Model Output Discussion - moving into Winter

[snowking]

I must say that whilst this is the one year where if everything goes proverbials up I'm actually okay with it against the background of rising energy costs, and I am always wary of scenarios reliant on Greenland blocking when primarily being peddled most strongly by ECMWF output until we're within a much closer range to T+0, the imagery being produced by NWP right now is simply beautiful.

We've seen a lot of dream synoptics already laid out in 2D, how about a peek at what an internal wave break over Greenland does to the tropospheric and lower stratospheric vortex in 3D:

Very easy to identify where a cross-polar flow finds its way through there.

[Robbie Garrett]

Not sure if posted yesterday, but Aidan McGivern posted this yesterday.  As I expected, UKMO very much on the fence - due to it being Christmas period and the threat to infrastructure. 

 

[East_England_Stormchaser91]

2 hours ago, bluearmy said:

I think the issue is North Sea and n Atlantic temps 

anoms

If we do see some of that proper cold advected over from the Asian part of the vortex, then this will be a real snow making machine! Sub -15 uppers if we miraculously do get them will give us “lake effect” type snowfall probably not seen since 1987! BFTE came close, but the sea was anomalously cold! 

Edited November 29, 2022 by East_England_Stormchaser91

[Rain All Night]

I know this morning's runs are old news by now, but I thought it was interesting to note that all three ensemble spreads show their greatest uncertainty on heights to be along the western edge of Greenland, rather than over Norway where the trough might fall.

Edited November 29, 2022 by RainAllNight

[bluearmy]

Just now, East_England_Stormchaser91 said:

If we do see some of that proper cold adverted over from the Asian part of the vortex, then this will be a real snow making machine! Sub -15 uppers if we miraculously do get them will give us “lake effect” type snowfall probably not seen since 1987! BFTE came close, but the sea was anomalously cold! 

We haven’t seen much in the way of any extended modelling showing anything sub -10c making it as far as the U.K. though. Probability in period 10/15 days around 5% max. Those low uppers held over scandi and the Baltic states. 

and the last few days have rowed back on that Asian vortex pushing into the n European sector of the NH with an extension from it the best we can hope for. 

of course if we see a new cycle develop beyond this later in December then who knows 

[knocker]

Time for this again from an old forecaster

 

Edited November 29, 2022 by Paul
Replaced the old archive link with the newer one (same content, different place)

[Jordan S]

To be honest even as early as this weekend/early next week, we have the risk of wintry precipitation moving northwest into eastern areas, along with the potential for snow on hills in the north, most likely in heavy precipitation, though it is rain if anything for most, just fairly cold with frost for some. 

Whilst upper air temps won't be particularly cold for most of next week and may not be supportive of snow for some at first, the 2m temps just keep getting lower as next week progresses and the pattern persists and there's good reason to believe this will take place..

Bar the odd interruption of any rain/sleet from dying weather fronts getting caught/ forming within the flow, there looks to be much drier weather than has been the case recently as well as a very seasonal feeling next couple of weeks, then there looks to be a repeating pattern later next week and onwards of low pressure systems potentially moving north/northeast into the UK from the south/southwest, such as the latter part of the GFS update..

Although this timeframe is unreliable usually, it does seem realistic and plausible that something similar will take place as we approach mid December, could be looking at some very interesting battleground scenarios where some places are in with the chance of seeing some more significant sleet/snow as cyclonic patterns and less cold air (not mild) try to establish over the uk..this actually looks like happening aswell, ofcourse any significant snow from these most likely for the north later in the second week, with less cold following though probably temporarily, for many.

Before that change, The main theme and what looks most likely before any possible significant battleground situations close to mid month, is that cold prevales for most, particularly the north of the UK (obviously), with ongoing shower risk for many/ especially for the north, from variable directions mostly from the east/northeast/north, wintry mix to showers further south, though emphasis on dry and cold for many. 

