Model output discussion - Closing in on Christmas

[frosty ground]

1 minute ago, Scott Ingham said:

Yeah I get you mate. My point was its an excellent run when you factor in eastward shifts nearer to time 

Can’t it also shift west? 

[Guest]

1 minute ago, frosty ground said:

Can’t it also shift west? 

I would've thought that was less likely given the huge high in the Atlantic.

[northwestsnow]

EC mean suggests the amplified solutions in the 120-168 timeframe rule the roost ...

A cold frosty Christmas and the growing chance of snow for some,  complete contrast to last Christmas...

[BLAST FROM THE PAST]

I really liked the 00z ECM with a real cold plunge at the end.  The 12z mid term smells the GFS set up and then initially t216 to t240 maybe underwhelming in what one would expect after t192?

t216

T240

look at the movement in North America from both....there’s no Atlantic onslaught due, that trough    between Greenland and Iceland looking ready to plunge. Trough on ESB not coming to us....unless on very southerly track.  And US is one big HP!  Great end imo

 

BFTP

Edited December 20, 2020 by BLAST FROM THE PAST

[Weathizard]

7 minutes ago, Met4Cast said:

Where is the background forcing for sustained blocking? Where is the EPS support? It's going to turn chilly, yes. But those expecting a huge Greenland block are going to be rather disappointed. 

Would make up for all the winters we’ve had with fantastic back ground signals wouldn’t it, the amount of winters I’ve heard that the background signals are great and we end up with a terrible winter.

I don’t understand how you can make that statement either, there is certainly a big chance of a Greenland block, it’s nearly in a reliable timeframe now it’s not exactly in the depths of FI, whether it delivers or whether it’s too west based or a transient ridge we will see, but the signs even at 240 in the models is that the Atlantic is dead, so we could easily have further chances in new year.

[Scott Ingham]

11 minutes ago, KTtom said:

With all due respect to this concept that we need to be XXX miles west at + 168 hours because it will 'always' shift east when we head towards T-0, bearing in mind these 'super' computers must cost more than ill ever earn to make and run, dont you think the software experts would factor this in it it were true? ..Just a thought..?

Youd think so yeah but they dont. Look at GFS with split jet scenarios always sends too much energy over the top. Greenland highs with ECM always under amplify near the eastern Seaboard. Greenland highs modelled. Always modelled too far west. Steve Murr will back that up hes a huge believer. American meteorolgists. They are a big believer thats why they talk about runs and dismiss certain ones that dont look right. Its part of parcel of human interpretation of the charts and a big factor in making forecasts. Seeing beyond whats in front if your face. Its a skill

[Methuselah]

The longer the Uppergate scandal goes on, the more convinced I become: we are staring down the barrel of a highly marginal situation; some folks will see snow, but others will see nothing other than cold rain -- and some will see nothing at all? But, then doesn't rime count as 'wintry precipitation' too?

Whatever we get, it's got to be better than 8C and anticyclonic gloom!?

[Mike Poole]

6 minutes ago, Lukesluckybunch said:

Not such a bad mean there mike,but the lack of cold to mix in with is concerning in my opinion.did you think this is a good mean then?

To be honest, I would prefer to wait to see the clusters to give an opinion, it is further east than the op, yes, but weaker, if that makes sense, so that could mean with the lower resolution that some of the members are still running with the ECM view of yesterday, which was less favourable than GFS.  It looks like the uncertainty around Greenland remains, so I would await the 0z ensembles to firm this up.  

I wouldn’t worry about the cold yet, let’s get the pattern established and worry about that later, if it’s the sustained pattern which we want, the temperatures should drop pretty quickly.  

[Scott Ingham]

15 minutes ago, Griff said:

9 days ago towels were being thrown in and pram toys ejected. A week ago the charts were ridiculed as pure fantasy. 

Ever since almost all of us have been sensible enough to say it's speculative at best, yet here we are. 

Netweather panto season in full swing, oh no it isn't - oh yes it is. 

This year's production is Goldielocks... It's too warm, no it's too cold... Etc etc. 

Some excellent comments, some reverse psychology evident too. 

