Model Output Discussion - Staying cold into the new year

[Tim Bland]

A snowy GEM run tonight. A relaxation of the cold towards day 10 but with no PV at all left in our local - I’d bet it will only be a temporary relaxation ... 

[nick sussex]

This looks like a  battle of two blocks .

With the UK sandwiched in between and that’s where all the shortwave drama is likely to take place .

It could be that the models are undecided as to whether the Russian high is going to push further west or whether the Atlantic blocking is going to be the key player .

 

[snowlessayr]

3 minutes ago, sukayuonsensnow said:

Looking at the overall models, I would be surprised at this point if most of southern UK has a notable snowfall (7cm accumulation or more) in the next couple weeks. There's still potential but this cold spell is more for northern England, Central and Northern Wales and Scotland.

There's still matters to be determined with how cold the air is over the UK next week, and that will determine what falls out of the sky for many.

Far far too early to say that. Features pop up at very short notice and can give a good dumping, battleground and sliders can give a hell of a lot. Obviously southern England struggles more than other areas but definitely chances that will come down the line 

[Mike Poole]

GFS // T294, the vortex now confined as far away from us as is physically possible - to be fair all models have been trending to this - but the look on its face, it knows the end is coming:

Edited December 30, 2020 by Mike Poole

[Snowman.]

1 minute ago, Mike Poole said:

Ignore the GFS this 12z run, it has gone wrong!  The other models paint a very different picture, and I’m sure the ECM will back this up in an hour or so!  

But the other models I would argue could be worse! 

GEM has heights sat to the south of the UK, sure its cold in the north but its no incredible.

GFS PARA gets a pass... a channel low is its saving grace but considering a few days ago the south was looking in the game for one but alas it currently sits in the channel high risk high reward.

UKMO is so far west with the ridge I might as well be looking E to russia for my cold.

Overall the output continues to looking rather mixed in my eyes, perferred yesterdays runs compared to todays..

 

[bluearmy]

6 minutes ago, Mucka said:

 

We may, but we also have the trough pushing N at the same time which means even if we get that basic pattern nailed there is likely to be very different scenarios of how that happens and what it means for Britain followed by even larger divergence thereafter than the norm.

Great for model watching but a nightmare for forecasting.

There are a few standard evolutions we would expect to see - some of which mean we miss the euro precip (which never makes it far enough north against the cold blocking which can be a ridge or a trough, some which place the U.K. in the battleground and some which drive a sou’wester across nw Europe .......clueless which one we are looking at though ! 

[northwestsnow]

1 hour ago, bluearmy said:

Gfs 12z has heights not as low as the 06z run. Ukmo (and icon) even less low. Hence thicknesses and uppers not as low. Hence more rain than snow from the streamers early next week.  There is plenty of precip showing on icon and gfs - damn shame ! 

UKMO has 850s -6/-7 120 & 144 nick .. not low enough ?

[bluearmy]

The ens modelling has indicated that the blocking to our north will relax roughly in our longitude to allow the trough to drop down - whether that’s to our west or just east we have no idea - the envelope is wide. We await the ops to give us some guidance on this together with ens clusters - add in the complication on the southern arm always trying to get north and its fun.  

[sukayuonsensnow]

1 minute ago, snowlessayr said:

Far far too early to say that. Features pop up at very short notice and can give a good dumping, battleground and sliders can give a hell of a lot. Obviously southern England struggles more than other areas but definitely chances that will come down the line 

Of course! There is potential but it really depends on how cold the air is into next week and what type of precipitation is moving in off the North Sea. 

Will need to monitor this in the upcoming model runs.

If the air is cold enough next week then some southern parts could get a decent snowfall. It looks likely we will get some type of precipitation off the North Sea into next week for a time, just a question of how cold it is and how heavy the precipitation is.

Based on the current trends I'd be surprised - BUT - things can change of course even at short notice. Some of the heaviest snowfalls I've seen in my local area in the UK have popped up at short notice, sometimes even by complete surprise.

[bluearmy]

Just now, northwestsnow said:

UKMO has 850s -6/-7 120 & 144 nick .. not low enough ?

I mentioned Ukmo is a little lower than the other models .....as Steve said, intensity may make a big difference if we see those uppers verify 

[Mike Poole]

2 minutes ago, Snowman. said:

But the other models I would argue could be worse! 

GEM has heights sat to the south of the UK, sure its cold in the north but its no incredible.

GFS PARA gets a pass... a channel low is its saving grace but considering a few days ago the south was looking in the game for one but alas it currently sits in the channel high risk high reward.

UKMO is so far west with the ridge I might as well be looking E to russia for my cold.

Overall the output continues to looking rather mixed in my eyes, perferred yesterdays runs compared to todays..

 

At the risk of sounding boring, at this stage it is still about setting up the general synoptics over the NH rather than what is forecast for the UK right now.  And it is taking time.  But it is still going in the right direction...

