Model Output Discussion - Into Winter

[LRD]

43 minutes ago, Catacol said:

and for this reason 2 points to make:

1. Enjoy what is here now. It will last about a week in total, bring frost and blue skies at times (glorious here today! - though I'm stuck indoors  ) and is a great start to the season.

2. This spell arrived because of an MJO passage through 7/8/1 on the back of a rising AAM context and a canadian warming helped along by a Nino-style north pacific low in place. It has probably been helped by atlantic SSTs. Those same drivers have faded as AAM has fallen, MJO gone back into 2/3/4 and - hey presto - the pattern flattens a bit. These patterns are not created by "shortwaves" south of Greenland or spoilers in the North Sea. They are driven by large scale developments that originate in the Pacific. And just as the pattern arrived and now is set to decline in response to those drivers, a blocking pattern is likely to reemerge in the second half of the month (or perhaps final third) as those drivers switch back to a more favourable combination. This is the waxing and waning of a pattern that is standard stuff.

I probably won't post again for a week or so as I am not expecting to see anything change all that much. But by the end of next week, once the cold has faded and we are all wondering what happens next, I think we might see some good runs start to appear in the outer edges of NWP. Chase II will be on! My head will come back up.

Final thoughts. I note that there is still a NW/SE slant to the jet projected next week. The trough that will gather over us will be a fairly cold one as residual blocking hangs on over Greenland. So - wetter and average but not often mild. And I think the cold over Scandy will hold. Assuming this happens, we will have an excellent context for the next round of amplification. 3 weeks further into the season, more entrenched cold to tap into. And this is before we start to consider the state of the Strat Vortex - signs continue to emerge that the pressure on it will create a slowdown, maybe a significant slow down, and that would be another great context looking further into Jan and Feb.

If folk want to continue to scan charts every day while the next 7-10 days plays out, go find those charts that show the state of the Pacific and watch out for a high amplitude MJO wave. On that - all hail the mighty Australian Met. Their BOMM model remains staunch in the belief that the next wave is going to be a strong one (other models currently less certain....)

Exactly the point I made earlier but you've put it better. Shortwave this or shortwave that - they're only a drama 'cos the teleconnections and other global stuff has allowed them to cause drama. If the global drivers didn't allow that, they wouldn't. But these shortwaves or spoilers or whatever are not driving (or destroying) a given (cold) pattern like some seem to suggest they can

Edited November 29, 2023 by LRD

[stewfox]

1 hour ago, Met4Cast said:

Looks like my expectation for an unsettled start to December is going to come to fruition after all, just with a bonus cold spell before hand. 

Quite a few turn their noses up at background drivers/teleconnections in this thread, I suspect due to a lack of understanding them but I think that’s a shame, they are an incredibly useful tool and add a lot of context to NWP outputs

 

 

 

Always read your posts with interest.  One of the first to suggest the low may not hit the UK at all last Sunday.

Also suggesting on 21 November Atlantic driven weather may return early mid December. When some were still looking at a Dec 2010 comparison.

Are we in a situation where on a macro scale we can predict trends for the next 3 weeks ?

However on the micro scale things may pop up. ?

This cold snap did make many consider the validity of the background signals,probably due to lack of understanding.

 

[Derecho]

So we can be confident now the Atlantic will start fighting back next week (though a few ens members keep it quiet). However quite a lot of members on the GFS 06z ensemble suite bring in some severe cold over eastern Europe.

So if we do get some mild air pushing across fingers crossed the cold air over Scandi can hold on and we get some trough disruption. The Svalbard high still features a fair bit bringing the frigid air from Russia into Europe. Some examples

 

[LRD]

7 minutes ago, stewfox said:

Always read your posts with interest.  One of the first to suggest the low may not hit the UK at all last Sunday.

Also suggesting on 21 November Atlantic driven weather may return early mid December. When some were still looking at a Dec 2010 comparison.

Are we in a situation where on a macro scale we can predict trends for the next 3 weeks ?

However on the micro scale things may pop up. ?

This cold snap did make many consider the validity of the background signals,probably due to lack of understanding.

