Model output discussion - Christmas approaches

[Chris.R]

Omg so many toys. Be patient!

[sheikhy]

Brilliant absolutely brilliant!!and the main thing is the gfs has not moved tiwards ukmo at 96 hours in taking that norway shortwave into the atlantic!!it goes with the ecm instead!

[Chris.R]

1 minute ago, Met4Cast said:

Classic GFS..

Another one for the bin. Look at ECM/UKMO/00z GFS to see how the low should disrupt & behave. 

The 06z is getting there, but again the weird bowling ball of a low is the GFS being the GFS & not having a clue how to resolve the undercutting energy. 

Exactly so.

[IDO]

The GFS Atlantic low is the issue and no doubt that is a factor of other components:

GFS>  EC> 

Just minor adjustments could mean the colder air from the Scandi trough gets further south and we have the whole of the UK in cold enough air for snow. Thankfully it is the GFS and 6Z at that so we would be more than hopeful that the low is modelled poorly at this range.

[Methuselah]

2 minutes ago, Updated_Weather said:

It should be binned because it had literal no support - just like @Met4Cast said.. 
 

This doesn’t look at all right.. GFS loves dartboard lows, this doesn’t seem like an outcome imo. 
 

And there was me thinking it should be binned because it still refuses (like an incalcitrant toddler) to do what it's told!

[Singularity]

How amusing - GFS is disrupting the trough far more 24th-25th, but did so less on 23rd, so the polar front is a lot further north than it could have been.

Maybe a classic ‘GFS will be GFS’ moment. Perhaps, possibly .

[TSNWK]

This could be an interesting Boxing Day and beyond run I think….

[Catacol]

5 hours ago, Kasim Awan said:

5 hours ago, Kasim Awan said:

All this talk is interesting but without concrete scientific evidence, as relevant as they are, our theories are just that atm @CreweCold

 

Except there is oodles of scientific evidence for the shift in the sub tropical high pressure belt, and a cupboard full of observational data on UK weather patterns over recent decades. This is not original stuff.

And yet for all the negativity surrounding the pattern there is still considerable potential for wintry conditions - indeed I would say the last week has seen this upgrade significantly in terms of broad pattern. Here is the jet streak starting this weekend, modelled by GFS a week or so ago as a result of +EAMT conditions 

To be honest the broad pattern for the weekend we are in has not changed much at all over the previous 7 days. NWP success story. Then the jet pattern for the key period at Xmas

You can clearly see the jet streak has reached the US and is set to hit the Atlantic. However the modelling here has changed a bit. Charts posted a few days ago showed that streak heading in a NW to SE access. The modelling has flattened that prediction out and so we are looking at a much more marginal setup for the trajectory of low pressure systems into the block that has spawned. Why then is this an upgrade?

Put simply because of this. The UK high has managed to achieve Greenland status before we even get to Xmas, something I was personally not expecting but the result surely of the MJO and supportive tropical typhoon engineering the long wave amplification signature required. I would have bet a fair bit on the high sitting over the UK for longer - but instead we appear to be about to cash in on swifter developments. Rarely do high pressure cells move faster than originally forecast.

What this in turn means is that the colder air from the NE is being sucked in that bit more quickly, and the Scandy trough has more room to breath as the broadly meridional pattern forced out of the tropics encourages it southwards. Nothing whatsoever to be gloomy about here.

This in turn is bringing snow opportunities forward to Xmas itself. Remember that this wasn’t really on the cards a week ago. People were focusing on individual runs, seeking the grail of a white Christmas - but the charts were not really showing it. Now we have an accelerated and improved context, and this very marginal but potentially high reward scenario is a possibility.

What is not to like? Answer = nothing.

And what of the period just after Xmas, the period that realistically was the beginning of cold opportunity prior to the upgraded pattern? It’s gone from good to very good. We now have an Arctic High being modelled as the seasonal forecasts are sent scuttling for cover with their tails between their legs, and the optimistic background drivers dig in.

And if you go back to that jet forecast for Xmas above - notice anything? Another pacific jet streak waiting in the wings, helping to maintain the amplified pattern. The MJO remains favourable for a bit longer at least too. The ONLY small negative in all this is that the Greenland block is nudging a bit further west than we would like, as retrogression occurs at serious speed, but with this kind of signal this is not as bad as it sounds. Cold air in place over Scandy and Europe, wedges of heights remaining to the north as a result, overall amplified and meridional pattern - of course there remains the risk of us catching the mild edge of this at times….but there is also the significant opportunity to hit the boundaries between Atlantic moisture and Arctic cold. Is this not what we crave every year?

The current pattern sits in the top 3 for wintry potential from the last 20 years. 2010, 2018 and now 2021. 

