Model Output Discussion - moving into Winter

[Lukesluckybunch]

Lets hope we can improve further on the 12z..less of that low in Iberia that just keeps spinning around,if it's further South it shouldn't be a issue..due to the easterly influence..But if it does come north and bumps up against the block..it could leave us in mild southerlies..that's not what we want at all..I would only give this around a 20% chance though...as all the background signals point to cold weather from the east dominating!

[feb1991blizzard]

1 hour ago, chionomaniac said:

This type of pattern verifies far better than a downwelling riskier SSW. Yes deep cold is always a lottery for this country, but an upwelling Greenland split are definitely the tickets I would want to have......

would it be a leap of faith to suggest we could hit the jackpot and get both? - ie- an upwelling wave 2, to keep us going for xmas, then just as the pattern is relaxing, a huge over the top downwelling shred to wipe the vortex out for the rest of winter. 

[damianslaw]

A big change taking place tomorrow in the overall pattern, after about 6 weeks plus of incessant mild southerly/south westerly/westerly soruce airflow with a trough seemingly stuck on rotation to our west, high pressure that has been in position for most of this time further to our NE is on the attack, and with a very weak jet, will have easy time in taming the atlantic - very abnormal for what traditionally is the most 'westerly' period of the year.

The rest of this week will bring continuous easterly flow, nothing particularly cold for the time of year, just a little below average, with frost reserved for sheltered western parts, sunnier and clearer further west and north you go, duller to the east and south. Not very inspiring conditions for the south and east. The main theme is dry after 6 weeks of endless rain.

I've banged on about the 5th for quite some time now, and it is from then on things become more interesting, models showing a low/trough feature to the south developing as heights begin to advect to the NW, in the shorter term the models show these to have some influence - possibly giving fairly mild conditions for the south at least, but the north most likely to hold onto the cold, and we then have a recipe for a stand off, with the cold in with a good chance of ousting away any milder attempt from the south. All a long way off, but such battlelines make for very difficult forecasting and I would expect the risk of snow will increase markedly. 

In the meantime, expect the models to play around with the position of high pressure to the NW and lower pressure to the south - swapping places all the time.. until things creep into the reliable.

[legritter]

5 minutes ago, damianslaw said:

A big change taking place tomorrow in the overall pattern, after about 6 weeks plus of incessant mild southerly/south westerly/westerly soruce airflow with a trough seemingly stuck on rotation to our west, high pressure that has been in position for most of this time further to our NE is on the attack, and with a very weak jet, will have easy time in taming the atlantic - very abnormal for what traditionally is the most 'westerly' period of the year.

The rest of this week will bring continuous easterly flow, nothing particularly cold for the time of year, just a little below average, with frost reserved for sheltered western parts, sunnier and clearer further west and north you go, duller to the east and south. Not very inspiring conditions for the south and east. The main theme is dry after 6 weeks of endless rain.

I've banged on about the 5th for quite some time now, and it is from then on things become more interesting, models showing a low/trough feature to the south developing as heights begin to advect to the NW, in the shorter term the models show these to have some influence - possibly giving fairly mild conditions for the south at least, but the north most likely to hold onto the cold, and we then have a recipe for a stand off, with the cold in with a good chance of ousting away any milder attempt from the south. All a long way off, but such battlelines make for very difficult forecasting and I would expect the risk of snow will increase markedly. 

In the meantime, expect the models to play around with the position of high pressure to the NW and lower pressure to the south - swapping places all the time.. until things creep into the reliable.

Hi gang, the above post is very similar to what i was about to post .Very interesting synoptics will play out , each day at a time with many twists along the way .take care all all round .

 

[Lukesluckybunch]

Long range ICON coming out right now..will be interesting can we upgrade this easterly further for the weekend and beyond!

[BLAST FROM THE PAST]

I think the extremity being shown is a combination of several things combining to produce potential extremities.  The Record breaking volcanic eruption (touted in my sig due to what I believe is our entrance into Grand Solar Minimum) in the Pacific supercooled the SH strat with very good correlation of HLB in NH in following winter.  This in turn saw record cold spread to the SH continents wave after wave and still going.  Indeed Spring hasn’t arrived and it’s about to turn to Summer.  We have a 3rd La Nina and a recent study has shown that there is now a cooling trend in the Pacific (The recent study, ‘Systematic Climate Model Biases in the Large-Scale Patterns of Recent Sea-Surface Temperature and Sea-Level Pressure Change’, looked at temperatures at the surface of the ocean recorded by ships and buoys from 1979 to 2020.

