Some beauties in the GEFS , the trend is firming up

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

Higher up, last night's 12z shows the SSW continuing from now until the end of its run - 10 days away,

Zonal wind profile forecasts have also improved now showing the reversal all the way to the surface at 70deg and above.

Doesnt guarantee anything though as you say. I would expect to have seen a greater frequency of HLB in the OPs and suite at this stage so in that respect it’s dissapointing at the moment.

The odd run still of interest in the far reaches of FI but those jam tomorrow charts do nothing but slightly pull the ENS mean down.

At 10hpa there still seems to be slight eastward drift forecast in the setup at the moment at about 60N.

https://www.theweatheroutlook.com/twodata/chart.aspx?chart=///www.theweatheroutlook.com/charts/gfs/00_0_arctic10.png?cb=881

https://www.theweatheroutlook.com/twodata/chart.aspx?chart=///www.theweatheroutlook.com/charts/gfs/00_63_arctic10.png?cb=720

This finally stalls early on 4th and then a day later the pattern starts to shift E to W.

https://www.theweatheroutlook.com/twodata/chart.aspx?chart=///www.theweatheroutlook.com/charts/gfs/00_111_arctic10.png?cb=666

Here's the 7th:

https://www.theweatheroutlook.com/twodata/chart.aspx?chart=///www.theweatheroutlook.com/charts/gfs/00_141_arctic10.png?cb=90

And 10th:

https://www.theweatheroutlook.com/twodata/chart.aspx?chart=///www.theweatheroutlook.com/charts/gfs/00_189_arctic10.png?cb=709

This seems to continue until around 12th or 13th by which time the high temperatures above the Kara Sea are nondescript at only around -40°C and the stratospheric PV starts to re-establish itself over Hudson; by 16th the W -E pattern is back in place.

https://www.theweatheroutlook.com/twodata/chart.aspx?chart=///www.theweatheroutlook.com/charts/gfs/00_336_arctic10.png?cb=254

I was just wondering that if reversal at 10hpa doesn't get going until 4th then when could the expected propagation to the troposhere and effects at the surface be expected? Could the 10hpa projections mean that low -mid stratospheric reversal hasn't started yet?

Layman's view.

Good frost here -3c ....the models will continue to chop and change from run to run you cannot form that conclusion from one overnight run ...patience.

Patience still required - but something is likely to give very soon.

In theory, the NWP should be showing stellar charts at around day 10 by now - where are they?

I put a lot of faith in this SSW, considering what happened in March 2018, but I am now getting a desperately bad feeling this one won't deliver for some reason.

They are at day 13 maybe? http://www.wetterzentrale.de/maps/GFSPARAEU00_348_1.png 

Seriously though I’m not sure that people can have failed to notice the large number of very cold options from midmonth that have been appearing in the model output in the last few days.

This has been accompanied by quite a few swings and big differences between consecutive op runs and models (last two ECM op runs are a prime example). That was not really present a week ago. For example the repeating cold northerly trend is still very much there in the GFS output. 

Give it a few days and if things don’t start to look good from mid month (say 14th to the 16th at the latest) then I could understand some negativity. Until then I think it is premature.

Will the GFS op or GFSP06z run show a potent northerly blast in that time scale? I would not bet against it!

Is that reversal at 10hpa or higher? Also, if you have a link to that source I would find it useful(if I can interpret it).

Edit: if anybody has a link to a rel straightforward source showing strat winds I would be grateful!

Down to around 30hPa over the pole but 10hPa more or less at 60 degreees north http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwfzm_u_a12.gif 

Edit: Read across the x axis (along the bottom) for the latitude and then go up. When it gets to the blue that is a reversal to some extent and you can check the corresponding hPa for that value and latitude on the y axis at the left (if that makes sense!)

Thanks Doc; might have dashed hopes a bit.

I think I've asked this before- I can see latitude & altitude & zonal wind speed in that chart- how do I interpret wind direction from it?

See my edit above - hopefully it answers the question. 

We're a long way from any prolonged deep cold this morning looking at the ECM mean

Tbh, I think that people could do worse than cast their minds back to last February and the amount of volatility there was in the model output during the time of the SSW that month before the models had properly got to grips with what has happening in the stratosphere. As I commented yesterday, I think we may well be in for a similar spell of volatility this time around.

From what Neil has said a few posts up, it looks as though we now have an actual SSW. The question that needs to be resolved now is that effect it has in time on the model output and whether or nor it will do our chances of getting a cold spell any good. As Neil also said, patience is the name of the game just now.

Vast majority of ECM postage stamps at 16th show a westerly type flow...Almost no evidence of any blocking.

That only goes out 10 days and the effects of the SSW won't be there yet.  The consensus view is that the models don't handle the transfer from stratosphere to troposphere very well and need to see the actual impacts before being able to model accurately.

The ensembles cannot reflect what is not there and not in the computer programming.

Big step backwards by the ECM LAST NIGHTS 12Z @ 240 suggested blocking with heights rising over Iceland and Greenland :

Today's ECM shows Low pressure: - dark blues and purples etc!

I was just wondering when it was that the models picked up on the SSW last Feb? Like how long after the SSW did we see models picking up on this and then the cross model agreement? It's been a week since the SSW now and still the GFS has really failed to produce anything blocked or any eye candy like runs etc.

Exactly - that's so so strange! I mean we are in 1st week of Jan now as well, the SSW occurred over a week ago? Bare in mind met Office had us down for colder weather from mid month and many longer range models forecast Jan to be the coldest month of winter so if we are going to get a colder than average month we do really need to get on with it soon? Still not one single frosty morning here in Exeter this winter thus far. We had to go back to October 2018 on 27th when it was -3.5c.

Morning Mr porter.  Been reading the post avidly all year and promised myself I wouldn't make any comment this winter, particularly as things start to get interesting, makes me feel like a dipper (well OK I am).  But you are absolutely correct with your comment above, we can't tell for certainty what's happening this weekend let alone middle of the month.  You could go back to last years post and cut N paste them into this current episode and we still wouldn't be any the wiser.  However my glass is always half full (literally, Lol).  Our understanding of SSW's is still in its infancy, even though we have been aware of them since the early 50's, but, this is our third major NH one (that I'm aware of) since 2010 and what followed each were winters to remember.

The following link is a very interesting read and helps explain in a little more detail (well lots of detail) what and how an SSW actually is and and its relationship to weather patterns in the NH. 

https://journals.ametsoc.org/doi/full/10.1175/JAS-D-13-0349.1.