Model Output Discussion - Into the new year

[chionomaniac]

2 minutes ago, bluearmy said:

Sst’s between the Netherlands and e anglia are as high as we’ve seen since 2015 

that 2c above where we would expect to see them does make a difference to the easterly and Dp’s /air temps 

Lol. And all I can think of is lake effect thunder snow making machine if 850’s are cold enough in the heart of winter

[feb1991blizzard]

7 minutes ago, chionomaniac said:

Lol. I’m daft enough to have thrown my hat into the ring a fortnight ago with the 10th. 

 

Nothing has changed my thoughts too. Will be very happy if it verifies as signals were suggesting later than this at the time.

Good call its looking like, i should have listened, thought a 3rd round of batterings were going to be needed, i said 27th Jan for my reversal, have to say though you are the goto man when it comes to the stratosphere, rarely, if ever let me down, better than most of the pros even. Still just a nagging doubt though that these fantastically placed splits (W2 straight through Griceland) showing on the GFS seem to be gone on the next run, and from a lot of experience, i have watched every GFS run at 10 and 1mb for about the last 8 years during winter and you need a consecutive run of a good few runs with the split showing in the same place and to get it below 300, then confidence massively increases, also think we will need it if we are going to drop a chunk of vortex into Europe to bolster the cold pool so as to get a real stonker of an Easterly.

[Allseasons-Si]

5 minutes ago, chionomaniac said:

Lol. And all I can think of is lake effect thunder snow making machine if 850’s are cold enough in the heart of winter

I was just going to comment on this,sure it would aid more convection over warmer waters,just like the Irish sea is doing now which has dumped quite a bit of snow NW England.

Edited December 27, 2020 by Allseasons-si

[bluearmy]

1 minute ago, chionomaniac said:

Lol. And all I can think of is lake effect thunder snow making machine if 850’s are cold enough in the heart of winter

I guess it also means the usually dry raw easterly will be drizzly unless we can get those uppers towards double digit negatives ?  Further than that may be the case ......

the largest eps cluster (not by much) late week 2 is that one with the northerly drop in of low heights into n scandi 

[Weathizard]

1 minute ago, Allseasons-si said:

I was just going to comment on this,sure it would aid more convection over warmer waters,just like the Irish sea is doing now.

Probably a balancing act, if 850’s are cold enough it would be a good thing but with 850’s looking less cold from the east than you would usually expect at this time of year it could work against us.

Not that that’s even worth the worry at this point obviously, our Icelandic wedge is my focus at the minute, seen too many of them go up the creek down the years, hopefully this time it’s different.

[Tim Bland]

11 minutes ago, bluearmy said:

Sst’s between the Netherlands and e anglia are as high as we’ve seen since 2015 

that 2c above where we would expect to see them does make a difference to the easterly and Dp’s /air temps 

Presumably though if we do get a beast from the east (uppers >-10c) then the snow showers would be immense ? 

[stodge]

Evening all

A day of two distinct halves here in lowland East London - early heavy rain and strong winds led to a dramatic clearance to fine skies and an increasingly chilly breeze during the afternoon and into the evening. Will we get snow overnight and into the morning? A question for others on another thread...

The cold theme persisted on last night's output with the end of 2020 and the beginning of 2021 seeing well below average temperatures for most but let's see some of the peregrinations on offer this evening:

12Z GEM: T+120 takes us into 2021 and New Year's Day. The new year starts cold and as heights build through Iceland, the airflow over the British Isles shifts NNE'ly with a shallow but complex trough over Scandinavia and the Low Countries and stretching down into France and Northern Spain. The airmass is cold with 85-s of zero to -4 widely and some colder air moving in.  Not much changes by T+180 - winds are slack or calm with the LP now over Italy and a ridge extending WSW from heights to the far NE of Scandinavia. This is keeping the jet well to the south and 850s are widely at -8 as the UK seems to develop its on cold pool and I can imagine any snow cover leading to some very low minima under this synoptic set-up. On then to T+240 and again only slight changes - the trough extends from the Gulf of Genoa up over southern Britain with heights to the north building from Scandinavia through Iceland into the mid-Atlantic. Just a hint of a marginal easing of the cold airmass.

