Model output discussion - proper cold spell inbound?

[Nick F]

Looking at the extended 12z EPS H500 mean, it does get there with Scandi ridge in the means from day 12-14, even retrogression toward Greenland at day 15.

EC wants us to wait longer for the Scandi ridge to build therefore? I guess the models are still not quite there with resolving how quickly the downward propagation of the SSW will impact the heights at 500mb level just yet. more runs needed before jumping in with one model when they differ.

[Froze were the Days]

30 minutes ago, Steve Murr said:

UKMO supporting GFS- nice angle of attack!

 

 

Not sure you can say that Steve without looking at higher latitudes and what the profile is like over Scandinavia...

[ICE COLD]

7 minutes ago, Froze were the Days said:

Not sure you can say that Steve without looking at higher latitudes and what the profile is like over Scandinavia...

See @Singularity post above and your see why steve says that it supports GFS . 

[ghoneym]

Mean sea level pressure (colours) with 10mb strat winds overlaid. To me there appears to be a lot of stratosphere / troposphere coupling from that image

[karlos1983]

Well that does tie in with the eps. GFS usually pretty good at picking up on a developing pattern early doors. So perhaps patience is key here. I mean we’ve waited 5 years down south, what’s another week hurt ☺️

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

 

to me things could change about 120 hr  all eyes bbc news  24  at 9 55!!

[bluearmy]

so most of the modelling has broadly settled on the solution offered by the ecm on its four runs prior to this morning. But ecm op (and it’s ens) have found a different route today. The AO for the second consecutive suite is failing to go negative until after the 20th and then it’s hardly enthusiastic about it. This is in stark contrast to gefs and geps which drop negative around mid month and go markedly so. 

So why the change from the ecm suite? Well as nick F has posted earlier, it does find the scandi ridge post day 10 so it’s just the way it deals with upstream early on that sets it apart from the other models. I don’t think there is a lot between the ecm and the gfs. I expect the ecm is a bit overdone on the Canadian forcing and the gfs is a bit overdone on the ridging. A half way house solution would leave us under a block and perhaps a weak continental flow on the way to the scandi ridge taking control post day 10.

 

[tinybill]

big  snow event monday tuesday  coming acc to the bbc  wednesday snow sleet  after  that snow!!

[MattStoke]

18z turns Tuesday's front to snow earlier. Just a shame it's snow charts are normally way overdone. One to watch though, given that the BBC have been highlighting it for a few days. In fact, their latest forecast said settling snow widely to low levels.

[Weathizard]

18z on track, bit more active coming out the eastern seaboard though

[SMU]

18z out to 174 is pretty much identical to the 12z bar slightly different by 6 hours - so almost neglible -

ECM is likely to come on board tomorrow-

[karlos1983]

ECM 12z v GFS 18z Miles apart

GFS sticking to its guns.. but that’s nothing new. So shouldn’t be taken for granted. When the gfs shows mild and ecm cold we always expect the gfs to stomp its feet before following the ecm, so if we are consistent in that thought process......... we can’t just use that analogy when it suits us. Time will tell

Edited February 10, 2018 by karlos1983

[ICE COLD]

GFS 18z looking lovely jubbly at 192hrs - 

[snowblind]

28 minutes ago, tinybill said:

big  snow event monday tuesday  coming acc to the bbc  wednesday snow sleet  after  that snow!!

That's a bit at odds with the Met office. Snow over the hills Monday/Tuesday. Milder Wednesday. 

[Weathizard]

1 minute ago, Steve Murr said:

18z out to 174 is pretty much identical to the 12z bar slightly different by 6 hours - so almost neglible -

ECM is likely to come on board tomorrow-

Indeed remarkable consistency from the GFS of all models... I'm still not convinced the ECM will be so drastically wrong but we shall see.

[Guest]

After my long post yesterday where I desperately tried to maintain a high degree of balance, I feel that I must give my actual take on all this with a short post! So, with due warning.....

                                                                                                                        

Seriously, I am not ramping but just speculating a little and I'm jumping off the top of the fence into the cold pool! As many of our strat specialists have been telling us such as @chionomaniac, this is a truly spectacular sudden stratospheric warming event. It will be fascinating just to see how that plays out. There are other key drivers which would "normally" be at play too. Not least, the continuing (but now rather weaker) east Pacific based La Nina; the rise and fall back in atmospheric angular momentum with the time lags into rising and now falling frictional torque and rising and now falling mountain torque, would as @Tamara (and others) have said normally have a strong impact on the degree of HLB. Several of our MJO specialists, like @nick sussex must be developing a split personality (and I'm not talking about the polar vortex, just yet!). We sometimes see significant disagreements between the GFS and ECM output but the consistent difference of their MJO forecast charts over the last few days is quite exceptional. Now, I feel that they are both partly right! 

