The models continue to display the hallmarks of a Run in to Winter that certainly is far from the Norm - of course if your just living under the umbrella of zonal is coming just like every winter then that direction may be displaced.

This ( & net weather ) have been around for a good 10 years & at the very least that produces a bank of data where the period 01 Nov to say 20-30 Nov generally produces info that can safely predict the overall hemispheric pattern for December-

More so the pattern heading from Mild zonal Nov into mild zonal Dec & less occasionally Cool / Cold Blocked Nov into potentially Cool / cold Blocked Decembers.

If we stand here on the 20th of November there are 3 key hallmarks of the stratospheric imprint that will certainly shape the December forecast.
1) Strength of stratospheric vortex & how thats coupled with the atmosphere
2) 10HPA zonal wind speed at the Entry point to winter & Any disruptions ( ie Warming )
3 ) Are we in a Strong +Nino phase

What is easy to identify is the Novembers where the strat has coupled into the tropospheric vortex Mid / Late November & its +AO all the way through December ( Especially in Nino Years ) 2015 is a great example.

November 2019 almost at the midway point & one would be forgiven in thinking that we are going to be blown away to kingdom come with a very strong vortex- Today we hit + 40M/S & the technical definition of a strong vortex is +41.2 M/S.

However the Stratosphere is still disconnected from the troposphere - so up the top 1-30HPA she is spinning away however sub 150HPA things are pretty placid- infact the NAM index in negative mode actually reinforces the disconnect with NH weather patterns that further create disturbances upwards ( upward heat flux ) to the strat ( namely the Aleutian low & Scandi High )

The route cause of why 2019 is so disconnected could be attributed to Arctic Amplification due to the ice loss however the Sunspot activity impacting the jet could also be a factor.

This means that with 19 Days of November to go we find ourselves in the position where the forecast is for the Strat jet to be under continual attack & forecasts go across a 16 day speed from record Positive to around 10-15 M/S - ( Rem the start of December is usually in 30 M/S.
The lowest number found on the GFS 00z Ellipses today was T384 just 5 M/S
( The Mean was about 15 M/S )

Late Nov 2009 Merra date recorded the wind to get to 7M/S which really impacted the December AO coming in at -3.4.

So, with a long but less volatile timeline the models at 10HPA paint a picture where we move into a position last seen 10 years ago & that timeline being late Nov is the precursor to Decembers AO pattern.

Its important to note the trending at the moment is with every run at 16 Day the zonal mean drops further which is great however lets get to day 8 & see where the trend is then.

We all know that a steeply negative AO isnt always a slam dunk cold shot for the UK however its a good start point....

I wish I could add graphics / Images etc however I think people get the gist.

This is why the models are churning out those big blocked Siberian & poss undercutting High pressures---
Long may it continue

S

Thanks Steve, very informative and great to see an opinion/prediction with facts and information to back it up.

December will hopefully be a very interesting winter month 👍

Yes, a fantastic detailed analysis yet again from Steve.
Thank you for such an interesting read.
How ironic to think that arctic sea ice melt may contribute to winter severity in the Northern hemisphere.

The glosea computer model gives me even more hope that a very severe winter is coming.
It's latest seasonal update for D J F has high pressure to the South West  and low pressure to the North of the UK,yet last winter it forecast a cold season with northern blocking and the opposite happened and it forecast an above average autumn temp wise this and the opposite is going to happen again,with October being below normal and so will November looking at the current sypnotics.

So looking more than likely a bitter long winter is coming!

And glosea showing its as useful as James madden in its forecasting skills,or rather lack of them 🤣

It was a total waste of time last year it was just so wrong 

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Ensembles trending cooler this morning, much more spread but the many heading toward the -5 zone later on with a few sneaky -10’s

http://old.wetterzentrale.de/pics/MT8_London_ens.png

 

The jet stream continues to run strongly to the south of us, only letting up when it forms a loop around the UK, so either pushing depressions across or anchoring one over us. A brief let up in the disturbed weather at the weekend, after Thursday's LP has drifted southwards, but more LPs develop and in particular one is anchored over the UK Wed 20th - Sun 24th, eventually decaying in situ. Yesterday's deep LP over Norway around the 28th is still there but the northerly is now weaker and doesn't really affect us.

