Model Output Discussion - cold spell to end Autumn

[karyo]

6 minutes ago, karlos1983 said:

So primed for influence of the MJO then if it moves into a favourable phase..?

It is a weak enso so other factors can override it and the MJO may be one of them.

[nick sussex]

2 hours ago, Draig Goch said:

I'm not being funny or anything but you say a "displaced Azores high" but aren't those islands under that high the Azores? I'm confused as I thought that was an actual Azores high that's showing? 

Well yes but the reason I’ve referred to it as displaced is because we often see the Azores high ridging east into southern Europe in response to the more common winter jet stream pattern.

Its not allowed to do that here because the jet is curving se into the Continent.

So you’re right it’s over the Azores but has been blocked from extending eastwards and displaced from where it’s normally located especially during recent winters.

 

[nick sussex]

2 hours ago, Glacier Point said:

a little premature with those Scandinavian blocks Nick given the likely influence of the mid Atlantic ridge ? Deeper into December and January, hmm, different story.

You’re such a tease!  Can we have a pseudo Scandi block , so not a typical one but the Svalbard to towards Norway one! 

I’ll call it the Svandi Block. 

[GeordieX9v]

Doesn't look too pleasant for me on the 9th though it's way out.

[Chesil View]

2 hours ago, Draig Goch said:

Much colder 850mb temperature range in the GFS 6z, here in Porthcawl (near Swansea) South Wales with a max of 8C to a minimum of -10C and the snow risk appearing again (albeit <20%) but unfortunately this isn't expected to happen until a week's time.

Don't think I 've seen the 850's fall off a cliff like that since Dec 2010. It will be interesting if this remains a consistent feature through the weekend runs. Certainly seems to be some support from the ECM clusters for the synoptic set up to back up the gfs 850 cliff plunge.

As ever run to run consistency is the key.

[karyo]

The 12z ICON is out till 120 hours and it is notable more amplified in the Greenland area than its earlier run.

Looking good for a northerly shot at least.

 

https://www.meteociel.fr/modeles/icone_cartes.php?&ech=120&mode=0&map=0&archive=0

[karlos1983]

1 minute ago, karyo said:

The 12z ICON is out till 120 hours and it is notable more amplified in the Greenland area than its earlier run.

Looking good for a northerly shot at least.

 

https://www.meteociel.fr/modeles/icone_cartes.php?&ech=120&mode=0&map=0&archive=0

yes, looks very similar to the 06z GFS ATM

Edited December 1, 2017 by karlos1983

[radiohead]

ICON is on board with the cold spell

[Man With Beard]

9 minutes ago, karyo said:

The 12z ICON is out till 120 hours and it is notable more amplified in the Greenland area than its earlier run.

Looking good for a northerly shot at least.

 

https://www.meteociel.fr/modeles/icone_cartes.php?&ech=120&mode=0&map=0&archive=0

1050mb Azores High by T168!! Never seen it that strong!!

[Frosty.]

So we have a slight change in the jet stream from tomorrow into early next week with milder air wafting in off the atlantic but looking at the earlier 6z shows quite a dramatic change later next week as the pattern becomes meridional and arctic air sweeps south with increasingly wintry conditions..fingers crossed for very good 12z runs regarding later next week onwards!

[Tamara]

Still uncertainties, but from my point of view things are starting to get a bit more interesting for the way ahead beyond this amplified Atlantic ridge phase

These :

 

 

Global atmospheric angular momentum tendency (two day lag also on updated plot) is upwards off the scale. Notice how it eclipses the October rise in tendency which coincided with that amplitude MJO wave progression which helped set up our very amplified late autumn.