Relax with a Grolsch... You can't rush these things

 

 

Hahaha brilliant and so true!

[swfc]

12 minutes ago, Catacol said:

Loving this now. ECM at 240 won’t end up being exactly like this, but the core ingredients desired throughout the winter are still there

Note again the rise of pressure of ScEuro zone and a profile in the North Pacific that encourages low pressure fizzing across to the Rockies and helping promote a ridge higher up into the arctic.

I think this spells curtains for the vortex. I wouldn’t want to put a strict timeline on it, but first half rather than second half January now looks a decent bet.

For us? Let’s put together a best case scenario forecast:

1. Cold air arrives at Xmas. Favoured spots bag some sleet and snow as temps fall.

2. Greenland ridge gets enough traction to the north to embed, and given falling vortex wind speeds, a GLAAM profile that is relatively neutral and an MJO still in favourable phases it sticks around. Late December the trough over the U.K. therefore embeds also, colder air drawn SW from Scandy. Wintry mix.

3. Wave 2 forcing on the vortex around New Year adds increased strat stress. Frictional torque will begin to rise again during the first week of January. The trop pattern may relax a bit, but as frictionals promote increased mountain torque we will see amplification rise again. This amplification may be the knock out blow and an SSW. Week 2 of January.

4. For the U.K., given lengthening seasonal wavelengths this would see the block ridging east to Scandinavia

5.  The vortex splits and drops daughter vortices either side of our block, and a 2018 repeat occurs with trop impacts within 2 weeks. Vortex shard drops into Eastern Europe, reversal of the pattern pulls bitter air under the Scandy block as we hit the last 10 days of January.

This process would guarantee a cold January and in particular a very cold end to the month. No significant Atlantic influence at any stage. This represents my best case scenario mapped out in November but about 2 weeks ahead of time. The vortex has been hit harder in December than I expected back then.

Lots that can go wrong with this very cold-centred forecast but broadly speaking it stands a chance of sorts. This kind of severe potential event is what I’m on the winter forums for - and to see if we can spot things ahead of time and get one over on gloomyglosea...!

Tbh pal most just rubbished the 10 day ec, god only knows why

[Joe Bloggs]

27 minutes ago, damianslaw said:

A word on comments about uppers, it's one factor that influences precipitation type, but just one, crucial other factors include:

Thicknesses - generally sub 528 dam air is needed for snow

Dewpoints - need to be 0 or below, crucial and usually cannot be forecast with any accuracy until 24 hrs

Uppers - well I've seen snow fall and lie with uppers barely below 0 degrees

Intensity of precipitation - cannot be forecast until the precipitation is overhead, heavier it is, greater chance of evaporative cooling

Wind strength - lighter winds or slack airstreams increase chance of snow

Lapse rates - drier continental air tends to be better than maritime air for snowfall

Many other factors come into play, local topography, time of day, surface temperatures etc etc.

Please do not get hung up on uppers alone. We saw in early December snow falling in less than particularly cold uppers, parts of the Fens and south coast had lying snow, and this was not forecast well until the snow was falling out of the sky!

The wet bulb freezing level is another good parameter to use. This data is certainly available for the GFS, not sure about the other models. Again only very reliable at relatively short range. 

300 metres or lower is a very strong indicator for snow. 

[Kasim Awan]

ECM mean has us in the optimal place. Indicates that some runs are further east like the gfs mean.

Area 1 would have a lack of convection, area 2 an optimal combo of convection / cold air, and area 3 a higher risk, potential greater reward scenario. Air not as cold but more potential for higher precip totals. Area 2 please.

[Jeremy Shockey]

ECM 12 z ensemble mean

850 s for Dec 24th and 25th still looking very good indeed and conducive to a few snow showers in the East.......

And an improving mean in the medium term too 28th - 30th ( compared to the ECM 0z ) 

[swfc]

1 hour ago, swfc said:

240 ec is extremely good, bye atlantic

Strangely North West you found that funny, Catacol post covers it and it's a yes

[Mark Parsons]

28 minutes ago, Lukesluckybunch said:

Hi so given the current output would you say snow is likely,I mean are any of the models showing anything cold enough?

