Model Output Discussion - the cold has arrived

[IanT]

15 minutes ago, Mark Smithy said:

Anyway, I wish you all peace. 

Only time will tell.

Because this is a model output thread not a daily snow report

Does model output start at T+144…?

[iceman1991]

Snow Risk Forecast Maps For The UK - Netweather.tv

WWW.NETWEATHER.TV

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Latest snow risk forecast maps for the UK - updated four times a day

Guys what this model like for accuracy got the south nearly 48hours of snow from early hours Wednesday morning ? 

[January Snowstorm]

The 06z Icon has the weekend low further South again. Of course it only runs to 120hrs but its a good trend

[Ravelin]

1 hour ago, Matt Jones said:

Models currently showing how easily the cold gets shunted away despite many believing a so called cold block is hard to shift.

Models are showing that they think the cold is going to be shunted away. The models might be right, they might be wrong, we'll need to wait and see. I've seen whole ensemble outputs completely flip over the course of one or two runs in the past, admittedly normally from cold to mild, but they do flip on occasions. 

In the meantime I'm going to enjoy the lovely sunny morning, temp at 0C and around 20cm of lying snow. By the end of this week I might be happy for it to warm up as currently its barely forecast to get above freezing right through to next Sunday. 

Edited December 11, 2022 by Ravelin

[snowspotter]

1 minute ago, IanT said:

Does model output start at T+144…?

Didn't there used to be split model discussion for up to 5 days to focus on the more detailed (likely) outcomes in situations like this. I'd be more interested to hear what's happening in next 72 hours quite frankly  in situations like this rather then a discussion on fantasy island charts for 8-10 days out that hardly ever verify

[geordiekev]

One thing I've noticed over the years is the overnight runs have a tendancy to be underwhelming and 6z for that matter, only for evening charts to improve.

I suppose that's why many often recommend comparing 0z to previous 0z etc. Unsure why or if less data on overnight runs, less flights etc but just an observation. So let's see where we are in 9 hours before calling it on a single set

[Skullzrulerz]

26 minutes ago, Mark Smithy said:

The danger here is cherry picking what we want to see versus the empirical reality of how the main model outputs are trending. There is definitely a signal to mild 6-7 days from now.

That doesn't mean it's a done deal. Judging by the ensemble spread on the GEFS for instance I'd say it's somewhere between 70:30 and 80:20. Whilst the 0z operational is on the mildest side there are only a couple of members which don't trend mild at the key point:

 

It's definitely the favourite outcome what ever you like or not.

That's been the case for some time, we can cherry pick all we want but it the models are coming to a general outcome then that's that.

In the mean there will be plenty of opportunity for snowfall surprises which we have seen in recent days.

It's not also to mention that maybe the models will backtrack somewhat on the less cold/milder air?

[Paul_1978]

45 minutes ago, Mark Smithy said:

I'm afraid the flaw in your argument lies right at the outset. There aren't really "six main outputs".

There is a clear hierarchy of reliability with 3 main model outputs: GFS, ECM, and UKMO. All 3 of the main outputs suggest milder outcomes at around the 6-7 day point.

It's not a done deal but once we start scrabbling around for minor model outputs to back up our preconceived wishes then we're not really being objective or empirical.

Based on those 3 and the ensembles it's somewhere between 70:30 or 80:20 that it's heading milder. 

Not necessarily. Ian F replied to a couple of Tweets recently and suggested that his preferred models were UKMO, ECM, GEM, ICON, and JMA, with GFS in last place! 

[Tim Bland]

Still looking good for central southern areas / south miss today and the south east tonight..

[bluearmy]

35 minutes ago, FetchCB said:

Reading the Met Office further outlook seems to suggest that they believe that the low approaching from the south west will slide into France as the only mention milder in the south and west and cold in the North. This scenario which would drag colder air from the North. 

They have more data than we do but have to react to changes in the modelling 

I suspect they see any relaxation of the cold behind next weekend being a temporary thing - it’s not easy to paraphrase the forecast for the whole country over a 10 day period! 
 

the phasing of the low heights to our west looks pretty certain now. Ukmo is isolated on this. But that doesn’t necessarily lead to what the ec and gfs ops are showing. There remains lots of moving parts on the evolution -  getting the trough to clear further east (because heights look to stay reasonably high to our northwest) seems pretty important to get cold back across nw europe 

as others have pointed out, the NH profile offers much encouragement for amplification to continue 

[FetchCB]

As if to reinforce my impression of the over progressivsness of the ECM it goes from a 968mb low in Biscay on Wed night to a 1020mb high 36 hours later and then a further 36 hours later has biscay under the influence of a 948 mb low in the mid Atlantic. That is a lot of dynamism in a model and with that comes a big possibility that if it is wrong early in the time frame then the differences thereafter will be significant 

[iceman1991]

11 minutes ago, Tim Bland said:

Still looking good for central southern areas / south miss today and the south east tonight..

