Model output discussion - Winter has arrived and the hunt for cold is on

[feb1991blizzard]

I will have a number 14 please - Feb 1991 redux in terms of snow totals for the East.

[ICE COLD]

Some interest Picking up towards the end of the GEFS. 

[swfc]

7 minutes ago, feb1991blizzard said:

I will have a number 14 please - Feb 1991 redux in terms of snow totals for the East.

Yes Feb pick of the bunch there.bit of a non descript set of ens there which pretty much says it all tbh

Edited December 11, 2019 by swfc

[IDO]

4 minutes ago, swfc said:

Yes Feb pick of the bunch there.bit of a non descript set of ens there which pretty much says it all tbh

Yes, difficult to make sense of them, but no sign of classic zonality, which is a plus. The spreads also highligh the "potential":

The variance is on the Pacific ridge, maybe Atlantic ridge and Scandi heights? So maybe changes afoot, or gremlins or GFS just struggling in FI? Who knows? Up to Christmas pretty average fare after the next 5-days colder flow.

[ItNeverSnowsInWindsor]

Soemthings a foot towards Xmas period!

 

[Frosty.]

Looking at the longer term GEFS 6z there is certainly some wintry interest around Christmas time..oh I love P14 !!!!!!!!!

Edited December 11, 2019 by JON SNOW

[Methuselah]

Well, in the pursuit of honesty, Monday's 'smart money' is now fast approaching Poomageddon!

    

    

I'm sad to announce that all talk of a BBQ Christmas has, from this point on, been erased from history!

[Anthony Burden]

GFS 06z ditching the idea of pressure rises,returning to met office unsettled probabilities over festive 

season,could get a cold shot over Christmas period.

[mountain shadow]

4 minutes ago, Anthony Burden said:

GFS 06z ditching the idea of pressure rises,returning to met office unsettled probabilities over festive 

season,could get a cold shot over Christmas period.

I think our only shot at some snow on Christmas is a brief Northerly toppler/sinker I think.

[Purga]

The latest ENS 06z do indeed seem to be hinting at some colder options post Xmas

[Frosty.]

The longer term Ecm 0z ensemble mean is cooling on the idea of the euro trash high bringing a benign mild christmas..it looks wetter..if it can't be cold, at least let it be wet!!..

Edited December 11, 2019 by JON SNOW

[jonboy]

18 minutes ago, JON SNOW said:

The longer term Ecm 0z ensemble mean is cooling on the idea of the euro trash high bringing a benign mild christmas..it looks wetter..if it can't be cold, at least let it be wet!!..

We don't need any more wet thankyou very much. What we need is cold and dry at least until the new year then it can snow as much as it likes

[swfc]

3 minutes ago, jonboy said:

We don't need any more wet thankyou very much. What we need is cold and dry at least until the new year then it can snow as much as it likes

yes id agree.We in Sheffield are still saturated after our floods like a lot of areas.There isn't a significant cold spell looming altho some snow to high ground.Im not a wintry shower cold fan so ill take bright and dry until or if something to my liking cold wise arrives.Im not greedy just -15 850s from the ene please

[Mucka]

Picking the bones out of the output.

It can be difficult to pick up on small changes when we are viewing the output run to run and pick up on any trend, especially when the output is quite volatile.

At the risk of overstating this, GFS is not really worth the time at the moment as it almost certainly wrong quite early re Polar heights (even at 72h it has missed the boat according to the Euros)

Just to illustrate this once more here is ECM V GFS just 120 hrs. (Area of interest just NE of Greenland)

.

So filtering that out and concentrating on UKMO and ECM we can see that the trend is for high pressure to build over the arctic in the short/mid term.

 

Trend 2 is for a ridge of high pressure to push NE from Russia and perhaps through E Scandinavia. This has two effects, 1 it reinforces Arctic high pressure with a bout of WAA and 2 it slows the Atlantic trough (GFS either overruns this completely or has it further E and has no Arctic high)

And trend 3 is a question mark because it may or may not become a trend but filtering out GFS a ridge in the mid term (exactly where is even more uncertain but perhaps just W of Scandi) think this mornings ECM for very rough guidance.

The background signal of a strengthening PV is obviously counter to any pattern change and this may be why GFS is hell bent on sending the jet over any potential blocking not withstanding it being incapable of modelling the Arctic,

When I originally posted a window of opportunity for a pattern change 16th/19th Dec I would have said it had about 25% chance, now I would say it is about 50% and we have seen the MO reflect these increased chances.

It is arguable what exactly constitutes a pattern change but in the context of the Meto Forecast then being for weeks of unrelenting zonal and charts back then being very flat I think any change away from that to a quieter regime with the Atlantic held back or deflected well N of the UK would be considered one however if it is quickly overrun in a couple of days then it wasn't really a change, just a lull, so any blocking needs to stick for at least a few days.

Cold prospects? 

