Model Output Discussion - Into the new year

[sebastiaan1973]

22 minutes ago, feb1991blizzard said:

Have you got any info where the blocking transfers to on average? does it collapse or topple to Scandi? And is there a difference between different SSW type, area and split/displacement?

Hi feb1991blizzard (over here in The Netherlands I really enjoyed that month with lots of snow,up to 20cm). They didn't make a difference between split and displacement. Just the tropospheric 'picture' of 5 days before the onset of the SSW and 5 days later. I'm sorry I can't help you with the other question. It's area 60-90N, 80W-40E.

But perhaps you can take a look for yourself

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

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<p><strong>Abstract.</strong> Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in particular in the North Atlantic–European (NAE) region...

Simon Lee gave a reaction:

 

Edited December 29, 2020 by sebastiaan1973

[Froze were the Days]

28 minutes ago, Day 10 said:

Day 10 - Polar bears heading south.

I wish that chunk of the LP/vortex over Scandi would head south rather than stay in situ or eventually move north...then the fun and games would really start and actually experience some deep cold.

[sheikhy]

Not even -7 850s are giving snow showers!!now i know the north sea is warmer than normal but that is truly shocking!!if gfs 18z shows the same as the 12z run then i am expecting a slightly better run from ecm in the morning!!

Edited December 29, 2020 by sheikhy

[Mike Poole]

1 minute ago, Djdazzle said:

It just seems that at the moment, we’ve accepted our invite to the cold party. But we can’t seem to get an invite to the special VIP lounge where deep cold is located.

I can sense why folks are frustrated because most people haven’t seen snow or even a frost out of this spell yet. 4C by day and 1C by night with grey skies and drizzle don’t cut it for most people! It may as well be 13C which would save on the heating bills.

There seems to be no clear model consensus as to where we are heading, which is frustrating considering the overall positive NH profile.

 

 

That’s why some of us factor in the background signals as well.  It is a balance but with a SSW in the wings that balance tips against the model output, and in the favour of understanding what might be expected either side of that SSW.  

Just look at the NAM plot:

That is effectively the AO index but at all levels of the atmosphere.  We are just entering a period where it is negative everywhere and not just by a bit.  This is the real SSW - I know the technical one hasn’t happened yet, but it is all part of a longer term narrative which is well underway now.  

[Allseasons-Si]

I don't know what people are complaining about!, some parts of the country have had one or two bouts of snow events with marginal uppers and there is more to come but let me point this across, not everywhere will get snow and that's a fact and depending where the wind blows different parts of the UK will be effected where as others won't,we are in a cold spell and people are moaning of a breakdown ten+ days out

the synoptic patterns are looking good for the next week and who knows what will happen after that.

[chionomaniac]

35 minutes ago, sebastiaan1973 said:

Well looking at the EC oper output it seems, that a Greenlandblocking at the onset of the SSW is good possible. This is the profile of the SSW composition. In this way not good. Chio pointed out we have to watch at 100 hPa. I question how long will the weak vortex stay there, without 'help' of the SSW.

The issue is here that the SSW may or may not propagate and if it does will it produce the goods because undoubtedly without a major split it will affect the Pacific pattern. You may end up wishing that a SSW never occurred in a month or so if the Pacific amplification occurs as a result of post SSW Tropical feedback. I don’t know how long the lower Atlantic trop disruption will continue for, but I have never been more wary of an SSW not being long term beneficial than this one.

[Paul]

Locking this one now, I've split out the last couple of pages to start a new thread here:

 

Edited December 29, 2020 by Paul