Model output discussion - Into 2021

[Kasim Awan]

21 minutes ago, MATTWOLVES said:

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.

Well we currently have 20cm++, hi res model's snow depth's starting points are well off - show 8cm here. A point of discussion for high res model snow acccuracy.

Edited January 2, 2021 by Kasim Awan

[Battleground Snow]

Just now, Tim Bland said:

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

Ohh, I see.

These maps are more useful for frontal snow I think, but even then it's just a general guide.

[Scott Ingham]

1 minute ago, Tim Bland said:

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

Tim honestly buddy i really would not be using them charts for any accuracy. It always pops up about an easterly looking dry then come the day your looking out on to youe garden with 6 inches

[bluearmy]

6 minutes ago, Kasim Awan said:

Well we currently have 20cm++, hi res model's snow depth's starting points are well off - show 8cm here. A point of discussion for high res model snow acccuracy.

You can quickly go off someone kasim .......

[Chasbrown]

Which is the most reliable model please? 

[Battleground Snow]

ECM mean  here at 144,  marginally better than the det with the ridge placement...  On to the 18z's we go!

 

Edited January 2, 2021 by Battleground Snow

[Mike Poole]

ECM mean T240:

Not as sharp as previously as the models start to get to grips with the SSW.  But vortex still thousands of miles away.   

What is more interesting is the spread:

Uncertainty in areas of the NH where we haven’t previously seen it, particularly in the new upstream, the east.  We continue to watch...

Edited January 2, 2021 by Mike Poole

[Frosty.]

Now this is more like it from the GEFS 12z / GFS 12z op!!!....a day 10 winters dream!.... ...there’s tons of wintry weather ahead of us next week too!

 

[Paul_1978]

2 hours ago, Anthony Burden said:

Hi Matt Hugo Twitter 

Matt Hugo is not at the Met

[Guest]

19 minutes ago, Kasim Awan said:

Well we currently have 20cm++, hi res model's snow depth's starting points are well off - show 8cm here. A point of discussion for high res model snow acccuracy.

What ever are you folk doing on here when you've got snow in your garden!,,Im in my 50's but I'd be out there making snow angels!..yes I'd get some weird looks from the neighbours! but as you lot know it's a disease! 

[AdrianHull]

22 minutes ago, Chasbrown said:

Which is the most reliable model please? 

Most within 48 hours but still sometimes wrong...

And if any one model gets a day 10 chart right it's either coincidence or a lucky guess.

Any charts after 5 days should be used as a trend and not for the finer details

Edited January 2, 2021 by AdrianHull

[stodge]

Evening all

I commented earlier on the vagaries of model discussion. Some would claim any discussion of model output beyond T+120 to be pointless and maybe that's true but we all like to spot a trend and for that reason I find the model output up to T+240 to be informative as to which way the wind(s) are blowing.

Any road up, on to this evening's output and let's see if the projected break of the current pattern to something milder mid-month is on track and any indication as to whether that will be a significant change or a temporary blip.

12Z GEM: T+120 takes us to next Thursday and one or two interesting changes to previous evolutions at this time. The LP over Iceland is not moving south but moving away NE to the Norwegian Sea with LP more pronounced to the far south off the west coast of north Africa. The Atlantic HP is oriented north-south from the south-west of Iceland forming I believe it's called an Omega block. There's a narrow ridge of HP into Scandinavia and all this leaves the British Isles in a col under calm conditions. 850s generally at -4 but some colder air filtering down from the north-west. Moving into Phase 1 FI and a new LP forms to the east of Iceland and runs SE to the northern North Sea bringing a N'ly flow across the British isles by T+180. The Atlantic HP is giving ground to the south and signs of heights falling over Greenland but the complex European trough over or just to the east of the British Isles dominates the weather. Perhaps the briefest of mild interludes before much colder air encroaches from the north with -8 850s widely across the British Isles by T+180 and -12 uppers fringing Scotland. From there, the LP to the north-east of Scotland phases with the trough developing over Southern Greenland and deepens in situ to become a significant storm by T+240 due north of the British Isles with some secondary features in its circulation. Heights are rising further south as a more Atlantic-based pattern takes over.  Milder air takes over briefly but a new push of colder air is coming back from the north-west.

