Model thread discussion - cold spell looming

[Sawel]

Excellent agreement from all the main models for a Scandinavian High - JMA wants in on the fun too.

[Blizzard]

4 minutes ago, Weather-history said:

Those temperatures don't look as cold on wxcharts. Midday on 14th and 15th February, it has many parts above freezing. 

 

They wouldn't - the charts you're showing are from the 0z....

[nick sussex]

2 minutes ago, Weather-history said:

Those temperatures don't look as cold on wxcharts. Midday on 14th and 15th February, it has many parts above freezing. 

 

That wouldn’t surprise me . It would be a different matter if this was mid January but the sun is getting a bit more strength by mid February . Dew points should be very low though so snow should hold up well .

Its remarkable just how good snow retention is with low dew points even if temps get a few degrees above zero.

[StingJet]

Interesting model ends run for the ECM, begs the question of what will the HP Cell over the UK do next ....?  If read in conjunction with the GFS 12z @ +240  a shift back north / north east is plausible, opening the door for the 975mb LP south of Greenland to track Se , under cutting the HP,.. classic slider anyone ? 

Edited February 6, 2021 by StingJet

[Lukesluckybunch]

2 minutes ago, nick sussex said:

That wouldn’t surprise me . It would be a different matter if this was mid January but the sun is getting a bit more strength by mid February . Dew points should be very low though so snow should hold up well .

Its remarkable just how good snow retention is with low dew points even if temps get a few degrees above zero.

Hi there Nick I see you post on here quite often,and I assume that you are one of the big hitters .how do you see this cold spell planning out then do you think it will last all week and the whole weekend also?I am quite an amateur here really.

[Weather-history]

6 minutes ago, Blizzard said:

They wouldn't - the charts you're showing are from the 0z....

Sorry I posted the 0z by mistake, however they still go above freezing on the 12z, but still cold. 

Edited February 6, 2021 by Weather-history

[Man With Beard]

22 minutes ago, Skullzrulerz said:

Typical Cornwall is always in the warm air  We always miss out

Have you checked the charts for Tuesday? The channel streamer is on!

On the general scenario, worth remembering there's been quite a shift in the past 24 hours, from rain pushing to the Scottish border on Thursday, and now for the precipitation not to make it out of Wales. Worth holding your horses till the morning at least for anything past D4 - a Scandi High looks guaranteed at some point, but how it affects the UK is on a kinfe-edge - there'll be a point which separates continental air from lol ng drawn SWly air, and next to no middle ground.

[Anthony Burden]

Not normally into over estimating things but charts really do show something very cold,

looking 1980s style several SSW must be at the core of what is showing.I would be prepared 

for some records to be broken in many different scenarios.

 

[stodge]

Evening all

It seems we are on the threshold of a significant spell of winter weather with snow (hopefully) for many and perhaps even here in lowland East London I'll see some of the white stuff. Today started pleasantly mild but rain has arrived this evening which I suspect id the harbinger of the significant change tomorrow.

I squeezed five days out of this cold spell on last night's models but by Thursday/Friday the game was up as the Atlantic LP aligned positive and the Scandinavian heights mostly collapsed south. A growing minority of options, however, kept a cold flow going by holding the Atlantic at bay and let's see if tonight offers any hope for prolonging the immediate to perhaps this time next week or beyond .

T+120 is the 11th, T+240 the 16th, T+312 the 19th and T+384 the 22nd

12Z GEM: The T+120 chart shows an HP over south western Scandinavia with a ridge to Shetland. To the south east, the residual trough from this weekend is over Romania and a new Atlantic LP sits in mid ocean. Calm conditions over northern and eastern Britain with a strengthening SE'ly over southern and western areas. 850s remain below -8 over most areas with only the far south west of England and Ireland coming into slightly milder air.  From there, heights continue to strengthen over Scandinavia and by T+180 the main core of heights is over northern Scandinavia with a ridge south west just to the east of the British Isles and a further ridge extending to Greenland. The Atlantic LP has withdrawn west north west but a light S'ly covers much of the British Isles.  In terms of uppers, not much has changed - eastern areas remain cold with uppers below -8 while positive uppers have reached Cornwall and south west Ireland.  From there, the stand off continues with a large Scandinavian HP in situ and Atlantic systems swinging north east then north to the west of Ireland. By T+240 a SSE'ly air flow covers all parts. In terms of 850s, the stalemate continues - positive uppers are confined to the far south west and if anything the colder air has made more inroads into central Britain.

