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

[Mucka]

I think it is just run to run variation, the 12z control and a few other ensembles weren't that different.

I spoke earlier about this sort of time-frame being the window for any shock turnarounds but the issue is always no undercut so we just get variations in how far N and W heights get before the jet flattens it back out.

If we got a succession of upgrades in this time-frame and more ensemble support it would be worthy of some excitement for sure but we will need a few runs and cross model support before it is worth taking too seriously.

[Dean E]

2 minutes ago, radiohead said:

The jet is just too strong, but the potential is there with a few adjustments.

 

One of the strongest jets of the season as well! GFS going into standard Atlantic default I think!

[bluearmy]

Please don't hang your hats on a pub run!  I suspect this is the furthest end of the envelope currently available for 7/10 days re possible continental cold surface flow into the east. 

[Seasonality]

13 minutes ago, nick sussex said:

As I mentioned on the previous page its that T96 to T120hrs timeframe which is crucial. Because its at that point you have that phasing and then the energy shoots off ne over the high, with just a bit more going se the high would end up further north and west.

When trying to force energy under a block though you do want this type of high orientation running more ne/sw, you want the high facing the enemy in the Atlantic.

 

 

So do you go back on all your winter is over histrionics then? (one run I know but I couldn't help taking the proverbial)

[Cheshire Freeze]

1 minute ago, bluearmy said:

Please don't hang your hats on a pub run!  I suspect this is the furthest end of the envelope currently available for 7/10 days re possible continental cold surface flow into the east. 

It'll have knock on effects going forward though further into FI...you can see the difference across Europe straight off by day 10. It might just be variation within an envelope but everything has a knock on effect further down the line...especially when we're talking about a trop which is supposedly still disconnected from the strat. Every last ounce of amplification needs to be squeezed out- otherwise we end up like the 12z FI.

[A Frayed Knot]

Cold weather probably won't return in mid December. Most of the GEFS ensemble runs show quite a mild air mass aloft and the 2m temperature forecasts suggest it will be quite mild with a temperature inversion unlikely. ??

Think above is right and we are being led down the garden path once and again and AGAIN .

[knocker]

It actually did this very evolution on the 12z run which I pointed out earlier but on this run it has developed the cut off upper low to the SE much more It is very much dependent on the disconnect within the ridge allowing some energy to sneak  south.east

Edited December 9, 2016 by knocker

[blizzard81]

5 minutes ago, bluearmy said:

Please don't hang your hats on a pub run!  I suspect this is the furthest end of the envelope currently available for 7/10 days re possible continental cold surface flow into the east. 

You maybe correct BA but on the other hand and I am sure you will know this, most "successful" scandi highs are only picked up at short range. There is time for upgrades in the next 24 to 48 hours.

[feb1991blizzard]

Just now, blizzard81 said:

You maybe correct BA but on the other hand and I am sure you will know this, most "successful" scandi highs are only picked up at short range. There is time for upgrades in the next 24 to 48 hours.

Disagree with that, theres always some ensembles that have corking Easterlies in from at least 300 out when they verify.

[karlos1983]

2 hours ago, Spah1 said:

There's hope! 

The MJO has taken the short and curly route 

[nick sussex]

Heres a quick checklist of things for newbies to look out for tomorrow. These tell you whether prospects improve for cold, lets start with the T72hrs timeframe.

The trough to the west is crucial, the more south this digs the better,  also the angle ahead of the troughing, keep an eye on that the more south/north the flow ahead the more likely you are to develop a better high near Scandi. You also want that troughing to be as elongated as possible and further west.

Onto the T96hrs, and you'll see the shortwave circled red is the trigger to get the cold air westwards, the further sw towards the Low Countries the better the chance and finally the low circled black you want that further south and tilted more nw/se.

Although the GFS does manage to get some of that cold air westwards if you want to aim high and have a chance of the deepest cold and possible convection off the North Sea then the high needs to be further north.

In this type of set up its those early changes which can make a big difference going forward. Lets see what tomorrow brings and although we've seen this upgrade from the GFS its really knife edge stuff with events within T120hrs being so important going forward.

