Model output discussion - Into 2021

[Scott Ingham]

6 minutes ago, Kasim Awan said:

I still think a Greenland high "slider" scenario as suggested on the ECM 12Z yesterday is a valid option. Synoptically, this would be the result of a greater easterly component and a stronger -NAO signal, which would be more favoured given the rather high AAM budget right now.

Yep.

Id favour the same. This run is better than the 0z and GFS is worlds apart from 0z and 06z. Things will firm up close to time

[Gregulator]

5 minutes ago, Scott Ingham said:

Only high res can model streamers etc bud. The ECM and GFS shouldnt be used for convective showers from the North sea so i wouldnt worry a jot

Is it possible to get convective showers from the English Channel..IMBY

[Daniel*]

Just now, MKN said:

That's not true. During the Beast from the East parts 1 and 2 a few years back it showed the showery activity days in advance. They don't do well with specifics but they usually highlight the risk.

Certainly nowhere near extent remember watching BBC forecast based on ECM.. “chilly with wintry showers“ anyone who has model experience knows the models even h-res aren’t great at sea convection, particularly I observe an issue with precip getting inland it often does in these stronger flows.

[IW Met]

1 minute ago, MKN said:

We have been looking at and experiencing very good synoptics for some time, Its clearly just showing how difficult it is for low lying snow in the UK these days. 

I wish people would stop saying things like this . 2018 and 2019 saw significant snow in lowland UK including right along the south coast of the UK.
I have said this many times and I will say it again. It hasn't been cold because it has been displaced over the other side of the northern hemisphere. Its pure synoptics that have meant the cold isn't in Europe, that's it, plain and simple. 
A change in the synoptics over the coming week or two may well introduce much colder conditions into Europe, then....if that Strat warming has enough influence, we may then see that cold advected westwards......maybe.....
 

[Kasim Awan]

4 minutes ago, MKN said:

That's not true. During the Beast from the East parts 1 and 2 a few years back it showed the showery activity days in advance. They don't do well with specifics but they usually highlight the risk.

Gfs is ok at this range. ICON, Arpege highlight the main streamer areas quite well >50H like now, but intensity is too low + underestimates shower activity between the streamers. Use these & amplify it a bit, Euro 4 is good with streamers <30h. 

Edited January 2, 2021 by Kasim Awan

[That ECM]

Just now, Gregulator said:

Is it possible to get convective showers from the English Channel..IMBY

Yes but as rare as rocking horse poo when it’s snow

[radiohead]

28 minutes ago, Snowmut said:

 Im no Wincy Willis, but somewhere will get a pasting from that!

 

Here's the ECM for that 

[Mike Poole]

4 minutes ago, Scott Ingham said:

Only high res can model streamers etc bud. The ECM and GFS shouldnt be used for convective showers from the North sea so i wouldnt worry a jot

That’s certainly true, the 2018 BFTE only the HIRLAM really got anywhere close with the convective snowfall off the North Sea.  Some of the other high res especially ICON-EU were poor.  Am looking forward to using those models in anger for snowfall - but as I said earlier, I thinks the models are all a mess at the moment, alL should become clearer after the 4th Jan (revised SSW date)...

[Frosty.]

Hmmm I think the ECM 12z op has lost the script!...day 10 is supposed to be bitterly cold..hope it finds the script before the 0z!!!...it all adds to the drama though doesn’t it.

[Scott Ingham]

3 minutes ago, Catacol said:

Yep. Under modelling of strat disruption, even at 48/72 hours range, has been evident in EC runs throughout this extended slow burn run to cold, and the origins of this under modelling lie in a consistent under modelling of wave break impacts. I’m as sure as my instincts can be that the ridging will hold as the final westerly dribble is purged from the Atlantic sector.

From there we need to watch for cold air working its way westwards as the signal for an easterly increases. I’m a bit irritated to see another positive anomaly E/NE of the Black Sea on the extended EPS again suggesting more obstacles to be overcome in getting that cold advection....but other than this there’s nothing not to like today.

If you read mine and @Kasim Awan personal chat last night youd see we discussed exactly the same thing. They have under modelled rises in AAM and consequently from that wave breaking and strat impacts. I noticed wave 2 has been under modelled. Todays wave 2 modelled was a much stronger event than what was shown 3 or 4 days ago.

Understanding of the background signals gives you enough confidence to see past runs that dont have logic

[Kasim Awan]

1 minute ago, Mike Poole said:

That’s certainly true, the 2018 BFTE only the HIRLAM really got anywhere close with the convective snowfall off the North Sea.  Some of the other high res especially ICON-EU were poor.  Am looking forward to using those models in anger for snowfall - but as I said earlier, I thinks the models are all a mess at the moment, alL should become clearer after the 4th Jan (revised SSW date)...

ICON was very good if you know how to read it properly - it highlights the main zones i.e. worst hit areas very well - then use Hirlam for elsewhere.

