Model output discussion - Winter has arrived

[feb1991blizzard]

3 minutes ago, bluearmy said:

Extended eps clusters show something I’ve never seen before with three sets of 33%! 

That only adds up to 99 - which one had 34% or did they all have 33.3%?

[bluearmy]

9 minutes ago, feb1991blizzard said:

That only adds up to 99 - which one had 34% or did they all have 33.3%?

Yes mr pedant  

12 minutes ago, Mike Poole said:

Very happy for them, but what does that mean for our cold prospects?

(Or is there a chart in your post that i for some reason can’t see?)

 None look mild ....... everything remains on the table ....

Edited December 5, 2020 by bluearmy

[NorthernRab]

10 minutes ago, feb1991blizzard said:

That only adds up to 99 - which one had 34% or did they all have 33.3%?

That only adds up to 99.9% - which one had 33.4%? 

[Singularity]

Certainly of interest to see the Atlantic troughs tending to be adjusted toward making less progress in the 3-5 day range. Perhaps GFS will follow suit tomorrow?

Reminds me of the glory winters of 2008-9 and 2009-10 in that respect. Back then, GFS' tendency to be too progressive was even stronger, while GEM had similar traits. ECM could be that way too, but tended to have the opposite behaviour in the 8-10 day range with too much 'wavy jet stream' going on. Some spectacular but rarely accurate charts used to come of of that!

Anyway, an unfortunate difference this year is that the high to our east as been more 'saggy-bottomed', drawing an exceptional amount of air up across Central and Eastern Europe from the Middle East or thereabouts. So, we find ourselves looking at scraps of cold air interacting with the Atlantic troughs, rather than broad areas of sufficiently cold, negative-dewpoint air.

It'll be scientifically interesting to see how much the big ridge manages to disrupt the Atlantic troughs when they're so lacking in the deep cold air that's been known to 'tilt the balance' at times in the past (deep cold air is denser than mild maritime air, making it more like a boulder than a mere stone in the stream).

[feb1991blizzard]

3 minutes ago, bluearmy said:

Yes mr pedant  

 None look mild ....... everything remains on the table ....

Actually you could have been even more pedantic back and said 33.3 x 3 doesn't add up to 100%, its 33.33333 recurring digit!

[SMU]

Evening All -

Are people still going on about lack of cold pool & not enough for snow

This must have been imaginary this eve then - I just stopped at Maidstone services 65M ASL

Still had good snow cover nearly 48 hours after the event

This all fell in air where the 850 Mb layer was between -1c & -2c

This evenings ECM sucks in a continental cold pool of -6C 

The temperature response at the surface over 2 days where is allowed to remain in situ certainly supports snow

Liking the long term prosects this eve & @Kirkcaldy Weather Yes that control run was off the AO charts !

 

S

Edited December 5, 2020 by Steve Murr

[STRiZZY]

9 minutes ago, NorthernRab said:

That only adds up to 99.9% - which one had 33.4%? 

33.33333.......3333% and so on. Aka 1/3 

[Allseasons-Si]

@Steve Murr

was you driving whilst taking photos

here's hoping that the gfs switches to the ecm solution on the 18z soon but i feel that it will be in the morning before showing that.

[DAVID SNOW]

31 minutes ago, bluearmy said:

Extended eps clusters show something I’ve never seen before with three sets of 33%! 

Not quite sure what to make of the response from Ireland, but their met people are talking about a turty tree and a turd possibility .

[SMU]

10 minutes ago, Allseasons-si said:

@Steve Murr

was you driving whilst taking photos

here's hoping that the gfs switches to the ecm solution on the 18z soon but i feel that it will be in the morning before showing that.

Just a creep at 2 MPH - services mostly shut anyway  

Eyes down on for the 18s

[Mike Poole]

There really have been some great posts in here in the last couple of days, thanks to everyone.  It all feels a bit weird, to be honest, to be starting winter without the usual Atlantic dross; the models are churning out good synoptics mainly, but cold air is in short supply.  And we discuss this against the backdrop of long range forecasts suggesting nothing but a mild winter.  I think they are wrong. I think they have over-egged La Niña and over and above that, have failed to notice that La Niña hasn’t really connected with the atmosphere anyway.