Edited December 9, 2016 by nick sussex

[Cheshire Freeze]

11 minutes ago, CreweCold said:

It'll have knock on effects going forward though further into FI...you can see the difference across Europe straight off by day 10. It might just be variation within an envelope but everything has a knock on effect further down the line...especially when we're talking about a trop which is supposedly still disconnected from the strat. Every last ounce of amplification needs to be squeezed out- otherwise we end up like the 12z FI.

So, those knock on effects I mentioned...

A much more hopeful end to FI than the abomination that was the 12z (effectively a jet circling tightly around or just N of our latitude)

It's essential now that we eke out as much as we can from that block in the short term.

Edited December 9, 2016 by CreweCold

[Jason M]

The one wildcard is whether the GFS is overplaying the extent of the Atlantic here. IF it is (even slightly) then things could get very cold indeed.

Of course the cruel irony is that we would be looking at a very dry airmass and pressure would be too high for convection. We need a flow from the east with pressure in the 1015 - 1020 range over the UK. For that the center of the high needs to be further north.

GEFS will be interesting this evening.

[Seasonality]

3 minutes ago, feb1991blizzard said:

Disagree with that, theres always some ensembles that have corking Easterlies in from at least 300 out when they verify.

Nonsense statement. All kinds of options can pop up and verify from 300h due to the spread at that range. Not just easterlies.

[Banbury]

Shame it doesn't last long

[stewfox]

2 hours ago, stewfox said:

First 'models drunk' post of the winter .  However  I don't think the models are drunk at present

Trouble is although the GFS,UKMO, ECM etc have all meandered , they have all shown reasonable consistency in the last few days out to la la land (T240)

We want the GFS to get p**** over the next few runs and get us  to say wtf  BOOM BOOM with the usual  'of course it wont verify' .  I would give anything for a 'of course it wont verify'

GFS 18z as heard me, starts with a small B, more runs needed

[Banbury]

Laugh my socks of if its one of the mildest members .......................very doubtful though brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

[feb1991blizzard]

4 minutes ago, nick sussex said:

Heres a quick checklist of things for newbies to look out for tomorrow. These tell you whether prospects improve for cold, lets start with the T72hrs timeframe.

The trough to the west is crucial, the more south this digs the better,  also the angle ahead of the troughing, keep an eye on that the more south/north the flow ahead the more likely you are to develop a better high near Scandi. You also want that troughing to be as elongated as possible and further west.

Onto the T96hrs, and you'll see the shortwave circled red is the trigger to get the cold air westwards, the further sw towards the Low Countries the better the chance and finally the low circled black you want that further south and tilted more nw/se.

Although the GFS does manage to get some of that cold air westwards if you want to aim high and have a chance of the deepest cold and possible convection off the North Sea then the high needs to be further north.

In this type of set up its those early changes which can make a big difference going forward. Lets see what tomorrow brings and although we've seen this upgrade from the GFS its really knife edge stuff with events within T120hrs being so important going forward.

Agree with your theory Nick but the fact that at such a range, the MO, and hardly any ens suggest this that its very very unlikely regarding a big convective Easterly, the Jet is probably too strong even for the battleground but that is slightly more realistic.

[Scandinavian High.]

5 minutes ago, nick sussex said:

Heres a quick checklist of things for newbies to look out for tomorrow. These tell you whether prospects improve for cold, lets start with the T72hrs timeframe.

The trough to the west is crucial, the more south this digs the better,  also the angle ahead of the troughing, keep an eye on that the more south/north the flow ahead the more likely you are to develop a better high near Scandi. You also want that troughing to be as elongated as possible and further west.

Onto the T96hrs, and you'll see the shortwave circled red is the trigger to get the cold air westwards, the further sw towards the Low Countries the better the chance and finally the low circled black you want that further south and tilted more nw/se.

Although the GFS does manage to get some of that cold air westwards if you want to aim high and have a chance of the deepest cold and possible convection off the North Sea then the high needs to be further north.

In this type of set up its those early changes which can make a big difference going forward. Lets see what tomorrow brings and although we've seen this upgrade from the GFS its really knife edge stuff with events within T120hrs being so important going forward.