 

I'm not an expert but I always look at teleconnections as a forecast too. Just because MJO is predicted to be in a particular state it doesn't necessarily mean it will manifest. And, even if it does, just increases chances of 'something' happening rather than guaranteeing it. The way I've always thought about it is if, for example, the MJO looks to support cold in NW Europe but it doesn't arrive it doesn't mean that micro stuff (shortwaves, spoilers, etc) has blown that away. It means a stronger teleconnective variable has just over-ridden the MJO

If teleconnective signals are neutral or weak then, I think, that's where more local influences can take over. But I'm just putting it out there - someone with more knowledge than me can make me right or correct me if I'm wrong

Edited November 29, 2023 by LRD

[Methuselah]

5 minutes ago, Blessed Weather said:

A Canadian Warming of the stratosphere in January and February 1963 played a huge part in making that winter very special. Such warmings don't always have such an impact (some have very little impact) but this type of warming puts pressure on the SPV and can weaken, displace and lead to a full blown SSW.

Source: The Mid-Winter 1963 Stratospheric Warming and Circulation Change

The current warming expected to rumble on for a couple of weeks yet; here's the geopotential height and temperature anomaly at T384 14th Dec from this morning's GFS 06z.

So what caused the cold weather (along with a few blizzards) between Xmas and early January then? It seems to me, that the extreme cold had set-in weeks before the Canadian warming exerted its effect? 

[Tim Bland]

Sorry to be the Grinch but isn’t it hilarious how tv news are headlining ‘up to 2cm in parts of Scotland’. I’ve scoured all the charts and there’s no snow for 95% of the population. Tomorrow it’s rain and drizzle and by Sunday it’s rain for most. This is a a couple of days of frosts not a severe cold spell as some people would have you believe !  High res UKV for tomorrow and Sunday below. 

[LRD]

3 minutes ago, Tim Bland said:

Sorry to be the Grinch but isn’t it hilarious how tv news are headlining ‘up to 2cm in parts of Scotland’. I’ve scoured all the charts and there’s no snow for 95% of the population. Tomorrow it’s rain and drizzle and by Sunday it’s rain for most. This is a a couple of days of frosts not a severe cold spell as some people would have you believe !  High res UKV for tomorrow and Sunday below. 

Does make you wonder how the media would react to a proper fall of 15, 20 or even 30cm

[feb1991blizzard]

14 minutes ago, Methuselah said:

So what caused the cold weather (along with a few blizzards) between Xmas and early January then? It seems to me, that the extreme cold had set-in weeks before the Canadian warming exerted its effect? 

i thought there had been a canadian warming in nov 62, hence why the usual excitement in here whenever those type of winters analogue vaguely with whats happening now.

[TSNWK]

1 minute ago, LRD said:

Does make you wonder how the media would react to a proper fall of 15, 20 or even 30cm

Or yesterday's 12gfs if it verified.... one day maybe! 

[Cold Winter Night]

36 minutes ago, Blessed Weather said:

A Canadian Warming of the stratosphere in January and February 1963 played a big part in making that winter very special. Such warmings don't always have such an impact (some have very little impact) but this type of warming puts pressure on the SPV and can weaken, displace and lead to a full blown SSW.

Source: The Mid-Winter 1963 Stratospheric Warming and Circulation Change

The current warming expected to rumble on for a couple of weeks yet; here's the geopotential height and temperature anomaly at T384 14th Dec from this morning's GFS 06z.

 

9 minutes ago, feb1991blizzard said:

i thought there had been a canadian warming in nov 62, hence why the usual excitement in here whenever those type of winters analogue vaguely with whats happening now.

1962-1963 had a Canadian Warming in late November, but that one was, like most CW's, no formal SSW with a 10 hPa reversal.
Later on, at the end of January, there was a proper SSW.

[Mike Poole]

13 minutes ago, feb1991blizzard said:

i thought there had been a canadian warming in nov 62, hence why the usual excitement in here whenever those type of winters analogue vaguely with whats happening now.

Yes, I thought that as well, Canadian warmings are an early season phenomenon, and one that seemed until this year to be a thing of the past.

That’s why it is so interesting to see one, and even though it is not a reversal, it seems to have a very clear signature on the model output.  One more thing very much in our favour as we head towards the heart of winter 

Edited November 29, 2023 by Mike Poole

[Dennis]

MJO 29-11

[Battleground Snow]

Very interesting EPS at 144 on the 06z

Maybe the fat lady hasn't sung yet on this cold spell.

Always have to remember FI is 144 at a push, even  with a very strong trend  showing across the suite of runs it's never certain

Edited November 29, 2023 by Battleground Snow

[TSNWK]

1 minute ago, LRD said:

Does make you wonder how the media would react to a proper fall of 15, 20 or even 30cm

Or yesterday's 12gfs if it verified.... one day maybe! 