What time this ment to be coming in I’m right I’m up Salisbury plain there was a light fall hour ago for 10 min ? 

[bluearmy]

Just a note on the Ukmo run - the system coming across next weekend has a warm sector and brings rainfall across much of England and Wales away from higher ground  

day 6/7 Ukmo charts are, like all other ops, unreliable. Of course if there is decent cross model agreement then you can extend that reliability timescale. 

[Gowon]

Snow for the south tuesday into wednesday from the GFS

Edited December 11, 2022 by Gowon
got my days the wrong way round

[Johnp]

16 minutes ago, Tim Bland said:

Still looking good for central southern areas / south miss today and the south east tonight..

I’m too far east for this mornings lot and then too far west for tonight’s. I’m right in that 0 precipitation area on the last chart. Gutted

[bluearmy]

4 minutes ago, Gowon said:

Snow for the south tuesday into wednesday from the GFS

You’ll note that this run is south of the last run 

looks like a typical gfs run by run correction to me (not entirely dismissed yet) 

Edited December 11, 2022 by bluearmy

[Gowon]

Just now, bluearmy said:

You’ll note that this run is south of the last run 

looks like a gfs run by run correction to me 

I did notice. Is it wrong with the snowfall, then?

[Midlands Ice Age]

1 minute ago, bluearmy said:

You’ll note that this run is south of the last run 

looks like a gfs run by run correction to me 

Yep its the normal method of getting back on track.

[sheikhy]

Just now, Gowon said:

I did notice. Is it wrong with the snowfall, then?

Yeh most probably!!expect it to go further and further south now!!

[damianslaw]

It feels akin to when we are in the midst of a long high pressure heat fest in summer, all attention on when any 'breakdown' may occur, this is often the case when the reliable timeframe about 5 days is quite clear cut, naturally attention turns to what may happen next - when will the change take place. The models and trends appear to suggest a change taking place next weekend, by Sunday from the west as low pressure exerts its influence and heights that will have settled over the UK ahead of the low are shunted away, warm air advection takes place, with a frontal feature moving in. However, this is 6-7 days away, and there is plenty of time for this to be pushed back or indeed the feature become more negatively aligned or struggle to move north and east. 

Will become clearer or may not be, by Tuesday, expect some further twists and turns on the theme in future runs. The northern hemisphere looks ripe for further heights building to the NW I think.

[Seasonal Trim]

36 minutes ago, snowspotter said:

Didn't there used to be split model discussion for up to 5 days to focus on the more detailed (likely) outcomes in situations like this. I'd be more interested to hear what's happening in next 72 hours quite frankly  in situations like this rather then a discussion on fantasy island charts for 8-10 days out that hardly ever verify

This 100% ^^^

Problem is, most on here want to be chasing FI charts most of the time, which if I'm honest, is pointless when the models don't even agree at <72hrs.

[Gowon]

1 minute ago, sheikhy said:

Yeh most probably!!expect it to go further and further south now!!

[sukayuonsensnow]

8 minutes ago, bluearmy said:

You’ll note that this run is south of the last run 

looks like a typical gfs run by run correction to me (not entirely dismissed yet) 

Would be a nice little snowfall for us but could end up being in northern France instead.

[danm]

How well was the snow over Gloucestershire this morning forecast/modelled? Seems fairly unexpected- at least the extent of it. 

Edited December 11, 2022 by danm

[mushymanrob]

Sorry, too much to wade through so sorry if this point has already been made...

Which ECM run to believe?
Well as this concocted frame below illustrates, IMHO the ECM 12z is close to what the NOAA charts are predicting. The Anomalies are centred on the 18th, the two ECM charts are the 12z and 00z for the 18th.

IMHO the current ops are over stating the incoming atlantic system, the Anomaly charts does not support a low of that depth, but suggests the ECM 12z is closer to the mark.

Plus..... deep cold doesnt usually get swept away so easily, theres often a lengthier battle, thats experience talking! I dont believe the current ops.