Model output discussion - 5th December 2016 - Into Winter we go

[mcweather]

26 minutes ago, Steve Murr said:

 

I will try to do a longer post in a while however it would appear the EC seasonal model is broken. That would be along side the Glosea. 

This isnt a dig @ Matt or Ian- however how can we maintain northern blocking that we dont aready have?

How can we have a distinct -NAO for December when its been neutral since the start- the key word here being 'distinct'- suggestive of something lower than -1.5 on the scale-

well sadly theres nothing within the next 8 days that suggests that so as a minimum we will be halfway through December with no trace of any blocking that had been forecast all the from the outset of November-

Also, another reason why I must assume that is the inference that the trop vortex is running disconnected to the strat one-

It looks pretty connected to me, At the end of Nov the 10HPA 60N zonal mean forecast a steady rise from the outset through to the middle of the month & beyond & thevtrop vortex has followed- The AO which is the best measure has had a smooth increase from negative values to a current mean that is in touching distance of +2 in a couple of days, thats a hefty rise of 3 sigma in 2 weeks- it mirrors the strat perfect-

The dates are mirrored

 

Excluding the GFS ensembles which will always throw out a few peachy runs theres been nothing to indicate that there would be anything other that a 1/2 day transitory cold shots all the way to xmas...'

I will look at the zonal mean forecasts today but I fear it makes poor viewing...

S

Hi Steve

Ian F suggested this afternoon that what Matt actually mean't was Jan and Feb as in his words the EC seasonal December update doesn't actually cover December

so that actually gives us three weeks and a few days by which time the output could look very different indeed.

[karlos1983]

2 minutes ago, CreweCold said:

Either way, disparity cannot carry on indefinitely. I'm inclined to actually side with the GEFS on this one in the long term...Never thought I'd say that! I think the EC ENS will sharpen up in the next week for towards the festive week

makes sense to me, they have been more consistent to my eye Crewe. In terms of the pattern, obviously with varying theme(s)

[karlos1983]

1 minute ago, mcweather said:

Hi Steve

Ian F suggested this afternoon that what Matt actually mean't was Jan and Feb as in his words the EC seasonal December update doesn't actually cover December

so that actually gives us three weeks and a few days by which time the output could look very different indeed.

there was a slight Ian F back track though a bit further on, saying December inclusive, and i quote "apols Matt"

Edited December 8, 2016 by karlos1983

[blizzard81]

14 minutes ago, joggs said:

I've said it for years on here,a bitter states most of the time gives us the opposite.

Alot of our best (coldie) spells,82,87,91 have had east America mild.I think records were broken around Washington in Feb 91.Checkout Ian mcCaskill on YouTube. Then drool over what happened in Britain lol.

The brutal cold is over the central and western states this time though and although it is far from mild over on the eastern side, it is not the brutal cold they have experienced over the last few winters.

[Cheshire Freeze]

 

Just now, karlos1983 said:

makes sense to me, they have been more consistent to my eye Crewe. In terms of the pattern, obviously with varying theme(s)

Can't say I've been impressed with any ECM product over the last month or so, with this whole fiasco. I certainly wouldn't want to be forking out for its services.

[bluearmy]

Just now, karlos1983 said:

makes sense to me, they have been more consistent to my eye Crewe. In terms of the pattern, obviously with varying theme(s)

The ec mean/anomalies are also fairly consistent Karlos. Strengthing Atlantic low anomoly and persistent sceuro high one. W Europe slowly losing any anomoly 

from memory, the movement in the Siberian segment was shown on the GEFS 

[mcweather]

Just now, karlos1983 said:

there was a slight Ian F back track though a bit further on, saying December inclusive.

Thanks Karlos I stand corrected, although I stand by the fact that come later in December the output could look very different indeed

[shaky]

1 minute ago, bluearmy said:

The ec mean/anomalies are also fairly consistent Karlos. Strengthing Atlantic low anomoly and persistent sceuro high one. W Europe slowly losing any anomoly 

from memory, the movement in the Siberian segment was shown on the GEFS 

Is this a good thing or a bad thing for cold prospects/snow for uk

[karlos1983]

1 minute ago, bluearmy said:

The ec mean/anomalies are also fairly consistent Karlos. Strengthing Atlantic low anomoly and persistent sceuro high one. W Europe slowly losing any anomoly 

from memory, the movement in the Siberian segment was shown on the GEFS 

Fair enough, but in terms of the Op, which admittedly probably isn't the best comparison, the GFS always seems to get some form of heights in or around the UK. But i dont have any graphical evidence of this, just memory from watching 4 runs a day for what seems like forever now. 

[Man With Beard]

Steve M - I wish I wasn't on your page but I can't help but be...

But I am getting some entertainment in following the GFS parallel in FI. It continually throws out stormy scenarios - the latest isn't the most severe it's produced, but at least you could get a white christmas if you stand close enough to the sea to get covered in sea foam:

Hard to take seriously though when yesterday and the day before it was retrogressing heights back to Greenland

 

[bluearmy]

3 minutes ago, shaky said:

Is this a good thing or a bad thing for cold prospects/snow for uk

I think it allows for HLB to establish to our north/northeast if the aleutian ridge permits any movement between the vortex centres to exchange on the side of the NH. Of course, an exaggerated aleutian ridge could well force a polar split through to our north. Given that this e Siberian segment establishment is quite a new idea, suspect we need to allow a few runs to see if it sustains. 

