[Model Output Discussion - Into Winter]

Gfs 18z has deeper low to the west of Atlantic ridge at 120 hrs. May amplify ridge and provide a push of wwa northwards. Hopefully 

[Model Output Discussion - Into Winter]

1 minute ago, northwestsnow said:

Hope so mate we are all sick 9f crappy rain !!

GEM pick of the bunch for me 

GEM

[Model Output Discussion - Into Winter]

Fgs enough of individual charts and selective ops

Look at the ens and cons

[Met Office and BBC Weekly/Monthly Outlooks]

1 minute ago, Methuselah said:

oo er, missus, my birthday is January 12! 

[Model Output Discussion - Into Winter]

1 minute ago, TSNWK said:

Losing the SSW is big kick in the nuts…we are now taking our chances with background drives and teleconnections which failed on forecast during the summer and early this winter… not liking the trends past 2 days since SSW was removed from forecast… 

eye candy not bring reeled in…

Tbh the ec was for the bin yesterday amd now looks ok? Id suggest giving it a few more days and see where things sit. Relax its all out of our control anyway

[Model Output Discussion - Into Winter]

4 minutes ago, Met4Cast said:

Strongest signal yet from the EPS for cold weather beyond week 1 of January.

Again, following det runs when the spread is this vast is a pointless exercise, 06z GFS det already on the warmer end of the pack by the 2nd Janaury. No worries or concerns from me at this stage.

Maybe that post will cut down on the panic

[Model Output Discussion - Into Winter]

6 minutes ago, northwestsnow said:

6z is just more of the same out to 180hrs.

I'm so desperate to ramp

You should probably contact your gp or a psychiatrist for that pal

[Model Output Discussion - Into Winter]

8 minutes ago, Jason M said:

I hope I'm wrong (and probably will be ), but this run matches my expectations. I think we will get a UK high once the models sort themselves out.

In recent years we have increasingly struggled to get HLB and whilst there were a lot of easterly options in the 12z suite, many (not all though!!) were more mid lat highs that had just about got far enough north to bring in an easterly for a short period. 

 

Tbh the 18z control is on the ropes also. Hopefully better outlook tom. One run at the end of the day

[Model Output Discussion - Into Winter]

Looking further into fi on the gfs 18z still has a great nhp. In all honesty patience is going to be needed here. The atmosphere os in such a state of flux that imo gfs will revert to type or default. The ens and further runs will show either way. My punt is still a cold outlook mid jan onwards.

[Model Output Discussion - Into Winter]

7 minutes ago, Lukesluckybunch said:

It's poor run tbh..we've got to day 10 with nothing to speak about,I find it a little strange with the decent ensembles from the 12z..the op run can't turn out something decent?maybe the ECM is right here!

Tbh that low exploding looks wrong imo. Theres nothing to instigate such a huge drop in pressure. Imo its wrong on the 18z

[Model Output Discussion - Into Winter]

3 minutes ago, Lukesluckybunch said:

Watching those Iberian heights at day 10 ..could be the spoiler like on the ECM

Indeed its a close call. The 850s south of iceland are excellent also

[Model Output Discussion - Into Winter]

17 minutes ago, WYorksWeather said:

Think we need to go back to first principles a bit when watching the model output. Firstly, the background chance of a prolonged cold spell with a significant amount of snow in any given winter month is generally quite low, possibly even very low for some of the least favoured areas further south. Hence, background signals and tendencies for an increased chance need to be taken in that context, by both cold ra+mpers and cold pessimists (or mild lovers).

An increased background chance of a cold spell as the Met and others are suggesting for the second week of January onwards still doesn't mean it's guaranteed, so don't count your chickens if you're looking forward to it. On the flipside, even if it doesn't happen, it emphatically does not mean that the background signals are wrong, just that the odds didn't fall in our favour despite the increased chance.

The next point is that the ensemble forecasts are nearly always going to be more useful than any given deterministic operational run, unless you just like looking at pretty charts (which is an acceptable way to look at the models, I'm not policing what people post here!). The other point is that there are so many models, runs, and charts, that you'll nearly always be able to find a 'game over for Winter' chart or a '1 in 100-year snow bomb' chart.

With all that in mind, going to have a look at a few things.  Going to cover background drivers first.

SSW chances

Here's the ECM mean zonal wind chart for today.

And here's the last week.

 

The notable thing is that after getting closer and closer to predicting a major SSW, followed by the vortex remaining seriously disorganised afterwards, we finally saw the mean showing a reversal yesterday. The vortex does become very weak, as has been suggested for some time, but the mean is now in the 5-10 m/s range. The pattern afterwards has also shifted, with the vortex recovering fairly quickly to just below its climatological mean by February. Of course, these charts will continue to change, but the odds of a major SSW in the next two weeks have certainly diminished, but there may be some effects even if we don't actually get a reversal.

Sea surface temperatures

As others have said, well worth mentioning that sea surface temperatures will continue falling in the weeks ahead, despite the fact that we're now past the shortest day. There is a huge amount of inertia in this system. Of note is that most of the waters to our east will drop from the 8-10C range to the 6-8C range over the next two weeks or so.

