[Model output discussion - here comes the beast!]

Will it won't it? Interesting few days trying to figure out whether the winter Azores low slides harmlessly to our south and keeps us in cold north easterlies with a reinvigorated Greenie high or whether it makes a disruptive journey north to mix in a nail-biting amount of mild air. Control shows what does happen if the end-of-week low (or procession of lows if you're the GEM) all depart without too much fuss but either way, one of the top ten (possibly top five) coldest weather events in a generation about to land, unstoppably, unbelievably, on our doorstep. Enjoy!

 

[Model output discussion - here comes the beast!]

Think ECM just won the biggest BAFTA of the night (Bloody Amazing Frigid Troposphere Award). Not sure what happens after this chart but there’s still blocking in places we’re not used to seeing it. Am guessing the UK would remain iced for some time to come.

[Model output discussion - here comes the beast!]

SIGNIFICANT upgrade to ensembles this morning. Plus you could probably touch -16 uppers if you jumped off Cleethorpes pier (before you quickly froze to death)

[Model output discussion - here comes the beast!]

17 minutes ago, johnholmes said:

flactuate!!!

Are you predicting a lot if wind then?

Flactuate (VERB): Pron: Flack-Tu-Ate. Def: To agitate weather forum members beyond the point of excitement. In extreme circumstances flactuation can lead to site-host failure, off-topic posts, banning of over-zealous contributors, and individual delusion leading to "winter is over" "where's the breakdown" and "not as good as nineteen something" posts. Also (ADVERB), flactuate, spouting of hot air when a model is summarised prematurely. GFS too far north! Breakdown imminent! When said model goes on to produce snowiest evolution yet.

I requote @SnowBallz Next week is mega.

 

[Model output discussion - here comes the beast!]

15 minutes ago, SnowBallz said:

Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and major private infrastructure will begin a daily briefing cycle as of tomorrow. To revisit previous post, latest MR output (MOG) resolving to further mute ‘breakdown’ scenario; with continental blocking signal reinforcing through well into March. Atlantic incursions are expected with southerly deflection; considerable potential for extensive and disruptive snowfall as these air masses interact. Short term, ECM:UKMO evolution favoured and considered likeliest; corresponds well with other products and illustrates fair consistency.

Small ramp.  Next week = mega.

SB

A @SnowBallz and @Team Jo ramp in the same week?...must be some sort of 10-20-30-30,000-year event approaching  Overall consistency from the models has been exemplary today and the METO's preference for the ECM:UKMO synoptic outlook further highlight's next week's potential for an historic cold spell. GFS continues to taunt with variations on a theme but the cold's coming, that's not in doubt, the issue now is how hard it might snow and where. Too soon to say beyond general guidance oft repeated this week but for once let's enjoy the ride rather than hang ourselves with specifics in the confident knowledge model watching for the next week or two is going to be not just interesting but almost certain to pay dividends for many. Great stuff. If the Met are issuing daily guidance you can be assured the fan's about to ice over.

[Model output discussion - here comes the beast!]

Site crash arrived at the worst possible time. Wife's birthday and was forced to do the hoovering. Thankfully the distraction allowed me to view the ECM in one sitting. Jeez, did we die and go to heaven?

JMA sums up today's output pretty accurately (stella).

 

[Model output discussion - here comes the beast!]

59 minutes ago, Day 10 said:

Waits patiently for someone to mention the word breakdown....

They'll certainly be plenty of those if today's charts don't verify...and probably a few on the roads if they do.

[Model output discussion - here comes the beast!]

7 minutes ago, Yarmy said:

That chart confused me a bit until I realised that the scale down the right is not temperature anomaly, but standard deviation. So England, Wales, and Ireland are forecast to be 2.5-3 sigma below average. 4+ below for the Alps too, which is what Carinthian was discussing.

You're right. Also fits in well with Ventrice's recent comments about AO tanking by minus three sigma (current record 2.7 I think). Could be a record breaker this one.