A real battleground and a significant extension of colder conditions especially for northern and eastern areas into the week after next making it a 10 day cold spell for many parts. Further west, milder air returns next weekend and you'd wonder if, between the two, there were opportunities for snow.

12Z GFS OP - GFS is generally the most progressive of the models and I'd be surprised if it wasn't more bullish about the Atlantic breaking through. At T+120, the battleground is defined with an HP over Scandinavia holding up progress of an Atlantic airmass oriented positively. A SE'ly covers all the British Isles at this time - positive uppers have already returned to Cornwall but much colder air remains in situ elsewhere with 850s below -12 in the north and generally below -8 over most northern and eastern areas. From there, the Scandinavian HP strengthens considerably and stays over southern Norway holding the Atlantic trough well to the west but with a SE'ly airflow over much of the British Isles tending more SSE further west. The push of milder air has been reversed with uppers of -4 to -8 back over southern and eastern areas and positive uppers confined to far western areas by T+180. From there, the Atlantic trough splits with a new system trying to approach from the south west but getting nowhere while by T+240 the HP has started to retrogress west and is over or just to the north of Scotland and drawing in an ESE'ly airflow to most parts. By then, the coldest air is over southern Britain with uppers of -8 close to the Channel coast while uppers of -4 to -8 cover southern and western parts. Conversely, 850s are only slightly negative further north.

A brief attempt at a milder incursion is driven back and in the end, while not the brutal cold some might expect from the synoptics on offer, it's a very satisfactory evolution for a continuation of cold especially for southern and eastern parts which look in the "sweet spot" tonight.

12Z Control - again, no Parallel. T+120 follows OP and from there the basic evolution is very similar so that by T+180 an intense anticyclone sits over Scandinavia and the Atlantic trough has bene pushed back WNW leaving an ESE'ly flow over much of the British Isles. Uppers of -4 to -8 cover most of eastern Britain with positive uppers confined to Cornwall and the west of Ireland. As with OP, there seems a little mixing out of the coldest air as we move into next weekend but it's still pretty cold for many parts. As with the OP, Control starts the retrogression process after T+180 and by T=240 the HP is moving west out of Scandinavia and continues as an intense feature dragging in an increasingly bitter E'ly flow for southern and south western parts leaving much lighter winds over Scotland and especially the north. Yes, those are -12 uppers over southern England by T+240 with -16 uppers close by so very cold for southern counties into the week after next.

It's rare I gasp at a synoptic evolution but this is very close to nirvana for cold fans - any brief less cold respite is swept aside by the Scandinavian HP and it turns even colder though not snowier into the week after next. That chart is almost perfection for cold for me - if we have a snow covered continent and snow lying over southern England, that synoptic regime is perfect for advecting the coldest conditions.

12Z ECM - why do I think this will be the fly in the ointment? I don't know but I have a sinking feeling (as might the Scandinavian HP). However, the T+120 looks all right - little concerned about a couple of shortwaves but hopefully they'll not get in the way. Uppers remain very low - generally -8 but with some pockets of -12 uppers over southern England. Here goes...from there, the HP over Scandinavia continues to strengthen and by T+192 core heights extend south west from Scandinavia to south east England. The Atlantic trough has been driven well back to the west and a light SE'ly air flow covers eastern and southern Britain with a stronger S'ly based flow further west and north. Milder air with positive uppers has reached northern and western Britain with colder air restricted to south east England. From there, the HP moves to sit over the British Isles with 850s either side of zero over all parts.

As I feared, ECM is the fly in the ointment with the Scandinavian HP sinking rather than retrogressing. In truth, we have three different evolutions at T=240 and while we'd all love the GFS notion of retrogression to come to fruition, it's far form confirmed.  That said, the colder spell looks set to continue through this week and into next weekend for many especially in the south east oddly enough.

Looking further ahead, the T+312 and T+384 charts from OP and Control respectively:

OP is cold throughout but Control lifts out the coldest air from the south further into FI. The two things on neither evolution are a raging PV and a zonal Atlantic and indeed heights persist to the north and east throughout.

