Model Output Discussion - Snow for some, but what else is in store?

[stodge]

Evening again all

Two points - first, much more consistency across the models at T+120 and T+240 tonight than there has been for several days.

Why?

The higher DAM air mass over Greenland exits to the left over Canada and from that point on any UK cold spell is in big trouble. Keeping that keeps the Greenland HP block in the game and the jet to the south.

Second - the persistent indicator of heights rising to the south. I think I saw this first on an ECM run a week ago. My only explanation for this is that it's down to the fall off in zonal winds. As LP exit North America, instead of heading east and flattening everything in their path supported by a powerful jet, they move more slowly and as they deepen they throw forward heights. As the Greenland block has kept the jet to the south and the LP are exiting North America at lower latitudes, the slow motion leaves the heights rising through Iberia which in turn kicks the jet back north and aligns the trough positively through the North Atlantic and that's it for cold fans until another amplification.

I still think there will be a significant pattern change into February with heights rising over Scandinavia in response to the PV moving back over to Canada. 

[Kasim Awan]

3 minutes ago, Team Jo said:

The rhetoric around ‘I’m so sad it won’t snow in xxxxx’ isn’t model or location analysis though is it?

Point taken. Users just need to be objective and scientific about the spatial aspect of the model output.

For example the snow tomorrow which has marginality for London / pure non conducive conditions in South Kent though this maritime layer will become phased out approaching the North Downs with uplift it will become eradicated allowing for a base line FRZ of 400m / Snow level of 150m in the cold sector.

[Tim Bland]

3 minutes ago, IDO said:

 

I really think this is nailed on for the long wave pattern for our region until around d10, just the detail to be ironed out, and we take it from there.

Look at the snow line day 8 - 12z Vs 18z. It’s not inconceivable that it shifts another 200 miles south tomorrow to include everyone? We don’t need a major pattern shift for that  

[Man With Beard]

1 hour ago, Man Without Beard said:

Right enough complaining from me - time to make an actual forecast. Looking through the ECM ensembles for D8, its clear most are keen on secondary lows running into the base of the primary low, and a great number of them have a snow event on the northern flank. That means, next Friday/Saturday, look out for a snow event 100-150 miles from the northern extent to the southern extent. The question will be: where? South of the M4? M4 to Birmingham? North midlands? Lancs/Yorks? Or even in the channel? A nail biter. But the ensembles are quite keen.

Yep, GFS parallel a perfect example of what's on many of the ecm ensembles tonight for next Saturday

[chris55]

4 minutes ago, Kasim Awan said:

Point taken. Users just need to be objective and scientific about the spatial aspect of the model output.

For example the snow tomorrow which has marginality for London / pure non conducive conditions in South Kent though this maritime layer will become phased out approaching the North Downs with uplift it will become eradicated allowing for a base line FRZ of 400m / Snow level of 150m in the cold sector.

MLM! Sounds complex, but makes sense. im glad im way away in Gloucestershire. Straight up rain here.

 

[Tim Bland]

18z Aperge good for snow in East Anglia until lunchtime. 

[Vikos]

Just for fun, doesn't mean anything

[chris55]

5 minutes ago, Tim Bland said:

Look at the snow line day 8 - 12z Vs 18z. It’s not inconceivable that it shifts another 200 miles south tomorrow to include everyone? We don’t need a major pattern shift for that  

Boundary frontal snowfall is a high risk going forward IMO, as I have said before. Where that boundary sets up is anyones guess but id punt for somewhere over the UK!

[stodge]

Much better 18Z Parallel for cold/snow fans:

Note the heights to the south are suppressed with the ridge orientated east rather than north east.

[winterof79]

14 minutes ago, Team Jo said:

The rhetoric around ‘I’m so sad it won’t snow in xxxxx’ isn’t model or location analysis though is it?

He hasn't said that and there are far too many posts in here that only show models with snow in the south east. Murr was one of the best but we said nothing. If I posted graphics of snow in Yorkshire constantly I'd be lambasted. Karim has posted about this weeks snow event which happened to be up North this time.. Leeway required. 

[Tim Bland]

5 minutes ago, Man Without Beard said:

Yep, GFS parallel a perfect example of what's on many of the ecm ensembles tonight for next Saturday

2 days later there’s another low in a similar position...

[BLAST FROM THE PAST]

 

so nigh on the whole of North America is under one HP cell....what a strange chart

 

BFTP

 

[O'Maille80]

GFS para is a gem. Bank.

[Vikos]

I think we have a problem with ECMWF

 

   

[Griff]

3 minutes ago, O'Maille80 said:

GFS para is a gem. Bank.

You mean the advancing purple to the east? 

Most definitely in the reliable

[feb1991blizzard]

GEFS mean trends another 200 miles North at 180 hours with the boundary between cold and mild air, gets worse with every run, oh dear, oh dear, oh dear.

[bluearmy]

6 minutes ago, Vikos said:

I think we have a problem with ECMWF

 

   

The very end of the eps show the jet becoming more suppressed into Europe which would bring pretty much the whole of the U.K. into the raffle with a ticket from the winning book! 
 

the fact that there is only one cluster isn’t great for the likely spread at that range but it’s an interesting development at day 15 on the mean 

[Don]

3 minutes ago, feb1991blizzard said:

GEFS mean trends another 200 miles North at 180 hours with the boundary between cold and mild air, gets worse with every run, oh dear, oh dear, oh dear.

Just hope the models can swing back in our favour at the last minute but looking less likely with every run?!

[Don]

28 minutes ago, stodge said:

I still think there will be a significant pattern change into February with heights rising over Scandinavia in response to the PV moving back over to Canada. 

I hope we are not looking towards the end of February into March with that?!

[joggs]

2 hours ago, bluearmy said:

not much good news from the eps but the spread is to the south at day 10 
 

Spread? What does this mean please?.

[Tim Bland]

6 minutes ago, feb1991blizzard said:

GEFS mean trends another 200 miles North at 180 hours with the boundary between cold and mild air, gets worse with every run, oh dear, oh dear, oh dear.

Those ensembles have been as fickle as the last few days. Para tonight is 200 miles south of its 12z. Who knows where the boundary will be show tomorrow  

[weathercold]

The last few days model runs are definitely a tough pill to swallow for coldies. You do get the feeling this winter is fast becoming one of great potential, ultimately never truly realised.  It’s also notable how few runs (if any) across NWP have bought in -10 hpa across any runs. Roll on spring!

Edited January 15, 2021 by weathercold

[bluearmy]

Another observation on the gfsp is that it’s week 2 solution of the greeny ridge dropping west into the conus and then reappearing back into the W Atlantic is a also mean eps theme  

[Tim Bland]

1 minute ago, joggs said:

Spread? What does this mean please?.

Uncertainty. Ie how many ensembles have a different outcome in that region. 

[bluearmy]

 

2 minutes ago, joggs said:

Spread? What does this mean please?.

The area of uncertainty away from the mean   .....

 

Edited January 15, 2021 by bluearmy