Model Output Discussion - 05/01/2016 18z onwards

[chionomaniac]

What the 18Z GFS does illustrate is that after day 5 with such a preponderance of cold around the UK, and, that any crossing trough could potentially deliver a 'red' snow event should the position, angle and timing be favourable. That should keep this thread busy and the mets on their toes during the period should the modeling stay similar! 

[Liam J]

A right dogs dinner!! GFS lost the plot with utter mayhem, I wouldn't take anything past day 5/6 too seriously atm never mind day 10, sure it will look very different again on the 00z... 

[TomDav]

GFS flattens out the pattern and sinks the high into Europe... just one solution:

[stodge]

Evening all

Back from the US and hard to believe after the torpor on here before Christmas just how active it's become.

Next week looks set for something colder then we've had especially in the south though snow is, as always, in the nowcast.

The restoration of the PV has been a constant feature of GFS FI for a week or more - now, is this a default reaction or is this the likely outcome ? Last winter, I recall Tamara and others saying powerful PVs couldn't be knocked down in one go and might need two or three attempts before they are weakened enough to allow blocking. I suspect we are seeing Round 1 upcoming but the PV will rebuild and possibly we will need to endure 10 days or so of Atlantic zonality before the atmosphere initiates Round 2 (say toward the end of the month).

That co-relates with many LRFs suggesting the colder end of the winter would be February or even March so while it may disappoint many on here to see the cold curtailed after a week or so, the medium to longer term possibility of a colder February remains very much alive.

[rory o gorman]

1 minute ago, SN0WM4N said:

It's almost like you know 

 

Because the GFS low res will always revert back to zonal when the pattern is as erratic as shown. Expect a wide scatter on the suite later with the lack of upper air sampling  this run is better off binned,  there is obviously feedback within the algorithm regarding hemisphere pattern change.

[Cheese Rice]

6 minutes ago, chionomaniac said:

What the 18Z GFS does illustrate is that after day 5 with such a preponderance of cold around the UK, and, that any crossing trough could potentially deliver a 'red' snow event should the position, angle and timing be favourable. That should keep this thread busy and the mets on their toes during the period should the modeling stay similar! 

Yup! Though the GFS snowfall accumulation charts suggest a North south divide developing. I'd be surprised going by the GFS if there is low level snowfall accumulation in the south. A poor outlook for 50% of the country. Hopefully an improvement in the output tommorow.

 

[Bullseye]

10 minutes ago, chionomaniac said:

What the 18Z GFS does illustrate is that after day 5 with such a preponderance of cold around the UK, and, that any crossing trough could potentially deliver a 'red' snow event should the position, angle and timing be favourable. That should keep this thread busy and the mets on their toes during the period should the modeling stay similar! 

Further down line, do you still think we will see heights rise in Greenland maybe becoming more suitable for UK or should we be looking to Scandinavia/Russia? Thanks.

Edited January 8, 2016 by Bullseye

[TomDav]

7 minutes ago, Greenland1080 said:

Tom when can we get hold of those charts

Soon!

[Snowman.]

4 minutes ago, rory o gorman said:

Because the GFS low res will always revert back to zonal when the pattern is as erratic as shown. Expect a wide scatter on the suite later with the lack of upper air sampling  this run is better off binned,  there is obviously feedback within the algorithm regarding hemisphere pattern change.

Correct, I am a firm believer in just letting the run end at T240.

[chionomaniac]

Just now, Cheese Rice said:

Yup! Though the GFS snowfall accumulation charts suggest a North south divide developing. I'd be surprised going by the GFS if there is low level snowfall accumulation in the south. A poor outlook for 50% of the country. Hopefully an improvement in the output tommorow.

 

The cold/ mild line is certainly not set though. It may be too far north of the country or a lot further south. That is difficult to ascertain. So more uncertain than poor. 

[Mucka]

ECM London ensembles

Better than 00z off memory.

[Snow shut work]

13 minutes ago, SN0WM4N said:

It's almost like you know 

 

 

Also the PV looks real angry after being dominated.

Can't post charts on my phone, that's 13 days away!!!!!!! No wonder people get lost in transit.