The Global Wind Oscillation is consequently registering a decent sized addition of westerly winds to the atmospheric circulation as a challenge to Nina like easterlies and reflected in a jump out of Nina phases 1,2,3 into an amplitude phase 4 as +ve torque mechanisms get to work and start to suggest possibilities of amplification programmes looking NE later in December

If tropical convection can stay the ride and keep heading destination Pacific then the omens of this are a reduction in the Pacific/Atlantic northern arm combo and some extra ammunition for arctic height rises and ridge development to the NE looking to maybe ambush UK/Western Europe with deeper cold heading towards but more especially into the New Year. Its also a path towards better possibilities for a -NAO. Any consolidation into winter proper of the Azores/ Atlantic ridge in tandem with effects of seasonal wavelength cycle changes is counter intuitive to this.

The lagged effects of any tropical forcing >+ve extra tropical torque mechanism >stratospheric destabilisation progression could make quite a difference to any thinking to date this is simply going to be another La Nina winter that starts quite cold, but ends up with familiar Atlantic westerlies.

Lets see what happens

[karlos1983]

into next week, GFS 12z is on track to bring a northerly as we head towards the end of the week still.

UKMO at +96 not showing any dramas

Dare I say it, we could be getting some form of agreement here....

Edited December 1, 2017 by karlos1983

[karlos1983]

Yup UKMO looks solid at +144, happy days

In fact, it's better than Solid, it awesome!

Probably the best UKMO chart of the season..

Edited December 1, 2017 by karlos1983

[karyo]

2 minutes ago, karlos1983 said:

into next week, GFS 12z is on track to bring a northerly as we head towards the end of the week still.

Indeed and if anything marginally more amplified than the 6z. The huge low west of Greenland pushes warm air slightly further north.

[radiohead]

Heavy rain turning to snow in the north as the cold air creeps down while the deepening low tracks over us.

[feb1991blizzard]

2 hours ago, karyo said:

The latest plume of model enso conditions has la nina peaking at -0.8 which is weak la nina.

CFS has a valua of -1 but it has been more enthusiastic with its predictions throughout.

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

Weak nina's - blimey, wasn't expecting the Feb chart!!

 

EDIT : messed up the Jan one - should be 2017, had to do them manually - site giving me some error message when I composite on 3.4

 

Edited December 1, 2017 by feb1991blizzard

[northwestsnow]

GFS 12z shows biblical amounts of rain or snow depending on where you live, and how much altitude you have !!!

[Frosty.]

Yes the Ukmo 12z T+144 is a definite Boom chart for coldies, the alignment is good for a stonking  Arctic blast!..awesome stuff.

Edited December 1, 2017 by Frosty.

[weirpig]

Could well be a snow fest for some next week if it comes to pass  shovels at the ready. Apart from Norfolk  

[northwestsnow]

Could be a memorable snow event somewhere in the UK?

[Guest]

At the critical time of T+144 we now have the 12zs from GFS, UKMO and GEM agreed on another Arctic reload:

                                   GFS                                                                   UKMO                                                                GEM

                             

 

Some excellent agreement at last.  Just need ECM now. Fascinating updates lor later December into January. Could this be the real deal for coldies????????                          

 

Edited December 1, 2017 by Guest
Correct typos

[Mucka]

Next Thursday is beginning to look potentially very snowy for some. Plenty of ppn mixing with cold arctic air from the North.

A lot will depend on track and depth of any low of course but looks certain to be a Northerly meeting ppn from the West at some point.

Edited December 1, 2017 by Mucka

[northwestsnow]

1 minute ago, Mucka said:

Next Thursday is beginning to look potentially very snowy for some. Plenty of ppn mixing with cold arctic air from the North.

Its too far out to have confidence but if GFS12z is on the mark the hills round here will be absolutely pasted!!

[Methuselah]

1 minute ago, weirpig said:

Could well be a snow fest for some next week if it comes to pass  shovels at the ready. Apart from Norfolk  

Thank goodness the me's in Suffolk!

[Iceberg]

It’s impossible to over state the effects of gfs from t144 to t180 or so.  The amount of snow and 70-80mph winds would be a story for the next 50 years. 

The really unusual point is that it’s all quite realistic given the Synoptics and timeframe, if still unlikely at this range.