My assessment is for continuation of the blocking patterns throughout most of the rest of December with potential for snow, but with, unfortunately, a dearth of cold air to tap into, followed by a (brief or not so brief) Atlantic return, before a SSW which will lead to a much colder February.  We will see...

 

[BlueHedgehog074]

The GFS and ECMWF always at each other’s backs lol. Like this morning, as soon as the ECMWF goes for a similar evolution to what the GFS runs were showing, the GFS thinks to itself “oh no, I don’t want that stupid ECMWF to follow me, I’ll just throw up something different”. 

It’s about time those two stopped their petty fighting. Why not just settle your  differences guys and shake hands.

 

After all, the models can only do their best  Worth saying, models don’t also make the weather happen

Thought it might be worth showing some issues below that some people touched up on earlier with regards to the way models, like the GFS, blows up Low Pressure in the Atlantic quite early in the run:

You will notice the 2 string of Lows to our West upstream, and then the Low Pressure over the UK. All circled in black. All pretty separate at first, but essentially the GFS quite rapidly merges all these Lows together. The one in the first circle in the far left runs into the second Low, but as they get close to merging, they then run into the Low over the UK and that gets absorbed into those other 2 Lows. We then end up with this organised, circular blown up Low in the Atlantic. 

 

This breaks through to the North of the UK with the Atlantic getting a bit of a foot hold. It’s not able to slide to our South or South-East bringing us a flow from the continent. To be fair, the Russian block pretty much remains throughout the run. And generally, there’s not a massive raging Vortex to our North-West dominating with a flat, full-on, Westerly flow over the UK (even if the primary direction over us beyond later next week is between the West and South). 
 

The 12Z ECMWF has much less problems with blowing up Low Pressure in the Atlantic around the same/similar sort of timeframe as the GFS. And, at least until 168 hours, keeps Lows to our West more squashed and disrupted.

It does still start with two areas of Low Pressure upstream to our West wanting to merge together (see charts below). But considering the first chart I used from the GFS was for Tuesday 6pm next week, and that the 12Z ECMWF chart below is for Wednesday 12pm next week, then it seems the ECMWF is a little slower with the evolution.

Which goes onto this below

 

More promising than the GFS so far. Nevertheless, further issues develop down the line. At 144 hours on the ECMWF below, the black circle shows that squashed Low to the West of the UK attempting to slide South-East to the West of the UK. 

But some trouble develops. The chart above (although not circled) also shows a little Low developing off the coast of the Newfoundland area upstream. At 168 hours below, some merging issues happen again between some Low Pressure systems:

And that then leads to this at 192 hours 

 

That Low does eventually drift further North to the West of us and become shallower. 


 

I know for the UK, it may not look pretty for cold weather with heights building back over our South-East. And even though the pattern could flatten upstream, the 2 Northern Hemisphere charts does show both the Russian/Scandinavian High and the Northern Pacific High putting continued pressure on the Polar Vortex. This of which could lead to something more favourable for deeper cold and wintrier weather for the UK. (As longs clearly, all the High Pressure blocks were to set up in the right place. And that’s not guaranteed. But nice to see some possibilities). Amusingly, despite the 2 Lows out West on the ECMWF merging together between the 168 to 192 hour mark, had that merged Low been a bit more vertically aligned, it could have sent lots of warm air Northwards towards Greenland. Would then encourage heights to form in that area and make it even more of an obstacle for the Vortex to try returning to its home. So, when favourable, Low Pressure areas merging together doesn’t always have to be a bad thing. 

Admittedly, the 12Z GFS and 12Z ECMWF are just 2 runs, which I imagine will change again on the next runs. The above however was to demonstrate some things. Some people understandably might have a different take of what I have shown. But hope is of some help

One of the most evident things is that blocking to our East/North-East seems persistent. Next few weeks or so will reveal I guess if that Russian/Scandinavian block becomes a good, or a bad, guy for the cold weather fans.