 

12Z GFS OP - a strong start for fans of cold from GEM this evening. As for GFS OP the T+120 picture tells a slightly different story. It's cold and we see successive LP areas within the trough develop over the Norwegian coast and swing south - not Polar Lows of course but they would accentuate any instability and trigger a new round of shower activity. Uppers of -4 to -8 don't tell the whole story of course but you'd think snow for anywhere with altitude and probability for lower ground as well. On to T+180 (January 4th) and the overall pattern looks very similar to GEM. A strong wedge of heights extends SW through Iceland and this is forcing the Atlantic to the south-east well away from the British Isles. A shallow but complex trough remains over Europe with centres over Italy and southern Britain. Uppers of -4 to -8 suggesting very old nights with moderate to severe frosts.  On then to T+240 and a chart that reminds me of the Beast from The East of March 2018. In the interim, the core of heights has transferred to Greenland but the Atlantic is fighting hard to come back in from the south and the wind direction has moved from East round to a more ESE'ly point. Milder air is coming up into southern Britain but it remains very cold further north. The evolution from there reminds me of the discussion about west-based negative NAO synoptics the other day and this is one of those. The LP tries to move north and draw up a SW'ly flow but by T+312 the LP are crossing southern Britain with very cold NE'ly sourced air for many. There's a steep temperature gradient and all the ingredients for someone to get a right blizzard but who and where I'm not certain and no one could be at this time. These evolutions don't happen often and what's even more unusual is for the cold airmass to prevail but that'swhat happens and by T+384 there is a NNW'ly flow covering most of the British Isles. For northern Britain, the cold never leaves.

 

12Z GFS Parallel - the OP is a dream run for cold fans in the north and snow fans in many other areas. The FI evolution offers a real chance of some serious snowfall. On the Parallel, T+120 holds few surprises though perhaps not quite as pronounced heights over Iceland. T+180 keeps things on track with the centre of HP to the north-west of the British Isles and between that and the European trough, there's an ENE'ly flow. Uppers at this point are generally -4 so cold. From there the HP thinks about retrogression but doesn't quite go through with it staying around or just to the south of Iceland. The ENE'ly tightens to an E'ly as LP approaches from the south into BIscay by T+240. Cold and bitter for the south by this time. However, the LP can't push through the block which builds down over Scotland by T+312 leaving the LP as a cut-off feature but the Azores HP is building into North Africa and Iberia threatening to push the jet back north. Less cold air is now infiltrating the British Isles even as frigid air builds to the north and east. By T+384, battle is joined between the warmer and colder airmasses and there's likely to be some heavy snow somewhere from that conflict.

 

12Z ECM - both GFS OP and Parallel have hints of big snow events as warmer and colder airmasses do battle as we approach mid-January. That can be a result of retrogression and a west-based negative NAO or simply of the jet fighting to come back north. Back to the more immediate and at T+120 ECM follows the trend with heights over Iceland and a NE'ly flow for most of the British Isles with the LP centred over Belgium. Uppers of -4 in the middle of the day suggest snow for many but not all. By T+192, heights have built to the north with a broad ridge from Iceland to northern Scandinavia and between that and a broad but shallow trough over Europe there's an E'ly for the British Isles. 850s still not overwhelming at this time.  By T+240 not much has changed - the HP is to the south of Iceland with the LP over Biscay and an ESE'ly flow for the British Isles. This is importing even colder air with -8 uppers in charge.

Looking elsewhere, 12Z Control is cold throughout but with clear signs of a reversion to a more Atlantic-based type at the very end of FI. As for the 10HPA, the Parallel initiates a split by the end of next week but the PV recovers in FI though nowhere as strong or as cold as usual. Both OP and Control postpone the split to far FI.

Conclusion: - another excellent evening of output for fans of snow and cold and GFS tantalises with some really snowy possibilities in far FI if we see a clash of warmer and colder airmasses. It's quite possible we'll see a brief incursion of milder air to the far south before the cold re-asserts and the milder air never gets that far north. The theme tonight is for HP to the north and north-west and the cold air to come from the east rather than the north which works for many. The pattern through to T+240 is starting to look set on GFS and ECM but the devil will as always be in the detail for those hoping for snow.

Edited December 27, 2020 by stodge

[Frigid]

I think after the atrocious winter last year, we deserve better. And better are we getting! Here's a comparison of the AO forecasts from last year to this year. Big difference 

 

[topo]

2 minutes ago, Frigid said:

I think after the atrocious winter last year, we deserve better. And better are we getting! Here's a comparison of the AO forecasts from last year to this year. Big difference 

 

I am a bit surprised because most of Central and Northern Europe had temperatures much warmer than normal even with minus AO this December.

Actually it is probably one of the warmest ever in Scandinavia, warmer than last year's with a positive AO

[Weathizard]

UKMO looks much more like the GFS at day 6 than the ECM which is unusual, all three for comparison. All 3 I would snap hands off for as a starting point mind you but from a greedy perspective I’d prefer one of the GFS/UKM pairing.

[Man With Beard]

1 hour ago, Kasim Awan said:

Hmm I disagree somewhat with this comment. I think these areas can be predicted with due care to hi res analysis.

I think I've got a good case! Look at these for Tuesday early hours!

[Allseasons-Si]

Finally EPS day ten and EXT clusters are out as is the cpc

this is getting exciting now isn't it...

