Model Output Discussion - Deeper into Autumn

[Ali1977]

4 minutes ago, Liam Burge said:

Well, we need see a CET of less than -2.2 to not break the all-time highest CET record. Could this be achieved???

sub zero would be highly unlikely I’d say - could be one of the coldest on record though looking at these charts and if they became reality , 2010 was on the extreme scale so doubt that’ll be close to being touched.

long way off though, let’s see!! 

Nice looking chart at 240 but not that cold , the ENS will be interesting to see.

Edited November 25, 2022 by Ali1977

[Rayth]

15 minutes ago, Mark Smithy said:

 

However, I do wonder whether anything is really gained by the GFS having runs every 6 hours rather 12. .

Reason I followed @johnholmes advice a while back and picked one run to follow either 12z or 00z for me, then dissect the nuances from there , dissecting every 6 hours doesn’t give you the changes/progression in pattern for me 

[TSNWK]

14 minutes ago, Ali1977 said:

sub zero would be highly unlikely I’d say - could be one of the coldest on record though looking at these charts and if they became reality , 2010 was on the extreme scale so doubt that’ll be close to being touched.

long way off though, let’s see!! 

Nice looking chart at 240 but not that cold , the ENS will be interesting to see.

The high sinks southwest  over us from 216 to 240. Need this retrogression high up.. really.not sure what to think it.. 

[sheikhy]

Well brilliant all around this morning!!maybe a tad further east again but is that just the 00zs doing what they normally do!!awesome blocking all around!!!

[mulzy]

42 minutes ago, Liam Burge said:

Well, we need see a CET of less than -2.2 to not break the all-time highest CET record. Could this be achieved???

It’s the anomaly that needs to be less than -2.2C to not break the record.

So need the CET for December to come in at 2.3C or lower. 

 

[Johnp]

29 minutes ago, Rayth said:

Reason I followed @johnholmes advice a while back and picked one run to follow either 12z or 00z for me, then dissect the nuances from there , dissecting every 6 hours doesn’t give you the changes/progression in pattern for me 

And I always argue against this. Doing this means the run you are looking at is 24hrs out of date. A lot can change in that time!

[markw2680]

Have to say it’s hard not to get a tad excited when looking at current charts/models etc. I know we have been burnt many times before but this just seems different to me. More like 2010 as in everything seems to be counting down and not constantly getting pushed back.

still feet firmly on the ground for now but with the way things are looking currently it would be sooo harsh for all this to disappear into the wilderness.

remember the trend is your friend not every single model run every few hours.

onto the 06z then we go

One more thing before I go. Common England and common wales  ️ 

Edited November 25, 2022 by markw2680
Spelling

[Chesil View]

As we head towards a spell of colder drier weather, (length and depth to be determined) it is worth remembering pretty much all our decent winters or wintry spells have ebbed and flowed.  None have ever been wall to wall screaming Easterlies for three months. Even 1947 and 1963 ebbed and flowed somewhat albeit within their extreme envelopes.

Even with good strong blocks, Scandi or Greenland the isobars will open out now and again to give quiet and cold rather than endless snowy troughs and disturbances. Like wise scandi block may slip southwest a bit before retrogression pulls it back northwest to Greenland. 

My advice if this winters starts to get really interesting is to go with the (ebb and ) flow.

Edited November 25, 2022 by Chesil View

[Mike Poole]

ECM ensembles hold steady, T240 mean anomaly:

No ‘black hole’ this time, perhaps reflecting a greater uncertainty in position of the block - in fact I felt the ECM op was slightly disappointing as the block had sunk to a UK high by T240.  

Position and orientation of the block on the mean continues to look really excellent.

I mentioned uncertainty at this timescale, and that is reflected in the clusters, here T192-T240:

All blocked (all red borders) but some differences here.  I think I’d have put the op in cluster 5 rather than cluster 1 but that’s maybe from a parochial UK perspective!  Clusters 2 and 3 nicely show the vortex split options, while cluster 4 is just one ginormous block, full stop.

Moving to T264+

Cluster 4 goes belly up with the Atlantic making inroads - unlikely it seems to me, and has only 6 members.  The other 3 show varying degrees of retrogression west with cluster 1 the least (the block stays mainly Scandi) and cluster 3 the most (full on Greenland high).