[Dennis]

gfs6z ideas

[Frostbite80]

13 minutes ago, Dennis said:

gfs6z ideas

Hi Dennis, always look at your posts with interest but would it be possible for you to put just a little explanation as to what you are posting for those that arnt quite as good at reading charts as you clearly are

[Dennis]

6 minutes ago, Frostbite80 said:

Hi Dennis, always look at your posts with interest but would it be possible for you to put just a little explanation as to what you are posting for those that arnt quite as good at reading charts as you clearly are

sorry ive so much to check for the strato to dec23

 

[sheikhy]

30 minutes ago, Battleground Snow said:

Very interesting EPS at 144 on the 06z

Maybe the fat lady hasn't sung yet on this cold spell.

Always have to remember FI is 144 at a push, even  with a very strong trend  showing across the suite of runs it's never certain

Mate if any of those happen im gona go on a mad one!!!!we live in hope!!12zs about to roll out.....

[*Stormforce~beka*]

8 hours ago, sheikhy said:

What a bloody implosion this morning!!!!and to make it worse that shortwave i mentioned yesterday near iceland at 96 hours phases with the low in the atlantic at 72 hours today and downgrades everything even more!surprised no other poster on here mentioned the dangers of that shortwave shortening this spell even further!enjoy the next 4 days of frosts lol!!unbelievable!!

The cold air is entrenched ... It won't be easy to shift ... Blahy blah. Yet again old timers knew not to fall for this tosh so our hearts aren't broken! Once bitten twice shy!

Edited November 29, 2023 by *Stormforce~beka*

[Battleground Snow]

4 minutes ago, sheikhy said:

Mate if any of those happen im gona go on a mad one!!!!we live in hope!!12zs about to roll out.....

The models always seem to dangle a carrot and then take it away again on the 00z runs

[Dennis]

There is the scandi setup again after a short mild week in dec (5-12)

[Stabilo19]

59 minutes ago, Tim Bland said:

Sorry to be the Grinch but isn’t it hilarious how tv news are headlining ‘up to 2cm in parts of Scotland’. I’ve scoured all the charts and there’s no snow for 95% of the population. Tomorrow it’s rain and drizzle and by Sunday it’s rain for most. This is a a couple of days of frosts not a severe cold spell as some people would have you believe !  High res UKV for tomorrow and Sunday below. 

Well what's to come over the next few days is what the modelling has suggested - chilly days and frosty nights for most.  The duration of the cold spell has been cut short but the intensity hasn't changed. 

I don't recall there being a forecast for a severe cold spell 

[sheikhy]

9 minutes ago, Battleground Snow said:

The models always seem to dangle a carrot and then take it away again on the 00z runs

Been happening for a number of years now buddy!!!!

[Big Gally]

Going by the met office they also seem uncertain about this “mild” weather. If it becomes less cold for a time I’m hoping for a return just before Christmas. Have a nice day.

[MATTWOLVES 3]

1 hour ago, Blessed Weather said:

A Canadian Warming of the stratosphere in January and February 1963 played a big part in making that winter very special. Such warmings don't always have such an impact (some have very little impact) but this type of warming puts pressure on the SPV and can weaken, displace and lead to a full blown SSW.

Source: The Mid-Winter 1963 Stratospheric Warming and Circulation Change

The current warming expected to rumble on for a couple of weeks yet; here's the geopotential height and temperature anomaly at T384 14th Dec from this morning's GFS 06z.

Thanks for that Blessed.

I think we may have the forum doing a check on the hour every hour for the next few weeks on that Canadian warming...now that it's been mentioned as one of the key drivers behind 63.

Some may get that excited the Xmas presents may be opened earlier than expected

OK I'm a tad excited..now let's just have a look at that warming over Canada..think I'm gonna have to give Judah a nudge on this one.

But I definitely feel the momentum will increase as we move further into December.If I'm wrong then so be it..we live and learn..but this year just seems different....yeh we've heard that statement numerous times before but there seems to be much more going on this time around.

Regarding met update it amazes me how you can have reduced confidence in the mid term over inroads of milder air,and the fact it may hold on further North..yet go on to say it will become milder towards mid month with more certainty! I tell you folks its not that straight forward when it comes to moving cold blocks that have been bedded in for weeks! I feel the met are gonna be caught with there trousers down on more than 1 occasion this Winter...pardon the pun.

Food for thought folks...but imagine this...if we did go into a 63 type set up you would still have the met and other pros saying there are now signs of milder Atlantic air moving in! I remember my grandad saying to me years ago this...during 63 everynight they would sit there listening to the world service radio station,and so many times they would say milder air is on the way! Yes forecasting as moved on heaps and bounds since then..but I think you get the general point I'm making here.

Edited November 29, 2023 by MATTWOLVES 3