 

[BLAST FROM THE PAST]

2 hours ago, Catacol said:

Everyone will be playing coy when considering this question....but a few pointers. Amy Butler a while back plumped for 9th Jan. Chio earlier today has said 10th. My first guess a while back of 23rd Jan looks way out. A warming is definitely going to happen - what is less clear is whether it will displace the vortex or split it in half..,.and associated with that whether we get a reversal of the flow.

Im always glass half full.....so let’s paint the best picture possible. Reversal kicks in 7th January (some runs have this so I’ll take this date as the starting point) and the vortex splits. As @snowking mentioned just now we get a vortex shard drop into Siberia and then rotate clockwise with the reversed flow. Greenland block strengthens and ridges across to Scandy because of the gap left by the split vortex. Siberian air undercuts. With such a blocked pattern already in situ thanks to favourable trop led forecasts and processes at the moment maybe downwell impacts within 7-10 days. This would mean a cold, maybe brutally cold, easterly pattern from mid Jan onwards. Duration uncertain. 

Correct.  The cold in Siberia currently is close to unprecedented, there is incredible cold in the NH.  If the models are heading in the right direction....then a 20th century Great matcher is on.
 

Extract from RHC

Temperatures predicted to hit -50 degrees (-58 F). 

Russia’s Hydrometeorological Center has forecast that Western and Central Siberia will see temperatures as low as -50 celsius before the end of the year – around 20 degrees lower than the typical December cold.

 

BFTP

[tight isobar]

Just been to mr singhs and.........  let’s not forget the ecm was the 1st to pick this signal -days bk !!!..   some newsmaking/noteworthy.. is making inroads... @no doubt!!!

Ecm 12z 18/12/2020

Edited December 27, 2020 by tight isobar

[Zak M]

Lots of colder options showing up now in FI in the GFS ensembles. Here's perturbation 26.

   

And I apologise for going off-topic here, but the rash of snow showers over N. Ireland was well forecasted by a few models, and there was even some spectacular lightning in some of the showers.

 

[Frigid]

3 minutes ago, topo said:

I am a bit surprised because most of Central and Northern Europe had temperatures much warmer than normal even with minus AO this December.

Actually it is probably one of the warmest ever in Scandinavia, warmer than last year's with a positive AO

True, the second week in the UK was quite warm also, lifted the CET from 3.9 to 6.1. Not sure why this is tho.

[Purga]

26 minutes ago, bluearmy said:

Sst’s between the Netherlands and e anglia are as high as we’ve seen since 2015 

that 2c above where we would expect to see them does make a difference to the easterly and Dp’s /air temps 

Yes, hopefully massive lake effect snow deluging the country when the proper easterly cold arrives!

[sparky1972]

Evening all, just seen bbc forecast for the week ahead and they say a chilly but dry week, does this tie in to others opinions of what the models are showing? 

[BLAST FROM THE PAST]

2 minutes ago, Zak M said:

Lots of colder options showing up now in FI in the GFS ensembles. Here's perturbation 26.

   

And I apologise for going off-topic here, but the rash of snow showers over N. Ireland was well forecasted by a few models, and there was even some spectacular lightning in some of the showers.

 

That’ll be no lowland snow then 

BFTP

[Tim Bland]

14 minutes ago, tight isobar said:

Just been to mr singhs and.........  let’s not forget the ecm was the 1st to pick this signal -days bk !!!..   some newsmaking/noteworthy.. is making inroads... @no doubt!!!

Ecm 12z 18/12/2020

Eh? That’s for tomorrow? The Synoptics tomorrow look nothing like that? 

Edited December 27, 2020 by Tim Bland

[Chesil View]

Didn't comment earlier because I didn't want to jinx the ECM but great to see pretty much cross model agreement on the direction of travel. 

Not every notable cold/snowy spell or notable winter arrives with a great fanfare like the 2018 beast from the East sometimes they slide in almost unnoticed while everyone is looking the other way worrying about a temporary flattening of the upstream pattern.

 

[tight isobar]

7 minutes ago, Tim Bland said:

Eh? That’s for tomorrow? The Synoptics tomorrow look nothing like that? 

I didn’t suggest they were!? .. I was noting the comparable signal.  Via operational!

[Harsh Climate]

Quite a varied difference in where the models are predicting how far east the feature currently over northern Ireland tracks.. It looks like it's breaking away from the northern arm of showers. I wouldn't be surprised if it dived south and only affected wales and the South West missing areas further east.

[Mark wheeler]

The final frame of the Navgem 

[Catacol]

29 minutes ago, sparky1972 said:

Evening all, just seen bbc forecast for the week ahead and they say a chilly but dry week, does this tie in to others opinions of what the models are showing? 

There will be the odd surprise through the week I suspect, but we don’t have a convective easterly yet nor battleground synoptics - so probably not far off. This is just the beginning of what could be a memorable spell, but it is going to be a slow burner....