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

[Summer Sun]

2 minutes ago, SLEETY said:

Big swing to cold there,where do you find those charts I can never find them (

London - http://www.meteociel.fr/cartes_obs/ecmwfens_display.php?x=306&y=141&run=12&ville=Londres&type=0&runpara=0

Regional (click on the map for your location) - http://www.meteociel.fr/modeles/ecmwfens.php?carte=1

[Snowjokes92]

2 minutes ago, Banbury said:

Stating the obvious I know

For those who keep saying it’s always at D10 well the Easterlies have to be forecast at some point .

The Met mentioned Easterlies on Feb2nd and forecast them to arrive between 16th Feb and 2nd March , well they are slowly getting here . Let’s see how far out they are in 168hours . 

Good charts again today , we are slowly counting now . Let’s hope there is something special at the end of this rainbow 

I agree, iv'e never understood this 10 day business stuff posters mentioned. I think we can say the building blocks are built for it and nailed we just need to get it down to detail later on e.g cold pools, temps, precipitation or how dry high is etc. The timing of the easterly was heavily regarded on here for 21st or so and its spot on. The major impact was always the closing week of the month as well. We also have some models bringing in that deep cold a lot earlier on

[thetipster]

12Z ECMWF run is a little beauty for those that like the coldest weather of winter with snow the beast from the east is comeing from bitter Siberian air 

Edited February 17, 2018 by thetipster

[kold weather]

4 minutes ago, Leon1 said:

why is it always day 10?!

Worth noting the ECM ensembles originally picked up on the DEEP cold(-15C) as a risk about 300hrs out, it has now moved into the 216-240hrs range,so it is coming down in time, I've been watching it steadily hone in.

Don't let the first two stabs at an easterly fool you into thinking its staying at 240hrs, its just they have been moderated downwards somewhat, that won't happen if we do access that cold pool.

[bradymk]

6 minutes ago, Man With Beard said:

Quite a scatter though!! 

  

Very rare to see -13C 850s within the ensemble range (Worth noting that the shaded bit doesn't include complete outliers, so there could be runs that are colder still)

Yes still a wide scatter, as to be expected. But even though the scatter is still as large as previous runs, the min and max values have definitely decreased.

Eg) Comparing to 00z ens using the charts you posted, they show a 5c drop in the max envelope and 3-4c drop in the min envelope.

Ens seem colder in the earlier timeframe than op too. 

[Daniel*]

12 minutes ago, Man With Beard said:

Quite a scatter though!! 

  

Very rare to see -13C 850s within the ensemble range (Worth noting that the shaded bit doesn't include complete outliers, so there could be runs that are colder still)

Interesting up to 25th majority were colder than OP and the OP itself is within the spread don’t discount it! 

[The Beast From The East]

So this is what the Beast looks like when it finally arrives..... it  looks like its going to take a bite at the UK.... ?

PLEASE DO.. ?

[Daniel*]

7 minutes ago, thetipster said:

12Z ECMWF run is a little beauty for those that like the coldest weather of winter with snow the beast from the east is comeing from bitter Siberian air 

It is remarkable I’ve never seen modelled such cold air as extensive as that what makes it really exceptional is that it’s almost March I can’t see that would go south of us. Our SSW and split has thrown a lifeline. I think we would have gone colder without it however the potency of cold air possibly available, is directly related. Some very interesting model output to come.

Edited February 17, 2018 by Daniel*

[Banbury]

17 minutes ago, Leon1 said:

why is it always day 10?!

It’s not 

It started on D26 it’s coming down

[Singularity]

 

Comparing the 12z ECM of yesterday with that of today for Saturday noon, we can see that this is an occasion on which a shift toward N of the WAA driven by the Atlantic trough has actually delayed the cold onset by removing that shallow disturbance trailing across N. Scandinavia and allowing for the ridge by the UK to develop an independent circulation from that of the block over Siberia; this circulation helped drive the cold over to us.

So now instead we await the Siberian High moving over in full - a rare event to say the least. We then face the interesting situation in which we could do with the Atlantic troughs staying nicely west but without taking on too much of a negative tilt (i.e. elongated shape aligned from NW to SE) too soon; the resultant approach of lower heights from the SW is only going to work out well for us if the deep cold has already had time to make its way over.

GFS actually came close to the right balance but was undone by that particularly deep LP development within the cold pool that both held it up and eroded away the ridge a bit on the S flank, so allowing the Atlantic front to push right on in rather than giving it a mighty wall against which to crash and capitulate. 

 

Given the historical tendency for models to be either side of what ultimately comes our way from an easterly direction, perhaps it is encouraging that a halfway house between ECM and GFS for days 9-10 would be a particularly good mix of very cold and laden with snow opportunities. Though if I was picky I'd want 75% ECM .

Agree with the suspicions of a few on here that the easterly could well be brought a little forward in time (not going to waste time speculating on how - too many variables!); we saw that happen with the one just under two weeks ago, after all.

[SMU]

you could almost day 6 looking at the mean & the -6 line...

[Deep Snow please]

Really nice cold pool sitting waiting for us at you guessed it Day 10-15. That would cripple the countries infrastructure.

 

[bluearmy]

7 minutes ago, Steve Murr said:

you could almost day 6 looking at the mean & the -6 line...

Good stag weekend is it ???.   Hic 

[Met4Cast]

8 minutes ago, Steve Murr said:

you could almost day 6 looking at the mean & the -6 line...

You could almost indeed! 