Edited November 25, 2022 by Mike Poole

[SLEETY]

That high pressure stuck over central Europe for weeks giving us a very mild Autumn, has done us a favour for once by building North and West and bringing a colder Easterly flow instead 

Could be a prlonged spell of colder weather ahead. 

[Lukesluckybunch]

what would peoples  guess be with the ECM at 240,,afteri think there could be a reload from the northeast with weak heights possible around scandi?

[Adam lufc]

3 hours ago, CreweCold said:

Yes the theory was correct...here it comes, nice big, correctly orientated block coming with extension to Greenland. This is what we need to see for a prolonged freeze rather than a spell

If only. We'd be drooling.

[MattH]

Definitely getting somewhere now next week with the handling of the trough disruptions, there remains a lack of consistency over the evolution, but models are certainly getting better aligned and it is also interesting and of note to see the MOGREPS switch as well to the general weak E or SE'ly solution and more blocked pattern from the middle of next week, which IMO, is a big 'thing'. I don't often see these referenced on here often, but I certainly recommend using the MOGREPS plots as much as you would look at the GFS ENS postage stamps and the EC Clusters, as a combination of them all will help to provide better guidance. We can see that most go blocked by next Wed/Thu as per the below plot.

With the up-coming EAMT (East Asian Mountain Torque) on the way which will provide a jet extension across the Pacific and alter the USA pattern, then there is no better set of variables right now that supports a sustained blocking pattern for NW Europe and, perhaps, over the N Atlantic with time. The retrogression of any high pressure though is still within the medium and long term and should certainly not be taken as a gospel transition, whether we tap into any more significant cold on the E'ly flow, in time, is also highly uncertain, but at least it's a drier and more seasonal outlook and we finally say goodbye to the cyclonic spell of recent weeks.

What also needs to be watched for closely is the next MJO wave, something the EPS and the GEFS are highlighting now on VP200 anom plots (below), while still a relatively weak signal, there is clear evidence for the MJO to return to the Maritimes and W Pacific as December progresses and as has been the case of late, it may well make a transition across the Pacific through phases 5-6-7. To what extent  (amplitude) will be very important, but when coupled with some of the up-coming N Hem anomalies (MSLP and GPH, etc) then I really do think we are in for a good shout of a disrupted strat vortex or even an SSW late Dec and into the first half of January.

Also, regarding the MJO what is interesting is how different the composite anomalies are depending on ENSO type and phase for December. As usual, use these plots with caution and with the usual caveats, but if we look at December, MJO phase 5 within a negative ENSO state (La Nina) then the outcome is noticeably different than compared with a more neutral ENSO phase. Clearly, atmospherically we are within a Nino state, oceancially, it is still Nina, albeit increasingly weakly, so difficult to gauge that one looking ahead. It does highlight how important this next MJO passage could well be though in maintaining or reinforcing amplification to the pattern deeper into December.

Cheers, Matt.

[sheikhy]

24 minutes ago, Mike Poole said:

ECM ensembles hold steady, T240 mean anomaly:

No ‘black hole’ this time, perhaps reflecting a greater uncertainty in position of the block - in fact I felt the ECM op was slightly disappointing as the block had sunk to a UK high by T240.  

Position and orientation of the block on the mean continues to look really excellent.

I mentioned uncertainty at this timescale, and that is reflected in the clusters, here T192-T240:

All blocked (all red borders) but some differences here.  I think I’d have put the op in cluster 5 rather than cluster 1 but that’s maybe from a parochial UK perspective!  Clusters 2 and 3 nicely show the vortex split options, while cluster 4 is just one ginormous block, full stop.

Moving to T264+

Cluster 4 goes belly up with the Atlantic making inroads - unlikely it seems to me, and has only 6 members.  The other 3 show varying degrees of retrogression west with cluster 1 the least (the block stays mainly Scandi) and cluster 3 the most (full on Greenland high).

Also keep an eye on the orange splodge of heights around italy and greece!!idealy we want lower heights around there in future updates!!but everything else looking rosey!!

[bluearmy]

Really strong signal on the day 14.5 eps mean spread for the upper ridge west of the U.K. 

note the uncertainty s Greenland where it could be high or low heights …….. need to scan the stamps for that 

 

 

[phil nw.]

Not much to add this morning just to note as Matt H posted that we have good support for the transition towards the block building next mid week.

That's the first stage ie stopping the Atlantic and reversing the the flow to a continental one.

