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

[Seasonality]

1 minute ago, BLAST FROM THE PAST said:

GFS 06z following ECM and am not surprised.  Unsettled Xmas the fav in my view and hopefully a fair bit of pM air too.  This period went Pete Tong due to the very stubborn HP so onto next watch period for me.  

 

BFTP

Is it not calling it a bit too early based on one run?

[nick sussex]

The GFS 06hrs run still has that shortwave near Finland dropping south but theres less cut back in the jet because of more energy to the north. In these circumstances the only thing to watch is that shortwave, thats the bellwether for your chances of getting some of that cold from the east.

This is why Singularity's post re AAM is especially important this morning, we need more amplification upstream to stop the PV from just piling east to the north, you need something to hold that back and keep it further west. You'll note on the GFS 00hrs that upstream over the central USA the jet gained more amplitude, its flatter on the 06hrs run.

[Summer Sun]

GFS backing down to ECM temps are a good 8c to 10c higher on the 23rd when comparing the 00z and 06z

Edited December 13, 2016 by Summer Sun

[bluearmy]

29 minutes ago, Paul_1978 said:

Why can't we have it where we get "zonality", but the block holds = "zonality" sliding under the block. Then we get the best of both worlds  (but with a potentially snowy result).

That evolution is looking like the only viable route to the white stuff paul. and it looks decidedly unlikely pre the end of the year but late week 2 is still up for grabs imo re the strengthened atlantic trough and the block fighting back 

[Seasonality]

As the ensembles come out there doesn't appear to be overwhelming support for the 06z operational. 

[Man With Beard]

GEFS 06Z ensembles have moved half-way towards ECM ens by T192 (in comparison to 00Z ens).

By T240, 4 members with blocks to the east and low heights underneath; there were 10 members on the 00Z run that did this. Still not the preferred route.

Edited December 13, 2016 by Man With Beard

[Summer Sun]

The Op shows a very mild Christmas day across the board...

The mean suggests otherwise

More runs needed

[TSNWK]

8 minutes ago, Man With Beard said:

GEFS 06Z ensembles have moved half-way towards ECM ens by T192 (in comparison to 00Z ens).

By T240, 4 members with blocks to the east and low heights underneath; there were 10 members on the 00Z run that did this. Still not the preferred route.

Can I have the pink  one for Christmas please. Sub zero Max's from 22nd to 28th.. trendsetter:)

[Ali1977]

3 minutes ago, Summer Sun said:

The Op shows a very mild Christmas day across the board...

The mean suggests otherwise

More runs needed

Xmas day looks about coldest there, we aren't talking snow with those 850s, but if we can get some slack air from the SE a nice frost would go down well in here i'm sure.

[warrenb]

4 minutes ago, Summer Sun said:

The Op shows a very mild Christmas day across the board...

The mean suggests otherwise

More runs needed

I wish people would post correct charts, above is a t2 chart posted with 850 temp chart. Very misleading, as we alll know. If posting a t2 chart at least post the t2 Ens chart as well.

 

Edited December 13, 2016 by warrenb

[Summer Sun]

2 minutes ago, warrenb said:

I wish people would post correct charts, above is a t2 chart posted with 850 temp chart. Very misleading, as we alll know. If posting a t2 chart at least post the t2 Ens chart as well.

 

 

Hi, I can never find those on meteociel I can never navigate my way around my French isn't very good

[warrenb]

Just now, Summer Sun said:

Hi, I can never find those on meteociel I can never navigate my way around my French isn't very good

When you get to the chart you posted, look at the title information at the bottom and that is where the links are for the other ENS chart types.

[Summer Sun]

1 minute ago, warrenb said:

When you get to the chart you posted, look at the title information at the bottom and that is where the links are for the other ENS chart types.

Thank's I've found it now

[titchjuicy]

9 minutes ago, warrenb said:

I wish people would post correct charts, above is a t2 chart posted with 850 temp chart. Very misleading, as we alll know. If posting a t2 chart at least post the t2 Ens chart as well.

 

It tells the same story though no?  The 2m chart and 850 chart both show cold (ish) on christmas day. Or am i reading them wrong?

[warrenb]

Just now, titchjuicy said:

It tells the same story though no?  The 2m chart and 850 chart both show cold (ish) on christmas day. Or am i reading them wrong?

You are correct on this occasion, but when dealing with High pressure, 850's are not a good guide for ground temperatures.

[BLAST FROM THE PAST]

1 hour ago, Seasonality said:

Is it not calling it a bit too early based on one run?

Maybe S but knowing how past results have gone I believe ECM way forward-ish will be the path taken

 

BFTP

[titchjuicy]

9 minutes ago, warrenb said:

You are correct on this occasion, but when dealing with High pressure, 850's are not a good guide for ground temperatures.

Understood, cheers.

[Catacol]

Holding pattern at the moment. Pattern of convection certainly suggests to me MJO phase 6/7/8 and consequently a signal for increased amplification in our part of the world, but we could do with a pepping up of this forcing before too long.

Removal of aleutian high and replacement with aleutian low once again not a bad thing to see as it may help promote wave 1 forcing towards Xmas week with consequent vortex impacts later on.

 

 

Where our European super high ends up is going to be very interesting. I would suggest now that GP's prediction of a movement NW is unlikely - but the drift NE is certainly signalled on all charts. The strength of this high is visible on the Berlin charts right up to 50hpa and it is going to be a pig to shift. If it drifts more East then it will help promote wave 2 forcing down the line, but once again we would be in a position of having to wait for any juicy charts from vortex forcing.