12Z GFS OP: - a breakdown from the north - who'd have thought it? I'm not sure about the GEM evolution but let's see what GFS OP has to offer in the same timeframe. By T+120 perhaps more progressive than GEM with a more defined N'ly and clearer signs of the Atlantic HP starting to withdraw south. Plenty of -8 uppers across the British Isles by this time. Moving on to T+180 we see the new LP which developed to the east of Iceland more directly north of the British Isles with the trough extending south to Iberia. Heights remain in the Atlantic. As might be expected, there's a less cold section through the frontal boundary but behind the cold front there's a new push of cold air from the north or north-west. From there, the GFS OP evolution begins to diverge from GEM - the Icelandic LP continues to move slowly south and by T+240 is over NE Scotland with a secondary centre over Cornwall. Heights remain over Greenland. There has been some mixing out of the coldest uppers by T+240 and some milder air is close to the south west presumably in connection with the secondary LP. I'll cover Phase 2 FI further on.

12Z Parallel: On then to the Parallel and by T+120 some divergences already in place. The Atlantic HP is throwing a  ridge east across western Britain keeping the troughs to north of Scandinavia, close to the Azores and over central and eastern Europe. Uppers at -4 to -8 but perhaps more issues with fog and frost than snow from this set up at this time. By T+180 a new LP has developed to the east of Iceland and deepened to be a significant feature to the north of Scotland with the whole of the British Isles in a NW'ly air flow. Heights remain over Greenland and the Atlantic at this time. As we see elsewhere, a milder section in the frontal boundary before a new push of colder air to the north-west. Moving toward the end of Phase 1 FI (T+240), the LP fills and moves south to be over northern Britain but it's a complex trough with a small but vigorous secondary feature approaching from the south-west bringing a SW'ly flow to eastern and southern areas while a cyclonic flow dominates elsewhere. Uppers of Zero to -4 by this time.

12Z ECM - at T+120 closer to the GFS OP than the Parallel to my eye. The trough perhaps less defined to the east and uppers of zero to -4 for most but with some -8 air close by. Moving on into Phase 1 FI and by T+192, the original trough is now over southern France with a residual NE'ly feed to southern and eastern parts but a ridge of HP us producing calmer and more settled conditions further north while the LP sits far to the NE at this time. Uppers still -4 to -8 but milder air approaching from the west. By T+140 the Atlantic is back - heights to the south and, it has to be said, a broad but weak trough extending from the north of Scotland west - we're not talking 950MB storms heading across from Canada by any stretch. 

Looking into Phase 2 of FI - from T+240 to T+384, I'll offer the equivalent charts from GFS OP and Parallel from T+312 and T+384. OP first which ends very mild and the Parallel which keeps a broadly cold evolution throughout - the Parallel, in particular, looks set for further amplification.

Looking elsewhere, 12Z Control ends zonal-ish but not zonal. Perhaps we're seeing GFS charts looking for a downwelling of westerly winds to pick up the jet and reduce amplification - that's been my thought for a couple of days. We aren't talking a monster PV or massive storm systems racing west to east - it's all a bit meh, if I'm honest. It just seems to suggest there's a thought of some residual westerlies as the PV fragments - could also be other teleconnections at work of course?

Looking at the 10 HPA and Control ends with the -60 zone of the PV over Scandinavia and Eastern Europe. OP is similar but with a slightly colder and larger residual PV (-64). Parallel fragments the vortex more or less completely with some residual -60 remnants over Siberia.

Conclusion: tentative signs of an easing of the cold pattern are coming into view at T+240 but it's far from resolved. GEM and ECM are keenest tonight to see an Atlantic flow return while GFS keeps the cold pattern a little longer. There's no great battleground between competing air masses which I find curious - it seems as though the cold just runs out of cold and the Atlantic, weak as it is, can move in. There are signs in Parallel at the far end of Phase 2 FI of further amplification and, as other have said, the ongoing SSW is throwing an enormous SSW-shaped cat among the atmospheric modelling pigeons. ECM is alone in fading the Greenland heights completely while other models bring the HP south and then east into Europe allowing the westerlies back in. There's a lot to be resolved.

