Model output discussion - Closing in on Christmas

[blizzard81]

3 minutes ago, Daniel* said:

 

It’s totally in line with what we’ve been seeing no significant long-standing block has been presented on means the ridge has always looked most likely a toppler, the ECM 12z is more progressive than 00z mean. 

The problem is on here I feel some only look at the operationals and they wonder that something has changed when really it hasn’t at all.

.

Indeed. In fact when you compare this morning's day 10 op with tonight's, the difference isn't that stark. 

[Valleyboy]

30 minutes ago, Skullzrulerz said:

A bit confused here with some saying it's bad and some saying it's good in regards to the ECM run?

I still think we are going to get a halfway house between the two 

That’s because no one has a clue

[LRD]

3 minutes ago, That ECM said:

That was his point

Yeah I re-read and then edited. Everyone makes mistakes 

Edited December 16, 2020 by LRD

[Daniel*]

1 minute ago, mountain shadow said:

I disagree. They've not all been topplers.  

What you said was false no mean has showed anything but a mid Atlantic ridge destined to topple. What is contained within ens well you can get December 2015 to December 2010... extremely normal to see and not helpful.

[PolarWarsaw]

The issue is, people start taking a computer generated forecast as gospel at +T200. At no point this winter have we got one single cold chart that's likely to produce either snow at the surface or go on to produce a cold spell that's sufficient enough for snow. Again, some pretty charts appeared at the day 10 range and the carrot is nibbled. The reality is, things change too much in our atmosphere for even the most expensive computers to live with, what is at day 10 this evening will end up being nothing like the chart the verifies. 

Chilly, but not cold is the most likely outcome for Christmas and into the New Year. 

There's no strong enough, long lasting ridge in the Atlantic modelled anywhere near a realistic timeframe to be calling anything other than average weather. It's clear tonight that there's another pattern around the corner for the Christmas-New Year period, cold or mild is up for debate. But you won't nail that down for another 4-5 days yet. 

Edited December 16, 2020 by PolarWarsaw

[Froze were the Days]

Well that's the poorest ECM D10 on the 12z I've seen for sometime...if that materialises you can say goodbye to anything the GFS FI is showing.

Edited December 16, 2020 by Froze were the Days

[chris55]

Just caught up with the 12z runs from the big three! 
 

Answers on a postcard please.

 

Catch up in the morning!

 

Early night for me. 

[stodge]

Evening all

Last evening's 12Z output was a clear split between GEM/ECM which found a way to a N'ly at Christmas and GFS which produced a new burst of energy to flatten everything and return to a more traditional Atlantic-led pattern. Onwards and sideways again tonight as we consider today's pronouncements.

12Z GEM - by T+120 (next Monday), the small LP coming off the United States has been absorbed in the flow of the main LP and run to the north-west of the British Isles. A mild or very mild SW'ly covers most parts but more heavy rain (perhaps orographic rainfall) affecting northern and western parts.  By T+180, a final secondary feature has crossed southern Britain and the complex LP is over Scandinavia. There's a light WNW'ly flow over the British Isles with a ridge coming in and some shortwaves over Iceland complicating matters (as they tend to). Pressure rises across the British Isles first as a ridge and then as a new HP cell before retreating to a major new HP in the Atlantic but there's a flow of mild or very mild air around the top of the HP and a new vigorous LP coming out of Canada. No easy path to cold from that set up I fear.

12Z GFS OP - a disappointing Canadian output for cold fans and GFS was awful last night so if there's a time for redemption, this might be it. It seems more substantial differences with GEM at T+120 than is often the case (suggesting FI could be T+96 and there's a lot to be resolved). GFS OP holds the LP to the north west and the LP to the south west is a more noticeable feature.  By Christmas Eve (T+180), we have a clear PM airmass and a NW'ly airflow down across the British Isles with a ridge upstream which, I suspect, won't be enough to hold back the next Atlantic trough coming out of Canada. Up to a point, that's true but the evolution gets a little more interesting by T+240 - an extensive but shallow trough from Iceland to the British isles is keeping the weather chilly and unsettled with another attempt to raise heights upstream. I also note lower heights over Europe offering the possibility of negative trough alignment. In effect, that's what happens as the trough drops through the British Isles and heights build to the east. The next Atlantic LP also disrupts south and south east through the British Isles by T+312. However, with no real upstream push, the Atlantic HP can build north and north west and the LP can drop right through ending up just to the south and a T+384 chart that is the polar (pardon the pun) opposite of last night's offering and a great start to 2021 for fans of cold and snow.

