Model Output Discussion - Into Winter

[blizzard81]

Cast your minds back to many seasonals pointing towards cold in Jan and Feb from quite a long way out. The means are now showing this consistently. The seasonals can't have been hedging all their bets on a major SSW happening. Enso, EQBO, sst's, teleconnections etc will have factored much more in their predictions. So, maybe we should be less obsessive about the downgrade in the major SSW predictions. 

[bluearmy]

3 minutes ago, blizzard81 said:

Cast your minds back to many seasonals pointing towards cold in Jan and Feb from quite a long way out. The means are now showing this consistently. The seasonals can't have been hedging all their bets on a major SSW happening. Enso, EQBO, sst's, teleconnections etc will have factored much more in their predictions. So, maybe we should be less obsessive about the downgrade in the major SSW predictions. 

Indeed - I don’t see it’s that much of a silver bullet next month.  Let’s see how the deceleration plays out and how much reversing we actually get and at which levels. . Within the next 48 hours that should be pinned down. 

[Catacol]

It is time to take a step back and wait for model chaos to disperse. I have shown twice in the last two days how modelling gets to the 6/7 day mark and then doesn’t have a scooby… and I think until we see what happens post Hogmanay storm (that is certainly coming) the rest is like a basket of odd socks.

I’ll trust the drivers as I try to do all the time because they tend to deliver more often than not - though once again it is worth acknowledging we play a probability game when trying to forecast the future and nothing is ever certain. And those drivers, semi predictable though they are, are also apt to change.

I think many of the big guns out there are waiting to see what happens with the next 2 or 3 rounds of strat modelling. Quiet has descended and the nature of the strat profile is going to have a huge say in how the majority of the rest of winter unfolds. In the near term we are continuing to see a signal for height rises as we move beyond New Year but timing is unclear and the extent to which we get a block rather than a wedge - and how the Atlantic interacts with this is still up in the air. But a zonal profile for January this is not despite the claims of some earlier today.

On the positive side of things trawling for opinion is a useful exercise. Cohen last night has come out and thrown a tentative hat into the ring for a split vortex SSW despite the uncertainty in the modelling. Webb has rather distanced himself for now from the SSW discussion but gone for persistent -NAO through Jan and Feb no matter the outcome of strat developments. And he has been quite bullish on this trajectory for a while. And the third interesting bit of browsing is this dataset. This is the shape of Jan and Feb in years where a displacement SSW occurred when ENSO was an El Niño,

It makes for good viewing and matches the direction of travel currently of EPS anomalies.

A hell of a lot changes in two weeks of weather watching. I have no doubt that, once we get to Thursday 11 Jan we will be looking at a very different picture and my money is on a blocked and cold pattern, either in place or soon to be in place. Enjoy the ride…

[Cold Winter Night]

About that SSW that "disappeared"/"dropped"/"was taken from us,"

Here's EC46 mean zonal wind at 10 hPa from one week ago, December 21:

Slowest ensemble mean: +/- 5 m/s, about January 6.
- Around January 3, all members are below 30m/s, the strongest reversal outliers hit -30 m/s.
- Late January, the ensemble mean returns to about 15 m/s.

Now the latest one, from yesterday:

Slowest ensemble mean: +/- 5 m/s, about January 6. Yes, that's the same values as a week ago.

What has changed is the spread that has reduced (logically at that closer date).
- Around January 4, all members below 15 m/s, the strongest reversal outliers hit -25 m/s.
- Again, late January, the ensemble mean returns to about 15 m/s.

The output from December 20, 22, 23 and 24 is very much along the same lines.
Then how about the impression that "the SSW" is now gone?

Well, that's especially the 26th, the only day EC46 showed a reversal on the ensemble mean.

In other words, EC46 has consistently not showed a mean reversal for more than a week, with one exception. The one off that should be rejected for that reason.
Not much has changed with regards to a potential SSW.

And that's ignoring the fact that a considerable number of members still go on to reverse at some point in January, and also ignoring the fact that an SSW does not equal a cold spell, nor that the absence of a SSW does not equal the impossibility of a cold spell.

The current blocking signal in the extended is a trop led feature, let's watch that, and keep in mind that the stratospheric slowdown can still very much have its effect lower down.

No need for nervous breakdowns at this point.

Edited December 28, 2023 by Cold Winter Night
Typo

[Lukesluckybunch]

A slight shift south with the jet T84 on the ICON!could lead us too something later on..

[TSNWK]

1 minute ago, Lukesluckybunch said:

A slight shift south with the jet T84 on the ICON!could lead us too something later on..

Eager beaver @Lukesluckybunch

[MJB]

7-10 day out , doesn't look much of an Atlantic influence to me , HP settling around or over us, days getting colder as time goes by, increased threat of winter hazards .

10-15 no change

So not all doom and gloom I say adding to the recent SSW posts above 

[Kasim Awan]

An improvement from the ICON weakened Azore heights.

[Lukesluckybunch]

15 minutes ago, TSNWK said:

Eager beaver @Lukesluckybunch

Much better ICON here

[TSNWK]

2 minutes ago, Lukesluckybunch said:

Much better ICON here

Indeed. That early move south of jet! 

[TSNWK]

Exeter holding a steady line.  Let's see if the 12gfs will treat us nicely 

[Battleground Snow]

Some real cold lurking to the north, if a northernly happens a few days further on

[tight isobar]

Away from the usual cold shenanigans! Another about to be named 1- incoming 30/31.. needs an eye this !!@ no pun intended …

[Mike Poole]

7 minutes ago, Battleground Snow said:

Some real cold lurking to the north, if a northernly happens a few days further on

Yes, the push of heights of interest is about a day away at the end of the run, but it looks positioned OK to me.  On to the GFS/GEM…

[MJB]

GFS 96

UKMO 96

Lets see how things progress 

[Polar Maritime]

Come on chaps let's have a nice evening of model watching. Posts will go missing if disruptive or off topic. Please report any posts to the team...

Thanks all

[Allseasons-Si]

We don't want to keep on deleting post's peeps so just think about what you are about to post,and do not respond to off topic post's

keep it friendly,...thank you

Edited December 28, 2023 by Allseasons-Si

[Kasim Awan]

9 minutes ago, MJB said:

GFS 96

UKMO 96

Lets see how things progress 

The jet looks slightly to the south with some moderate height rises to our North. Upper air mass doesn't look particularly cold but with surface cold building inland due to light winds and slow moving fronts there is some snow chances within the 4-8 day time frame I'd have thought.

[That ECM]

Thankful for not having to forecast. Looks tricky.

[MJB]

144 UKMO 

GFS 144

For comparison purposes in the model output thread   

Greenland set up looks quite different. 

Looking at GFS I think 144 is really FI , look at the LP at 168, it wasn't there on the 6z 

Edited December 28, 2023 by MJB

[Polar Maritime]

We can certainly see that jet slowly sinking south on each run..

[Allseasons-Si]

1 minute ago, Polar Maritime said:

We can certainly see that jet slowly sinking south on each run..

Yep,thanks to a better amplified ridge in the Atlantic

[Battleground Snow]

I imagine the deep cold will be close when the 144 ukmo chart updates, it's almost an easterly flow 

 

Edited December 28, 2023 by Battleground Snow

[Lukesluckybunch]

Make or break time on the gfs at 192 that ridge..is either gonna build into somthing..or we are left nowhere..

[mulzy]

Just now, Battleground Snow said:

I imagine the deep cold will be close when the 144 ukmo chart updates, it's almost an easterly flow 

Indeed.  UKMO day 6 close to a good chart.  Close but no cigar I reckon.