Model output discussion - into Christmas

[Methuselah]

10 minutes ago, Don said:

Reading GP's thoughts above, it sounds like we have been led up the garden path again only to be brought back down?

Well Don, I feel that (had I seen reason to feel 'led up the garden path') it'd be more to do with some posters' far-fetched predictions, than with anything the models have been indicating...?

[Ali1977]

7 minutes ago, feb1991blizzard said:

Well that was a short lived chase wasn't it?

Horrific, I’ll let the 12z role out before conceding to that garden path again. Between Xmas and New year a HP over central MED now looks odds on (not ideal for skiers overs that period with regards fresh snow). After New year is still open for anything 

Edited December 18, 2019 by Ali1977

[Dennis]

lets say so : we all know the Xmas LoW (960Hpa)  - shows it up than the winter is off for a time ; if it not does then a surprise is ahead  

I see no XMAS LOW forming til now

[Nimbusman]

5 minutes ago, feb1991blizzard said:

Well that was a short lived chase wasn't it?

Yes looking a those ensembles and just reading GP thoughts looks a very brief respite to the wind and rain. Will be nice to have a more seasonal feel to the Xmas period before Atlantic onslaught begins again unfortunately 

[swfc]

16 minutes ago, Ed Stone said:

Well Don, I feel that (had I seen reason to feel 'led up the garden path') it'd be more to do with some posters' far-fetched predictions, than with anything the models have been indicating...?

Post of the winter so far.hope springs eternal but realism isn't s bad trait.i think Steve murr is respected and rightly so.he does seem to be becoming the Michael Bublé of net weather tho.

Edited December 18, 2019 by swfc

[MATTWOLVES 3]

12 minutes ago, Don said:

Reading GP's thoughts above, it sounds like we have been led up the garden path again only to be brought back down?

Have we been led up the garden path though! All we are seeing is one set of runs going colder, then the next going milder, on a daily basis. Just how on earth are we meant to reach a conclusion from the ens, when they throw up a completely different scenario... Run to run! I've got serious doubts over this new re jigged GFS. Last year it constantly overplayed the cold, this year it seems to underplay it. The more the models get dissected with a fine tooth pick, the more confusing it gets!! We basically need all the models on board showing a cold scenario, within several days out! And personally I don't think any of these models are ever gonna agree on a timescale a few days out. Getting a cold snap back in the day was made to look like a walk in the park! These days with the Internet era and all the info we have.... Its made out to look like rocket science. 

[Ali1977]

I don’t get how this looks so good after a less than great set of ENS!! Any ideas??? 

Edited December 18, 2019 by Ali1977

[Catacol]

26 minutes ago, Glacier Point said:

I reckon it will flatten out soon into New Year.

There is a narrow window for a wave 2 induced pattern (high pressure centred close to UK) arising from a recent enhanced trade / reduced westerly across the central Equatorial Pacific and spike in tendency in angular momentum. Worth noting the direct correlation with this in the polar stratospheric pattern.

However, that won't last long. GFS suggesting a westerly wind burst across the central regions of the Equatorial Pacific in the next week.

That will increase angular momentum and trend more to a wave 1 pattern (both tropospheric and stratospheric) with associated lowering of surface pressures in the North Atlantic and dropping of Arctic air mass into the mid West States of the US. That should fire up the jet across the North Atlantic displacing any mid latitude ridge across North-west Europe. Strong presumption for jet angled NW-SE into Europe with moderate level +ve heights to our north within this regime. 

GEFS 06z ensemble mean makes perfect sense to me within that broad context.

What does strike me from current modelling is the propensity for scrambling of the mid layer flows across the North Atlantic, probably the low solar conditions beginning to take effect. Therefore, heights likely to be greater to our north than analogue guidance would suggest - but still overall signal is for troughing across NW Europe beyond next week's ridge.

