Model output discussion - deep cold inbound?

[Singularity]

10 minutes ago, kold weather said:

If it was just the ECM I'd agree, but the GFS has a very similar looking profile as well, just a hair cooler

Because of that the GFS literally just stays on the right side, dew points get to 1-2c rather than 2-3c like it does on the ECM 12z.

 

I can't see anything above 1°C here and that's only in a few spots?

I'm relying on experience as to when the models tend to show the wrong precipitation type.

Admittedly it's not a guarantee as sometimes there is a legit reason such as a warmer layer aloft. Here, though, I think about the over-modification bias I just mentioned. So, while it could be the case, it might only just be so, in which case the model bias could be causing it to show the wrong thing.

Anyway, this is very much what's called over-analysing a particular scenario at 5 days range, so I'll stop there .

[bluearmy]

4 minutes ago, mbrothers said:

Suddenly this thread had become the ‘when will the cold spell that hasn’t arrived yet breakdown thread’ .

It’s generally like that ..... understandable because that’s what the models are showing 

1 minute ago, Frosty the Snowman said:

You'll have to englighten me here?

 

Surely careering the Atlantic low pressure system into the existing Easterly cold air would provide a nationwide snow event, rather than sending it to the North of France to retain us in an Easterly which is less likely to provide a nationwide snow event? 

Never understood why people look forward to a snow to rain event ....even if it stays as snow the positive Dp’s that follow mean the snow so. becomes slushy and drip drip drip

the renewed easterly delivers some troughs and snow plus more to follow ....

[Eastbourneguy]

The low is ever to slightly too far north for coastal counties in the south on the 12Z ECM according to the raw output. But it's go time 30miles or so inland!

[nick sussex]

6 minutes ago, Tom Jarvis said:

Nick when do we expect your committee meeting report tonight. Hope there hasn’t been any lasting damage to the members over the last few days!!!

Later on after my dinner I’ve scheduled a meeting ! Thankfully after the ugly scenes from the other night I’m happy to report all Committee members are fit and well . And it looks like on the agenda we will have to discuss fine tuning the BCP ( Blizzard Contingency Plan ) ! Certain areas look like having some wild and wonderful weather if you like snow ! 

[Biggin]

32 minutes ago, Speedbird said:

Totals in the SE would likely be somewhat higher with any convectional snowfall having taken place

 

And Streamers, dont forget streamers. Or is that what you mean SB ?

[Cheshire Freeze]

5 minutes ago, bluearmy said:

It’s generally like that ..... understandable because that’s what the models are showing 

Never understood why people look forward to a snow to rain event ....even if it stays as snow the positive Dp’s that follow mean the snow so. becomes slushy and drip drip drip

the renewed easterly delivers some troughs and snow plus more to follow ....

Hard to see how we deflect that Atlantic barrage without keeping some heights to our immediate N or NE

[Speedbird]

3 minutes ago, Biggin said:

And Streamers, dont forget streamers. Or is that what you mean SB ?

that's exactly what i mean, Steve

Streamers are the product of convection 

Edited February 3, 2021 by Speedbird

[Harsh Climate]

This is my current take on this upcoming cold spell/snap from reviewing current data. Yes I've gone big 

 

CURRENT WARNING 5th/februrary 12z - 10th/februrary 12z.

Warning structured into 3 tiers. Yellow/Amber/Red

 

Red area: 10-30cm low ground, 30-40cm 200m+, 300m+ 40-70cm

 

Orange area: 10-30cm all levels, perhaps more at highest elevation.

 

Yellow area: 2-10cm all levels.

 

SYNOPSIS:

Areas of rain/sleet/snow over central/southern/eastern scotland and cumbria should turn readily to snow at all levels as friday progresses, giving significant to large accumulations in places. This area of snow should extend southwards later saturday to northern england then the rest of eastern uk later sunday, giving significant accumulations in places especially the further north and east. It will most probably be lighter and more patchy the further south east. After that a cold showery polar airstream from the east establishes itself over most of the uk (sunday-wednesday) delivering frequent snow showers and streamers to many eastern areas, at this moment in time the further north east the more likely for higher accumulations. The far south east should have more organised bands of sleet/snow circulating around the centre of low pressure towards france, crossing the channel time to time. There maybe the opportunity for a large snow event from this but too early to say, but on the flip side for avid snow fans being close to this low pressure centre you are less likely to have the frequent snow showers, a possible DRY ZONE between the two airmasses.

