking)  and if the ens retain consistency over next couple runs for next weekend then we should have some confidence out to day 10/12.  For now, there are too many clusters in the 10/15 day period 

[TSNWK]

1 minute ago, Ghost of winters past said:

Indeed you are correct..they have ...your eyes are fine

 

Mild spell cancelled next weekend ? 

[Harsh Climate]

Also for the outlook, I am giving greatest credence to UKMO and then ECM. GFS absolute fodder in this setup if you ask me.

[Norrance]

3 minutes ago, Nick123 said:

Yes just nice to look at, couldn't have been drawn better for me If I'd done it myself lol

Think that it looks more like a trough which was moving South but may stall rather than a streamer bringing in a succession of showers from the North Sea. Anyway getting a wee bit imby so we shall leave it here please.

[Ali1977]

T63 on icon and stronger heights in the Atlantic vs last run - expect a quicker and colder northerly 

Edited January 11 by Ali1977

[Ali1977]

This is great at T96, defo upgrade 

[MATTWOLVES 3]

Its officially Mattwolves day  @AdrianHull the met do indeed signal a milder push by next weekend

But there's scope for significant falls of snow during the run up to it! And as always and like Tams points put there's alot going on and this may only be a minor blip with drivers looking good again later this month.

To sum up I reckon lots of exciting times in the days ahead.

Now let me just buy my informant a beer

Edited January 11 by MATTWOLVES 3

[Mike Poole]

5 minutes ago, Ali1977 said:

T63 on icon and stronger heights in the Atlantic vs last run - expect a quicker and colder northerly 

Yes, this looks a cleaner northerly, and at T90, quicker plunge of cold south than 6z, T96:

[Malarky]

Icon, like UKMO, has been resolute of the evolution, and will deserve some credit if it comes to fruition.

[Mike Poole]

1 minute ago, MATTWOLVES 3 said:

It officially Mattwolves day as the met do indeed signal a milder push by next weekend

But there's scope for significant falls of snow during the run up to it! And as always and like Tams points put there's alot going on and this may only be a minor blip with drivers looking good again later this month.

To sum up I reckon lots of exciting times in the days ahead.

Now let me just buy my informant a beer

There’s a lot going on.  I will be fascinated to see how the models manage to contrive a snowless breakdown to mild out of this!  

[steveinsussex]

3 minutes ago, MATTWOLVES 3 said:

Its officially Mattwolves day  @AdrianHull the met do indeed signal a milder push by next weekend

But there's scope for significant falls of snow during the run up to it! And as always and like Tams points put there's alot going on and this may only be a minor blip with drivers looking good again later this month.

To sum up I reckon lots of exciting times in the days ahead.

Now let me just buy my informant a beer

The 19th was when we were looking at the low pushing into the south wasnt it? thats next friday, thats "by next weekend".... so would suggest its likely to be rain?

[Lukesluckybunch]

Afternoon guys...this ICON run looking really good!..it appears we can't have it all in when one part of the run is good the other part isn't...that's evident in the icon run,not as good over greenland this run..but better over iberia

Edited January 11 by Lukesluckybunch
Addin

[BLAST FROM THE PAST]

 

much better….and likely imo

 

BFTP

[Mcconnor8]

7 minutes ago, Lukesluckybunch said:

Afternoon guys...this ICON run looking really good!..it appears we can't have it all in when one part of the run is good the other part isn't...that's evident in the icon run,not as good over greenland this run..but better over iberia

It is reamplifying much more though it looks like off the ESB, which maybe should hold the Atlantic off for longer down the line

[bradymk]

An even better ridge on the ESB on this 12z ICON run. It joins up with the Greenland High and stops the real cold air in the states from spilling east into the Atlantic.

To compare:

00z left

   

[TSNWK]

7 minutes ago, Lukesluckybunch said:

Afternoon guys...this ICON run looking really good!..it appears we can't have it all in when one part of the run is good the other part isn't...that's evident in the icon run,not as good over greenland this run..but better over iberia

Another run that upgrades mid term.. 

Would not be surprised if gfs gem and ecm upgrade to 198 and then downgrade   defo theme with mid-term upgrades.  Hopefully we can keep kicking mild can down the road 

[Ice Day]

There's more than a hint on the Icon of what the GEM was showing a couple of days ago, before dropping the idea.  Possible North Easterly on the cards!?

Lovely run