[Model Output Discussion. 3/12/2022. How cold will it get?]

New thread here. Hopefully this will be the best cold spell for years. But what will the models forecast? Discuss. 

[Model Output Discussion - moving into Winter]

1 minute ago, bluearmy said:

The years have dulled your memory Ed - this is a brilliant run for its large scale pattern - that one was brutal for cold and snowfall across the U.K. 

my memory definitely isn’t what it was. That’s for sure.  

but, but, I see an opportunity for a historic cold spell despite the climate changing massively since 2010. 
 

Reminded of that Carpenters track

Its only just begun

[Model Output Discussion - moving into Winter]

That ECM. Mark 2. 
 

 

 

[Model Output Discussion - moving into Winter]

Just now, Liam Burge said:

I never said he didn't have an opinion. Just very confusing on where people stand when they keep changing their mind every single model run 

Passion. It takes a bit of self control to step back and look at the bigger picture. Just stick to day5-6 and past that just for fun. 

In 2010, the models constantly showed the end of the cold spell, but this was put back time and time again. With this being a strong split into the lower Strat, rather than a transient Greenland High, I suspect the same will happen again. 

[Model Output Discussion - moving into Winter]

I would just like to point out that the jet stream profile on that icon run does not support an Azores high. It’s messy, granted, but it’s past day 5 so not worthy of other than just a fleeting mention

[Model Output Discussion - moving into Winter]

Before the afternoon fun starts I will just put out a link to the upper Strat forecast animations

GSFC Arctic Met Animation: Temperature @ 0010 mb

ACD-EXT.GSFC.NASA.GOV

 

first at 10hPa. Note how the distorted vortex that is being overwhelmed by the lower split then starts getting attacked by a strong upper wave 1 event. This was the timeframe that I suspected to see this occur - so all good. 
 

now just to confirm that this is Strat through check out the upper Strat at 1hPa. Yep. Strong wave 1 here too

 

so what does this mean? Well, it very much suggests that the upper vortex is under attack too and we are making steps towards an SSW too in the second half of the month…..

 

[Model Output Discussion - moving into Winter]

2 hours ago, Nick F said:

The tropospheric polar vortex yes, but not the stratospheric polar vortex as far as I am aware, only two vortices when it splits, but I may be corrected by the strat experts.

I have seen something similar to a wave three pattern in the past, so yes it can happen. Especially if wave 1 hits first and wave 2 second. Glad I had a night off model watching yesterday. Sometimes it does benefit to do this. And I only have gone back 10 pages today to catch up. I think I may have spared myself a painful read. 
 

I am still only concentrating on the long wave pattern that is very close now. Once the cold becomes entrenched next week then I will look at snow possibilities. With a cold slack low heights air mass trying to predict precipitation type or amount is futile. My daughter commented earlier that he weather app kept changing from rain to sleet to snow and back again. Exactly, I thought - no point in looking at the specifics other than for fun. The risk and reward of this game. 

[Model Output Discussion - moving into Winter]

7 minutes ago, cold snap said:

Sorry to say this but this isn't a great run.

Mild air never far away. Could be a blink and you miss it event.

Iberian low playing havoc and mild air trying to push up from the south west 

That should tell you something…..

is it past day 5?

is day 5 looking good?

are other models and background signals suggesting that the block will hold and pretty steady on day 5? 
 

are we more likely to see cold from a day 5 scenario than any other?
If you answer yes to any of these questions then disregard your own statement and wait to see what happens. 
In a compendium of poor runs over the last 10 years this doesn’t even make it into the top1000

[Model Output Discussion - moving into Winter]

3 minutes ago, Singularity said:

The AAM drop will initiate a poleward propagation of westerly momentum anomalies and they usually overpower blocking highs... but when one of those effectively extends well up into the stratosphere (in terms of positive geopotential height anomalies), that momentum can be diverted southward, resulting in a strong, flat jet stream that's well south of the UK.

That's what we're seeing in the modelling for later next week.

The thing is, this also encourages retrograde motion of longwave features to the north, such as blocking highs. So, we're left looking at whether that happens in one smooth transition, or 2+ steps that keep the UK in a cold weather regime for longer.

I expect the latter becomes more likely the stronger the stratospheric support for the initial blocking feature is.

This month, we also have the added possibility of a cold surge out of East Asia across the Pacific initiating new MJO activity, or something similar to it, over the tropical West Pacific sometime in the 2nd half. So, there exists a possibility that the HLB pattern gets reinforced, in which case it would become a very big deal how much the pattern has retrograded. At least some retrograde is pretty much inevitable, so I daresay the question would actually be whether there's been enough retrogression to place a blocking high close to our northeast (or even due north of us) by then.