A flattening was always the likely longer solution, but It is still good to see a number of colder drivers progressing as they are. Jet angle, if is remains at that angle, will eventually create better options once climatological peak of Atlantic strength has passed and next round of forcing creates ever more potent wave breaking in second half of winter.

I still find myself thinking though that models have misread the Pacific this month and more forcing is present than they are spying. EAMT will help with Pacific wave break and downstream amplification. Flattening of the pattern may take longer than expected.?

[feb1991blizzard]

Remember - Those EPS clusters - the anomaly is coloured - the contours show where the ridges and troughs are although it represents the upper pattern not the surface, if the higher number is to the South and the lower number to the North, that means the ridge is to the South, regardless of shading, the shading just indicates deviation from the norm, which is good for an indication of how strong or weak the ridge or trough is.

[knocker]

11 minutes ago, Catacol said:

In the more reliable there are a range of cluster options

demonstrating the variation in height anomaly location. Posting a 300h+ cluster spread is more for fun than for accuracy as you well know but it does demonstrate an ongoing trend when combined with GEFS runs. Not a snap viewing. Given your Met background I wouldn’t dream of comparing my own chart reading skills with yours honed over many seasons.

And as I've said before on a number of occasions, I do not find it that easy deducing the surface analysis from these map projections

[Beanz]

4 minutes ago, Mattwolves said:

Have we been led up the garden path though! All we are seeing is one set of runs going colder, then the next going milder, on a daily basis. Just how on earth are we meant to reach a conclusion from the ens, when they throw up a completely different scenario... Run to run! I've got serious doubts over this new re jigged GFS. Last year it constantly overplayed the cold, this year it seems to underplay it. The more the models get dissected with a fine tooth pick, the more confusing it gets!! We basically need all the models on board showing a cold scenario, within several days out! And personally I don't think any of these models are ever gonna agree on a timescale a few days out. Getting a cold snap back in the day was made to look like a walk in the park! These days with the Internet era and all the info we have.... Its made out to look like rocket science. 

Back in the day there used to be 2 rules of thumb.  
 

1. Don’t bother looking past 192hrs 

2. Wait for the Majors to agree

These rules still apply, goodness knows why folk seem to be so engrossed in what’s happening at 300+ hrs, it will ALWAYS change.  
 

 

[Catacol]

10 minutes ago, Ali1977 said:

Horrific, I’ll let the 12z role out before conceding to that garden path again. Between Xmas and New year a HP over central MED now looks odds on (not ideal for skiers overs that period with regards fresh snow). After New year is still open for anything 

?

[Glacier Point]

Just now, Catacol said:

A flattening was always the likely longer solution, but It is still good to see a number of colder drivers progressing as they are. Jet angle, if is remains at that angle, will eventually create better options once climatological peak of Atlantic strength has passed and next round of forcing creates ever more potent wave breaking in second half of winter.

I still find myself thinking though that models have misread the Pacific this month and more forcing is present than they are spying. EAMT will help with Pacific wave break and downstream amplification. Flattening of the pattern may take longer than expected.?

My thoughts would be as highlighted. Think of loading a dice. Currently 35-65 against. The more we progress down the road of +IOD / +ENSO climatology / weakening of the wQBO, the greater the loading in favour of colder outcomes.

+EAMT might be overdone on 5 day averages, an angular momentum uptick / GSDM may be more low amplitude that first thought.

[Catacol]

1 minute ago, knocker said:

And as I've said before on a number of occasions, I do not find it that easy deducing the surface analysis from these map projections

Yes - anomalies are only relative indicators and do not demonstrate surface patterns, but they do indicate forcings in that pattern. However 120h is the sensible window for surface detail and in that sphere you hold top spot.

[Ali1977]

5 minutes ago, Catacol said:

?

HP over Central Europe I meant (it’s why I mentioned Skiers) , looks drier for us as I said. But compared to earlier ENS runs its rubbish. Not writing anything off though, just saying it how it is, going off this particular run. 