[Model output discussion - here comes the beast!]

If that's true it provides further evidence of the unlikely depth to this incoming frigidity.

[Model output discussion - here comes the beast!]

23 minutes ago, Connor Bailey Degnan said:

2018 v 2010 LET THE BATTLE COMMENCE

Bring it on. 

Certainly 2010 remains the best winter snowfall in Lincolnshire since anything I saw in the 70's and 80's. Based on this morning's GFS ensembles for the same area there are a few perts that could run it close. (Rob K on TWO posted this table for Oxfordshire this morning - clicking my area raised an eyebrow or two). Actually this new table from Meteociel is well handy - think @lorenzo talked about it on here the other day and I've started using it regularly to get a quick handle on ENS fundamentals. 

 

[Model output discussion - here comes the beast!]

GFS ensemble shows Op and Control very much at the milder end of the spectrum beyond the initial plunge. Good.

[Model output discussion - here comes the beast!]

Nice perspective from WRF. Tomorrow's run likely to become a popular screensaver...

[Model output discussion - here comes the beast!]

Go back to sleep. Nothing to see here....

Oh go on then. Ignore the GEM it's a (weird) disaster. Otherwise, rest easy.

The Beast Cometh. And she is looking pretty fierce this morning. Grrrrrrrr!

[Model output discussion - here comes the beast!]

Early stages of ICON showing a larger/bigger continental cold pool and better alignment for the cold to advect West faster.

[Model output discussion - here comes the beast!]

Pleased to see snow showers streaming a long way inland according to the ECM for Monday. 

[Model output discussion - here comes the beast!]

Well we all like a fast and predictable plunge into record-breaking cold (most of us at least) but sadly in most winters the UK does it's best to thwart us at every available opportunity. This year's historic SSW and subsequent cold spell appears rather different to our standard fare on so many levels but looking at some of the emotive posts this morning it's probably worth comparing eggs with eggs. Here's yesterday's 00z run ensembles (GEFS) alongside today's - also from the 00z run, for the same part of the country.

Looking at these charts, I actually think it's fair to say that the deepest cold came in slightly faster on yesterday's run with mean uppers beaching -13 by midday Mon and staying exceptionally cold for the next three days before gradually rising back above -5 by Sun where they sit pretty much until the end of the run.

This morning's uppers on the ensembles still break through -10 on Mon (so plenty cold enough for snow of course and therefore also fine to suggest that the "cold" still arrives on Mon) but the deepest cold doesn't breach -13 until Thursday, some three days later give or take. I can therefore see how some forum members are suggesting the cold has been delayed but really I think it's a question of semantics. The deepest cold is delayed, but overall the pattern is entirely similar.

Perhaps more importantly, not only does it still turn cold on Mon, then get even colder, but the uppers don't rise back above -5 until Wednesday 7th. 

In a nutshell:

- the cold still gets here Monday.

- it gets just as cold as was predicted previously (or at least the mean does).

- the deepest cold might not arrive immediately but It stays colder for longer.

Happy days. 

EDIT: For those who care about such things the 06z ensembles follow an extremely similar profile to last night's 0z run, perhaps fractionally (and I mean barely) less cold, but there are two notably milder members dragging the overall mean in the wrong direction which would explain the difference. Still cold from Monday, still deep cold thereafter, still extended.

[Model output discussion - here comes the beast!]

1 minute ago, snowblizzard said:

Really?

The majority below -10c for 5/6 days

Not sure I understand. Was saying how incredible they were, if only fractionally less spectacular than yesterday?

[Model output discussion - here comes the beast!]

40 minutes ago, bluearmy said:

It was there if you wanted to see it jimmy - the ec op is a more extreme version but it’s out of the far less convective  snowy cluster. This op gives us around 36 hours of convective potential but heights are higher as is slp so it’s simply not good enough for widespread snowcover if you compare with the previous runs. Working on the basis that we have seen two good ec ops followed by one meh run, we’ll be back in the game come tonight on this model. However, the ukmo day 6 is headed in a similar direction (though the upper ridge slightly better aligned). More runs needed and ed’s salt deposit losing some of its value! 

all based on ec output I should add !

as for the ecm following the gfs @frosty ground...... really? you  think they are alike?

