Model Output Discussion - Christmas and New Year

[O'Maille80]

Crazy the way the best uppers( lowest) seem to alternate between Ireland and the UK day by day on the latest ECM. Even then they're nothing to write home about.

Not convinced there will be enough cold pooling taking place to give low land snow, like some suggest.

I want anything but cold rain for a week. That's the worst case scenario for us all. Fingers crossed we all see some snowy weather in the next 4-10 days.

[Anthony Burden]

ECM interesting but changes past 144 hrs will be inevitable,northern blocking

key to every door regarding continued cold.Still looking very good for all cold lovers.

 

 

[Geordiesnow]

8 minutes ago, Man With Beard said:

I'm feeling like did June 2019, when uppers were forecast 25C yet maxima around 30C ... I was screaming "The models must be wrong!!!" Yet of course they were right. What I'm feeling this time round is "Surely there has to be precipitation than that on a low this big and this deep"!!! I mean come on, normally when you see a low like this you think "Flooding!" So for this, one of this biggest and most unstable lows ever, why is there not more rain/snow around this time? Yet no doubt the models will be right and I will be wrong - I guess it's because the fronts have cleared out of the centre (but surely there'd still be developments within the centre?) 

I think when people look at charts like this, people may think there is going to be bags of PPN but that is not always the case. Your correct in saying it will be because of lack of weather fronts but troughs and the such like may not get picked up until the shorter range.

[Valleyboy]

23 minutes ago, Tim Bland said:

Incoming from the north west!!

Never a good direction, if it’s snow you want.  Low pressure from the north will nearly always bring lowland rain.  Hopefully we will see a more continental feed later, with low pressure coming from the southwest.

[Kasim Awan]

Lots of negativity popping up now..

I would be surprised if the magnitude of blocking modelled doesn't manage to produce some decent low level snow in the next 2 weeks.

Also, I would stay away from analyzing 198-240h too much right now. The evolution before this is fantastic, and gives us a good chance of decent solutions afterwards, combine this with a strong signal for a highly unusual pattern anyway.

Edited December 24, 2020 by Kasim Awan

[stodge]

Evening all

First, Merry Christmas to everyone on NW. After the year we've had, perhaps we deserve some Christmas cheer and last evening the 12Z output was in helpful mood with several days of chilly if not cold weather forecast and the hardy perennial of 850s, 925s and dewpoints getting a healthy airing.

As Santa continues his miraculous circumnavigation, what are the models suggesting for the coming days and into 2021?

12Z GEM: T+120 takes us to next Tuesday - GEM takes the LP as a significant feature over the British Isles and it's still a large but shallower trough over the North Sea by this time. Uppers generally at -4 with the coldest air displaced further west. By T+180 not much has changed - the LP is centred off the Norwegian coast but the trough extends south through the British isles and a cold airmass remains in charge with heights over Greenland and a new LP well to the south at this time.  Again, the coldest air sits out to the west. By T+240, the LP still covers the British Isles as a complex but shallow feature. There's an LP near the Azores and you'd wonder if it will phase with the existing trough and pull some milder air up over us from the south-west but that's quite uncertain with pressure rising to the north and north-west. 

12Z GFS OP - a strong start from GEM keeping the weather on the cold side into 2021. GFS OP broke down the cold spell in far FI last evening and let's see where it takes us. By T+120. the storm, as a significant feature, has moved down over the British isles and remains the controlling influence on our weather. It's centred in the southern North Sea and while there are heights over Greenland I'm looking at the instability off the east Greenland coast to see if we get another LP forming.  Again, the really cold air is off to the west. By T+180, some notable differences star to emerge. The trough is now shallower but elongated from west to east across the British Isles and across southern Scandinavia and to the Baltic. Strong heights to the north-west and an LP in lower mid-Atlantic latitudes. The re-orientation of the LP finally allows the colder air to spread down over the British Isles by New Year with -8 850s. On then to T+240 and significant differences from GEM. The Greenland heights have gone though there's still a strong HP ridging north-east to the Faeroes. The LP has sunk south over Europe and a NE'ly flow covers much of the British Isles. The air mass remains cold with -8 850s in the mix. However, moving further into FI and by T+312, the Atlantic HP has sunk further south and milder air has come round the top of the HP anad over the British isles while a new LP has deepened sharply and moved SE into Southern Scandinavia.  There's a brief but quite potent N'ly before the Atlantic HP starts to re-exert its influence and by T+384 milder air is back on a WNW'ly with LP moving round the top of the HP centred just off the west coast of Ireland.

12Z ECM - GFS OP didn't end the cold spell as dramatically tonight and no sign of the much-discussed west-based negative NAO.  It's more of a whimper than a bang if I'm being honest but we would still get several days of cold weather from that evolution. On then to ECM and differences with the other models as early as T+120. As with GEM, the LP has filled slightly and eased back NE to be over southern Scandinavia but there's already a new LP forming to the west of Iceland (not sighted on GFS or GEM). The HP remains in mid-Atlantic. Again, the coldest air just to the west of the British Isles. By New Year's Day (T+192), it's a messier evolution.  The new LP phases in with the original LP and the complex feature first extends over the British Isles with a new centre forming over southern England. By the same time, a new P is developing to the west of Iceland while HP remains in situ supported by a new lower-latitude LP far to the south. -4 to -8 850s widely by this time so still cold. The evolution from there is interesting - first, heights build strongly over Greenland and the LP starts to move south but it phases with the mid-Atlantic feature and that in turn allows a small push of HP into Iberia which, you'd think, would stop the LP sinking any further south. This time we are looking a west-based negative NAO. The 850s confirm the push of milder air towards southern Britain and the steep temperature gradient in mid-Atlantic characteristic of this set-up. All very knife-edge.