It was discovered that the Pacific Ocean off South America had actually cooled over that time, along with ocean regions farther south, too).

….more La Ninas?  Thirdly I’ve spoken of 84/85 as an anecdote as similar cycles were in play then.

The runs are currently more extreme than I expected initially.  But there’s forces in play that we will have to sit and watch play out.  Let’s enjoy the ride

 

BFTP

Edited November 28, 2022 by BLAST FROM THE PAST

[Rayth]

This is the last thing we need in this saga 

A worse GFS  

 

 

[phil nw.]

Well the generally colder outlook seems to be still on track with a new much different NH pattern set to show in the near term.A complete switch to a -AO/NAO setup.

A couple of images just to simply illustrate the effect of a negative AO/NAO 500hPa pattern,taken from the latest gefs  day10.This may be helpful to folks new to chart watching perhaps.

The first image is the height anomalies and the second the 2m temperature anomalies.

The first image shows the +ve hts to the north(red colours) and the blue lower heights to the south. 

The  second image is showing anomalous cold pushed out of the Artic into mid-latitudes by the warmth headed into the polar regions at the 500hPa level. reflective of a solid -AO setup.

This is quite a stark move away from our normal westerly Atlantic pattern and shows at quite short range now- in fact the change gets underway this week with the development of a blocked Atlantic and the onset of the easterly as temperatures drop.

We can see this from an overview chart for Friday

This is a very uncommon early Winter setup and very promising for cold lovers with all the main landmasses going colder than normal  down to those middle latitudes.

As we look further out then the ens. guidance continues to show a Greenland high developing in week 2. Yes there may be blips on the way such as the Iberian low in the medium term but really the bigger picture couldn't be much better than what is modeled currently.

 

[TSNWK]

6 minutes ago, Rayth said:

This is the last thing we need in this saga 

A worse GFS  

 

 

So why release it then ?  

[sheikhy]

6 minutes ago, Rayth said:

This is the last thing we need in this saga 

A worse GFS  

 

 

I been sayin this for a number of days now!!its just as bad if not worse than the op lol!!!thats why i just continued to view the op lol!!

[feb1991blizzard]

8 minutes ago, Rayth said:

This is the last thing we need in this saga 

A worse GFS  

 

 

Then why in gods name are they going ahead with the 'upgrade' then?

[sheikhy]

1 minute ago, feb1991blizzard said:

Then why in gods name are they going ahead with the 'upgrade' then?

Just to create more animosity in here!!nah jokes aside it does seem pointless!!icon steady at 96 hours!

[Singularity]

While we can't compare the available cold air to Nov-Dec 2010 (not even close until at least the end of this week), the high-latitude blocking sequence has enough similarities that I'm really interested in how well the various forecast models perform this time around.

I'm relying on memory here so please don't take this as for sure how it went down, but I recall that in mid-Nov 2010, the forecast models did a decent job picking on the broad-scale change to a prolonged HLB setup, but struggled to resolve two main features: The nature of lows tracking well south of usual (just how far south and how well organised i.e. rounded as opposed to flattened shape) and, perhaps more importantly, the cut-back of the polar jet down the eastern flank of the blocking high. If I'm recalling this correctly, the magnitude of cold air advance west across Europe was underestimated, though I can't recall at what lead times.

There has since been a dozen years of model upgrades (well, mostly upgrades...), during which we've had a few strong HLB episodes, of which 2018s was the most comparable but was driven by a split-vortex SSW, limiting relevance. As far as I'm aware, this upcoming event is the first strong directly troposphere-led one since 2010. So, who knows whether the old biases are still applicable now? Well, before long, we'll find out!

[Midlands Ice Age]

57 minutes ago, damianslaw said:

A big change taking place tomorrow in the overall pattern, after about 6 weeks plus of incessant mild southerly/south westerly/westerly soruce airflow with a trough seemingly stuck on rotation to our west, high pressure that has been in position for most of this time further to our NE is on the attack, and with a very weak jet, will have easy time in taming the atlantic - very abnormal for what traditionally is the most 'westerly' period of the year.

The rest of this week will bring continuous easterly flow, nothing particularly cold for the time of year, just a little below average, with frost reserved for sheltered western parts, sunnier and clearer further west and north you go, duller to the east and south. Not very inspiring conditions for the south and east. The main theme is dry after 6 weeks of endless rain.