[karlos1983]

I do worry about the extreme cold that the NE US and Canada are going to be experiencing next week, never good if a weak jet is what you're after.

[Singularity]

4 minutes ago, bluearmy said:

The ec mean/anomalies are also fairly consistent Karlos. Strengthing Atlantic low anomoly and persistent sceuro high one. W Europe slowly losing any anomoly 

from memory, the movement in the Siberian segment was shown on the GEFS 

This combination will bring about complex small-scale interactions that determine whether we see undercuts or overpowers... with the drop in resolution by the extended range this probably won't be resolved very well. Indeed the indicated pattern is a 'perfect nightmare' for NWP models in general.

Of course, if GEFS are closer to the mark with respect to Pacific activity becoming significantly dominant within just over a week as opposed to more than a fortnight away going by the EC ens. (Huge discrepancy!), that should change the story substantially with respect to that Sceuro High anomaly (tendency to either retrogress to the northwest of us - most likely via the UK - or rebuild there after flattening).

I sure hope the EC too-slow MJO bias for the Pacific is responsible for the disagreement with GEFS as opposed to GEFS being far too progressive. Notable that they've sped up the progression a lot over the past couple of days - which could be the model assimilating the changes that GP mentioned?

[knocker]

Decently the anomalies have been in pretty god agreement so tonight's are of some interest given today's det runs

And a look at the 6-10s goes a fair way to explaining the different evolution's of the latter. The EPS has the upstream pattern vis the Aleutian high pressure and the Canadian vortex lobe a tad further east than the GEFS which has a similar knock on effect downstream making the Atlantic upper trough more progressive and pushing the Azores HP further east to the southern Baltic. This obviously will effect amplification phases but the also the perturbations created by the upper trough which with the EPS signalling a westerly upper flow are going to take the direct route to the UK. The GEFS with more amplification and the upper flow inclined more south westerly and the jet tracking SE will track any systems more to the NW of the UK. NOAA is leaning towards the GEFS solution but obviously this needs to be sorted before confidence, even within the ten day time frame, is restored.

Given the differences mentioned above it's rather pointless looking to deeply into the 10-15 time frame but just out of interest.

What one can say is that NOAA and the GEFS are still on the same page with less amplification, a weakening Atlantic trough and the Azores nestling quite nicely adjacent to the UK. The EPS is without question the odd one out with trough to the NW of the UK and semblance of ridging away east.

Sidney is in a quandary but still expecting north westerly zephyrs for Xmas Day

[Cheshire Freeze]

People were bemoaning the 'negativity' by me in mid November when I was saying such things as the following-

I'm convinced that episode was the 'watershed' moment for this December.

[booferking]

My question is how long can this Uncertainty go on for surely we are getting near the breaking point, what sort of time frame should this be sorted 1-3 days by the weekend??  After all the clock is ticking today is the 8/12.

 

[SMU]

18 minutes ago, mcweather said:

Hi Steve

Ian F suggested this afternoon that what Matt actually mean't was Jan and Feb as in his words the EC seasonal December update doesn't actually cover December

so that actually gives us three weeks and a few days by which time the output could look very different indeed.

No - he recorrected it was Dec/Jan

so yes the tweet wording could mean continues to sigal - however there will indeed need to be a big turnaround post H1 of the month- not just of the current modelling - but as the strat vortex cranks up to positive territory so the alleged troposheric disconnect would have to be even more apparent-

Its not 'impossible' just unlikely- now that I have the Merra data which would probably mirror the ERA data I will look over the next year to see what the base state numbers are - IE 30M/S zonal mean should look like 'x' on the 500'S - & so on- There will be common trends- especially the troposheric responses to the 20 SSWs there have been-

Anyway, I think it was highlighted earlier that way back at the start of Nov the EC & Glosea were highlighting Northern Blocking for Dec, this started out week 1, then went to week 1+2 ( there was a clear post about a T2M median temps for the 9th being well below ave ) it then went to week 2 + 3 & recently its been moved to week 4 - then Jan then a bimodal blend-

At some point we have to call time & say the model got it wrong, the only redemption would be *if* we did manage to get a long period of negative NAO ( not neutral ) late Dec into Jan -you could say the phasing was just out-

For now there is no clear trend- which means that what you have is likely to continue- So westerly interspursed with southerly ( poss SE ) - nothing on the horizon until at least day 8 poss even past 10-12 -

Lets hope we get lucky with a bit of amplification to the west to get some polar air in our vicinty like some of the GFS runs yesterday & by the same token lets hope those rancid parallel runs dont land with the mega vortex otherwise it will be goodbye december for any cold...

S

[Cheshire Freeze]

2 minutes ago, Steve Murr said:

 

Lets hope we get lucky with a bit of amplification to the west to get some polar air in our vicinty like some of the GFS runs yesterday & by the same token lets hope those rancid parallel runs dont land with the mega vortex otherwise it will be goodbye december for any cold...