[Scott Ingham]

8 minutes ago, Daniel* said:

The models looked dry on run up to BFTE and we all know how that turned out.... 

They look dry because operational models dont have the correct resolution to model troughs and convective elements

[MATTWOLVES 3]

Model irritability showing up now,I must admit I'm looking forward to some Stella runs in the not to distant future. But the JMA is a peace today..

And just to finish off,its currently whiteout conditions here right now.. I was not expecting this at all.

Edited January 2, 2021 by MATTWOLVES

[Scott Ingham]

9 minutes ago, MKN said:

That's not true. During the Beast from the East parts 1 and 2 a few years back it showed the showery activity days in advance. They don't do well with specifics but they usually highlight the risk.

If it cant model snow off -15 uppers then it shouldnt be in operation.

Only high res can model the activity next week.

I bet you my grandparents those days oj question are far far far from dry. 

In all due respect it is common knowledge that only models such as arpege euro4etc should be used in this scenario 

[bluearmy]

4 minutes ago, Mike Poole said:

That’s certainly true, the 2018 BFTE only the HIRLAM really got anywhere close with the convective snowfall off the North Sea.  Some of the other high res especially ICON-EU were poor.  Am looking forward to using those models in anger for snowfall - but as I said earlier, I thinks the models are all a mess at the moment, alL should become clearer after the 4th Jan (revised SSW date)...

Why after the ssw Mike?

that’s just the date that the winds reverse at 10hpa 60N 

they have now reversed at the top of the strat. 

so if your argument is that the nwp won’t fully reflect the reversal until it’s happened then surely we’ve now reached that point ??. 

[Scott Ingham]

8 minutes ago, Gregulator said:

Is it possible to get convective showers from the English Channel..IMBY

With the right wind direction and parameters of course it is

[Mapantz]

2 minutes ago, Scott Ingham said:

They look dry because operational models dont have the correct resolution to model troughs and convective elements

Sorry, but that's just not true at all. Lower resolution models can pick out convective areas just fine, but on a broader scale.

Higher resolution for more detail nearer the time.

[Battleground Snow]

31 minutes ago, Tim Bland said:

Here is the ECM snow depth .....

I have more than 0.2 inches on the ground right now, so it's wrong at t0 

[Scott Ingham]

18 minutes ago, MKN said:

We have been looking at and experiencing very good synoptics for some time, Its clearly just showing how difficult it is for low lying snow in the UK these days. 

Ive had two days of 2-3cms plus of snow. Its just been some areas have been lucky to catch a trough in a flow or an organised streamer. But i understamd if you mean nationwide low ground snow.  Next weekend is looking interesting in this regard

[Mike Poole]

5 minutes ago, bluearmy said:

Why after the ssw Mike?

that’s just the date that the winds reverse at 10hpa 60N 

they have now reversed at the top of the strat. 

so if your argument is that the nwp won’t fully reflect the reversal until it’s happened then surely we’ve now reached that point ??. 

Just my experience of a sample of maybe 3 or 4!  Once the official SSW happens things tend to calm down a bit.  Maybe we should look at it the other way round, why is reversal at 10 hPa 60N the criterion, it is usually  the point of no return for most SSW?  

Edited January 2, 2021 by Mike Poole

[Paul]

2 minutes ago, Mapantz said:

Sorry, but that's just not true at all. Lower resolution models can pick out convective areas just fine, but on a broader scale.

Higher resolution for more detail nearer the time.

To be fair, you're both right. Broader scale models can pick out broader scale features and try to model them, but their resolution is never going to do well with mesoscale features and not going to do well with the detail on either. I personally always take medium range precip modelling with a pinch of salt. 

[Scott Ingham]

12 minutes ago, Mike Poole said:

That’s certainly true, the 2018 BFTE only the HIRLAM really got anywhere close with the convective snowfall off the North Sea.  Some of the other high res especially ICON-EU were poor.  Am looking forward to using those models in anger for snowfall - but as I said earlier, I thinks the models are all a mess at the moment, alL should become clearer after the 4th Jan (revised SSW date)...

Its one of the oldest bias in the weather book. 

Basically even discussing any snow any further out down two days is a waste of your own time. 

If you get the right pattern snow will be there come the day and be modelled modestly 24 hours out 

[AdrianHull]

12 minutes ago, Gregulator said:

Is it possible to get convective showers from the English Channel..IMBY

For convection the difference between the water temperature between the surface and 850 mb should be at least 13 degrees Celsius.

Might be other factors too but that's rule of thumb.

 

 

 

[Scott Ingham]

9 minutes ago, Mapantz said:

Sorry, but that's just not true at all. Lower resolution models can pick out convective areas just fine, but on a broader scale.

Higher resolution for more detail nearer the time.

They can within 48-72 hours but i was commenting on a chart 9 or 10 days away 

[Tim Bland]

11 minutes ago, Battleground Snow said:

I have more than 0.2 inches on the ground right now, so it's wrong at t0 

That’s the snow depth Thursday...so it’s saying some will melt by then...