 

30 minutes ago, Lukesluckybunch said:

Hi so given the current output would you say snow is likely,I mean are any of the models showing anything cold enough?

Put simply the potential is there but that's all it is..........it's better than no potential so be patient........

[Scott Ingham]

29 minutes ago, Met4Cast said:

Where is the background forcing for sustained blocking? Where is the EPS support? It's going to turn chilly, yes. But those expecting a huge Greenland block are going to be rather disappointed. 

Glaam is neutral to above.

Mjo is riding through phases to support high level blocking

We have an ongoing 2nd EAMT with another potentially first week in Jan

We have below average zonal winds and a very upset vortex about to go pop

If you look at the current means i expect eps to change within a day or 2 max

Just to also add i noticed @Catacol writ something similar. If you can't see reasons to be in a great mood about the rest of winter you will never feel optimistic

Edited December 20, 2020 by Scott Ingham

[northwestsnow]

5 minutes ago, Kasim Awan said:

ECM mean has us in the optimal place. Indicates that some runs are further east like the gfs mean.

Area 1 would have a lack of convection, area 2 an optimal combo of convection / cold air, and area 3 a higher risk, potential greater reward scenario. Air not as cold but more potential for higher precip totals. Area 2 please.

I'm not entirely sure many people live in area 1, I will consult the local seal population for their thoughts? 

[Allseasons-Si]

Taking the day ten models at face they look pretty good on the broad scale of things

ECM,GEM,gfs and control

looking at the EPS clusters to day ten and that's a pretty decent match with trough through the UK and +ve height's to our NW/NE

extended

so still lots of blocking knocking about

latest EPS day ten.

OK,who ate all the humble pv pie because there isn't any left to share,...sorry!!!

 

[Scott Ingham]

17 minutes ago, Lukesluckybunch said:

Well it's not pesimism people are just being realistic

I think enough of a case has been put forward to show it isnt really realistic. Its a 50/50 in terms of low level snowfall. To bluntly state we will get rain when we dont have hi res models or dew points to look at is misleading 

[Scott Ingham]

17 minutes ago, frosty ground said:

Can’t it also shift west? 

Of course it can but it would go against what historically happens with well known bias. Just look at the mean. Its further east as more ensembles are seeing this further east. Ill sell my left leg if it gets modelled further west within the envelope 

[Skullzrulerz]

Is anyone having issues with loading this thread? It's taking me ages to load and I was going to make a somewhat long comment on here but afraid it will get locked 

Edited December 20, 2020 by Skullzrulerz
Autocorrect

[sheikhy]

Im actually thinking of missing the 18z run tonight cos i know what its going to show!!its gona be the same as the last 9 runs!!maybe a shift eastwards but thats bout it!!aint been this confident since lets say......2010!!!

[Sweatyman]

2 minutes ago, sheikhy said:

Im actually thinking of missing the 18z run tonight cos i know what its going to show!!its gona be the same as the last 9 runs!!maybe a shift eastwards but thats bout it!!aint been this confident since lets say......2010!!!

Wouldnt count on it Shaky, it will probably go mental

[Allseasons-Si]

3 minutes ago, Scott Ingham said:

Of course it can but it would go against what historically happens with well known bias. Just look at the mean. Its further east as more ensembles are seeing this further east. Ill sell my left leg if it gets modelled further west within the envelope 

OK guys, raise ya bets

[Met4Cast]

EC Det is in cluster 2 with 10 other members days 8,9,10. The majority cluster of 12 has a slightly stronger block up towards Greenland with a majority of the other clusters favouring an Atlantic block. 

Latest gloseas run suggests a higher probability of high pressure over the UK out until the 10th January, somewhat fitting in with the EPS signal. Greenland blocking looks transient at best on the EPS to me with a greater focus for an Atlantic ridge and low pressure to the east/over Scandinavia. 

Cold yes, chance of snow across the hills certainly, but again, not seeing anything to suggest monumental blocking besides a few det runs. Long way to go, worth taking into account the ECM over-amplification bias at times too. How many times have we been here this season already only for blocking to become massively watered down?

Realism is often mistaken for pessimism on these forums..