Model output discussion - cold spell approaching?

[PiscesStar]

45 minutes ago, Rapodo said:

For me this is a big precursor pattern shift. If PV-forecast last night was right saying a PV split possible today then everything we've been looking at was surely wrong anyway. This looks like an instant shift to goings on above. I wouldn't trust anything being seen right now. Almost looks like something you see with a Tsunami response with the tide rushing out before a sudden surge. 

Agreed let's keep a lid on this guys 

[BLAST FROM THE PAST]

Certainly a change in how models are now projecting the way forward. All this the following morning or 2 when tweets from professionals get on board of an imminent PV split, v cold for NW Europe and UK etc etc.  So on that basis is it ‘just typical’ that the promised land of proper cold spell is getting taken away from us?  Or is this a model jitter to what’s happening with the PV of a split rather than displacement?.  And if it’s a jitter is the response going to head us away from deep cold or will they start adjusting to where they were showing nirvana a couple of days back.  

I know what’s on my mind...and usually the safer bet is the way to go

 

BFTP

 

Edited January 13, 2021 by BLAST FROM THE PAST

[Jamie M]

Anyone else fancy a guess on where it's going to snow tomorrow:

   

Fine margins by the looks. Gonna be close.

[That ECM]

 

[Battleground Snow]

Another push south on the icon EU with regards to Thursday snow.

There is talk on twitter that the MJO is interfering with the ability of blocking to establish.. can anyone expand on this in more detail and will it be easier for blocking to re-establish once it goes back into cod?

[ItNeverSnowsInWindsor]

As long as low heights persist to the west of Norway we will have a hard time getting cold uppers here as everything has to go round the low. 
 

Something’s not favourable in the profile to the north of us.

[Frosty.]

It’s fair to say there has been some watering down of next weeks wintry potential across the board..but that’s all it was / is..POTENTIAL!!!...until such a time that it enters the reliable timeframe..beyond the reliable, it’s only eye candy..and as we all know, the models giveth and then taketh away..etc..etc... ‘‘twas ever thus!...but until / if the ensemble support is terminated...there’s still a chance of a swing back, indeed the ECM 0z ensemble mean doesn’t look particularly mild next week does it..or indeed the GEFS for that matter!..charts posted earlier!!...

Edited January 13, 2021 by Jon Snow

[Tim Bland]

Even if we don’t see a swing back to the colder charts of yesterday : there is still snow opportunities for everyone at some point in the next couple of weeks. At the end of Jan you don’t need a huge Greenland or a scandi high to produce snow...just a bit colder than average with the jet stream heading south of us ...

[Methuselah]

So, here are today's GEFS 0Z temp ens. And something has clearly sent the homunculus into rapid lever-pulling/button-pushing mode:

    

But never fear, as despite the panic being suffered by the 'wee man', the NH profile is still on-track. I think!

    

    

 

[sheikhy]

8 minutes ago, Battleground Snow said:

Another push south on the icon EU with regards to Thursday snow.

There is talk on twitter that the MJO is interfering with the ability of blocking to establish.. can anyone expand on this in more detail and will it be easier for blocking to re-establish once it goes back into cod?

Midlands looks like a big hit here!!did the gfs 00z para show the same?

[XtremeUKWeather]

1 minute ago, sheikhy said:

Midlands looks like a big hit here!!did the gfs 00z para show the same?

 

[Tim Bland]

3 minutes ago, sheikhy said:

Midlands looks like a big hit here!!did the gfs 00z para show the same?

Yep ️

[Nick F]

Certainly bit of a u turn overnight from the models, both from GFS and EC ops and their ensembles, just goes to highlight that a potential cold spell can't be nailed 7 days out. If the models didn't go past T+144 it would save a lot of euphoria followed by pain, but then we'd lose the fun of speculating.

Always the danger when we don't get the split following a SSW and get a displacement instead - it likely increases the likelihood the SSW doesn't play in our favour. But there is still uncertainty over the effects of the SSW on the tropospheric patterns and the models may still not be correctly predicting the effects.

But we also have to be aware that the patterns upstream in the troposphere will often determine our fate. So although it still looks like a weak Greenland block will develop and deep cold will push SW across Norwegian Sea and NE Europe - so colder air will likely filter down from the north from the middle of next week in response, the strengthening jet coming east across the Atlantic at the same time will allow Atlantic lows riding it to phase with low pressure moving down from Iceland on the northern branch of the jet looping over Greenland and toward NW Europe. 

We have to hope that Atlantic jet racing across the Atlantic next week is either modelled too strong or that it's corrected south.

Otherwise I fear it could be Scotland / N England that reaps the benefits of any colder air that tries to move south from the middle of next week.

Edited January 13, 2021 by Nick F

[sheikhy]

1 minute ago, Tim Bland said:

Yep ️

Man are us snow starved east midlanders about to make up for the snow we missed last few weeks!!!!