 

 

Edited December 18, 2021 by Catacol

[bluearmy]

Imo, this is a good gfs op - the model doesn’t usually flip - it makes slow steps towards other models and over three or four runs it ends up there ! 

anyway, the lw Atlantic trough is suppressed and we see the cold heading back south 

could be a lot worse in the mid term from gfs!

[MattStoke]

1 minute ago, sheikhy said:

Brilliant absolutely brilliant!!and the main thing is the gfs has not moved tiwards ukmo at 96 hours in taking that norway shortwave into the atlantic!!it goes with the ecm instead!

Indeed. It looks far better (more slidey) from Christmas Day onwards but far from convinced it’s right before that point.

[Met4Cast]

1 minute ago, Singularity said:

How amusing - GFS is disrupting the trough far more 24th-25th, but did so less on 23rd, so the polar front is a lot further north than it could have been.

Maybe a classic ‘GFS will be GFS’ moment. Perhaps, possibly .

Was about to post the same - Could have been much further south had it not initially blown the low up into a dartboard first. 

Oddly quite encouraging, if the GFS can resolve the disruption in the earlier frames the later frames would be much better for the south. 

[BLAST FROM THE PAST]

 

Don’t worry, be happy 

 

BFTP

[nick sussex]

GFS 06 hrs run has a different troughing  set up over west Greenland and this helps to block in the high and stop a seepage of heights too far west .

And because of this more forcing on the pattern .

The splitting of energy with now two lows moving east rather than one system also helps .

Edited December 18, 2021 by nick sussex

[Lloyd1]

Am I right in saying that the ecm and gfs are showing two completely different scenarios at present. Bare in mind I’m west Wales so thats why temps are so high in the pics but ecm is really getting interesting in terms of snow if that is what they are showing even for us Westerns. Thanks 
 

[Uncertainty]

This is so 1978-1979 (Heavy rain across N England turned to heavy snow and moved south, channel blizzard eventually).

There’s been a general shift towards disruption this morning and a slightly stronger GH. The matter of Who gets the snow is going to have to wait…

FWIW those Mogreps stamps show a small but noticeable cluster where the south gets the snow so all tracks remain on the table…

Edited December 18, 2021 by Uncertainy

[Day 10]

Christmas morning.

Another run, another option, another improvement.

0z first

We are still at 168 so expect more changes.

[Snowman.]

6z could be about to make Boxing Day a one to remember for those in the south, very cold air rushing down the uk from the east.

Looks fantastic the 6z will say that

 

[That ECM]

This is getting exciting for coldies. Happy for the cold to come a couple of days after Christmas, wouldn’t want the in-laws stuck.

[Captain Shortwave]

The GFS also separates that low from the Atlantic trough. It will inevitably meander east until it engages the Scandi trough, a good solution after that (Though the big day is wet for the south with the snow boundary then sinking southwards).

Encouraging is the best description of the run.

[SqueakheartLW]

Just a catch up from me. Had a look at the ensemble mean charts for GFS 18z and GFS 00z for Christmas Day

It seems to be an upgrade between 18z and 00z as it shifts everything a bit further south

18z

00z

Hope the 06z pushes things a bit further south still to put more of the UK in the colder air for the big day itself. 

[Snowman.]

Just now, Captain Shortwave said:

The GFS also separates that low from the Atlantic trough. It will inevitably meander east until it engages the Scandi trough, a good solution after that (Though the big day is wet for the south with the snow boundary then sinking southwards).

Encouraging is the best description of the run.

It’s what the ECM lacks/doesn’t do as well as the GFS on this run. Ejecting a trough east just south of the UK is crucial to advancing that cold air. 

[Methuselah]

GFS 06Z at T+204 takes the southerly route. Still after the divergence though. More runs needed?

    

It's on a knife-edge!

Edited December 18, 2021 by Ed Stone

[winterof79]

Hilarious commentary again some will have to order new Knees for Christmas if they carry on jerking . I must have followed the wrong GFS as snow chances aplenty

Ridiculous chart this and puts us on the brink of something special

[BarometerCat]

23 hours ago, B-C said:

6z GFS bringing 528 line across the Uk on 25th

Not saying this will verify but will be great to see if models continue to trend around the same ballpark as we close in on late December.  Really looking interesting over next few days! 

 

GFS 6Z -same time frame.  

 
Interesting watching this evolve as we get close to the time. As an amateur I am following other more experienced peeps advice and comparing outputs for roughly the same time frame.  Far from being resolved but looking good still 

Edited December 18, 2021 by B-C

[The Northern Ramper]

18 minutes ago, Chris.R said:

Omg so many toys. Be patient!

There can’t be any left in Leicester!!!!!!!!!!!