S

Good post Steve,

however, I quite like the look of some of those Parallel runs from the GFS. Caught one earlier with desperately low thickness and uppers around -5/-6. Good enough for snow here in a NW'ly flow and definitely ripe for some active cold fronts etc. Infinitely better than this boring, static weather we're faced with at present!

[bobbydog]

7 minutes ago, CreweCold said:

People were bemoaning the 'negativity' by me in mid November when I was saying such things as the following-

I'm convinced that episode was the 'watershed' moment for this December.

So basically, you're saying that you put a jinx on it and ruined the whole of winter.

[Iceberg]

Re uncertainty. I am not sure it's chaos related uncertainty but more a case of speed and fluidity. 

The atmospheric blocks tend to hang around awhile. However this December so far and at least as far as the models go, we see a very fast paced hemispheric set up. 

In other words we are not rolling the dice every few weeks, but rather every few days. 

Rather than ruling anything in we just aren't ruling anything out.  

Pv lobes are moving at speed. For the 10-15 d time. One day we get a fast paced trough movement al la p gfs, the next we have the high moving in as shown in the gfs p that has just come out. Ens will be pretty useless in this set up. 

Edited December 8, 2016 by Iceberg

[Cheshire Freeze]

Just now, bobbydog said:

So basically, you're saying that you put a jinx on it and ruined the whole of winter.

Ooops Sorry! 

No, more the point about the WAA at the time. 'I don't think you quite understand the effects going forward of this' i.e WAA and Greenland high fail. It's why I reacted so glumly to the downgrade of that general synoptic as it was obvious that it would have had a significant weakening effect on the vortex going forward had it happened. However, people seemed to refuse to acknowledge the importance of that first very important step en route to a cold first month of winter.

[SMU]

12 minutes ago, CreweCold said:

Good post Steve,

however, I quite like the look of some of those Parallel runs from the GFS. Caught one earlier with desperately low thickness and uppers around -5/-6. Good enough for snow here in a NW'ly flow and definitely ripe for some active cold fronts etc. Infinitely better than this boring, static weather we're faced with at present!

Yeah good for hills of NW, especially NI always does well-

I was just scanning todays zonal mean update which is now up to 15 members above ave in the last timeframe-

The worst peice of news & something that really should resonate is at the tail end ( admittedly open to corrections ) the zonal wind ( day 16 xmas eve ) the mean has hit 45 M/S - thats only 5M/S behind 2015

On the face of it the model with the stormy outlook - IE GFS(P) would be the form horse ... 

[Singularity]

In an ideal world...

Quick doodle on the GFS 12z at 30 hPa which shows very nicely the classical response to MJO 6-7-8 type forcing.

The + symbols indicate where heights would increase (with trop. following suit), and - where they'd decrease (again, trop. following suit).

The 10 hPa stratospheric vortex isn't going to propagate down in a hurry with that sort of thing going on. Seeing an increase in zonal winds at 30 hPa and assuming that it's propagating down is too simplistic; the vortex stretches out across the pole ahead of the (probable) split, so the zonal winds increase despite the vortex actually undergoing increasingly extreme distortion.

Edit: I must of course stress that the pace of events is open to variation; anything up to 3 days quicker or a week slower seems viable to me.

Edited December 8, 2016 by Singularity
The caveat!

[Cheshire Freeze]

1 minute ago, Steve Murr said:

Yeah good for hills of NW, especially NI always does well-

I was just scanning todays zonal mean update which is now up to 15 members above ave in the last timeframe-

The worst peice of news & something that really should resonate is at the tail end ( admittedly open to corrections ) the zonal wind ( day 16 xmas eve ) the mean has hit 45 M/S - thats only 5M/S behind 2015

On the face of it the model with the stormy outlook - IE GFS(P) would be the form horse ... 

In all honesty any synoptic situation which doesn't involve HP sat just to our S or SE has to be a winner at this moment in time, given what we're seeing unfold at present. As I say, even in that scenario of storminess we stand the chance of enough PM air getting into the mix to at least offer something of interest. The pattern we're enduring at present, in my opinion, is just about the worst we can see in winter i.e HP limpeted in an unfavourable position bringing days and days of nothing of note.

[feb1991blizzard]

Just now, Singularity said:

In an ideal world...

Quick doodle on the GFS 12z at 30 hPa which shows very nicely the classical response to MJO 6-7-8 type forcing.

The + symbols indicate where heights would increase (with trop. following suit), and - where they'd decrease (again, trop. following suit).

The 10 hPa stratospheric vortex isn't going to propagate down in a hurry with that sort of thing going on. Seeing an increase in zonal winds at 30 hPa and assuming that it's propagating down is too simplistic; the vortex stretches out across the pole ahead of the (probable) split, so the zonal winds increase despite the vortex actually undergoing increasingly extreme distortion.

You've just illustrated the best pattern you can get IMO, a wave 2 split from pacific through to atlantic straight through Greenland, IF that type of pattern downwells, you've got a decent chance of at least a 2 week bitter cold spell as there's only one place the high will topple to after GL and that's Scandinavia.