[Jeremy Shockey]

ECM 12 z ensemble mean

If we cant get some snow between the 4th and the 8th then God help our tiny island.

Very decent mean until 10th and then who knows ?

[Mike Poole]

24 minutes ago, Chasbrown said:

Which is the most reliable model please? 

Hey, @Chasbrown welcome to Netweather!  

The obvious answer to that is the ECM.  Here are verification stats for the global models at T120:

UKMO usually second, GEM third and GFS and GFS // fourth, although the last three the differences wouldn’t be statistically significant.  

But two things: 

We are approaching a SSW which means all models will be struggling.

These global models are poor at predicting precipitation at short range, so there are a number of other models that we post when e.g. snow might be imminent.  Hopefully snow will be imminent soon, and you will see that in the posts on here.  Hope that helps.

Edited January 2, 2021 by Mike Poole

[Cheshire Freeze]

2 minutes ago, Jeremy Shockey said:

ECM 12 z ensemble mean

If we cant get some snow between the 4th and the 8th then God help our tiny island.

Very decent mean until 10th and then who knows ?

Very clear trend upwards now

[SLEETY]

 But ecm op mild outlier at end AGAIN,just like gfs as well,seems to be every run at the moment,all models are struggling with the current set-up,so dont rule much colder runs soon...

Edited January 2, 2021 by SLEETY

[bluearmy]

22 minutes ago, Mike Poole said:

ECM mean T240:

Not as sharp as previously as the models start to get to grips with the SSW.  But vortex still thousands of miles away.   

What is more interesting is the spread:

Uncertainty in areas of the NH where we haven’t previously seen it, particularly in the new upstream, the east.  We continue to watch...

I think that’s showing some of tpv dropping in there 

3 minutes ago, CreweCold said:

Very clear trend upwards now

The mean shows an upper ridge griceland in the extended period with the jet running below (a tad too far north for my imby liking ) - wedge??? 

[northwestsnow]

1 minute ago, bluearmy said:

I think that’s showing some of tpv dropping in there 

The mean shows an upper ridge griceland in the extended period with the jet running below (a tad too far north for my imby liking ) - wedge??? 

Any thoughts on the MJO Nick ?

Reading some snippets its on the move  or expected to be soon...

[Kasim Awan]

Remember the output can switch back as quick as it just did.. I'm keeping a hollistic view of the medium range.

[Man With Beard]

1 hour ago, Gregulator said:

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

Need ESE wind and a lot of cold to overcome the warmth of the channel! East Devon gets them sometimes.

[ArHu3]

16 minutes ago, Mike Poole said:

Hey, @Chasbrown welcome to Netweather!  

The obvious answer to that is the ECM.  Here are verification stats for the global models at T120:

UKMO usually second, GEM third and GFS and GFS // fourth, although the last three the differences wouldn’t be statistically significant.  

But two things: 

We are approaching a SSW which means all models will be struggling.

These global models are poor at predicting precipitation at short range, so there are a number of other models that we post when e.g. snow might be imminent.  Hopefully snow will be imminent soon, and you will see that in the posts on here.  Hope that helps.

Do you have the stats for 240h, iirc gfs actually beats ecmwf there?

[dhillcrest]

43 minutes ago, Chasbrown said:

Which is the most reliable model please? 

Not sure, but I think it's whichever ones says what you want to happen?

[Mike Poole]

2 minutes ago, ArHu3 said:

Do you have the stats for 240h, iirc gfs actually beats ecmwf there?

Hi, yes, here they are ECM a winner:

But from watching regularly, GFS does verify top at T240 quite a bit, very rarely does its beat ECM at earlier times.  

[snowbob]

48 minutes ago, Chasbrown said:

Which is the most reliable model please? 

As a rule any model that produces snow south of the m4 is barking up the wrong tree

if a model is showing cold and snow less than 48 hrs in the middle of the British isles, then that is to be taken with a ton of salt

further north a pinch of salt 

hope that helps

[bluearmy]

18 minutes ago, northwestsnow said:

Any thoughts on the MJO Nick ?

Reading some snippets its on the move  or expected to be soon...

Is it going anywhere before mid month ? And will it ever effectively get out of the COD ?  not seen anything convincing that it’s going to be relevant for a while yet .....