Model Output Discussion - Deeper into Autumn

[Ali1977]

37 minutes ago, CreweCold said:

I present the 0z GEFS eye candy run...

Jet stream heading on a similar southerly route on the ECM , with the PV weakening around Greenland. It’s Certainly looking better for early Dec. 

Edited November 14, 2022 by Ali1977

[Lukesluckybunch]

13 minutes ago, Ali1977 said:

Jet stream heading on a similar southerly route on the ECM , with the PV weakening around Greenland. It’s Certainly looking better for early Dec. 

But once again we are left with southerly winds and rain with temps in the low teens I would imagine..also a lack of cold air to the East here at 240!maybe we will be looking to the northwest to cold rather then east!

[IDO]

The problem we have is that a run like the control is just as likely, maybe more likely to be the reality, bearing in mind what has come before:

FI in GFS 0Z> 

The mean is showing high spread and really there is little confidence beyond D10. 

 

[mb018538]

Day 10 chart. Yawn. Drought concerns to be replaced with flooding ones at this rate.
 

[carinthian]

On 07/11/2022 at 09:24, carinthian said:

Morning all, the main models in some kind of agreement at 144t with the core Euro high located over Central Europe or possible a bit further north by this time next week. Basically keeping temps above average for many this coming week. Thereafter, remains disagreement as to the extent to the influence the Atlantic trough has on changing the forecasts. Daily we see changes in the main models as to the pressure patterns over the Arctic. However, one pattern that keeps occurring is a cross polar linking of Alaskan/Siberian HP, which generally encourages retention of European High pressure. The enticing prospect is for the European high to move further north and for the Atlantic trough to move SE into Western Europe and for a generally backing of the flow to flush out the current entrenched mildness across much of Euroland. Again , from what I see, Mid -month will see a falling of temperatures, whether it be of a continental source or maritime type.

C

Morning all. One week on from the above post, so lets have a look at what the models have out for this time next week. At 144t all in agreement to the positioning of the upper trough out in the North Atlantic to the South of Iceland and for the main core high pressure over Finland/ Northwest Russia. Both presently seem immovable . The models continue to show several wave formations at the base of the upper low to push into the British Isles this coming week and always coming up against the block. So looks like unsettled for you lot with temperatures heading back to near normal values this week.Longer term out to 10 days , shows ECM having less influence of the High, GEM showing a extension of the high westwards and even threatening snow to the Scottish Isles with CAA coming across from Southern Scandinavia. GFS sort of in the middle of ECM/GEM latest runs. I think quite an exciting week coming to watch developments . We over here now only 3 weeks from the start of the new ski-ing season and need snow soon ! Encouragingly, some snow possible with Atlantic troughing at times into the Alps, especially from about 7 days time.

C

[minus10]

2 hours ago, CreweCold said:

Something is brewing for late this month-

Last frame GFS-

The HP anomaly grows and expands west, total carnage for the TPV

Then we have the GEFS mean which is an excellent fit-

We're on the cusp

Not that far away from the ecm z500 mean for 10 days time either..

[ItNeverSnowsInWindsor]

1 hour ago, carinthian said:

Morning all. One week on from the above post, so lets have a look at what the models have out for this time next week. At 144t all in agreement to the positioning of the upper trough out in the North Atlantic to the South of Iceland and for the main core high pressure over Finland/ Northwest Russia. Both presently seem immovable . The models continue to show several wave formations at the base of the upper low to push into the British Isles this coming week and always coming up against the block. So looks like unsettled for you lot with temperatures heading back to near normal values this week.Longer term out to 10 days , shows ECM having less influence of the High, GEM showing a extension of the high westwards and even threatening snow to the Scottish Isles with CAA coming across from Southern Scandinavia. GFS sort of in the middle of ECM/GEM latest runs. I think quite an exciting week coming to watch developments . We over here now only 3 weeks from the start of the new ski-ing season and need snow soon ! Encouragingly, some snow possible with Atlantic troughing at times into the Alps, especially from about 7 days time.

C

Desperately need some snow in Kvitfjell, Norway in the next week as we’re going skiing at the end of November!

The charts keep changing but I’m hoping the high isn’t too close and some disturbances develop between the high and the low to the South West!

[Anthony Burden]

Morning all,ECM/GEM both showing low pressure on a more southerly track encouraging this easterly flow,although at 10 days out so subject to change but encouraging to see.Meanwhile the next 10 days of November feeling a lot more normal in regards to temperatures.Some technical stuff on this site regarding possible U.K. winter forecast very educational and a definite credit to this exceptional weather site.

