Model Output Discussion - The Start Of Winter

[phil nw.]

The colder trend for around Christmas continues then on the GFS and GFS p.

Some snowy charts on those around the big day and Boxing day.

 

The upstream buckling of the jet now coming towards the reliable with ridging up the west coast of NA and the Canadian trough.This run gives that trough a real dig south almost to the Gulf coast which throws the added Atlantic amplification into the jet and Greenland ridging.

 

Too early to be sure of how clean that ridge will be and indeed how effective and long lasting.There are little cut off lows being modeled coming off the E. seaboard which may undermine this so something to be aware of as we get closer.

A good progression so far though and with the main body of the vortex  being quite close to our north the charts show that only a modest amount of ridging is needed to bring that cold air south.

Edited December 16, 2014 by phil nw.

[mushymanrob]

 

The fun begins now, pattern change is on the way, how it effect our small island is up for debate.

 

...only its not a pattern change according to the gfs which is predicting a cold snap.... its just that, a cold snap before the gfs suggests the atlantic kicks back in and returns the uk to mild.

id have thought a pattern change would mean just that...a change in the pattern

 

The fun begins now, pattern change is on the way, how it effect our small island is up for debate.

 

...only its not a pattern change according to the gfs which is predicting a cold snap.... its just that, a cold snap before the gfs suggests the atlantic kicks back in and returns the uk to mild.

id have thought a pattern change would mean just that...a change in the pattern

[TonyH]

Heights moving towards Greenland at day 8 and a cold North Westerly flow arriving for Christmas eve. Should be a cold Christmas day and wintry for some. Much better than recent mild ones!

 

Yes if you have faith in a chart for 8 days out verifying..

Edited December 16, 2014 by TonyH

[Snowman.]

...only its not a pattern change according to the gfs which is predicting a cold snap.... its just that, a cold snap before the gfs suggests the atlantic kicks back in and returns the uk to mild.

id have thought a pattern change would mean just that...a change in the pattern

 

...only its not a pattern change according to the gfs which is predicting a cold snap.... its just that, a cold snap before the gfs suggests the atlantic kicks back in and returns the uk to mild.

id have thought a pattern change would mean just that...a change in the pattern

Mild?

 

This is mildest chart post 192.

 

 

 

 

Cold comes back.

 

 

But really.

 

Can we put this much faith in a chart this far out?

Edited December 16, 2014 by SN0WM4N

[carinthian]

hgt500-10005DFVZDAW.png

Ah would that such a chart should verify, some substantial snow would be falling for many. There's that build up of cold air again that I was talking about in my last post, stretching from Canada to Russia. The GFS keeps coming up with similar variations on this theme so definitely something to watch here I think!

Nice one Old Met Man, hope your hunch comes off against all odds. The fairly strong Baroclinic zonal developing to the north of the Azores high looks like creation of convergence and ultimiately the formation of low pressure system into Southern Britain that the GSF (PARA ) has aspired too over the latest runs. Not too un similar to what your instincts were a few days ago with a resultant NEer. Its a start.

C

[mushymanrob]

some odd things happening tonight... posts not appearing, or pages not refreshing..

[ItNeverSnowsInWindsor]

Mild?

 

This is mildest chart post 192.

 

 

 

 

Cold comes back.

 

 

But really.

 

Can we put this much faith in a chart this far out?

It's about the trend that the charts are setting. There has definitely been a strong trend towards colder synoptics today. Await to see if the ECM agrees with the growing trend.

[Alexis]

The high south of the southern tip of Greenland is the key. In the GFS it helps push the jet south. In the Parallel it has the effect of blowing up a mid Atlantic high (although it goes a bit odd after that and a low zips right across the centre of Greenland which I've never seen happen before).

[TonyH]

Great GFS charts I am though assuming it will be at the bottom of the ENS graph!

[mushymanrob]

Mild?

 

This is mildest chart post 192.

 

 

 

 

Cold comes back.

 

 

But really.

 

Can we put this much faith in a chart this far out?

 

you are correct, i shouldnt have called it 'mild', i should have said 'normal' or 'average', either way the gfs 12z does portray the cold spell as a short lived affair and not a defining moment of pattern change.

i put no faith it a chart that far out... ill believe it IF its still there next tuesday, for now its a rather minor possibility of verification.

[seabreeze86]

...only its not a pattern change according to the gfs which is predicting a cold snap.... its just that, a cold snap before the gfs suggests the atlantic kicks back in and returns the uk to mild.

id have thought a pattern change would mean just that...a change in the pattern

 

...only its not a pattern change according to the gfs which is predicting a cold snap.... its just that, a cold snap before the gfs suggests the atlantic kicks back in and returns the uk to mild.

id have thought a pattern change would mean just that...a change in the pattern

For the UK yes maybe a cold snap but i am talking about the global pattern.

 

500mb pattern for now,

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121612/gfsnh-12-6.png?12

 

500mb pattern for 10 days away on the GFS

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121612/gfsnh-12-240.png?12

 

We are seeing runs which raise heights around Greenland, how long they last and how they effect the UK is the question(if of course they come to fruition, also the AO and NAO showing sighs of heading towards neutral/negative values.

[garbagebags]

Ridging for Xmas. What a present that would be. 

[The Eagle]

We are at the very early stages of the evolution in the models. Very happy with what I see although by no means the perfect evolution yet. Hopefully we build on this in the next couple of days.

[Mucka]

The colder trend for around Christmas continues then on the GFS and GFS p.

Some snowy charts on those around the big day and Boxing day.

 

The upstream buckling of the jet now coming towards the reliable with ridging up the west coast of NA and the Canadian trough.This run gives that trough a real dig south almost to the Gulf coast which throws the added Atlantic amplification into the jet and Greenland ridging.

 

Too early to be sure of how clean that ridge will be and indeed how effective and long lasting.There are little cut off lows being modeled coming off the E. seaboard which may undermine this so something to be aware of as we get closer.

A good progression so far though and with the main body of the vortex  being quite close to our north the charts show that only a modest amount of ridging is needed to bring that cold air south.

 

 

Excellent, well balanced post.

I think the emphasis should currently be on the big picture and growing trend for at least a cold snap to develop around Christmas but there will as always be devil in the detail and that detail will be how energy flowing off the Eastern seaboard interacts with the main trough and on the timing of any phasing.

There are a multitude of options even at 120h so trying to pin any detail on our weather around Christmas is a fun though ultimately futile task currently.

 

Very exciting times and the timing of a potential cold spell could not be better but a long way to go before we can call cold spell or even a cold snap.

Edited December 16, 2014 by Mucka

[mushymanrob]

For the UK yes maybe a cold snap but i am talking about the global pattern.

 

500mb pattern for now,

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121612/gfsnh-12-6.png?12

 

500mb pattern for 10 days away on the GFS

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121612/gfsnh-12-240.png?12

 

We are seeing runs which raise heights around Greenland, how long they last and how they effect the UK is the question(if of course they come to fruition, also the AO and NAO showing sighs of heading towards neutral/negative values.

 

fair play

[Summer Sun]

Could be some pretty heavy snow fall late Christmas day and into early boxing day for parts of the UK if GFS P is correct

 

13:00 on Christmas day sees some small amounts of snow for higher parts of Scotland and ROI

 

 

19:00 now this is where it gets interesting keep an eye on north Wales the highest depth is 5cm (just over an inch)

 

 

Now by 01:00 just look how much its increased its gone from 5cm (1inch) to 18cm (7inches) in just 6 hours! snow area starting to widen as well

 

 

Onto 7am boxing day and the totals keep on mounting now upto 25cm ( 9 inches) for north Wales and upto 5 inches for other parts of England

 

 

The final chart I have is at 13:00 and the totals keep on rising 28cm (11 inches) for parts of North Wales and upto 19cm (9 inches) for parts of Northern England

 

 

A clear difference in temperatures for the UK as well below zero in Scotland and double figures for parts of the south and south west

 

 

Same on boxing day at 13:00 the north is around or below freezing whilst parts of the south and south west are in double figure

 

 

For balance the minimum temp charts have temps ranging from 7c to 11c for the same time as above

 

A quick look at the precipitation charts for where the snow and rain is

 

 

So its still very much game on for a spell of snow to develop over parts of the UK later next week usual cautions needed of course at this range but some consistency currently from GFS P and possibly a white Christmas for some parts of the UK

 

Edited December 16, 2014 by Summer Sun

[IDO]

Looking at the means on Christmas Day:

 

   

 

Still some way to go before any confidence in that Northerly. I do note that when GFS (and other models) spot this type of transient amplification, they do tend to, in the early days over do the signal, and downgrade as it nears T0. Hopefully it will be the other way round and it will drag the ensembles towards the hi-res.

Edited December 16, 2014 by i'm dreaming of...

[SE Blizzards]

Control run at Day 10 backing the GFS + GFS(P) 

 

 

All eyes now on the upcoming ECM. Please don't let 'us' down....

Edited December 16, 2014 by SE Blizzards

[Captain Shortwave]

Nobody giving the Canadian some love then

There does seem to be some signs that we might eek enough amplification to bring some proper cold down for Christmas day. A long way off though.

The one notable trend over the past day or so is that the US trough seems a lot less significant in potency and hence the Siberian lobe of the polar vortex becomes the dominant lobe.

So I do think that a block could develop to our north west, but it could set up anywhere between Greenland and Alaska (Canada between the two) and hence where this blocking sets up will determine what kind of weather we will get, the second caveat of course is how long it will hang around.

The other trend is that the Pacific ridge really cranks up towards the end of week 2

Edited December 16, 2014 by Captain shortwave

[johnholmes]

For the UK yes maybe a cold snap but i am talking about the global pattern.

 

500mb pattern for now,

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121612/gfsnh-12-6.png?12

 

500mb pattern for 10 days away on the GFS

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121612/gfsnh-12-240.png?12

 

We are seeing runs which raise heights around Greenland, how long they last and how they effect the UK is the question(if of course they come to fruition, also the AO and NAO showing sighs of heading towards neutral/negative values.

 

remember what you are showing are the anomalies not the actual contour lines?

[nick sussex]

Thankfully the GFS's have moved away from their earlier western based negative NAO, this would have led me to throwing my toys out of the pram big time!

 

As Phil nw mentioned earlier there are still nuisances about with those lows upstream, we don't want any phasing with the troughing in the eastern USA too early.

 

It's still difficult at this stage to know whats going to happen on Christmas Day,  the trend is for something colder but we want to tap into the coldest air, a slushy mess doesn't cut it so we need a strong ridge to the west sufficiently north.

[Weathizard]

It's clear within the GFS 12 ens suite there is still a lot of uncertainty for the Christmas treats we are looking for, the clearest trend I can see amongst them is the clearance of the annoying portion of the vortex that likes to lurk around Western Greenland.

Ridging is a real possibility but I wouldn't count any chickens(turkey's ) just yet but things are looking up, let's hope the ECM follows suit.

Fergie, we've not heard from you in a while just wondering what the MetO thoughts are, if it's not to much hassle. Thanks.

[Gavin Hannah]

Looking at the means on Christmas Day:

 

gens-0-4-216.png gens-21-4-216.png gens-21-1-216-2.png gens-21-0-216.png

 

Still some way to go before any confidence in that Northerly. I do note that when GFS (and other models) spot this type of transient amplification, they do tend to, in the early days over do the signal, and downgrade as it nears T0. Hopefully it will be the other way round and it will drag the ensembles towards the hi-res.

 

 

Oh yea, how many times have we all seen that happen the last couple of years.    

 

Once we are in the reliable timeframe, and this pattern is still there and / or looking even more prolonged, I will be happy.  This could all come crashing down around us by the weekend and a few of us could be feeling a mighty bit miffed lol,

[SE Blizzards]

Lol, Just take a look at this beauty.

 

 

   

 

 

 

[mountain shadow]

Come on ECM, do the business tonight.

If it does, the senior Met man will be muttering away, with a wee bit of pressure on
Come on ECM, do the business tonight.

 

Edited December 16, 2014 by Polar Maritime
To edit duplicate posting due to technical problem.