Edited December 18, 2019 by Ali1977

[feb1991blizzard]

10 minutes ago, Ali1977 said:

I don’t get how this looks so good after a less than great set of ENS!! Any ideas??? 

Yes - i know why - its yesterdays.

[Catacol]

2 minutes ago, Glacier Point said:

+EAMT might be overdone on 5 day averages, an angular momentum uptick / GSDM may be more low amplitude that first thought.

Possibly...and one of the conundrums of this winter so far. Magnitude of Pacific signal has been veiled and progress of the convection signal seems to have varied enormously in modelling. 
 

And yes - “eventually”

[Glacier Point]

1 minute ago, Catacol said:

Possibly...and one of the conundrums of this winter so far. Magnitude of Pacific signal has been veiled and progress of the convection signal seems to have varied enormously in modelling. 
 

And yes - “eventually”

One of the outcomes manifested by the unusual occurrence of a record strength +IOD event outside of a strong El Nino. 

[Ali1977]

4 minutes ago, feb1991blizzard said:

Yes - i know why - its yesterdays.

That’ll be why , doh!! 

[bluearmy]

1 hour ago, Catacol said:

Trend continues to be good. New Years Day clusters - 70% see a block heading closer and closer to high lat...

Will it get there properly and embed, or will it flatten in the days after? Still a decent amplitude Pacific signal on NYD so amplification signal still present at that point.

 

70%?
both high anomoly clusters are not upper ridges gaining enough traction (remember these are clusters not means so it’s reasonable that they show an upper high at a high enough latatiude whereas a mean will not at that range) 

looks like a 33% chance of an Azores ridge extending towards scandi .... overall, it looks like the pattern remains too fluid but it could be that the nwp is still adjusting 

still astride the fence and not currently  expecting to land on the wintry side .....,

[weathermadbarnsleylad]

It's one run wait until the 12z and see where for cold prospects 

[jules216]

17 minutes ago, Glacier Point said:

My thoughts would be as highlighted. Think of loading a dice. Currently 35-65 against. The more we progress down the road of +IOD / +ENSO climatology / weakening of the wQBO, the greater the loading in favour of colder outcomes.

+EAMT might be overdone on 5 day averages, an angular momentum uptick / GSDM may be more low amplitude that first thought.

@Glacier Point January will be interesting to watch unfold weather we manage to hang on to the southerly tracking jet stream to enable the throughing to dive in deeper in to Europe to prevent a Euro high pressure, from your thoughts it doesn't look like Euro high will be on the menu, quite the opposite, which is always a preferred option. Anomaly like this may not be far away from reality then

[Catacol]

6 minutes ago, Glacier Point said:

One of the outcomes manifested by the unusual occurrence of a record strength +IOD event outside of a strong El Nino. 

+IOD as a gateway to Nina in 2020? Lots going on that is unusual from season to season which I guess is why unusually weighted synoptics are possible when the drivers creating the wave pattern are disguised. Agree on tendency for energy flows to fragment - low solar weakening the flow further. Hence optimism for a pattern op that clicks eventually.

[Methuselah]

An interesting set of GEFS 06Z ensembles; though they don't tell us what the weather'll be like, in 12-days' time, they certainly do provide a measure of the level of uncertainty involved:

    

    

[Catacol]

11 minutes ago, bluearmy said:

both high anomoly clusters are not upper ridges gaining enough traction (remember these are clusters not means so it’s reasonable that they show an upper high at a high enough latatiude whereas a mean will not at that range) 

Which perhaps is a lead in to a debate on mean v cluster. I have come to think that means are somewhat misleading in that they don’t pay anything like enough attention to lower atmospheric flows. The cluster charts provide a better window into probability and also a slightly more useful way of trying to predict surface conditions, though as Knocker has said today they are a long way from being the key tap hat unlocks that door.

Anyway I agree - winter nirvana is not showing yet on NWP and it may fade before establishing a resilient block in the right area but there is enough evidence showing an upcoming change to tweak interest.