That was GFS; ECM is similar but slower to develop next week's LP and keeping it off the west of Ireland

Ens runs consistently cool until about the 20th, then with increasing scatter either side of the average for the time of year, which probably relates to exactly where the depression at that time parks itself. Plenty of rainfall spikes distributed across the period.

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yes it’s looking decidedly cool if some output is to be believed and always quite wet, a fascinating spell of model watching coming up as highlighted above by Steve M,s excellent informative post above 

Steve thanks again for an excellent piece detailing the coming weeks.

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For those watching the state of the stratosphere and the strat/trop connection (or disconnect at the moment) here’s another piece of the jigsaw that’s worth monitoring if, or rather ‘because’ if you study the science, there’s a strong relationship between the mean zonal wind at 10hPa-60N and the prevalence of surface blocking. As this figure drops towards zero HLB is more likely. The current forecast shows the mean zonal wind tanking in the next few weeks:
http://weatheriscool.com/index.php/stratospheric-forecast-zonal-mean-u-wind-60n-10hpa-gefs/

And here’s the link to show how it fits with the 1979-2016 archived spread. As Steve explained its almost at record levels now but forecast to drop significantly:

http://weatheriscool.com/prod/interactiveTserie.html

 

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Don't think the models have the pattern nailed at all after the end of the week.
Lots of colder runs have also appeared this morning too.

Could becoming very interesting before not too long ,perhaps the interest in this forum might improve as well!

Yesterday's ECM monthly has lost the cold signal in weeks 3 and 4. GEFS also backs this scenario (as far as it goes), although a cluster of colder runs is pulling the mean down. If those breakers disappear the mean will zip up noticeably.  Therefore I would expect the UK Met Office to start talking about temperatures returning to normal or above in the medium term. They may also flag up a low chance of it turning much colder. If I was writing their 30 dayer this would be my take at the present time.  

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6Z GEFS have plenty of decent looking charts in 

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Yeah I noticed some real stonkers in their.

Just need a very cold  op run to get everyone excited again

1) That is mentioned in today's update as expected

2) Not mentioned. I assume they consider the possibility too low at the moment

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It's a bit of a confusing picture at the moment with the long term models such as ECM monthly and Glosea going mild but other indicators showing a possible SSW and people such as Cohen. Ventrice etc talking up the possibility of cold into Europe.

Exactly a year ago Glosea flipped to a cold and blocked outlook so I'm hoping it's equally as bad this year.

Cannon fodder model. 

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GEFS 12z postage stamps are now available. You'd have to be very brave, daft or not understand basic probability to call a real cold spell (rather than chilly) in late November based on these. They could of course change in the coming days. https://t.co/ohzY9XaGlW) pic.twitter.com/jzdwQjDozi

— TheWeatherOutlook (@TWOweather) November 12, 2019

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here here, about as much use as a chocolate teapot 

You would be daft IMO to call any scenario for late November.

With charts like this at six days out (ECM 12z) I wouldn’t call next week one way or the other: https://www.wetterzentrale.de/maps/ECMOPEU12_144_1.png 

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Yes, the variability on ECM's mid to longer range charts in the Op on recent runs says enough to me that there's much to be resolved. That and the "confidence is low/very low" that decorates both the medium and long-term MetO forecasts.

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For all the promise the high looks like it is slipping away

Snow cover looking decidedly healthy so far this year:

https://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow_asiaeurope.gif 

 

Its about on par with 2016... but the arctic sea ice looks less around north Alaska

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Hard to work out where we go ,the charts look very messy to me,but nothing indicates we are going back to the default zonal pattern.

Looks like the seasonal models are already wrong