I've banged on about the 5th for quite some time now, and it is from then on things become more interesting, models showing a low/trough feature to the south developing as heights begin to advect to the NW, in the shorter term the models show these to have some influence - possibly giving fairly mild conditions for the south at least, but the north most likely to hold onto the cold, and we then have a recipe for a stand off, with the cold in with a good chance of ousting away any milder attempt from the south. All a long way off, but such battlelines make for very difficult forecasting and I would expect the risk of snow will increase markedly. 

In the meantime, expect the models to play around with the position of high pressure to the NW and lower pressure to the south - swapping places all the time.. until things creep into the reliable.

Great post Damian..

was about to post similar (though not as good), and particularly to point out that 90% of our snow falls occur on the boundary between the cold and mild air. We, in England, need the depression to the south to edge closer, from time to time, to get a decent snowfall (unless we have a BFTE).

So very much a two-edged sword.

MIA

[Ice Day]

Some fantastic posts on here today, great stuff.  I totally understand the 'it's always at day 10' and 'it's going to get watered down' viewpoints, but in my view it's better seeing this modelled than not.  If you look across the suites at 240, the variations on a theme are notable, with the ECM, GFS, GFSP and GEM all showing a huge amount of blocking in and around Greenland.  

    

Any one of these solutions would really put us in with a great shout of finally seeing a proper attack from the north, north east and/or east.  I just don't see a quick return to mild zonality from any of these options.  However, I think we just need to be patient, as other members have pointed out, we will probably need to wait for the middle of December for the possibility of something significant falling from the sky!  But at least we're in the game, which is already an improvement over last years debacle!

[bluearmy]

17 minutes ago, Rayth said:

This is the last thing we need in this saga 

A worse GFS  

 

 

If you check the verification stats, they are barely any different 

 

[sheikhy]

Very good start to icon!!150 hours iberian low squished!!

[syed2878]

What a fascinating period of model watching this has been third La Nina winter. I have a feeling that we will hit the jackpot this time. what interests me is with all those charts we been seeing for the last week or so I really am surprised that the UK Met is not on board yet that’s what makes me to keep my feet firmly on the ground for now here’s to the 12 hours runs. Let’s hope they are as good if not better. ️ in time, let’s hope we get plenty of that for all of us to enjoy

[Guest]

I'm no expert but surely this is a extraordinary chart for December 5th from the ICON 12z:

[irish1]

ICON 12z shows how we fail to tap in any real cold in the short term.

[pad199207]

2 minutes ago, Tidal Wave said:

I'm no expert but surely this is a extraordinary chart for December 5th from the ICON 12z:

It is but with just nothing to show for it and if anything the uppers look increasingly diluted

Edited November 28, 2022 by pad199207

[Mike Poole]

One thing that has struck me looking at the countless model runs over the last week or so, is how resilient both the formation of the initial block, and its eventual evolution to a Greenland high is, to whatever obstacles in the form of badly placed shortwaves, low pressures etc. the models deign to throw in the way on each individual run.  

It is as though the destination is known and the models will find a way - and on some runs that has even meant in extremis, the Azores high ridging west of the whole caboodle and shoving it onto the Asian side.  

This might be down to teleconnections, but it seems a much stronger influence than I can recall seeing before.  I’ve mentioned before the possibility that all roads lead to Rome on this, but why is another question?  It could be the +AAM, and MJO - I guess, but are we seeing some unknown driver at work? There is the wild card of the volcanic eruption, which we know affected the strat in the southern hemisphere, so it could be that, perhaps.

This is one reason why I’ve been less keen to look for ways it might go wrong than some.  I feel that the pattern, in the broadest terms, may, partly at least, be set.  That does not mean that here in the UK, on our small island, we will not contrive to mess it up locally, of course!

On to the 12zs!

Edited November 28, 2022 by Mike Poole

[lorenzo]

Awful outlook really..

[bluearmy]

Good start from icon 

the greeny ridge establishes  more griceland which lessens the west based risk a little - the pacific ridge extension into the Arctic is strong which should help drive the polar trough south into europe 

all about the wider trend for now and the nuances on the continental flow remains in the nearer term 

[Jackski4]

We are looking for that Iberian low to be squished, we are not looking for immediate cold. The real interest still remains from the 5th onwards and if we can get that Iberian low squished, then we can establish a colder E/NE wind, without any milder blip.