Edited February 3, 2021 by Harsh Climate

[Hodgheg]

7 minutes ago, Frosty the Snowman said:

You'll have to englighten me here?

 

Surely careering the Atlantic low pressure system into the existing Easterly cold air would provide a nationwide snow event, rather than sending it to the North of France to retain us in an Easterly which is less likely to provide a nationwide snow event? 

You have to remember that a low like that would bring typical Atlantic weather to the UK as the low pressure brings a milder air mass with it. Yes you might get a transient snow event at first but typical wet, windy weather would follow. We absolutely don't want this to happen if the cold weather is to stay.

[Polar Maritime]

6 minutes ago, Biggin said:

And Streamers, dont forget streamers. Or is that what you mean SB ?

I'm pretty sure that's what he means.. With these sorts of Easterlys being model's.

Edited February 3, 2021 by Polar Maritime

[Blizzard]

8 minutes ago, nick sussex said:

Later on after my dinner I’ve scheduled a meeting ! Thankfully after the ugly scenes from the other night I’m happy to report all Committee members are fit and well . And it looks like on the agenda we will have to discuss fine tuning the BCP ( Blizzard Contingency Plan ) ! Certain areas look like having some wild and wonderful weather if you like snow ! 

Blizzard standing by with the contingency plan.... 


 

[Weather of Mass Disruption]

15 minutes ago, mbrothers said:

Suddenly this thread had become the ‘when will the cold spell that hasn’t arrived yet breakdown thread’ .

Lol! I was thinking exactly the same. Makes no sense to me at all! I don’t understand why anyone want to look at a breakdown at day 8 when we have so much excitement before then. Surely such charts have the same chance of verifying as a day 8 nirvana chart does?  

[Continental Climate]

43 minutes ago, ICE COLD said:

ECM is a naughty run tonight 

T168 !!!!!!!!!!!! 

Once those purples start getting into the frame then we are into beast territory. 

[Speedbird]

14 minutes ago, Frosty the Snowman said:

You'll have to englighten me here?

 

Surely careering the Atlantic low pressure system into the existing Easterly cold air would provide a nationwide snow event, rather than sending it to the North of France to retain us in an Easterly which is less likely to provide a nationwide snow event? 

Because the 850's are nowhere near low enough, you've got a system passing over a warm Atlantic which will not offer any assistance in lower those figures. Yes, there could be frontal snow but it would not be the snowmageddon you visualise.

Unless you have some serious altitude.

[The Bevmeister]

Right.....I may have missed this in the last 65 pages as I haven’t read them all but I have a question.  Is the forthcoming days of cold/snow that at this point looks to be widespread, a direct result of the SSW and vortex displacement from a few weeks ago??

[Eagle Eye]

Some great uppers for significant snowfall seen on the charts. 

Most of the UK under snow. 

[Mike Poole]

I really can’t see this breakdown scenario any time soon.  I know the models show it, they always do, but it will correct.  The background signals portend a longer period of cold as per my post above, that might or might not come to pass, but this is due to the SSW, and there has been close to another one since, so maybe weather on the ground will be driven by this for 4 weeks or more...those saying it is a 5 day affair are wrong in ,my opinion, but we will see...

Edited February 3, 2021 by Mike Poole

[Anthony Burden]

Charts ECM GFS GEM keen on bringing Atlantic lows to control U.K. weather in fantasy island,

Met office 30 day having none of it.The different scenarios regarding mid February weather 

continues,Will northern blocking rule the roost or will the Atlantic take back over.Big issue 

for the Met and Glosea 5.

[kold weather]

ECM ensembles have slightly shifted the snow zone further south, some very big falls in S.Midlands and EA on quite a number of these runs. 