The GFS may be a little too progressive and the ECM a little too cautious. We can only judge the MetO (or UKMO) in this more extended (10 to 16 day) time frame on it's 30 day forecast, which is more closely aligned to GFS's output than ECM's. I feel that it's all a question of timing but that we will see some amazingly rapid pattern changes after mid month, perhaps delayed as far as the last week of February. In fact, even those of us who have studied weather charts for many years (I started in 1959) may be seeing something that we've hardly ever witnessed before. The scale of the forces at play is quite exceptional. Conventional wisdom will not be very helpful here. I see something quite similar (but far from identical) to March 2013 developing but perhaps starting several weeks earlier than that spell. The coldest weather with easterlies or north-easterlies far more likely than (briefer) northerlies will probably come around the turn of the month. I do not see us missing out on it this time whether it starts a few days earlier or later. This is likely to produce some ice days and very low uppers at times - nothing marginal any more and quite exceptional for very late winter. The Canadian PV will be broken up one way of another and that in itself will make for some exciting viewing. I'm expecting 2 to 3 weeks of cold or very cold weather, perhaps longer (far too soon to say whether it'll be dry or snowy but the longer it lasts the greater the snow chances).

Where's all the evidence? There's been plenty around but nothing which can give us absolute certainty - what's new about that? I could post 30 charts and provide one of my long and careful analyses but not this time. Just for once, I wanted to say how I see things developing. Now whatever happens, as others have said, we are entering a period of almost uncharted territory and there will be some charts on offer which may make "eye candy" appear to be a modest term. There may well be a few more wild swings. Most of the extended output is actually more consistent (including the extended EC and many of the ens) but we may need to be patient a little longer to see it moving into the 5 to 10 day time frame.

Next time I post, I'll be back to a much more balanced approah!.  

[blizzard81]

4 minutes ago, Steve Murr said:

18z out to 174 is pretty much identical to the 12z bar slightly different by 6 hours - so almost neglible -

ECM is likely to come on board tomorrow-

That's a brave call. If singularity is correct in his analysis, the outcome will depend on which model has got the correct handle on the mjo. 

[Daniel*]

GFS sticking by its guns TBH I was expecting 18Z to throw a curveball but nope.  

[karlos1983]

2 minutes ago, snowblind said:

That's a bit at odds with the Met office. Snow over the hills Monday/Tuesday. Milder Wednesday. 

Correct. The north might see a noticeable snow event on Tuesday, but those bbc precip charts for the south are laughable. No chance! MetO and pretty much every model disagree. 

[ICE COLD]

Cold air is coming ?

Edited February 10, 2018 by ICE COLD

[Frosty.]

Another great Gfs run unfolding, it's clear the 18z is sticking two fingers up at the Ecm!..hope the Gfs is right! ❄❄❄❄❄❄❄❄

[Met4Cast]

Well, the 18z is sticking two fingers up at the ECM

Very little change, blocking with if anything, stronger Easterlies than what the 12z offered. I can't wait to see what the control run shows!

[blizzard81]

Just now, Daniel Smith said:

Well, the 18z is sticking two fingers up at the ECM

Very little change, blocking with if anything, stronger Easterlies than what the 12z offered. I can't wait to see what the control run shows!

The Control might be similar to the ecm though! I will be shocked if the gfs trumps ecm in this situation. 

[bluearmy]

Looking at the eps clusters, there is a three way split at day 8 and the op could have easily picked the one which evolves like the gfs. I guess that means there is a 3/1 chance that ecm will come on board in he morning!

btw, the extended clusters are interesting if you like your troposphere running in reverse! 

[Met4Cast]

3 minutes ago, blizzard81 said:

The Control might be similar to the ecm though! I will be shocked if the gfs trumps ecm in this situation. 

The thing is, though. Is that this is the type of setup we're expecting the models to be throwing out because of the MJO/SSW etc.. so we can generally, for once have more confidence that a colder, blocked outcome is likely. 

ECM was the first to pick up the Easterly signal, just a couple of days ago it was showing charts similar to what the GFS is showing now, it just seems to have gone on a bit of a wobbler, it's out of kilter with other models earlier in the run. The strong PV over Canada/Greenland on the ECM does not fit with the background signals at all.

GFS wont have called this right, but the ECM is probably far more wrong here. The ECM did this a few days ago too, threw a massive wobbler them came back on board a run or two later.

ECM eventually gets the Easterly in, just had a timeframe beyond the output we can see.

Edited February 10, 2018 by Daniel Smith