 

Double take at this bit Blue. The big three all banging the drum for an inflated high in the transition to retrogression would be a concern. Is that a fair interpretation?

[Model output discussion - here comes the beast!]

Ensembles for London marginally less jaw dropping but frankly still pretty incredible. ECM and GFS might have made us pause for thought this morning but hiccups are best cured by a short sharp shock and we’ve definitely got a cold one of those coming 

 

 

 

[Stratosphere and Polar Vortex Watch]

Fellas, is this double dip reversal typical of a major SSW? Couldn't find any relevant commentary and was surprised at the intensity of second pulse? Apologies if this is a stupid question.

[Model output discussion - here comes the beast!]

15 minutes ago, Nick L said:

I wish people would stop posting these inaccurate charts, they're utter nonsense. I know they're the only freely available EC snow depths but they're utter tosh.

I fixed the snow chart. Can everyone stop posting pointless accumulation maps now please.

[Model output discussion - here comes the beast!]

As ever there are more than a few ways for any predicted cold spell to go Pete Tong whether that be shortwave dramas (ARPEGE), complicated trough disruption (GEM), inflated highs and too-dry air (GFS)  or the plain and simple problem of predicting what the weather will do, never mind attempting resolution in the middle of a record-breaking SSW. For those wanting to scrap in the backyard I suggest you fire up the Playstation and take out some aggression on Street Fighter rather than clog up the Mod thread. @bluearmy's advice to wait for clarity is no doubt well-judged. For those needing some cheer, @Catacol's recent ramps have been joyful reading. Otherwise, heads down for the ECM and a reflective review of today's ensembles later this evening. Methinks the inflated high and the Op likely to sit at the top of the ENS, although that doesn't mean it can't/won't happen. Be interested to see whether UKMO extended can shed any light on the shape/alignment of the troublesome high in the meantime.

[Model output discussion - Post SSW - Will it turn cold?]

2 minutes ago, ICE COLD said:

-17 850s knocking on the door again at t207 ?

Knock and ye shall enter. Cripes!

 

[Model output discussion - Post SSW - Will it turn cold?]

21 minutes ago, Gustywind said:

Quick question. Those runs that bring in less cold or even mild conditions at the beginning of March, is that due to low pressure from the SW pushing N/NE bringing a breakdown snow to rain event? Or is it due to another form of less exciting breakdown?

In a roundabout way @Mucka‘s excellent post below yours answers your question I think, GW. Well worth a read.

[Model output discussion - Post SSW - Will it turn cold?]

Another outstanding set of runs from every single model (that matters), putting the UK in the freezer by the end of this upcoming weekend and keeping us on ice for the following week. GEM/UKMO/GFS/ECM all rock solid. 

ECM midnight run yesterday vs ECM midnight run today. Both for next Thursday (0100 March 1). Will be interesting to do the same exercise with tonight's run bearing in mind how incredible the Euro model's charts were last night. Either way, beautiful synoptics and nothing to worry or complain about. Bring on the Beast!

Also, a like-for-like comparison with the latest GFS ensembles show the latest run is the coldest yet with average uppers of -12 or less for the first part of the week in Eastern counties. Quite the set. Seems B&Q will be on the phone to @chionomaniac wanting their salt back quick sharp this morning. Not sure I've ever seen such cross model agreement for any event so far out, not least one as potentially historic as the cold plunge surely coming our way. Only a day or two more before I dare tell the kids. By jingo it's exciting. Can't imagine what the atmosphere's going to be like in here by the weekend if the wheels haven't fallen off by then. God help the mods either way. Suggest we all do our bit in the meantime to save Him (or Her) the bother.