[Vikos]

Well, there are some things to be seen rational

30hPa, note the neg winds till the end of run

  --->    ---> 

150hPa (lower Strat)

  --->      --->

 

We have a dipole on the North American side, one could call it a Trump trough , Trump's days are numbered too. This will dissolve by January 18th. This change is already underway and of course that means a lot of dynamism in the weather kitchen. But all resistance is pointless, we remain in a wintry weather phase. Still (much?) snow, gradual cooling, then intensified frost. And when this permanent trough wants to log off, then there is a freezing phase. I think it would be possible as a time window from the turn of the month to February when freezers doors open up.

Outcome: Massive displacement of PV, the whole PV goes to the Eurasian side and wil be "glued down" there for a long time (with long term outcomes for the coming months)

 

 

 

 

[Day_9]

Wavy but universal agreement. 
 

i do not like it at all but thats what we are getting in the very short term.... however.... they ALL go colder in the relatively near term, even on the ‘disastrous’ latest run.  I don’t see any cause for concern the trend has been cool and cold all winter and we are only 5 weeks in really.  

[Battleground Snow]

10 minutes ago, sheikhy said:

Man are us snow starved east midlanders about to make up for the snow we missed last few weeks!!!!

The 06z GFS OP has finally realised it's going to be snow... Pretty shocking it's only picked up on this at 30 hours out. It's still a way out from the other models.

 

 

[sheikhy]

2 minutes ago, Battleground Snow said:

The 06z GFS OP has finally realised it's going to be snow... Pretty shocking it's only picked up on this at 30 hours out. It's still a way out from the other models.

 

 

Pretty poor from the op!!!its clear this will happen now and the midlands is a very good spot to be in!!how much is anyones guess!wonder what the 42 hour chart will show?

[Battleground Snow]

1 minute ago, sheikhy said:

Pretty poor from the op!!!its clear this will happen now and the midlands is a very good spot to be in!!how much is anyones guess!wonder what the 42 hour chart will show?

It's fizzled out by then, the main action will be 36-42... Expecting the para to show more widespread snow. It's good it's starting at sunset as it probably wouldn't have settled in the day in the Midlands away from high ground

[Severe Siberian icy blast]

38 minutes ago, Jamie M said:

Anyone else fancy a guess on where it's going to snow tomorrow:

   

Fine margins by the looks. Gonna be close.

Midlands is cop it tomoz

[sheikhy]

Just now, Battleground Snow said:

It's fizzled out by then, the main action will be 36-42... Expecting the para to show more widespread snow. It's good it's starting at sunset as it probably wouldn't have settled in the day in the Midlands away from high ground

Keep me up to date mate with the para!!!

[Singularity]

GFS(P) seems to be the closest of the 00z runs to the original game plan - but shifted back a few days from what might have been.

That being a transport of very cold air from the northeast to wrap into the trough while disturbances run into the base of it from the west, having peeled away from a trough southwest of Greenland.

No escaping, though, that the whole setup is further north than we'd usually expect during a strongly -AO regime with a -NAO accompanying.

I honestly don't know how likely it is to be adjusted south. These are atypical times - usual rules don't apply.

Can't say I find the runs that have the Atlantic trough marching east in full very convincing - usually we see lows peeling away and any breakdown starts with either the jet stream heading back north or one of those breakaway lows becoming the focus of a new trough formation while positioned to our southwest.

 

Nearer-term we can only wait and see whether cut-off low near the Azores can stay put longer - even 12 hours would make an appreciable difference but ideally at least 24.

[Singularity]

  

GFS 00z left, 06z right.

Let's see whether the low by the Azores being slightly weaker and less organised has any appreciable impact on its progressiveness later.

[Battleground Snow]

2 minutes ago, sheikhy said:

Keep me up to date mate with the para!!!

Para top image.. OP bottom for 48 hours

[Kasim Awan]

2 minutes ago, Singularity said:

GFS(P) seems to be the closest of the 00z runs to the original game plan - but shifted back a few days from what might have been.

That being a transport of very cold air from the northeast to wrap into the trough while disturbances run into the base of it from the west, having peeled away from a trough southwest of Greenland.

No escaping, though, that the whole setup is further north than we'd usually expect during a strongly -AO regime with a -NAO accompanying.

I honestly don't know how likely it is to be adjusted south. These are atypical times - usual rules don't apply.

Can't say I find the runs that have the Atlantic trough marching east in full very convincing - usually we see lows peeling away and any breakdown starts with either the jet stream heading back north or one of those breakaway lows becoming the focus of a new trough formation while positioned to our southwest.

 

Nearer-term we can only wait and see whether cut-off low near the Azores can stay put longer - even 12 hours would make an appreciable difference but ideally at least 24.

Yes I find this is usually the case nowadays that the polar jet is kept closer to the pole & the easterly section is too as a result. Not good for getting cold in and reflects a warming winter climate, whether it is caused by another poorly studied atmospheric mechanism such as expansion of the Azores & Hadley Cell etc is one which needs to be explored imo. Maybe you might know more about this.