ICON 18z is rolling, lets hope it upgrades on it's earlier run! We want to see that high a little further North a little earlier

[The Eagle]

8 minutes ago, Steve Murr said:

you could almost day 6 looking at the mean & the -6 line...

You make some good points.

[Snowjokes92]

 

11 minutes ago, Steve Murr said:

you could almost day 6 looking at the mean & the -6 line...

One of the best posters on here, but really didn't understand this post

Edit: thought i was the only one who didnt understand it. Just sat 5 mins trying to make sense of it lol.

Edited February 17, 2018 by Snowjokes92

[Daniel*]

I encourage folk to read @essexweather post made in SE thread. With regards to what’s being seen behind the scenes to speak - it’s encouraging to say the least wrt to MOGREPS and more. 

 

Edited February 17, 2018 by Daniel*

[SMU]

15 minutes ago, bluearmy said:

Good stag weekend is it ???.   Hic 

Lol its early doors at the mo- Just warming up with pitchers of cocktails  sitting with the pope !

So IKON up & running- I have been mighty impressed with it this winter- its only sprung into the limelight because of the run time - but its often been more stable than the 'Big 3'

IKON out to 42 has the atlantic high slightly better in terms of lattitude which could influence the Early Easterly !

[Nick F]

I think the one thing that the current SSW event has taught me and maybe others is to not follow the operational runs but stick with the ensemble means, because the operationals tend to, I think, exaggerate the frequent adjustments made by the models as they try to handle not only an historic SSW impacting the troposphere, but also the impacts of the MJO wave, La Nina forcing, wave breaking in the troposphere and also AAM. 

With regards to the MJO,wave - the models seem to be continually playing catch up with and now correcting to go through phase 8/1 as per VP200 diagrams had shown for a while. This obviously is probably having an impact on the trop pattern with the models maybe adjusting as a result. 

I did have some initial concerns that the La Nina background state, which favours +NAO, would try to cancel out the effects of the SSW which tends to force a –AO/-NAO pattern, so we’d end up with a neutral NAO and a MLB. Fortunately, it looks like the block with build far enough north, looking at the ensemble means, to get deep enough cold air advection and low enough heights/pressure to eventually bring low enough temperatures and snow. I was hoping we would see the deep cold come in sooner, but it looks more likely next weekend at the earliest , more likely start of following week that it’ll arrive, looking at the ensemble means. EPS means indicates good confidence, for now, that deep cold is coming too.

[karlos1983]

Great days output for the coldies! We’ve overcome a pretty big hurdle over the past couple of days, which was if we could raise heights over the uk and towards scandi, that looks pretty much a done deal now. So we are in a rare siutiation atm where cold is the more likely outcome, now it’s just to what degree. Usually it’s the other way round, can we get cold in rather than an Atlantic driven pattern or pesky Euro heights that so often ruin our winters in recent years, and we have to hope for a cold blip to get our snow fix. Been some fairly comprehensive commentary on the models with some in-depth summary along with some great humour because at the end of the day we are all pretty content right now. Understandably some will be cautious, we’ve been here before after all. From a model watching personal perspective, I don’t remember a more fascinating period, where differences at just +72 for days on end were massive, I’m really enjoying it. It won’t stop me looking at my phone between my fingers tomorrow morning when I wake up and look at the models! I’m nervous even though the odds appear to be stacked in our favour! Perhaps it’s becaus I’m a cold loving south coaster! Now to chill with a beer and watch the pub run 

wish I could sleep for 8 days and wake up to this at +24/48

 

[bluearmy]

There remains an eps cluster bringing the cold pool at days 8/9. Its still on the table but the day 5/6 option has definitely slipped to our south. We seem to have the deep cold arriving day 8 or day 10. (Or maybe later if we miss these - eps show 40/50% likelihood of sub -10 c uppers in the 9/11 day period. 

[karlos1983]

9 minutes ago, FiftyShadesofSnow said:

Copied this fantastic post to Mod thread Thankyou Essexweather.

Cheers for that, those temp graphs are freely available on weather.us of anyone wants to look.. nice update post though indeed. 

https://weather.us/forecast/2643743-london/ensemble/euro/temperatur850

Edited February 17, 2018 by karlos1983

[Mike Poole]

Today I think we've flipped from looking for ways this can possibly go right to looking for ways it could possibly go wrong.  As I said in my post at lunchtime, the SSW is delivering blocking in more or less the right place, the second warming should boost it higher, so while the risk that the eventual destination is a UK High diminishes, the possibility of it going too far north maybe increases a bit.  But the 12z suite was by and large good.

So to the 18 z's, first out the trap the ICON, and it is looking well OK at T81:

[kold weather]

Worth noting that the early easterly shots on the ECM ensembles become quite ugly quite quickly, usually due to the same issue with the 12z op GFS, low pressure becomes too dominant and takes over blasting away the nice cold pool. We get a 24-36hrs cold easterly shot (mean would be -12C I'd say) and then Atlantic dross for the next week.

Definately want a slower evolution here as it allows the cold pool to really deepen, the slightly slower easterlies nearly all contain -15C air within them and tend to last a solid 72-96hrs at least before easing up.

Also worth noting someof the mildest runs have a nice flow from the SSE, so it would be mild by day, but still frosty by night. I suppose I could with that if that happened...

Edited February 17, 2018 by kold weather

[The Eagle]

ICON 96 hrs, the high not quite as well orientated and under a bit more pressure from the northwest depression...