Model Output Discussion Autumn 2024

[tight isobar]

As per we are now creating dynamic cross wiring with Atlantic/ seaboard- waving…on notable scale so we really need to blend modelling from here on in, on the American chucking out systems into the pond- And the ec under/over amplifying dynamics.. we’re truly into the mad season now!! But also as per will watch with baited breath as there are many possible fruitions on the table.. keep watching

[That ECM]

Just me happy with this run then?

[TSNWK]

06z.. could have been a lot worse.. envelop wide enough with those synoptics at day 9 to improve abd of course worsen 

But still in the game with this if we take o6z

[Geordiesnow]

 northwestsnow I think the issue is as we go further into output it does not surprise me too see successful ridging, it always feels like 'jam tomorrow' type of thing. 

Still would not rule out some sort of a upgrade though but I think the general feeling is we will see a mid latitude block rather than a true high latitude block therefore whilst the UK may tap into cold air, it won't be cold enough for snowfall for the most part. 

[Lukesluckybunch]

20 minutes ago, That ECM said:

not over 

3 minutes ago, That ECM said:

Just me happy with this run then?

Greenland looks excellent,need that swing back of the trough now southeast can’t have it going west

Edited November 10, 2024 by Lukesluckybunch
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[TSNWK]

 That ECM nope.  I like it there. Ironically it miggr ge better going forward long term after new term let down

[AO-]

I think there are two problems at the moment between day 7-10. The first is the shortwave deepening too much preventing a true Northerly and the second is the flow of cold air is aimed Southwest rather than South, which is a consequence if the shortwave. Hence the CAA creates cyclogenesis at the Atlantic preventing the block expand North. 

Edit: note also the "DANA" over Spain and its cours away from the mainland. We lose the connection between this system and the through up North

Edited November 10, 2024 by AO-

[Mcconnor8]

 TSNWK

It has a Midlands snow event at day 10 from a slider, but the problem really is just it being pushed back to day 10 before we get anything decent again, seen that far too many times for it then to collapse completely.

Edited November 10, 2024 by Mcconnor8

[That ECM]

 TSNWK sustained or a 3 day northerly? All fi but I’d rather the first option.

Edited November 10, 2024 by That ECM

[sheikhy]

Being led up the garden path comes to mind again in the last couple of days!!!!as good as the gfs 06z looks im just gonna take whatever cold air comes in from the north this early in the season becuase to be fair that is all im expecting once again from this current saga!!!on to the 12zs....!!

[TSNWK]

 That ECM sustained. Cool ground for December goods obs!

[AO-]

In FI the pv still is completely shattered. So as long as this is the case, we only need a connection between the ATR and the Polar hp. It is a delay, but  amplification is still possible (yellow finger)

Edited November 10, 2024 by AO-

[Mcconnor8]

 AO- That would be an insane chart if it did come off, but we know what the GFS in particular is like with FI craziness.

[AO-]

 Mcconnor8

GFS is also king in FI in firing up the Vortex if that is to be the pattern. So game is still on. It will go back and forth, but that is normal. We need to pay attention to the downgrade of the EPS before getting disencouraged. At the moment I'm not really seeing that besides the swinging between the runs. Yesterday's 18 was an upgrade to the 12 which on its turn was a downgrade to the 06

Edited November 10, 2024 by AO-

[Cambrian]

The 0z ECM output is not at all disappointing to my eye, strong similarities too with the 6z GFS just running out. The high moves west at day 4, only to get pushed back east at day 5. It’s actually the Canadian Arctic lobe that’s doing the pushing, but in the process, it’s spending itself.

 

By day 6, the “shortwave” low forms over the Norwegian Sea, and the heights over the UK and Ireland are squeezed out. The low off northwest Spain is important here, as it moves northeast, the upper trough merges with the base of the Siberia-Scandinavian trough at day 7, as heights build north through Baffin. 

 

At this point, the eastern seaboard low deepens, pumping further heights north to the west of Greenland. As often happens, a proper surface low then forms at the base of the trough, in this case just to the north of Ireland here at day 8, steadily moving east through the UK during day 9, to the southern North Sea by day 10. 

    

The amplification up into Greenland is still happening at day 10, positive heights bridging through to the polar high, and the cold air is yet to arrive. But arrive it will by day 11 and onwards. 

The day 5 shortwave becomes the days 8-10 trigger low, and importantly, the northeast Canada lobe is spent. This has been the broad evolution for a few days now. And in any case, how else is the Arctic air going to get far enough south as to be of interest? 

The dynamics look spot on to me. The ECM ensemble mean is very supportive too, a broadening of the low at the base of the trough perhaps an indication that the models are struggling with precisely how elongated southwards the polar trough will be, an idea reinforced by the spread chart. Very confident on the spine of the trough down the Norwegian Sea though. 

  

And have a look at the ECM control for day 12, T850s for day 13. This is the next point, this setup is good for several days of cold weather.

 

But perhaps most of all, let’s go back, take a minute and look at the op, mean and anomaly charts we’re looking at day 10 for 20th November, the lining up of the isobars back to the core PV over Siberia and the liberation of Greenland from low heights.

Sometimes we can wait all winter to see a cross-polar flow to the UK and Ireland, perhaps eventually coming our way in March. This year it looks like we could well get one served up on a plate in late November. 

[Lukesluckybunch]

Gefs cracking mean at 168

[TSNWK]

Great early season sport currently in play.

Gfs 06z dangles the hope of sustainable cold after a initial wobble.

Suspect it's bottom of the pack at best in later stages if not an outlier..

But if gfs prints it I'm posting it

[northwestsnow]

The mean is a hefty upgrade .

[HarvSlugger]

 Lukesluckybunch i woke up to people saying downgrades, thankyou this post makes me feel better

[WYorksWeather]

The 06z means tell an interesting story here.

Decent snow chances for Aberdeen - mean goes down to -5C, and some scope for it to drop further as certainty increases.

Further south though, definitely more likely to be a rain event. A much greater number of mild outliers, and a lot of the cold ones cluster between 0C and -5C, rather than -5C to -10C.

Probably to be expected at this time of year, and with northerlies generally, that there is a significantly better chance the further north you are. All in all, probably not worth getting too excited at this stage, unless you live in a favoured spot in the far north or on high ground. Still subject to change of course as the output continues to show different possibilities.

[AO-]

 WYorksWeather

Ship hasn't sailed at all. At 2m the operational is on the top of the bunch for here. Uppers at 1,5 and 5 km are below average and even remarkably cold with -30 to -35 degrees Celsius. Could lead to snow showers. 

[HarvSlugger]

 WYorksWeather can i get excited at 180m above sea level in Pembrokeshire?

[Frigid]

 TSNWK That would be very cold with slack winds and clear skies. If snowfall were to occur before it, possible minus double digits. Certainly ain't looking mild if that's what people are worried about. The mean is also a pretty big upgrade. 

  

00z:   06z: 

[Dennis]

gfs6z snow idea 20th

[TSNWK]

 Frigid minus 8 over the Hampshire snowfields