  

In anomaly terms, not a huge amount of change except a cold spot emerging to the south-west of Iceland. And of course, the sea ice advance is visible on both charts. Still positive that we've lost some of the crazy anomalies around our immediate coasts. I would continue to note, however, that as we have seen at times recently, any south-westerly influence is likely to be notably mild, even compared to what we would normally expect from that wind direction.

GEFS and ECM ensembles

So, with all that in mind, onto the NWP output. Both ECM and GFS show something quite promising by the time we get to the second week of January. 

Promising for the north as well.

Here's my overall take - background factors aren't all that favourable for the next week or so - up to that point you're probably on a hiding to nothing chasing cold away from the most favoured spots (note the large amounts of snow for some parts of Scotland today, as an example!).

But, as we enter the second week of January and go beyond, the chance of cold does increase relative to average, and is starting to be picked up at longer range in the ensembles. All of this is regardless of what the individual OP runs decide to do - as we can see there are some very mild runs in here, alongside some very cold ones, so best not to spend too much time on an emotional rollercoaster. There will always be a mild outlier chart or a cold outlier chart each day.

Post of the day. Cracking

[Model Output Discussion - Into Winter]

18 minutes ago, Kasim Iberian Heights Awan said:

The guaranteed cold spell churned out a flat run

Whos guaranteed a cold spell? Tbh the meto seem confident of a spell of colder weather threw january. Given there expertise and access to major data they could be on the ball?? Id go with them but any thoughts of longevity or severity i woudnt have a scooby. Ec is ok imo

[Model Output Discussion - Into Winter]

Just now, Lukesluckybunch said:

Decent blocking is better for something more prolonged though swfc..isn't it?

Yes absolutely but im not imo expecting it to show its hand on ec atm.

[Model Output Discussion - Into Winter]

6 minutes ago, Lukesluckybunch said:

The rest of the run should be ok..but I said it early on it didn't look good for blocking..6/10 run for me

Remember you dont need major blocking to divert cold 850s to the uk. Ec isn't showing a west to east biased

[Model Output Discussion - Into Winter]

Just now, Rob 79812010 said:

Are we all agrees there's some type of cold spell coming!!

Maybe

[Model Output Discussion - Into Winter]

1 minute ago, Lukesluckybunch said:

The key thing here is nail in down the colds arrival between the 6-8th of January..what we don't want is it becoming the 10th 11th 15th and so on..we've done too much chasing over the years!

Ideally yes but i think the volatility and state of the atmosphere currently make that a big ask imo.

[Model Output Discussion - Into Winter]

There seems to be a lot of angst over output past ten days??? The warming signal remains without a finish point, wind reversel. If you include a current pv that must be dizzy and a nhp full of wedges and small areas of heighths. All this considered the whole nhp is in a state of huge flux.Picking a part of a specific run at 300 hours  is like trying find a McDonald's on pluto

[Model Output Discussion - Into Winter]

10 minutes ago, TSNWK said:

What do you look out for to see Warm Air advection?

When trying sustain or build heights you want any lows driving warm air up the west side od greenland Genenrally low pressure moving westwards under the tip of greenland"without"any heights to disrupt low, game over

[Model Output Discussion - Into Winter]

Gfs oz continues the theme of a large rise in pressure to the west and subsequent large drop in 850s threw our area. All fi but npt a bad start to the day

[Model Output Discussion - Into Winter]

5 hours ago, TEITS said:

I haven't seen Tamara post for a while. I might be still have my reservations on teleconnections but I always like to read Tamara's thoughts. She is someone I have huge admiration for and her posts are always a delight to read. I only wish I could be as articulate.

Getting back on topic. My only concern about the output is the timing of this change in the models occurring over Xmas. I always say im dubious of the output during Xmas Day, Boxing day and it would be hypocritical of me to not mention this just because of the cold output it is showing.

Yes Dave she contributes a lot to this forum. Hope your well health wise etc. You been having a look at the output in regard to any easterlies in the mix? You were along with SM the go to guys on this subject

[Model Output Discussion - Into Winter]

So pretty good output today. 12z and more so the 18gfs show be it fi should that set of runs come anywhere near its goodbye atlantic, door shut

[Model Output Discussion - Into Winter]

2 minutes ago, Scott Ingham said:

Things are moving on just nicely! Timing from the huge uptick in AAM and then the heat up in the stratosphere is about to send this place into a frenzy! Timing wise it feels like so long we’ve seen things aligned to hit us right in the heart of winters coldest weeks! It’s this part that excites me! As good as March 18 etc were you can’t beat snow in mid January!

Yes pal outlook none to shabby unlike our football teamsDo you see the pv splitting at 10pha.

[Model Output Discussion - Into Winter]

7 minutes ago, Alexis said:

Lobe of the vortex going walkies to the west with pressure rising behind over Greenland

 

Yes it was evident at 144/168 hrs. Good move nhp wise by the ec be it fi, caveats etc

[Model Output Discussion - Into Winter]

Big upgrade ec 12z