Conclusion:  I was wrong - well, to a point. Those who argued the cold spell would last longer than seemed evident from the Tuesday 12Z runs were right. After an uncertain start, the evolution of intense heights over Scandinavia now looks assured and while the Americans offer nirvana, there's still caution from the Europeans and Canadians over whether retrogression can and will happen. The cold spell now looks set for a week and while the snow prospects may well diminish with time, the cold won't. The upgrades for cold fans since Tuesday have been significant and it doesn't need much more to extend this into a 14 day cold spell or more. The intensity of the anticyclone looks to mitigate against snow further on but very low night time minima across any snowfields under clear skies look entirely possible.

I hope everyone gets the snow they want and some of the Regional threads will be wonderful in the next few days (hopefully).

[goosey007]

Feels like we we are about to hit the jackpot with this scandi high being shown on the models ....we are on the cusp of a memorable spell of weather think we are all in with a shout of deep snow that stick around

[Hullsnow87]

Is the ecm showing a scandi high or uk high?

[AWD]

These Meteograms have been trending colder and colder in the medium range.

The below are for Bristol (south western location), and are now looking cold at the surface well into the weekend;

 

Compared with the 12z ones from last night;

 

Look at how the pillars are reducing downwards from the high single figure temps to lower single figure temps over next weekend.

Edited February 6, 2021 by AWD
Added circle

[bluearmy]

6 minutes ago, Hullsnow87 said:

Is the ecm showing a scandi high or uk high?

At that range it’s showing a high ........... 

[Gowon]

JMA's lining up another beast  - so it's just ECM looking dodgy tonight.

 

[Penrith Snow]

Hmmm, ECM ends with a boring UK High and Athens Special.

Plenty of scope for upgrades there

Andy

[BlackburnChris]

9 minutes ago, Penrith Snow said:

Hmmm, ECM ends with a boring UK High and Athens Special.

Plenty of scope for upgrades there

Andy

If you look at Iceland between +192 and +240 it is also retrogressing West ....

[Griff]

1 minute ago, BlackburnChris said:

If you look at Iceland between +192 and +240 it is also retrogressing West ....

Yes the trend is quite clear, fair to say that's what it shows tonight, but tomorrow? Maybe  

[bluearmy]

Clear where eps see the favoured spot for the upper ridge to sit - that’s gonna place the cold flow to the se of that 

[Jason M]

3 minutes ago, BlackburnChris said:

If you look at Iceland between +192 and +240 it is also retrogressing West ....

What, Iceland is retrogressing west? Truly we are in remarkable times 

[sheikhy]

1 minute ago, bluearmy said:

Clear where eps see the favoured spot for the upper ridge to sit - that’s gonna place the cold flow to the se of that 

For now!!!!still plenty of time for change!!!wana see a push north on the 00z!!

[nick sussex]

28 minutes ago, Lukesluckybunch said:

Hi there Nick I see you post on here quite often,and I assume that you are one of the big hitters .how do you see this cold spell planning out then do you think it will last all week and the whole weekend also?I am quite an amateur here really.

Big hitter ! Lol nice of you to say that but others have  more technical knowledge. I’m the meat and two veg , no frills generally but try my best to give an impartial view even though I’m a hardened coldie ! 

In terms of the cold spell, yes the trend is now to extend the cold as the high to the ne is putting up a good fight .

The bigger uncertainty is whether the UK can tap into that amazing deep cold pool to the east .

As long as you keep a flow off the continent even if the upper air temps relax the surface will still be cold . 

So some severe night time frosts especially over snow cover .

I think we need a few more runs to see whether the models are going to go for a quicker attempt to bring in that cold pool , or whether they take the longer attempt . This is by no means guaranteed to land though , but I certainly hope it does ! 

[Daniel*]

Historic spell of cold weather in London on ECM 12z the coldest spell of weather in 30 years. The EPS also has a maximum of 1C in London on Friday confirming extension to cold spell! 

[Don]

2 minutes ago, sheikhy said:

For now!!!!still plenty of time for change!!!wana see a push north on the 00z!!

I thought that chart looked quite good?  Although I agree the pressure cell needs to be further north.

Edited February 6, 2021 by Don

[sheikhy]

1 minute ago, Don said:

I thought that chart looked quite good?

Oh dont get me wrong mate stunning chart but just wana see it further north so we can tap into the cold continental air!!

[Don]

Just now, sheikhy said:

Oh dont get me wrong mate stunning chart but just wana see it further north so we can tap into the cold continental air!!

Yes, I've just edited my post after looking at the chart again.