[damianslaw]

Models all show a very unsettled theme for the foreseeable. Atlantic longwave trough making a beeline for UK, coming unstuck against persistant strong heights to the NE. This is a battleground scenario, secondary features spawned on the base of the trough splitting the low pressure, but not quite trough disruption yet.. I say yet, with the jet forecast to sink south and heights going nowhere to the NE, we may see trough disruption aligned NW-SE this would be the trigger to allow heights to the NE to back west and wrap around, bingo we then see heights settle over UK, this is how I see a change to colder settled conditions occuring, but likely not until very tail end of Nov. Until then, very wet, temps more akin to Nov, chilly nights at times, possible frost and fog risk - all very November.

[bluearmy]

Continuing support for the p/v to markedly reduce its influence on the Atlantic sector as we head later in week 2. 

If we see daughter vortices setting up in E asia and Alaska then that should allow for the scrussian heights to back west and potentially with enough traction to eventually force the Atlantic jet into Iberia/sw France  and leave us on the cold side of the jet 

its the current trend 

[mountain shadow]

2 hours ago, CreweCold said:

I’ve been saying for a couple of months or so now that there is relatively strong historic teleconnective data that suggests a Greenland HP attempt will occur in December. It’s a feature of multi year Ninas.

Then we take a look at the current state of affairs…that blocking to our E and NE is a fairly strong harbinger of European cold.

Then we take a look at the ensemble guidance which suggests the HP anomaly to our NE persisting well into week two, with a propensity for it to back west (on latest runs).

Put all of this together and the outlook into December looks clear to me.

I admire your optimism Crewe.

My main concern for allowing retrogression of the heights to the NE westwards, is the above average Atlantic temperatures. The relative difference between the sea temperatures and the bitter cold moving into it from Canada will provide more power to the jet, making favourable heights more difficult to achieve.

Of great interest of course, is whether the multi year la Nina does indeed increase the risk of a December cold spell.

[MP-R]

22 minutes ago, damianslaw said:

Models all show a very unsettled theme for the foreseeable. Atlantic longwave trough making a beeline for UK, coming unstuck against persistant strong heights to the NE. This is a battleground scenario, secondary features spawned on the base of the trough splitting the low pressure, but not quite trough disruption yet.. I say yet, with the jet forecast to sink south and heights going nowhere to the NE, we may see trough disruption aligned NW-SE this would be the trigger to allow heights to the NE to back west and wrap around, bingo we then see heights settle over UK, this is how I see a change to colder settled conditions occuring, but likely not until very tail end of Nov. Until then, very wet, temps more akin to Nov, chilly nights at times, possible frost and fog risk - all very November.

In some respects it looks very Nov 2009-esque. How incredibly wet that month was. The change to cold was then of course sudden, albeit from a different mechanism ie Azores ridge shooting north and link with Scandi heights. Maybe that’s a backup option if the Atlantic trough backs west rather than disrupts south.

[ItNeverSnowsInWindsor]

The question is will the trough disruption at t240 on the 6z run reach Southern Norway to provide copious amounts of snowfall for the ski resorts ahead of opening this season ?

[cold snap]

Got to feel sorry for the ski resorts 

[damianslaw]

1 hour ago, MP-R said:

In some respects it looks very Nov 2009-esque. How incredibly wet that month was. The change to cold was then of course sudden, albeit from a different mechanism ie Azores ridge shooting north and link with Scandi heights. Maybe that’s a backup option if the Atlantic trough backs west rather than disrupts south.

Yes that is the second route, less favourable for those wanting a quicker route to cold, but possibly a less risky option for sustained cold weather into Dec.

I was looking at the charts of Nov 09 yesterday, we saw a northerly late Nov, after weeks of mikd wet weather, but then the mild came back, and heights lurked to the NE not too dissimiliar to how they are set to do in week ahead. The trough backed west and unusually the azores high shot north whilst heights to the east backed west. Look at the chart 9 Dec and then 11 Dec, it was a very sudden turnaround.

[carinthian]

11 minutes ago, prolongedSnowLover said:

The question is will the trough disruption at t240 on the 6z run reach Southern Norway to provide copious amounts of snowfall for the ski resorts ahead of opening this season ?

If the latest GFS run is to be believed , has the Atlantic flow over running the migrating high back into deepest Russia which appears to allow some extra moisture across the Scandinavian Alps and hence some snowfall modelled below. All this is post 10 days away and in the low probability range.