[MKN]

1 minute ago, northwestsnow said:

UKMO has 850s -6/-7 120 & 144 nick .. not low enough ?

Plenty low enough, Particularly further West as the air drys/cools as it crosses the country. The East would have the benefit of heavier showers though so snow still more odds on than against from what i can see. Some obsession over the 850s in here tonight. -5/6 will be fine for many.

[ALL ABOARD]

Our old mate Shannon entrophy will be knocking about for the next few weeks. 

There's to much going on for the models to accurately focus past a few days. 

A major reversal with a trop vortex that is almost non existent. 

We could all be sipping shandys in a few weeks with a golden tan or wondering why there are polar bears standing in the back garden. 

Would we have it any other way? 

NO.. 

Best model output watching for a long time. 

[Fozfoster]

30 minutes ago, snowice said:

To many contradictory posts it's will snow won't snow not cold enough,new members must be right confused.

Thats tells me most people have not got a clue........ like me !!!!

[Mucka]

11 minutes ago, bluearmy said:

There are a few standard evolutions we would expect to see - some of which mean we miss the euro precip (which never makes it far enough north against the cold blocking which can be a ridge or a trough, some which place the U.K. in the battleground and some which drive a sou’wester across nw Europe .......clueless which one we are looking at though ! 

Me neither but I feel the output is heading toward the trough to our N phasing with the one over Europe but with both having pressure decline over the UK at the same time ultimately meaning that phasing takes place somewhere over the UK leaving us in a slack flow with a ridge to our W and E and pretty much impossible to know any detail from there.

There would be less danger the further S those troughs phase IMO as that will keep things a little further E I hope the N wins the race and in an ideal world the phasing will happen in the channel or over the S which could potentially be very snowy.

Of course having stressed all that ECM will now go a different route!

Edited December 30, 2020 by Mucka

[stewfox]

1 hour ago, snowice said:

To many contradictory posts it's will snow won't snow not cold enough,new members must be right confused.

My understanding of following the weather for over 50 years is we need blues over us and yellows / oranges to go away . Supporting graph attached.

Edited December 30, 2020 by stewfox

[nick sussex]

In terms of the easterly the current 850 forecasts are liable to change and the forecast re any snow is problematic .

Its easier for the modeling when you have a cold pool which drops south into the circulation and then gets advected west .

Here this is a cold pool generated in situ so each run is likely to show varying depths of cold.

 

[Methuselah]

Perhaps the stratospheric data forgot to upload? Or maybe all the balloons burst? Who knows? But today's 12Z really has thrown a wobbly!

[I remember Atlantic 252]

rain risk on UKMO? havin' a laugh

[Jeremy Shockey]

GEFS 12 z ensembles.

A good cold mean until 6th Jan , ( especially cold 4th , 5th ) .......afterwards a bit too much scatter to draw conclusions .

[Mike Poole]

GEFS for uppers, well broad picture is it could snow anytime if other conditions are right, these are for London-ish:

Getting colder!

[Jason H]

2 minutes ago, I remember Atlantic 252 said:

rain risk on UKMO? havin' a laugh

Going based purely on that chart, precipitation away from the coasts will be of snow.

[Tim Bland]

7 minutes ago, stewfox said:

My understainding of following the weather for over 50 years is we need blues over us and yellows / oranges to go away . Supporting graph attached.

It’s a solid theory...blue good yellow bad should be the new mantra. Re being patient and getting the righ my Synoptics in place ...sod that! I want snow now!! It’s January this weekend and before you know it in 4 weeks time the annual ‘sun is getting stronger and will melt the snow’ in February line will be rolling out. IF this is going to be a memorable winter for snow then the next few weeks are the prime time! Fingers crossed for a snowy easterly next week and a battle ground the week after. If we get that  I’ll be happy. If we are still drooling over ‘nice charts ‘ in 4 weeks time but there hasn’t been a proper snow fall I might just find a new hobby

[Singularity]

A significant change by ECM (as of 00z), GEM, UKMO and parallel GFS today has been a move to a more compact HP circulation around Greenland, which moves an area of deep cold to our northwest next week.

Those models are trying to figure out how much LP development occurs in that very unstable environment. GEM 12z develops it a huge amount (seems a bit OTT) while the ECM 00z developed it only a little, allowing the HP to our northeast to work in tandem with a low moving across Iberia to move some colder air our way from the east.

Parallel GFS didn't develop it much but sent it toward the UK rather than keeping it to the west. It also, crucially, lacked a big low moving across Iberia. The results are a bit marginal for my liking, low-level snow-wise.

Meanwhile, the operational GFS sits up in its own tree, humming a tune that we struggle to understand.

[Cold Winter Night]

GEFS P8 shows what happens if a stronger Scandi high forces the cold to go around, instead of dropping down between Scandinavia and Greenland. With growing Scandi influence, this is one of the options. At first, we would be in the waiting room with many disappointed folks, but in the end we would look East, with a Trans Siberia express coming.

At 192 and 240: