Model output discussion - 5th December 2016 - Into Winter we go

[Iceberg]

Gfs ens continues to add more members to the colder scenarios post ny. 

 

[Methuselah]

20 minutes ago, Frosty. said:

Agreed, encouraging is the word for coldies so far today, much better than was being indicated recently so I'm cautiously optimistic rather than pessimistic!

But, Frosty, as devout followers of GFSism - lest we forget: that which the 06Z giveth; that which the 12Z taketh away?

Cautious optimism is the order of the day?

[Jason M]

Well the GEFS are nothing special so I think caution is needed otherwise another trip up the garden path could be the way forward.

Some interest at last though.

 

[Purga]

"Very strong support for a New Year Northerly from ecm ensembles this morning"

Quoted on TWO by TomC Met Office

Edited December 23, 2016 by Purga

[northwestsnow]

1 minute ago, Jason M said:

Well the GEFS are nothing special so I think caution is needed otherwise another trip up the garden path could be the way forward.

Some interest at last though.

 

Neither is the meto update.Although a mid Atlantic high offers scope for toppler like scenarios which is an improvement on the unrelenting dross so far..

[Frosty.]

4 minutes ago, northwestsnow said:

Neither is the meto update.Although a mid Atlantic high offers scope for toppler like scenarios which is an improvement on the unrelenting dross so far..

Agreed, it's an evolving situation, less dross, more encouragement for the new year!

[Backtrack]

4 minutes ago, northwestsnow said:

Neither is the meto update.Although a mid Atlantic high offers scope for toppler like scenarios which is an improvement on the unrelenting dross so far..

Wrong thread to discuss, but their update is very encouraging? They mention high pressure building to the west, bringing a potential blocked period with northerly winds dominating. Models are starting to put this scenario into play from just the medium term, rather than out in FI. The most encouraging update so far this winter. 

[northwestsnow]

Just now, Backtrack said:

Wrong thread to discuss, but their update is very encouraging? They mention high pressure building to the west, bringing a potential blocked period with northerly winds dominating. Models are starting to put this scenario into play from just the medium term, rather than out in FI. The most encouraging update so far this winter. 

Any northerly will be shortlived without high lat blocking highs, the jet will just roll over the top.Dont get me wrong its better than what we have seen so far but i aint going to be getting the ramp out for a toppler..

[Backtrack]

1 minute ago, northwestsnow said:

Any northerly will be shortlived without high lat blocking highs, the jet will just roll over the top.Dont get me wrong its better than what we have seen so far but i aint going to be getting the ramp out for a toppler..

Still an ever-evolving scenario. It's where we go from the building pressure. Let's get it in place, then worry about the longevity of any cold spell. Still in the medium term but there's hints from many members of a continuation of below average signal into mid-Jan. 

[Geordiesnow]

Although the chances of a Northerly flow is certainly possible, I refuse to believe any Greenland high is a possibility, as per usual its the same old story when it comes to these type of set ups, some runs(especially GFS) will show a nice simple evolution of ridging into Greenland but some won't and what we end up with is a half hearted attempt as amplification but the PV remains strong over Greenland and we see a toppler. Seen it so many times over the years unfortunately.

Still, some interesting weather in the short term although I think the UK has got away with it as far as these storms are concerned(it could of been much worse than it probably will be) although the possible sting in the tail for Boxing day across NE Scotland does need watching.

[tight isobar]

A couple of things to address. 

As much as a high latitude north westernwblock' is in the balance as -rep' toppler,/displacement dueto non compliance large lobe vortex...

Any met o' update will be a cautious as the output itself

And could and will change as factors do so.

There's at present mixed signals in supporting outp..However its pretty firmly undeniable that an' evolving evolution/évolutions of an outbreak ofcold for our shores is imminent around new year and post....

That in itself suggests there's equally as many pro's...as there are con's....

[booferking]

Does the tweet  below not indicate that the pv lobe over greenland looks to be placed far enough west over canada come new year to allow a chance of greenie high.

 We're looking at a major arctic air mass intrusion (cold snap) across western Canada in through the western half of the US during early Jan.

 

Edited December 23, 2016 by booferking

[bluearmy]

Whilst a sustained greeny high seems a long shot (without a perfectly placed polar ridge to support it  ), a transient ridge seems likely and then what? 

mid Atlantic ridge the favourite and griceland ridge the best bet for coldies. We could get a sausage scandi high but the scrussian trough in the extended seems likely to prevent that.  

The residual euro heights again the issue as to how cold we go and how long for

th gefs sniffing around a more mobile evolution end week 2 into that scrussian trough 

I do love a coldie chasing xmas model watching period !!

[Frosty.]

19 minutes ago, northwestsnow said:

Any northerly will be shortlived without high lat blocking highs, the jet will just roll over the top.Dont get me wrong its better than what we have seen so far but i aint going to be getting the ramp out for a toppler..

Even a toppler scenario would be grabbed at right now, considering we haven't  even had a toppler so far so it's a step in the right direction for sure!

[Geordiesnow]

2 minutes ago, Frosty. said:

Even a toppler scenario would be grabbed at right now, considering we haven't  even had a toppler so far so it's a step in the right direction for sure!

But what is the difference between a toppler and the brief polar maritimes blasts we are going to get after these storms pass through? Both will be short lived and the snow risk tends to be limited?

Its ashame pressure is forecast to rise fairly quicker after storm connor as there is quite a strong blast of polar maritime air following it but shower activity will be mostly reserved to Western Scotland due to the fairly rapid rise in pressure.

Can understand why some are getting excited about the potential but on the otherhand, I have seen the same thing many times before when it comes to this sort of set up but we shall see what happens. We may not even get any sort of ridge/atlantic block and things remain flat as per yesterday's GFS12Z run.

[Frosty.]

14 minutes ago, Geordiesnow said:

But what is the difference between a toppler and the brief polar maritimes blasts we are going to get after these storms pass through? Both will be short lived and the snow risk tends to be limited?

Its ashame pressure is forecast to rise fairly quicker after storm connor as there is quite a strong blast of polar maritime air following it but shower activity will be mostly reserved to Western Scotland due to the fairly rapid rise in pressure.

Can understand why some are getting excited about the potential but on the otherhand, I have seen the same thing many times before when it comes to this sort of set up but we shall see what happens. We may not even get any sort of ridge/atlantic block and things remain flat as per yesterday's GFS12Z run.

It's all about encouraging signs, and they have been plentiful from the Gfs 00z op run onwards, indeed, there were signs yesterday too. 

Edited December 23, 2016 by Frosty.

[Methuselah]

Can't say as I'm too bothered should what the models are currently indicating manifests as a series of 'topplers' (3 or more)...

I can recall many a winter, right back as far as the '60s, in which 2-4-day cold, snowy snaps were punctuated by 1-2-week-long spells of mild mush, as Atlantic lows came around the top of mid-Atlantic blocks...

While a quasi-stationary Greenland block would be the beezneez, it's far from necessary, IMO...

Edited December 23, 2016 by Ed Stone

[Jason M]

31 minutes ago, bluearmy said:

Whilst a sustained greeny high seems a long shot (without a perfectly placed polar ridge to support it  ), a transient ridge seems likely and then what? 

mid Atlantic ridge the favourite and griceland ridge the best bet for coldies. We could get a sausage scandi high but the scrussian trough in the extended seems likely to prevent that.  

The residual euro heights again the issue as to how cold we go and how long for

th gefs sniffing around a more mobile evolution end week 2 into that scrussian trough 

I do love a coldie chasing xmas model watching period !!

I'd imagine were looking at a topple and then a reversion to euro heights / pv combo. Can't see a long lasting set up.

[A.J]

lots of posts removed sadly............model output related posts only in here please

[Ali1977]

I like how people are now looking at how quick the potential cold spell will break down, lets get it here first. You never know some big changes can happen without warning

[Mucka]

ECM ensembles have pretty much flipped to predominantly cold signal this morning.

Edited December 23, 2016 by Mucka

[Daniel*]

Roughly 50% of GFS ENS bring a cold northerly on New Year's Day interesting! While I do not see anything exceptionally cold, at day 9 however you don't see that often so perhaps indicating some sort of clarity. Strong support for a mid Atlantic ridge - so definite interest, think some folk are getting way too ahead with talk of a toppler, let's see how the modelling evolves first.  

Edited December 23, 2016 by Changing Skies
Gremlins!

[Methuselah]

8 minutes ago, Mucka said:

ECM ensembles have pretty much flipped to predominantly cold signal this morning.

I know I really shouldn't say this (but why the hell not!): it could all 'flop' back again, come the 12Z...

[iapennell]

The Circumpolar Vortex is strong (higher up into the Stratosphere, it's very strong); that means there is a likelihood that those models building upper heights towards northwards towards Greenland for the New Year will have to modify/downgrade them before we get to this time: Any folk hoping for a full-on Arctic blast may be disappointed. 

That's not to say we might not get a day or two of north-westerlies behind the deeper depressions, these could certainly bring snow to high ground and a frosty night in the following ridge of high-pressure. All the best for Christmas.

[radiohead]

06Z GFS (P) is out. And it's disappointing.