12Z ECM - well, the GFS ends up really well for cold fans - why? The GEM pushes a new burst of energy out of Canada at T+240 which flattens everything but GFS OP doesn't and there's time for amplification. I have to say the T+120 looks closer to GEM (as you might expect) and doesn't bode that well for cold fans given the GEM evolution. T+192 doesn't look promising either with the LP already pushing toward Greenland and signs of the PV in evidence. The HP is looking more like a mild-enabling mid-latitude block. The T+240 doesn't end well for cold fans - once again we are left waiting for an opportunity for amplification upstream. 

Looking elsewhere, the GFS 12Z OP has a sustained warming at 10 HPA which looks like it will do some damage to the already-weak PV though it's a way from any kind of split. 

Conclusion - we're left tonight with a lot of uncertainty and two distinct evolutions. GEM/ECM suggest the Atlantic will be too powerful for any kind of blocking to be created let alone sustained but GFS OP shows what a slower process can or could achieve. The key looks as usual to be how the PV will behave and whether any return to its normal position and associated plunge of cold air and ramping up of the northern arm of the jet can be delayed.

 

[BLAST FROM THE PAST]

The Doom brigade will be jumping over the collapse run...as usual but don’t worry.  There will be an attack from the NW but unlikely until towards New Year imo.  Lot’s to resolve , a bumpy ride....and here we go....cold for Christmas to start with

 

BFTP 

[LRD]

5 minutes ago, PolarWarsaw said:

The issue is, people start taking a computer generated forecast as gospel at +T200. At no point this winter have we got one single cold chart that's likely to produce either snow at the surface or go on to produce a cold spell that's sufficient enough for snow. Again, some pretty charts appeared at the day 10 range and the carrot is nibbled. The reality is, things change too much in our atmosphere for even the most expensive computers to live with, what is at day 10 this evening will end up being nothing like the chart the verifies. 

Chilly, but not cold is the most likely outcome for Christmas and into the New Year. 

There's no strong enough, long lasting ridge in the Atlantic modelled anywhere near a realistic timeframe to be calling anything other than average weather. It's clear tonight that there's another pattern around the corner for the Christmas-New Year period, cold or mild is up for debate. But you won't nail that down for another 4-5 days yet. 

I generally agree with what you're saying. Cool not cold. Frosts but that's it

However, most (with some exceptions) on here know enough not to take a chart at silly range as gospel. It's about identifying trends. Why is it that some on here can't wait to sneer at those who get excited by potential cold showing in the models (not that I think anyone has been getting especially carried away anyway) when it starts to move away from cold. They're adults, most will know the vagaries of model-watching. If they want to get excited by a cold chart at 200hrs, so what? That's part of the fun and the emotion of the hobby isn't it? The chase and discussing possibilities? And some people just seem to want to suck the fun out it all

Otherwise it would be

-'Oh a cold chart has appeared at 216hrs'

-'Well it won't verify'

-'True'

-'OK. Night'

-'Night'

Mods will probably delete this but I had to get it off my chest

[MATTWOLVES 3]

I sense a little Monday morning blues in here this evening... Things ain't to bad currently,and we have the big old 46 tomorrow to dampen the spirits even further. I will do my best with a positive update...in the meantime how's a little...I've got that Friday feeling GFS deep fi Hysteria..

[Mike Poole]

20 minutes ago, Battleground Snow said:

Hi All,

First post from a long time lurker....

Some fantastic discussion over the years both in summer and winter.

I am a bit OCD when extremes are shown, ( checking model output when supposed to be at work)

Typical day in winter.

Check mjo plots at 230

Fire up meteociel to check the icon at 3

Flick into wetterzentrale for ukmo at 4

Then onto Gfs and gem

Then GFS ensembles

Then ECM and ECM mean 

Then 18z GFS before bed

Anyway.. thank you all for time you take out of your day to help people understand complex meteorology.