C

[MattH]

It's still a case of steady away for now, but there are definitely some 'unusual' conflicating evolutions taking place that, without question, have lowered the confidence for a rise in pressure before months end. I think there has been a lot of attention on this rise in pressure because it has been well signaled from the EC46 for a number of weeks and the seasonal models all indicating early blocking patterns. Clearly, for the majority of times, November is rarely looked at as being a month that provides the UK with any winter synoptics, the few exceptions of course along the way, but generally speaking November comes and go with little signficance.

As per usual trying to piece all the 'jigsaw pieces' together to get the end picture is often easier to do if you can physically see how the pieces will go together, at the moment that isn't the case. The MJO activity, for example, over the last few weeks really didn't come to any assistance, but the continued downstream block to the E and NE is, as I mentioned a number of days ago, a very interesting late autumn feature that may well have influences down the line, with regards to the strat.

The problem with November as well is the continued on-going seasonal wavelength changes that can muddy the water as well, obviously that becomes less of a problem by the time we get into December and beyond, as is the case in the summer. The continued signal for the MJO to return to phases 5-6-7 remains very interesting and, should maintain an atmospheric response that is more Nino, rather than Nina. As a general rule of thumb, Nino is better for colder synoptics, than compared with Nina so to get that currently is definitely an interesting piece of the puzzle.

The implications of a Nina-esque AAM regime through winter (obviously we are still in autumn, so bear that in mind re; seasonal wavemength changes etc) supports a pattern which props up sub tropical ridges to mid latitudes (e.g Azores high and associated +NAO) and also usually reduces the risk of wave activity and poleward EP flux that can help disrupt the strat, etc. Overall, the opposite is true when we see more of an atmospheric Nino response. 

Again it's all rather messy at the moment to be honest, but the overall building blocks towards a switch to more high pressure dominated regimes remains, albeit with lower confidence than was originally the case a few weeks back, for some of the reasons discussed above. The other key feature that we all have to continue to take on board these days is climate change influences as well. After being involved within meteorology for over 20 years now, professionally for 15 years long range forecasting is most certainly being made more difficult and uncertain because of the changes that are occuring because of climate change. Analog comparisons, for example, seem to be far less useful than they used to be and there are just far more unknowns.

All that aside, those hoping for any sig cold before months end is likely to be dissapointed, but at least temperatures return to near average values this week and looking ahead, which is seasonal and where we should be. I would still place a wager though that towards months end and into early December we will see a pattern change.

Cheers.

[carinthian]

@MattH I think you are correct in your post about the uncertainty regarding longer range forecasts caused by climate change , especially during the last 2 decades. An example is getting a correct prediction of a Scandinavian High to impact winter forecast into the British Isles. I know forecasters back in the 60s and 70s widely used the text book guide lines learnt at  Stanmore Met training College and as a rule were generally successful . Tried and successfully tested by quite a few winters in the 1960s  that were dominated by Europe/Scandinavian highs. During my training at Shinfield Park, basically the same criteria used in the 80s but gradually with less success rate over recent decades so it would appear.

C

[feb1991blizzard]

29 minutes ago, MattH said:

 

Again it's all rather messy at the moment to be honest, but the overall building blocks towards a switch to more high pressure dominated regimes remains, albeit with lower confidence than was originally the case a few weeks back, for some of the reasons discussed above. The other key feature that we all have to continue to take on board these days is climate change influences as well. After being involved within meteorology for over 20 years now, professionally for 15 years long range forecasting is most certainly being made more difficult and uncertain because of the changes that are occuring because of climate change. Analog comparisons, for example, seem to be far less useful than they used to be and there are just far more unknowns.

A

Yes i've noticed this with analogue based winter forecasts. a good few respected LR forecasts have gone up in smoke over last 7 or 8 years, from people who were usually bang on the money in 09-13 era.

Edited November 14, 2022 by feb1991blizzard

[ItNeverSnowsInWindsor]

1 hour ago, carinthian said:

If the latest GFS run is to be believed , has the Atlantic flow over running the migrating high back into deepest Russia which appears to allow some extra moisture across the Scandinavian Alps and hence some snowfall modelled below. All this is post 10 days away and in the low probability range.

C

The best hope is for the high to retreat northwards and allow an unstable easterly flow across Europe. For that to happen we would need the Atlantic to disrupt more easily and the jet to go under the high.

[Rain All Night]

I noticed there is an EPS cluster this morning that matches the EPS and GEFS ensemble means exceptionally well. It has a southerly jet with the UK left to cool itself down.