Finally, a warm welcome back to Chino 

 

[Mike Poole]

Looks like the ICON 18z is going down the slider route:

I think we do need a big retrogression of the main heights Scandi and Russia though before we can get a scenario that might deliver copious snow, so we wait for that...we will see...

[dragan]

interesting thoughts, i think we will see the low pressure system coming in from the west, with some cooler (not cold) and some very mild spells. This i feel will continue  all the way through to March, when we will see some colder weather from the east. 

[LRD]

4 minutes ago, dragan said:

interesting thoughts, i think we will see the low pressure system coming in from the west, with some cooler (not cold) and some very mild spells. This i feel will continue  all the way through to March, when we will see some colder weather from the east. 

Any reason for that mate? Any models backing that view? Or is it just a big old gut feeling?

Or are you just being all edgy? 

[LRD]

Signs of a brief warm up before a cool down on the GFS spaghetti. The op at the warm end of things. Being at the 'warm end' can often be a good thing but not this time thank you very much

[LRD]

39 minutes ago, Mike Poole said:

There really have been some great posts in here in the last couple of days, thanks to everyone.  It all feels a bit weird, to be honest, to be starting winter without the usual Atlantic dross; the models are churning out good synoptics mainly, but cold air is in short supply.  And we discuss this against the backdrop of long range forecasts suggesting nothing but a mild winter.  I think they are wrong. I think they have over-egged La Niña and over and above that, have failed to notice that La Niña hasn’t really connected with the atmosphere anyway.

My assessment is for continuation of the blocking patterns throughout most of the rest of December with potential for snow, but with, unfortunately, a dearth of cold air to tap into, followed by a (brief or not so brief) Atlantic return, before a SSW which will lead to a much colder February.  We will see...

 

Agreed. You'd have to favour some kind of milder spell before the festive season but it ain't nailed yet. The ECM run threw that into doubt tonight along with the clusters

CFS v2 going for very cold weather from 19 Dec until the New Year although I know that's about as solid and reliable as my bladder after 4 beers

[BlueHedgehog074]

15 minutes ago, dragan said:

interesting thoughts, i think we will see the low pressure system coming in from the west, with some cooler (not cold) and some very mild spells. This i feel will continue  all the way through to March, when we will see some colder weather from the east. 

You could very well be right, but I suppose we’ll see how things go. Some colder conditions couldn’t be totally ruled out during Winter, even if it meant waiting for a while. 

[LRD]

ICON goes milder this evening but, hemispherically, it's not without interest

[Matt H]

28 minutes ago, dragan said:

interesting thoughts, i think we will see the low pressure system coming in from the west, with some cooler (not cold) and some very mild spells. This i feel will continue  all the way through to March, when we will see some colder weather from the east. 

Well that’s winter sorted then.

[Mike Poole]

Scotch egg run rolling!  T90, compared to 12z T96:

18z doesn’t phase the lows on the incoming jet stream, so this will be a better run with sliders to come...

Or maybe not!  

Edit, just going to bulldoze through anyway, T132:

One for the bin, i think...

Edited December 5, 2020 by Mike Poole

[IDO]

GFS sticking to its guns this evening:

d5>>

We can see the interaction, force -v- force which should pump up the Russian high even more! This is the third run in a row with the GFS going this direction so will be interesting to see how all this unfolds on this run in case GFS is right?

[LRD]

Ouch, not pretty

Stark differences between GFS and ECM.

[chionomaniac]

7 minutes ago, IDO said:

GFS sticking to its guns this evening:

d5>>

We can see the interaction, force -v- force which should pump up the Russian high even more! This is the third run in a row with the GFS going this direction so will be interesting to see how all this unfolds on this run in case GFS is right?

Oh, I see a bit of a change in the 18z gfs up to T+120 when compared to the previous run. Not massive, but certainly significant regarding the heights to the north of Scotland. And I am not looking at 850’s which are not relevant.....at least not yet.

Edit remember the changes up to this point are more important than what comes after

Edited December 5, 2020 by chionomaniac

[Matt H]

These GFS runs are about as popular as tier 3...