Here is my first charts from the delayed 12z icon!

 

 

 

 

Welcome to netweather, Battleground Snow, and let’s hope we see some battleground snow in the next couple of months.  I relate to your OCD analysis, i don’t suffer from that myself, but it has become more of a go to hobby to check and post on the models, particularly the 12z suite, during the coronavirus restrictions which are making life so sodding boring.  Good to see the ICON at last!  

[Battleground Snow]

5 minutes ago, Mike Poole said:

Welcome to netweather, Battleground Snow, and let’s hope we see some battleground snow in the next couple of months.  I relate to your OCD analysis, i don’t suffer from that myself, but it has become more of a go to hobby to check and post on the models, particularly the 12z suite, during the coronavirus restrictions which are making life so sodding boring.  Good to see the ICON at last!  

Thanks Mike! Yes some battleground Snow would be great around the festive period..

I live a mile away from the centre of England at 185m ASL, so have had fair few dumpings of snow over the years where the Atlantic meets the cold from the east.

Only one hour until the 18z icon! (Hopefully)

[MATTWOLVES 3]

Going on the ECM ens I would say colder with some possibly widespread frosts looks a good call for the Xmas period out to the New Year..Im aware the longer range signals point towards Milder and wetter early next month,but let's not get to concerned about that at this juncture...

Have a great and stress free evening folks...tomorrow will im sure bring many more ups and downs...and thats the way we love it  

Edited December 16, 2020 by MATTWOLVES

[frosty ground]

31 minutes ago, PolarWarsaw said:

The issue is, people start taking a computer generated forecast as gospel at +T200. At no point this winter have we got one single cold chart that's likely to produce either snow at the surface or go on to produce a cold spell that's sufficient enough for snow. Again, some pretty charts appeared at the day 10 range and the carrot is nibbled. The reality is, things change too much in our atmosphere for even the most expensive computers to live with, what is at day 10 this evening will end up being nothing like the chart the verifies. 

Chilly, but not cold is the most likely outcome for Christmas and into the New Year. 

There's no strong enough, long lasting ridge in the Atlantic modelled anywhere near a realistic timeframe to be calling anything other than average weather. It's clear tonight that there's another pattern around the corner for the Christmas-New Year period, cold or mild is up for debate. But you won't nail that down for another 4-5 days yet. 

That 3 inches of snow must have been imaginary 

[mulzy]

Extended eps while continuing to show low heights over Europe now indicates a flatter Atlantic profile as hinted in the day 10 mean.  Still reasonable but trending the wrong way I am afraid.

Edited December 16, 2020 by mulzy

[Kirkcaldy Weather]

29 minutes ago, PolarWarsaw said:

The issue is, people start taking a computer generated forecast as gospel at +T200. At no point this winter have we got one single cold chart that's likely to produce either snow at the surface or go on to produce a cold spell that's sufficient enough for snow. Again, some pretty charts appeared at the day 10 range and the carrot is nibbled. The reality is, things change too much in our atmosphere for even the most expensive computers to live with, what is at day 10 this evening will end up being nothing like the chart the verifies. 

Chilly, but not cold is the most likely outcome for Christmas and into the New Year. 

There's no strong enough, long lasting ridge in the Atlantic modelled anywhere near a realistic timeframe to be calling anything other than average weather. It's clear tonight that there's another pattern around the corner for the Christmas-New Year period, cold or mild is up for debate. But you won't nail that down for another 4-5 days yet. 

Suppose I must have imagined this then (and the other areas that got some snow)  

You can always count on this thread getting unnecessarily panicky, we continue to progress on a positive note with both the tropospheric and stratospheric setup and as I mentioned yesterday I expect the blocked charts to continue being the theme as we head into the new year. ️  

[Daniel]

ECM clusters 

[Mike Poole]

ECM clusters T192-T240:

Atlantic blocked out on the two major ones, I would suggest.  So a cold Christmas looking a good bet, although not necessarily a snowy one of course. 

T264-T360, they’ve come up with 6 clusters:

Pick the bones out of that!  Or rather - and here’s a thought - don’t!  There’s stuff in an earlier timeframe that needs resolving before considering the period after Christmas.