Got way ahead of myself there, best concentrate on next week for a while yet!

Great post, and explains exactly why in plain English that this may well be a more than a transient cold outbreak. 

[Model Output Discussion - moving into Winter]

Just now, Weathizard said:

Much much better from the 18z here… 

 

*MUST NOT GET EXCITED*

The angulation of that channel low is perfect. 

[Model Output Discussion - moving into Winter]

1 minute ago, Singularity said:

In the midst of everything I hadn't noticed the +168 UKM with its sneaky little low near Iceland.

As you can see below, EPS are mostly less cyclonic than the ECM 12z for next Tue-Thu, which suggests little appetite for UKM's scenario, as that would be another path to a cyclonic situation in the vicinity of the UK.

Even so, I've seen enough of those sneaky lows to the northwest cause trouble in the path to know that it can't be dismissed. It should become clear by tomorrow's 12z runs whether it's a rouge feature or not.

Lol. I like the idea of a rouge feature. Sounds kinda like a red warning feature. A typo with meaning.  

[Model Output Discussion - moving into Winter]

2 minutes ago, Day_9 said:

How it starts and how it ends (at D10 anyway).

 

it was like this 2 years ago if you remember.  Ridiculously synoptics but always at or beyond D10 and the breakdown in here when it all ended was  spectacular.  
 

yes it could easily go pear shaped but this one feels unflinching.

 Just be aware though that for everyone clapping their hands in glee, there will be many millions for whom this will not mean good news.  Dazzling output, terrifying consequences at the moment for many.

I can remember the opposite with significant Strat splits. Day 10 in 2009 feb showed a split vortex from the Strat downwards, but no matter what scenario evolved in between, the end result drew closer and was always the same. With this Greenland block I have a similar feeling

[Model Output Discussion - moving into Winter]

I have been on here too many years to mention. I loved the thrill of comparing each model run, and will do so again when modelling comes down to within 24 hours with potential snow events. 
However, I now look at day five and see that as a base mark for what is likely going forward. If the long wave patterns are in agreement between models, then I will look at 850’s etc for fun only. Because these are likely to change considerably, with only slight broad scale changes. And changes in the 850’s and lower flow will have major impacts on surface conditions. So be patient with surface pressure and 850 temp differences on runs, but look firstly and foremost on the upper level Synoptics up to day five and don’t be concerned with surface activity. 

Also, take a break, and don’t feel the need to look at every model and every run. You will be better off for it, it’s not as if you can have any control either.  
The outlook is good, enjoy it. 

[Model Output Discussion - moving into Winter]

1 minute ago, Fozfoster said:

Another great post Edd,“this last bit of your post I quote because with climate warming we get increased weather extremes, and maybe this cold could be extreme . I also think someone else alluded to this earlier. 

It’s difficult to be sure, Foz. But it definitely one for another thread. 

[Model Output Discussion - moving into Winter]

6 minutes ago, bluearmy said:

As eagle eye has posted, the ec 46 zonal flow is again picking up another drop in flow around  mid month. The one in a weeks time looks to be to around 25/30m/s. The one last week was around 20m/s. We seem to be in a repeating sine wave pattern where the flow can’t get up to strength because as soon as it gets to 40m/s, a wave comes up from below and disrupts it. the drop mid month looks like it could be sub 20 m/s 

We have favourable Mjo type activity - possibly high amplitude, with trop precursors leading to these repeated dampenings  obstructing Strat strengthening. And add a possible late month SSW into the mix. Even if wave 1 displacement the lower Strat will already be damaged goods unable to resist

[Model Output Discussion - moving into Winter]

So so so….. another day has passed, and another day closer to achieving a superb looking Greenland high. Everything looks good at day 5 and post this we are somewhat unsure of the specifics other than deep cold will be getting entrenched. 
 

The background signals to keep the cold have remained and if anything have improved. If anyone has access to the 10hPa EPS anomaly chart at T +360 then the longer term signal is also fantastic. These suggest a wave 1 warming with a hint of wave 2 thrown in for good measure. And with the lower Strat set to be under pressure for some time, then the upper Strat will likely cut through this and continue the lower weak Strat vortex outlook. I can’t remember ever seeing this combination before, so this could be special, especially against the background of climate change warming. 
 

Time will tell…

[Model Output Discussion - moving into Winter]

I love the shape of this block at  T+114 - Id say its almost perfect 12Z GFS

 

[Model Output Discussion - moving into Winter]

Now I know I shouldn’t but I am liking this run so far. The weak low pressure is to the south and not the west around day 6. Should assist the northerly

[Model Output Discussion - moving into Winter]

I’ve not been concentrating on slight inter run differences today, but it still looks like the best  block is building for over 10 years, and that this won’t be some transitory event. Obviously there is no guarantee of snow falling over a particular place at a particular time, but there is a strong likelihood that the vast majority of us will see snow at some point. 
 