Thank you nick helps people like me to understand charts a lot better learn more.

[feb1991blizzard]

3 minutes ago, Seasonality said:

Nonsense statement. All kinds of options can pop up and verify from 300h due to the spread at that range. Not just easterlies.

So your saying that a big Easterly has verified when not one Ens member has supported it at 300 hours??

Edited December 9, 2016 by feb1991blizzard

[Banbury]

1 minute ago, feb1991blizzard said:

Agree with your theory Nick but the fact that at such a range, the MO, and hardly any ens suggest this that its very very unlikely regarding a big convective Easterly, the Jet is probably too strong even for the battleground but that is slightly more realistic.

I agree , look West its full of power , anything from the East will be very shortlived IMO

[pipsta]

...

Edited December 9, 2016 by pipsta
Sorry posted to wrong forum!

[bluearmy]

The eps did have a weaker jet in the 10/15 day period than the 00z run   but we're asking for it to be weaker earlier than that. I wouldn't expect that to be likely but we could see a more vertical alignment of the WAA build the ridge a little stronger and perhaps force a more split flow. That's  pretty doubtful which is why it's probably the edge of the envelope but it is feasible.

[fergieweather]

49 minutes ago, Gael_Force said:

Welcome! 

I'm afraid it is only the longer term models we cannot see which have built the idea of a cold early winter. Not one of the online (for all to see) models showed anything but a varying degree of positive for temperatures. The fact the UKMO had such confidence in their own products has allowed eyes to be taken off the ball and ignore the less palatable options from other forecast agencies.

Whoah.....hang about. That can't be allowed to pass unchallenged.

Do you *really* think Prof Adam Scaife - and the Hadley Centre scientists - sit in their monthly Seasonal Team meeting at Exeter and stare singularly and unscientifically at UKMO output and then dismiss everything else out of some sort of 'confirmation bias'?? 

The Contingency Planning 3-month document (which, stress, is a *probabilistic*, not *deterministic* outlook) is based on the consensus reached at those monthly meetings and written-up shortly afterwards. At those forums, the collective output across a number of respected seasonal modelling centres is viewed comparatively with weighting applied; and detailed areas of global forcings/teleconnections discussed. This includes output made available to UKMO from ECMWF, MeteoFrance, NCEP, plus Japan/Korea/S Africa and many others. Indeed you will often see reference made in those documents to where agreement exists between GloSea5 and "other seasonal forecast agencies/models". This isn't some cursory exercise of pulling bits of CFS off the web and comparing to UKMO products: it's a rigorous piece of scientific scrutiny with a duly critical approach applied.

The fact remains that as of mid Nov, excellent agreement on broadscale pattern existed between GloSea, ECMWF Seasonal and MeteoFrance-Climate. Not dissimilar output appeared in other (less highly weighted) models such as CFS.

Note that at NO point did UKMO probabilistic forecasts lean to 'very cold' categorisation: merely a higher than average chance of colder than average. Anxious that certain media types would blow it all beyond proportion to ape 2010-11, Adam blogged in detail on the UKMO website to offer context to the last two 3-monthly outlooks that were issued.

To suggest Adam and his team "took eye off ball" out of some deference to an in-house model firstly ignores the cross-model support available to them at the time. Secondly, it's actually quite insulting for a guy who has published or co-authored so many peer-reviewed papers in the field of seasonal to decadal forecasting; SSW's; etc etc. Whatever has gone pear-shaped so far in Dec, I'd wager Adam could explain unhesitatingly. 

And by the way: with cluster 1 of today's 12z ECMWF heading into building strong +ve GPH anomalies and rising MSLP above Scandinavia with a resultant easterly flow just before Christmas, it's also too early anyway to utterly dismiss what Glosea leaned to originally.

[Seasonality]

8 minutes ago, feb1991blizzard said:

So your saying that a big Easterly has verified when not one Ens member has supported it at 300 hours??

No. I'm clearly not stating that. Stop being silly.

Edited December 9, 2016 by Seasonality