Not too dissimilar to the OP to be fair. Quite a few have a 10-20cms zone between Norwich and Bham roughly.

If you want a visual, quite a few look similar to the 12z ICON.

[Cold Winter Night]

3 minutes ago, The Bevmeister said:

Right.....I may have missed this in the last 65 pages as I haven’t read them all but I have a question.  Is the forthcoming days of cold/snow that at this point looks to be widespread, a direct result of the SSW and vortex displacement from a few weeks ago??

The snow and cold ultimately isn't directly the result of the SSW, but the pattern that delivers it very likely is.
In tandem with an already weak tropospheric and stratospheric polar vortex, and an MJO that helps too.

Labelling patterns with 100% certainty is not possible, but the least you could say is it is very consistent with patterns that follow SSWs about 35 days after they have happened.

[Kentspur]

23 minutes ago, Eastbourneguy said:

The low is ever to slightly too far north for coastal counties in the south on the 12Z ECM according to the raw output. But it's go time 30miles or so inland!

The cold airs only just coming in though so that's actually pretty promising to see a mix already that far south as early as Saturday! I thought you were posting Sunday/Monday charts for a min

[sunnijim]

4 minutes ago, Mike Poole said:

I really can’t see this breakdown scenario any time soon.  I know the models show it, they always do, but it will correct.  The background signals portend a longer period of cold as per my post above, that might or might not come to pass, but this is due to the SSW, and there has been close to another one since, so maybe weather on the ground will be driven by this for 4 weeks or more...those saying it is a 5 day affair are wrong in ,my opinion, but we will see...

I agree 100% with this.

It is not hope casting, The evidence suggests that all models as we see them tonight have it wrong from the middle of next week.

My prediction,pressure to the North and East much more resilient than we see tonight.

Atlantic Lows not as vigorous or taking a Slide.

[tight isobar]

2 minutes ago, kold weather said:

ECM ensembles have slightly shifted the snow zone further south, some very big falls in S.Midlands and EA on quite a number of these runs. 

Not too dissimilar to the OP to be fair. Quite a few have a 10-20cms zone between Norwich and Bham roughly.

If you want a visual, quite a few look similar to the 12z ICON.

As with any snow-zone geographicals these WILL shift as we gain but even by now I think we can at least begin to gage the zones @somewhat!!

[steveinsussex]

It looks quite warm (uppers) over mainland Europe so it wouldn’t take much to scupper things for the southern half of the U.K. fingers crossed for the next 3 days!

[Thundery wintry showers]

I used to live in Lancaster so I can understand some snow lovers in sheltered western areas wanting a frontal attack from the west, as it has potential to bring rather more to central and western areas than showers and troughs off the North Sea in an easterly flow.  I think the issue is reading a chart off the ECMWF showing widespread snow, but failing to appreciate that it would be transitionary and followed by a rapid thaw and possibly widespread flooding as well with all that wind and rain following behind.  The ideal for many sheltered western areas is a slow breakdown with a frontal attack from the west stalling against the continental air, early February 1996 had a particularly famous example.

For the south-west the ideal is more for a frontal attack from the south-west with fronts aligned W-E or WNW-ESE stuck over the south and south-west, especially if the low slides eastwards and so we don't get a quick return to mild.  Again the ECMWF breakdown is a long way off this scenario but UKMO at T+144 strongly suggests this very scenario to me.

I remember having this argument in late November 2010 when the GFS overblew a low and there were many saying there would be a more widespread snow event and that "greater risk = greater reward", but I remember that in most of those runs the snow was again transitionary at low levels and was followed by 2-3C and rain at low levels in most places.  But if a depression had slid eastwards across the south we could have seen an all snow event from it, it's all about the angle of attack, how much warmer air is wrapped in with the fronts and how quickly the milder air pushes in.  In the end the snow showers off the North Sea gave lying snow almost everywhere apart from a dry slot from East Anglia across to the south-west.

 

Edited February 3, 2021 by Thundery wintry showers