I have seen some suggestion on here that pacific tropical activity will wain, and that the Greenland block will retrograde west opening the door for milder SWesterlies to materialise soon after the initial polar surge. Yes this is always a possibility but unlikely probability. In fact the tropical forecasts are somewhat suggesting the opposite of this, and the latest 12z Gefs and Eps mjo ensembles show a lot of members heading into phase 7 with some strong high amplitude members amongst them.

What does this mean, well any blocking is likely to repeat, meaning a longer lasting cold spell.  The tropospheric weakening of the lower Strat will continue and maybe long enough lasting that when the inevitable upper Strat attack comes it will have a lower Strat ripe for submission  

There are signs both tropospherically ( look up tripathi paper precursors) and hints at the 10hPa long range too that wave 1 is increasing and could be fully fledged towards the end of December  

I know this may differ from other thoughts, but I see strong signs to be optimistic if a prolonged cold spell floats your boat  

 

[Polar Vortex / Stratosphere Watch 2022 / 2023]

1 hour ago, bluearmy said:

anyone know where I can see 1hpa gfs out to day 16 (from previous few runs - climate is cool shows current ) 
 

instant weather maps doesn’t seem to work at the moment 

This site gives 00Z daily, but not every run and cant see where you can look at previous days that easily

Climate Prediction Center - Stratospheric Analyses and Forecasts

WWW.CPC.NCEP.NOAA.GOV

, 

[Model Output Discussion - moving into Winter]

29 minutes ago, MattH said:

Hi Mike. The MJO evolution through late Nov/Dec 2010 is similar to now, if anything the evolution of late has been more pronounced than was the case back in 2010 - https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ARCHIVE/PDF/mjo_evol-status-fcsts-20101220.pdf

Overall, it was often a frequent visitor over the Maritimes and W Pacific, so primarily phases 4-5-6, not 7-8 like we have had now, or having. This is why, to me, this next event will be very important indeed on the second half of December and into January, especially regarding the stratosphere and whether tropospherically we get another 'boost' from a 5-6-7-8 MJO progression, especially if it has any sort of amplification to it.

What is a key point at the moment though is that the troposphere is most certainly 'leading the early winter-time dance', if anything we don't actually want an SSW to muddy the water looking ahead. Clearly, this is rare, as usuallly from a UK perspective we are often on the 'holy grail hunt' for an SSW to help us break out of the usual dominant westerly pattern that setups up at this time of year. With clear evidence too for the troposphere to impinge on the stratosphere from below, looking ahead into December, which is rare, then, for now, the troposphere is the top dog, any sort of official/true SSW can, IMO, wait for down the line. The 'holy grail' setup here is the up-coming tropospheric blocking patterns and dominance to then be followed up by an SSW in say late Dec or first half of Jan. All very 1984 as well...

The primary cause for the bottom up split in 2010 and what is being signalled now is how the wave breaking occurs in association with the massive 'rock in a river' that is a Greenland block.

Kind regards, Matt.

Spot on Matt. The early winter upward trop split is the true holy grail. And to think that with the way the MJO is set up to hopefully reinforce the blocking pattern. Could we get a rinse and repeat, then followed by a riskier SSW when the lower strat vortex has already taken a bashing, and hopefully still on the ropes....

[Winter 2022-23 : Forecasts and Discussions]

49 minutes ago, Rayth said:

William Hill the only firm I can find a live market on it , was hoping my location would be on (Newcastle) but no avail  

 

Leeds and Manchester look good odds 

[Winter 2022-23 : Forecasts and Discussions]

Out of interest, anyone taken the plunge and put a bet on a white Christmas? Percentages wise this may be the year to do it. Risk reward and all of that. If I was going to then I would go for eastern coasts. Depends on the odds though. If anywhere gives odds greater than 4-1 then I would be inclined….

[Model Output Discussion - moving into Winter]

Happy with the trend. The block is there. 850temps are always petty semantics at this far out. Though….. I know when they are good it’s great to look at  

[Model Output Discussion - moving into Winter]

Just now, Allseasons-si said:

Thanks Ed,..it is Ed isn't it,...been a while that you have posted but thanks and welcome back

the anom's are forcast to be in place with +ve heights over Greenland,...it is 2010 esque do you agree?

Yep. It’s me. Always been keeping an eye on things but not necessarily chatting publicly. At this point we are looking at 2010 lite, 2010 repeat, or a new 2022. I suspect the pattern is a new 2022 with a SSW sting in the tail towards Jan. Early days, but first Block block block, otherwise we won’t even get started to reach 2010 lite