 

[Backtrack]

Indeed the 18Z is an improvement, from a cold viewers perspective; but last night's 18Z was a disaster of a run, and most discounted it, with the reasoning that 'it's just the pub run'. Now I do love cold, and whilst I don't think it should be discounted, I think extreme caution should be taken when approaching the GFS currently, with its extremely volatile modelling. It's flipping & flopping every run. It could go either way, but I would like to see absolute cross-model agreement before getting my hopes up. The NH profile and teleconnections are looking much better, but this is the UK, and if something can go wrong, it will go wrong. 

[Snowman.]

3 minutes ago, Snow shut work said:

Can't post charts on my phone, that's 13 days away!!!!!!! No wonder people get lost in transit.

 

It's more of a dig at the GFS, during these complicated situations in the far reaches of FI the GFS likes to revert to default bringing in the atlantic and the westerlies because it's what it knows best.

Edited January 8, 2016 by SN0WM4N

[chionomaniac]

4 minutes ago, Bullseye said:

Further down line, do you still think we will see heights rise in Greenland maybe becoming more suitable for UK or should we be looking to Scandinavia/Russia? Thanks.

Without going that far - weaker blocks are far more difficult to model..... but EPS are suggesting blocking over the UK at the end of the run and this can often lead to Scandi heights. So back to Scandi after the trough there modeled dissipates.

[cyclonic happiness]

wow! I've not seen anything from the GFS ever as messy and changeable as the past 4 days output.

How the heck can we even begin to forecast the weather at the end of next week when there are literally 5 or 6 shortwaves playing havoc with anything over 96 hours?

Even looking at the northern hemisphere charts for today, it's such an utter mess, this must be the worst model output period I've seen in 9 years on this forum!

[Nick F]

3 minutes ago, Mucka said:

ECM London ensembles

Better than 00z off memory.

And 12z GFS (NCEP) clearly on the warm side of that spread from the 18th ....

[radiohead]

Just now, SN0WM4N said:

It's more of a dig at the GFS, during these complicated situations it in the far reaches of FI it reverts to default bringing in the atlantic and the westerlies because it's what it knows best.

NWP doesn't have default settings like that. It splits the atmosphere into a grid and calculates what will happen to the atmosphere within each of those squares individually, taking the boundary information from the squares surrounding it each time.

Poor performance during complicated situations is just a factor of the situations being complicated. Like this one!

[Cheese Rice]

9 minutes ago, chionomaniac said:

The cold/ mild line is certainly not set though. It may be too far north of the country or a lot further south. That is difficult to ascertain. So more uncertain than poor. 

Of course but the cold air doesn't look to get particularly entrenched in the south so an emphasis on marginal/wet snow if we see a favourable angle of attack. I think if we can get the cold air to really establish itself in the south then it's all to play for, but typically the south struggles in this regard unless it's cold air sourced from the east. 

[Southender]

19 minutes ago, Mucka said:

ECM London ensembles

Better than 00z off memory.

Very pleased with those. GFS clearly on one from the 18th and in the top half dozen milder options. Below 5c for 10 consecutive days in london is not to be sniffed at. Should it verify of course...

Edited January 8, 2016 by Shrimper

[Daniel*]

Fax charts

Day 4 -

Day 5 -

Battery about to die, looks good to me.

IGNORE - not the updated UKMO Fax for tonight 

Edited January 9, 2016 by Earnest Easterly*

[Deep Snow please]

To everyone saying it's only the GFS running towards mild - have a look at the ECMWF + 192 and + 216

[feb1991blizzard]

Just now, Deep Snow please said:

To everyone saying it's only the GFS running towards mild - have a look at the ECMWF + 192 and + 216

But its still meridional and not westerly, you could easily see a return to cold from there but probably from the East as opposed to the North.

[Mucka]

3 minutes ago, Deep Snow please said:

To everyone saying it's only the GFS running towards mild - have a look at the ECMWF + 192 and + 216

Those charts would be cold at the surface.

 

GFS 18z 192 mean better than 12z

Edited January 8, 2016 by Mucka

[stodge]

1 minute ago, Deep Snow please said:

To everyone saying it's only the GFS running towards mild - have a look at the ECMWF + 192 and + 216

I'm not sure how "mild" these would be - going by 850s is a rookie mistake when considering winter anticyclonic features. Under clear skies, there would be sharp night frosts and the eventual re-location of the HP to Scandinavia at T+240 (not sure why you didn't post that chart as well) offers a tantalising chance at a continental drift which certainly wouldn't be "mild".