 

[Mike Poole]

ECM clusters interesting this morning, the most immediately obvious change since a couple of days ago, as often the case with these, is the border colour.  While I am unsure what algorithm ECM use to decide which cluster fits into which regime, the change from the T72-T96 cluster from a full house of red (scandi block) to green (-NAO) is notable:

Lots of options as you would expect in the later timeframes:

But the main takeaway for me is the signal for the block to persist, and possibly back west a bit later.  The cluster 2 on the T264+ chart is an idea that has been knocking about for a while now, southerly tracking jet and loses the Azores high, and possibly gaining traction.  

[damianslaw]

1 hour ago, MattH said:

It's still a case of steady away for now, but there are definitely some 'unusual' conflicating evolutions taking place that, without question, have lowered the confidence for a rise in pressure before months end. I think there has been a lot of attention on this rise in pressure because it has been well signaled from the EC46 for a number of weeks and the seasonal models all indicating early blocking patterns. Clearly, for the majority of times, November is rarely looked at as being a month that provides the UK with any winter synoptics, the few exceptions of course along the way, but generally speaking November comes and go with little signficance.

As per usual trying to piece all the 'jigsaw pieces' together to get the end picture is often easier to do if you can physically see how the pieces will go together, at the moment that isn't the case. The MJO activity, for example, over the last few weeks really didn't come to any assistance, but the continued downstream block to the E and NE is, as I mentioned a number of days ago, a very interesting late autumn feature that may well have influences down the line, with regards to the strat.

The problem with November as well is the continued on-going seasonal wavelength changes that can muddy the water as well, obviously that becomes less of a problem by the time we get into December and beyond, as is the case in the summer. The continued signal for the MJO to return to phases 5-6-7 remains very interesting and, should maintain an atmospheric response that is more Nino, rather than Nina. As a general rule of thumb, Nino is better for colder synoptics, than compared with Nina so to get that currently is definitely an interesting piece of the puzzle.

The implications of a Nina-esque AAM regime through winter (obviously we are still in autumn, so bear that in mind re; seasonal wavemength changes etc) supports a pattern which props up sub tropical ridges to mid latitudes (e.g Azores high and associated +NAO) and also usually reduces the risk of wave activity and poleward EP flux that can help disrupt the strat, etc. Overall, the opposite is true when we see more of an atmospheric Nino response. 

Again it's all rather messy at the moment to be honest, but the overall building blocks towards a switch to more high pressure dominated regimes remains, albeit with lower confidence than was originally the case a few weeks back, for some of the reasons discussed above. The other key feature that we all have to continue to take on board these days is climate change influences as well. After being involved within meteorology for over 20 years now, professionally for 15 years long range forecasting is most certainly being made more difficult and uncertain because of the changes that are occuring because of climate change. Analog comparisons, for example, seem to be far less useful than they used to be and there are just far more unknowns.

All that aside, those hoping for any sig cold before months end is likely to be dissapointed, but at least temperatures return to near average values this week and looking ahead, which is seasonal and where we should be. I would still place a wager though that towards months end and into early December we will see a pattern change.

Cheers.

Good post. sums up the rather conflicting forces at play recently and perhaps reason why early forecasts for a possible colder end to Autumn i.e. November never materialised. May be oversimplifying but can't help but think it is the la nina background overriden by an El Nino esque set up. Normally la nina in Nov would promote heights to the west, alas instead we have them sat to the NE, with a trough to the west, much more el nino like. Continued el nino behaviour allow heights to ridge west and possibly NW, as Dec arrives. As said all messy. Reason why atmosphere behaving as such? 

Strat- trop disconnects are talked about. Perhaps this year ENSO disconnects need to be. We are in unchartered territory third winter which la nina which is east based. 

Edited November 14, 2022 by damianslaw

[Mike Poole]

Just something else to look out for from the GFS // 6z, here T312:

WAA up the west coast of Greenland pumps up a block in a favourable position to give an easterly flow to the UK, although not with much cold bite yet in this instance, T384:

Edited November 14, 2022 by Mike Poole

[phil nw.]

56 minutes ago, Mike Poole said:

Just something else to look out for from the GFS // 6z, here T312:

WAA up the west coast of Greenland pumps up a block in a favourable position to give an easterly flow to the UK, although not with much cold bite yet in this instance, T384:

I prefer that evolution Mike.

The eastern block pushing west usually is a much slower way of getting cold in.It's usually  a case of last minute hurdles and often fails under pressure from the Jet.

The pattern showing in that 6 z GFS is a quicker route to forcing the jet south as heights rise over the top.

Much easier way of drawing the cold in from the east or north.