Can we begin to take a stab at the outlook beyond Xmas? Frankly - still beyond my skill at the moment. If the Euro high flattens due to insufficient amplification as a result of a modest MJO circle-of-death progression then a return of atlantic weather for a period looks likely, but I wouldnt want to be certain that the high will flatten yet. Modelling of the MJO and GWO has been poor of late. And even if it does flatten we look still to be in a period where Nino based signals could reamplify the pattern quickly afterwards. Or equally vortex forcing via propagation of zonal wind speeds in the troposphere could take over more substantially and outweigh a modest MJO signal leading to a more zonal January outlook.

It really is a tough call.

 

Edited December 13, 2016 by Catacol

[Seasonality]

30 minutes ago, Catacol said:

It really is a tough call.

Thanks Catacol, I really value your posts. Brilliant stuff.

Edited December 13, 2016 by Polar Maritime
To snip long quote.

[Gael_Force]

17 minutes ago, Catacol said:

Holding pattern at the moment. The only development to my eye this morning is the development of a super typhoon off the coast of Vietnam in an otherwise fairly benign pacific.

You are a bit out of date there, Nepartak was a typhoon in July of this year.

[Catacol]

28 minutes ago, Gael_Force said:

You are a bit out of date there, Nepartak was a typhoon in July of this year.

Yikes! - quite right. That's what happens when you start to use a new site and dont check dates! Original post amended... Thanks.

[Banbury]

1 hour ago, Summer Sun said:

The Op shows a very mild Christmas day across the board...

The mean suggests otherwise

More runs needed

Miles above the mean though, doubtful it will be those temps

[knocker]

1 hour ago, Catacol said:

Where our European super high ends up is going to be very interesting. I would suggest now that GP's prediction of a movement NW is unlikely - but the drift NE is certainly signalled on all charts. The strength of this high is visible on the Berlin charts right up to 50hpa and it is going to be a pig to shift. If it drifts more East then it will help promote wave 2 forcing down the line, but once again we would be in a position of having to wait for any juicy charts from vortex forcing.

 

 

True but weakening and moving east as the trough moves east also. Just taking 100mb

 

 

Edited December 13, 2016 by knocker

[Catacol]

16 minutes ago, knocker said:

True but weakening and moving east as the trough moves east also. Just taking 100mb

 

 

Hi Knocker - the interesting ECM parallel at 240 has a very peculiar shape to the 100 profile

and even up to 50 the signal at 10 days for a ridge in E Europe / S Scandy is present.

Weakening - yes. But once again I wonder how much of this is a reflection of MJO forecasts and a GWO oscillation that is confounding the models. For now modelled to be a slow sinker...

At the moment the trend has been to drift away from a cold scenario... a process we have seen happen countless times over the years. But unless we get charts like last year (when I hardly posted at all it was so obvious we were unlikely to get any cold) I'll keep putting out the cold options. At present it is still possible to see a cold evolution via a combination of teleconnections, though the GWO is getting perilously close to a negative state, and the MJO is slow getting going. I posted earlier that we are in a holding pattern at the moment... but from a Snowbs perspective we need something to change to give a kick to the pattern.

I daresay Sidney will be keeping his brush knotted for Nina to win out and the pacific pattern to stay quiet!

 

[Tamara]

Good post from Catacol once more

Thought for the day. As a rider to yesterdays thoughts

The I/O tropical forcing quagmire of frustration may yet play in our favour. Its a bit of a game of poker with some risk, set against a rapidly strengthening upper vortex, but for purposes of this post, I am going to deliberately look at the potential ace cards.

The timing of the next eastward moving amplitude MJO wave gets more and more interesting the closer and  closer we get to the end of the year - and more especially January. With expectations of the weak Nina/Nada (call it what you will) to fade out completely turning into the New Year then one signal of this could well be a decent amplitude MJO progression from the Western Pacific - essentially increasing westerly wind anomalies across the Pacific as a signal that the ENSO base state is to adjust further away from Nina back into neutral territory

Following the logic of this ocean base state evolution, the chances are that such a higher amplitude tropical signal propagating eastwards, would happen sooner rather than later. A good thing in terms of arresting vortex control (explanation to follow down the page)

On this basis, the disconnect between the ocean and the atmosphere will be logically diminished - with a re-launched high atmospheric angular momentum state set against a neutral ocean base state. With further added westerlies to the global circulation ( based on the default Nina disconnect which has prevailed through the autumn), it would be hard to put a case for the opposing low angular momentum disconnect supposition I wrote about (as a devils advocate) on Sunday. (The scenario that points to assisting flat mild and zonal and armoury to the vortex)

So what, you may ask, does all this loveliness thinking outside/dancing around the box/handbag mean in terms of the models and prospects for cold weather pattern favourites?

Well, the first indications, as posted a week or two back, would be a jump in +ve frictional torque, as the tropical signal gathers traction in the Western Pacific. Frictional torque is a lead to direction of mountain torque. A +ve mountain torque is a cue for stratospheric warming given suitable lead times.  This has to jive with the +QBO/other wildcards, so not necessarily a picnic in terms of any SSW.  However, some sizeable tropospheric amplification is conceivable from this domino topple and at the least it could create an interesting battle between the troposphere and the stratosphere during January.

Especially with the troposphere conducive to the repeated blocking signal as still perused through latest GloSea5 and ECM long range guidance

The key though to this enchantingly virtuous dream - is what might happen when a fast spinning top suddenly has a stick put into it? In that sense, the stronger the (apparent) vortex, the stronger the potential fall and tropospheric spectacular fall-out.

At the very least, the vortex hate psyche expressed here is good to take forward in spirit while we wait and watch - its a ramped up scenario for sure, but then I did say I would look at some ace cards

@Changing Skies  PM on its way soon to you

Edited December 13, 2016 by Tamara