[Daniel*]

43 minutes ago, PolarWarsaw said:

The issue is, people start taking a computer generated forecast as gospel at +T200. At no point this winter have we got one single cold chart that's likely to produce either snow at the surface or go on to produce a cold spell that's sufficient enough for snow. Again, some pretty charts appeared at the day 10 range and the carrot is nibbled. The reality is, things change too much in our atmosphere for even the most expensive computers to live with, what is at day 10 this evening will end up being nothing like the chart the verifies. 

Chilly, but not cold is the most likely outcome for Christmas and into the New Year. 

There's no strong enough, long lasting ridge in the Atlantic modelled anywhere near a realistic timeframe to be calling anything other than average weather. It's clear tonight that there's another pattern around the corner for the Christmas-New Year period, cold or mild is up for debate. But you won't nail that down for another 4-5 days yet. 

No they don’t people aren’t stupid like you make out, and well if we didn’t talk about it what would be the point in this thread? What’s generated some excitement is a cold snap, nothing impressive, coinciding around Xmas this is why it has got more attention I think, rather sad I know but a small hope for something more substantial following on. People are realistic and realise what we want... is probably not what we’re going to get. To many this is a form of escapism and expectations are low. People may get excited at one model output but don’t interpret that as they expect it to happen, people are prepared to be disappointed it’s something we’re very good at. The long range ens guidance for some days has been very good and consistent on showing a change to mild regime, credit where it’s due, it’s ticking down nicely for some seasonal weather at least. 

Edited December 16, 2020 by Daniel*

[Portsmouth Sun]

46 minutes ago, PolarWarsaw said:

The issue is, people start taking a computer generated forecast as gospel at +T200. At no point this winter have we got one single cold chart that's likely to produce either snow at the surface or go on to produce a cold spell that's sufficient enough for snow. Again, some pretty charts appeared at the day 10 range and the carrot is nibbled. The reality is, things change too much in our atmosphere for even the most expensive computers to live with, what is at day 10 this evening will end up being nothing like the chart the verifies. 

Chilly, but not cold is the most likely outcome for Christmas and into the New Year. 

There's no strong enough, long lasting ridge in the Atlantic modelled anywhere near a realistic timeframe to be calling anything other than average weather. It's clear tonight that there's another pattern around the corner for the Christmas-New Year period, cold or mild is up for debate. But you won't nail that down for another 4-5 days yet. 

Bang on, thank you for such a truthful honest post

[Earthshine]

Looking good for a seasonal Christmas at this point!

[Bricriu]

45 minutes ago, PolarWarsaw said:

The issue is, people start taking a computer generated forecast as gospel at +T200. At no point this winter have we got one single cold chart that's likely to produce either snow at the surface or go on to produce a cold spell that's sufficient enough for snow. Again, some pretty charts appeared at the day 10 range and the carrot is nibbled. The reality is, things change too much in our atmosphere for even the most expensive computers to live with, what is at day 10 this evening will end up being nothing like the chart the verifies. 

Chilly, but not cold is the most likely outcome for Christmas and into the New Year. 

There's no strong enough, long lasting ridge in the Atlantic modelled anywhere near a realistic timeframe to be calling anything other than average weather. It's clear tonight that there's another pattern around the corner for the Christmas-New Year period, cold or mild is up for debate. But you won't nail that down for another 4-5 days yet. 

This is true for most winters. However, in some previous notable cold spells the charts that appeared at day 10  did come to pass. I think this time we are going to end up in a halfway house solution between ECM and GFS. My bet is  on a significant cool down, but with mainly dry weather from Christmas day to around New Year, then our old friend Mr Atlantic will  take over. I hope I'm wrong and I get snowed during the last week of December

[fromey]

Hi, just read in Twitter land that the storm affecting the North East of the USA has taken a slight shift to the south! Don’t know by how much but it just goes to show that even at short range ( and we are talking a matter of hours) how things can change and will continue to change and evolve, so expect a lot more chopping and changing to come from the models.

[Mapantz]

If you wish to have a moan or post something in general, head over to here please.

Model discussion only in here.