Model output discussion - Post SSW - Will it turn cold?

[Paul]

The much talked about SSW has taken place, but as Nick blogged about a few days ago, it doesn't always mean cold for the UK. The signs are good though (if you like cold that is), and the model output is showing a lot of northern blocking currently. It's set to be a really interesting time to follow the models if nothing else, so please carry on the discussion here. 

As ever, please keep it to model discussion only in this thread.....

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[karyo]

The updated ICON is not in a hurry to bring an easterly. Just slack high pressure on top of us. The 0z was much more favourable at this stage.

https://www.meteociel.fr/modeles/icone_cartes.php?&ech=180&mode=0&map=0&archive=0

[Man With Beard]

And so we get into "squeeky-bum" time with the SSW and its impacts on the models.

Anyone looking for consistency in the fine details will be disappointed if they compare yesterday's UKMO T144 with today's T120:

  

[inghams85]

Very poor start to the 12z heights way lower around Iceland similar to the older ECM runs from 2 days ago

[prolongedSnowLover]

4 minutes ago, Man With Beard said:

And so we get into "squeeky-bum" time with the SSW and its impacts on the models.

Anyone looking for consistency in the fine details will be disappointed if they compare yesterday's UKMO T144 with today's T120:

  

Not a good start this evening with the GFs following in the same vein ?

[frosty ground]

4 minutes ago, Man With Beard said:

And so we get into "squeeky-bum" time with the SSW and its impacts on the models.

Anyone looking for consistency in the fine details will be disappointed if they compare yesterday's UKMO T144 with today's T120:

  

GFS agrees 

[frosty ground]

Before we get toys thrown about the GFS is not to different from the 06z

 12z vs 06z 

But as Nick would say the shortwave phased the wrong way, AKA no quick route to cold

[Mucka]

UKMO. GEM and GFS all flatter this evening?

Never easy is it?

[inghams85]

1 minute ago, frosty ground said:

Before we get toys thrown about the GFS is not to different from the 06z

 12z vs 06z 

Heights are 200miles further south. It's not a great start. It's delays well see if all routes lead to cold soon

[frosty ground]

Duck..... watch out for those toys.

The Jet is still behaving its self, with the curve back it will eventually pull Cold air westwards

[frosty ground]

uppers look the same.
 

[Singularity]

Arctic ridge better toward the pole than the 06z and jet cutting south a little further west. Small tweaks so far.

Today has so far seen the old solution of the Azores High building a ridge to Scandinavia put aside in favour of it being overrun by a low that then cuts down through Norway - thanks to that curve of the jet down south - and so acts as a 'trigger low' for the easterly as heights rise across Scandinavia from the north. This 12z run from GFS seems to be trying for yet another way forward though, as the low doesn't separate from the main Atlantic trough and we're looking to rely instead on the increasing heights down from the Arctic plus above in the stratosphere to disrupt the main trough.

 

A hint of that going on as of +135 (tiny low in the N Sea). 

Not as fun as the 06z but UKMO is keen to give this idea the thumbs-down with the low separating very cleanly indeed;

It's handled the Atlantic trough pretty strangely but that push of heights from the SW should interact with the forcing from the SSW to build a Scandi high by Tue/Wed.

Clearly, some details sorely in need of resolving before we can start expecting the easterly to land on any particular day.

[Daniel*]

There is very little difference the trigger low is missing so a less quicker route but we’ll get there I’m sure.

[Ali1977]

I’m not sure what the GFS is doing here, it looks like the blocking high could be flattened which is a bit of a shocker!!

edit - wrong , looks like a WAA reload will fix that

[Mucka]

Phase 1 is a fail I'm afraid on both UKMO and GFS with the ridge being overrun.

That means for any cold we would have to wait for the Atlantic to reamplify.

While that may be the case it is obviously much better to get the initial ridge because the next chance is again in FI and that could go wrong too.

Nothing to say the models won't switch back to the more amplified pattern they showed this morning so no need to panic yet but also no point pretending the output is not worse than this morning for cold lovers.

[Johnp]

3 minutes ago, Daniel* said:

There is very little difference the trigger low is missing so a less quicker route but we’ll get there I’m sure.

I'd call that quite a big difference.

[frosty ground]

2 minutes ago, Ali1977 said:

I’m not sure what the GFS is doing here, it looks like the blocking high could be flattened which is a bit of a shocker!!

edit - wrong , looks like a WAA reload will fix that

Exactly the high is building again.

No quick route to cold, but no flattening high either.

[frosty ground]

Just now, Johnp said:

I'd call that quite a big difference.

But in the grand scheme of things it really isn't 

[Daniel*]

3 minutes ago, Johnp said:

I'd call that quite a big difference.

Perhaps but looking at it broadly it’s not hugely different minor adjustments equate to big impacts on resultant surface conditions. The AO definitely seems more negative on this run...

[frosty ground]

Starting to see the formation of a surface low over Scandi that will cut through the high, this should advocate some cold air westwards, 2nd bite at the apple.

[Seasonality]

The cold air is obviously restricted further east on this run, then again it may just be a mild outlier or a rogue run. Lets see where it goes from here.

[Singularity]

 

While it's still making progress toward a similar outcome (trough breaking down, some of it likely headed for W. Asia with blocking to N of it), this run is a bit out of kilter with the other models terms of how much the Atlantic trough advances NE days 4-6, so is worth viewing with high(er than usual) suspicion.

It's pretty much a reversion to the 00z run, which was followed by the quicker 06z run (in terms of cold air arrival from east).

 

Here's UKMO top-down at day 6. Looks alright when taking into account the fact that the focus of heights is ready to shift from SW to NE of the UK - but true to say, it could easily have been better with the shape of the Atlantic trough.

[Paul]

So quick update, not even a page into the new thread and that's two more people added to the restricted list in here. Fun times, like trying to herd cats...

The odd o/t post is ok, sometimes a bit of thread drift happens, but continuous, repeated off topic stuff is not.

[frosty ground]

2 minutes ago, Singularity said:

 

While it's still making progress toward a similar outcome (trough breaking down, some of it likely headed for W. Asia with blocking to N of it), this run is a bit out of kilter with the other models terms of how much the Atlantic trough advances NE days 4-6, so is worth viewing with high(er than usual) suspicion.

 

Here's UKMO top-down at day 6. Looks alright when taking into account the fact that the focus of heights is ready to shift from SW to NE of the UK - but true to say, it could easily have been better with the shape of the Atlantic trough.

Worth Noting the Low has slipped south on the UKM whilst on the GFS it went back north west.

[Daniel*]

Crikey AO forecast sheer vertical drop likewise NAO but not to that amplitude.