Looking elsewhere, 12Z Control in FI is a good example of "cold zonality" with short-lived milder incursions and longer-lasting periods of colder air. 12Z JMA looks cold for New Year but the longevity of any cold spell looks uncertain.  12Z Parallel is now back to a 4-run-per-day format and tonight's offering is very interesting with a brief milder incursion just after New Year swept away by a much colder wave from the east as we go into the first full week of January.

Looking further up, the 12Z Parallel maps a split of sorts in the 10 HPA before the PV briefly recovers and then a new warming begins at the end of FI (January 9th). OP keeps the strat intact throughout which is the second night it hasn't shown the split. Control is also much less bullish on a split.

Conclusion: - there's a lot to take in tonight. The signs for cold weather fans are still very favourable - GFS Parallel is very good. ECM shows how a west-based negative NAO can spoil the party. The GEM evolution is a bit messier. Those looking for a significant SSW at the 10 HPA level may be disappointed at this time but there are plenty of other straws in that breeze to discuss. In the shorter-term Storm Bella is going to be a significant feature with wind and rain for many and snow for some (altitude always favourable for snowfall). Several days of cold weather into the New Year look likely but the evolution, as you'd expect, from there is far from resolved.

[Methuselah]

2 minutes ago, Geordiesnow said:

I think when people look at charts like this, people may think there is going to be bags of PPN but that is not always the case. Your correct in saying it will be because of lack of weather fronts but troughs and the such like may not get picked up until the shorter range.

And, at this time of year, under a near-stationary depression, there's bugger all insolation... Even during the summer months, many places (like here!) can get away with nothing in the way of precipitation/convection.

[Mike Poole]

4 minutes ago, General Cluster said:

And, at this time of year, under a near-stationary depression, there's bugger all insolation... Even during the summer months, many places (like here!) can get away with nothing in the way of precipitation/convection.

Are you talking about the weather there Pete, or a wider malaise with the current situation?  

[Methuselah]

1 minute ago, Mike Poole said:

Are you talking about the weather there Pete, or a wider malaise with the current situation?  

You've lost me there, Mike. Best I put it down to my blooteredness (It's nae only 'zonality' that's nae a word! ). Merry Christmas!

[I remember Atlantic 252]

5 minutes ago, General Cluster said:

You've lost me there, Mike. Best I put it down to my blooteredness (It's nae only 'zonality' that's nae a word! ). Merry Christmas!

it isn't no! invalid in scrabble

[Mike Poole]

3 minutes ago, General Cluster said:

You've lost me there, Mike. Best I put it down to my blooteredness (It's nae only 'zonality' that's nae a word! ). Merry Christmas!

The near-stationary depression bit Pete.  And the best Christmas to you too.  Now waiting for the ECM ensemble mean, the highlight of my day nowadays

[BLAST FROM THE PAST]

28 minutes ago, Skullzrulerz said:

Personally I prefer the GFS it seems to be a bit more stable in terms of cold air and as well as Greenland blocking 

ECM to me looks poised to fail 

Best you explain that.?  The ECM is a rock solid cold, blocked lock in.

 

BFTP

[sheikhy]

Ecm mean is puure cold lovers porn

[ICE COLD]

Another stunning mean on the ECM

[Mike Poole]

ECM mean, first T96, this is really good positioning for the centre of the low on a mean chart:

i.e. in the SE of the country.  T240 and with GEFS also:

I like the signal for the cut off low west as per the ECM op, not there in GEFS. 

 

[bluearmy]

The extended  eps are trended slightly back to the trough extension to the sw lifting a little further north which brings back the high risk high reward via the -wbnao. Be interesting to see how big that cluster is on this suite. 50% on the 12z yesterday dropped back on the 00z run a bit. 

still an excellent run for coldies .......

[Eagle Eye]

Meteociel - Panel GEFS

WWW.METEOCIEL.FR

An Arctic Northernly certainly looks like it's going to be on the Control Run for a while, say what you want but We may have something Like A 2010 again, it may not be as Cold but at least we will have Snow. 

Certainly A GREENLAND HIGH IS CUTTING US OFF from any more Arctic Northernl'ies happening for a few Weeks that will have Snow at least by the Time they get back down here but looking at the Charts we will at least have 2 WEEKS or so of Winter Showers. 

Still there at T+240.

Hope Everyone has A MERRY Christmas and if you want some SNOW. 

Xander. 

 

[SMU]

ECM is going to be a big mild outlier for the UK V the EPS mean. Excellent mean all the way through.

ECM keeps blowing up systems SW of Greenland.

Look at the OP 3 days ago for 31st now tonight for the 31st

[sheikhy]

A middle ground between gfs and ecm at 240 hours would be too good to look at!!!look for that greenland/icelandic high again on the 18z!!think gfs was a little too far to the east!also ecm mean suggests the op was slightly too far west!!!

[ICE COLD]

ECM was an outlier at the end on 850s . The downward trend continues on the ens . Not extreme uppers YET

[Allseasons-Si]

8 minutes ago, Mike Poole said:

The near-stationary depression bit Pete.  And the best Christmas to you too.  Now waiting for the ECM ensemble mean, the highlight of my day nowadays

It's rock on Tommy,i mean Mike

[Griff]

1 minute ago, ICE COLD said:

ECM was an outlier at the end on 850s . The downward trend continues on the ens . Not extreme uppers YET

Thanks, definitely my favourite chart of the day so far! 

[Griff]

Enjoy... 

Merry Christmas eve... 

[Mike Poole]

Crikey look at the spread upstream on the ECM ensembles, T240:

As the cold spell develops, so the uncertainties increase, as you would expect, Shannon Entropy and all that.  But no signs of that UK high?  

[Eagle Eye]

ECMWF has us with a massive LOW and GREENLAND HIGH BLOCKING.