It will naturally cool off as we wait on the development of this pattern.

As ever we see slight variations on this but overall the ens.are looking good.

[Mike Poole]

The tableaux plot of 850 hPa temperature for the ECM eps tells a compelling story, that of both increasing likelihood and increasing depth of cold on the one plot, right through to day 15.  Here, for roughly my location:

Worth checking from time to time how this plot changes as this colder spell gets closer.

Edited November 25, 2022 by Mike Poole

[SqueakheartLW]

2 hours ago, Liam Burge said:

Well, we need see a CET of less than -2.2 to not break the all-time highest CET record. Could this be achieved???

 

1 hour ago, mulzy said:

It’s the anomaly that needs to be less than -2.2C to not break the record.

So need the CET for December to come in at 2.3C or lower. 

 

A fair few Decembers between 1659 and 2021 come in at 2.3C or lower. The problem is that most of them are pre 1900.

Since 1950 only 7 out of 72 Decembers make the cut to prevent the annual CET record from getting broken.

Year    December CET
1995    2.30C
1961    2.20C
1976    2.00C
1962    1.80C
1950    1.20C
1981    0.30C
2010    -0.70C

1995 only just scrapes the requirement to prevent the record. Can't see us getting something that low even if the models are hinting at something colder.

Will need to see charts like these at regular points during December coming off to prevent the year ending as warmest on record

   

[northwestsnow]

35 minutes ago, bluearmy said:

Really strong signal on the day 14.5 eps mean spread for the upper ridge west of the U.K. 

note the uncertainty s Greenland where it could be high or low heights …….. need to scan the stamps for that 

 

 

Yep ,interesting chat on twitter about the SPV beginning to wind up to above average strength but not much sign of a coupling ,yet.....

[TSNWK]

45 minutes ago, bluearmy said:

Really strong signal on the day 14.5 eps mean spread for the upper ridge west of the U.K. 

note the uncertainty s Greenland where it could be high or low heights …….. need to scan the stamps for that 

 

 

Hello.. if I understand correctly the above does suggest a reasonably amount of high pressure certainly to our north east.. so we have a case of does the high retrogress to Greenland or not with those yellows over greenie 

[Cambrian]

Whoever thought of staging a World Cup at the same time as our potential cold spell is just crazy.

  

Substantial strain on the PV at 500mb as early as day 6, the turn of the month. From left to right - 492 dam over the pole on the 0z GFS for today; a football; 522-528 dam over the pole by day 6. The beginning to a memorable December hopefully. Far too much excitement. 

[MATTWOLVES 3]

Happy Friday folks and a happy set of gfs ens with yes you guessed it...blocking scenarios left right and centre...

[tight isobar]

The formidable blocking formats continue on the overnights! @ eps/ gefs.. let’s hope for similar- or more through today’s outs

[Quantock]

31 minutes ago, SqueakheartLW said:

 

A fair few Decembers between 1659 and 2021 come in at 2.3C or lower. The problem is that most of them are pre 1900.

Since 1950 only 7 out of 72 Decembers make the cut to prevent the annual CET record from getting broken.

Year    December CET
1995    2.30C
1961    2.20C
1976    2.00C
1962    1.80C
1950    1.20C
1981    0.30C
2010    -0.70C

1995 only just scrapes the requirement to prevent the record. Can't see us getting something that low even if the models are hinting at something colder.

Will need to see charts like these at regular points during December coming off to prevent the year ending as warmest on record

   

Low minimums are the key to getting a 2C CET.   More easily achieved under a northerly than an easterly, given the latter is more prone to giving cloudy conditions and while suppressing the maximum temps, the minimums don’t fall far enough.

[Eagle Eye]

14 hours ago, Eagle Eye said:

 

The GWO is moving towards a phase where over the next week or so when we'll likely lose Atmospheric frictional torque and the AAM goes down . Beyond that we should enter phases of postive friction torque then southward momentum and circumglobal troughs as the AAM increases again so a brief dip then back to normal. You should also refer that there is still a lag correlation with this (not sure how long it is sorry) so keep that in note.

Agree with @MattH further up and he puts it more elegantly than I can and looking further on, as the quoted part of my post yesterday says, the AAM does dip soon (but shouldn't affect next week) but should truth back to a proper Nino state AAM and so the consequences of that will be that we get that increased -NAO chances.