Clearly we need a pattern change to blocking before we get any proper cold across the UK but all blocking does not lead to cold.

So while we have improving prospects of some blocking appearing (and these are still around 50/50) this blocking has to deflect the jet SE or at least split energy and then we still nee the block to position and orient favourably, It really does take a lot to bring a proper cold spell to whole of the UK..

So chances of cold are slim but the trend is improving. Best case scenario we have our pattern change and Atlantic stalled by Dec 19th. We get undercut and mid/high lat blocking positions and orients favourably to bring in polar flow around Dec 22/23rd but we need a lot of things to go right and to confound the background signals for that to happen.

Long term prospects?

It is currently hard to see extensive N blocking developing so I think hoping for a 3/4 day cold snap around Christmas is about as optimistic as even the most optimistic coldie should be for now.

On a more positive note, the output can change very quickly once a pattern change is settled upon.

A journey of a thousand miles begins with a single step (Lao-Tzu) and that first step for us is to see a ridge consistently modelled just before we enter final 3rd of the month.

 

 

 

Edited December 11, 2019 by Mucka

[swfc]

Maybe nothing but icon at 108hrs looks to have better heights pushing down towards Greenland from the arctic.more importantly the nhp resembles a dog's face with a black eye

[SLEETY]

  Don’t look beyond 6 days and expect it co come off as shown,just look for trends in the far reaches of model output,is the advice for any new people reading the forum,they chop and change every day after 6 days,probably explain why the met change their long range forecasts so much.

So  the same posters in here  who only talk about long range upto day 16 should only be give a casual nod,as these charts never verify,and and chop and change so much,they are not really worth bothering to look at in the first place

[swfc]

18 minutes ago, SLEETY said:

  Don’t look beyond 6 days and expect it co come off as shown,just look for trends in the far reaches of model output,is the advice for any new people reading the forum,they chop and change every day after 6 days,probably explain why the met change their long range forecasts so much.

So  the same posters in here  who only talk about long range upto day 16 should only be give a casual nod,as these charts never verify,and and chop and change so much,they are not really worth bothering to look at in the first place

Tbh sleety I'd be looking for a trend over 6-10 days the way the models are going but I take your point

Edited December 11, 2019 by swfc

[weirpig]

Wintry showers are still on for Saturday     Snow across much of Wales  Scotland  and the midlands on this run      a few should see snow failing  at some point  going on these charts 

Edited December 11, 2019 by weirpig

[mountain shadow]

8 minutes ago, SLEETY said:

  Don’t look beyond 6 days and expect it co come off as shown,just look for trends in the far reaches of model output,is the advice for any new people reading the forum,they chop and change every day after 6 days,probably explain why the met change their long range forecasts so much.

So  the same posters in here  who only talk about long range upto day 16 should only be give a casual nod,as these charts never verify,and and chop and change so much,they are not really worth bothering to look at in the first place

Have to disagree with a fair bit of this.

Whilst, of course, a day 6 chart is NEVER going to be exactly right you can look past day 6 across the model suites and with other teleconnections have a decent stab at where things might be in 10 to 20 days.

So, for example, based on current output, there is a very low probability of a high latitude block being in a position which is favourable to bringing in a decent countrywide snowy cold spell. What is more probable is a continuation of what we have now, but perhaps slightly drier in the South and East as pressure could be higher down there.

[SLEETY]

You do find if their is a trend for milder weather in the latter stages of the models,it does appear more likely it will happen,as is being shown at the moment.,however if you get a lot of colder options in the far reaches of the model output,more often than not it doesn’t  happen,lol.

 

Thats the UK climate in the winter,frustrating for cold weather fans

[SMU]

Interesting UKMO 144

Good amplification & ZERO wind over the Uk. Pretty high potential for low temps overnight especially Scotland of this pans out-

Its near on impossible these days to get very still air !

GFS is further south with Sat eve snow potential-

Edited December 11, 2019 by Steve Murr

[shaky]

Dunno what to make of the ukmo 144 h chart!!think that low sliding in the Atlantic will just deepen and flattern everything out again !!

[mountain shadow]

Just now, shaky said:

Dunno what to make of the ukmo 144 h chart!!think that low sliding in the Atlantic will just deepen and flattern everything out again !!

The 168 out later will give us a clue. But any front running into the cold air embedded could be wintry.

[Weathizard]

The day 6 UKMO upsets me to look at, that damn piece of vortex over Canada and elongating troughing is the absolute killer for us on this chart, aside from that you’d say this chart actually has a bit of interest. Shame.

[ItNeverSnowsInWindsor]

The main thing is that the shortwave is getting disrupted in the Atlantic and forming a long stretch instead of the more rounded feature showing on icon and bringing SW’lies.

Nice heights building over Iceland/Greenland. Just hope all the cold air in Iceland helps to build heights there even more strongly.

Edited December 11, 2019 by prolongedSnowLover