Low pressure probably taking over the pattern over the whole of the UK for a time by mid month, similar to GFS, with more significant snow possibly effecting northern/northwestern areas along the boundary of stubborn cold over the north of UK/milder air into the south, further south temperatures probably back up close to average for a time with precipitation as rain, one thing looks very likely and that is Scotland atleast probably remaining in air cold enough for snow even in this less cold interlude for the majority of the UK.

What happens slightly beyond mid-month? Who knows but with the pattern showing as it is and given how unusual it is to see this in model output in recent times, I would say the pattern is increasingly likely to slowly shift back south/east with low pressure gradually moving away to our southeast bringing drier and colder conditions once again to all, along with lower upper air temperatures compared to the next week or so. A dominant mild southwest airstream with frequent low pressure is very unlikely.  Interesting times..

[bluearmy]

Icon run isn’t great over the polar field and certainly missing amplification over Greenland 

let’s hope it’s not a portent of the 12z suites …..

Edited November 29, 2022 by bluearmy

[Ali1977]

1 minute ago, bluearmy said:

Icon run isn’t great over the polar field and certainly missing amplification over Greenland 

let’s hope it’s not a portent of the 12z suites …..

I was thinking that, however when looking between the last 6 hours there’s defo an injection on WAA heading Greenlands way heading in a NE direction - so maybe it would work out well. 

[TSNWK]

3 minutes ago, Ali1977 said:

I was thinking that, however when looking between the last 6 hours there’s defo an injection on WAA heading Greenlands way heading in a NE direction - so maybe it would work out well. 

Yep. Can see it  but as @bluearmy suggests the polar is the poorest we have see for a while..

Do nit want any moves towards it on gfs and ecm at this range

[bluearmy]

4 minutes ago, Ali1977 said:

I was thinking that, however when looking between the last 6 hours there’s defo an injection on WAA heading Greenlands way heading in a NE direction - so maybe it would work out well. 

It’s possible but another route will just upset the natives ………

[Tamara]

 

Boa tarde e todos.   Excerto publicado da semana passada.

There seems to be some belief, not sure what it is based on (beyond hope?) that the tropics are inextricably set to repeat a further active Pacific orbit later in December- both assumedly as means to keep (or reload) an anticipated cold pattern for NW Europe and as means to initiate a festive season SSW to set the path for winter 22/23 on an ice-age of yesteryear.

Personally, at this time, I would very much question this based on empirical knowledge of tropical convection/MJO periodicity timelines. Active cycles, particularly seen during transitional ENSO phases (in this case a weakening Nina base state) follow an upwards of 60 to 90 days timeline recurrence for intraseasonal active progressions of the 'mini ENSO cycle'. The autumn has seen prolonged active cycling within the tropics focussed on West Pacific convergence, propagating +AAM anomalies to the extra tropics and carving out the very amplified downstream hemispheric patterns that are being seen.

However, cycling of tropical forcing phasing, irrespective of long-term base state trends, both waxes...and wanes.

A 'waning' of the sustained Nino-esque interference with the ENSO state is becoming increasingly overdue based on the periodicity cycle and suggests that the autumn of strongly a-typical high angular momentum decoupling of the atmosphere cannot continue indefinitely for yet further weeks to come. Ergo a fall /correction in angular momentum must be viewed within a lens of time 

........................................................................................................................................................

Some further thoughts to this discussion through the lens of the GSDM (Global Synoptic Dynamical Model) :

 

Tropical convection steadily fading in line with upper layer tropical waves. The convective impact on SST's will be to cool the surface -  further underpinning the periodicity/timeline lag for future active tropical convection. Therefore, I would maintain any further significant convection less likely for a 6-8 week timespan allowing for a more coupled ocean/atmospheric signal than the highly destabilised regime of the past several weeks.

Frictional torques lead mountain torques and with the former -ve c/o re-emerging trade wind inflection increasing across the tropics (as convection weakens) this implies that a tumble in mountain torque is signposted as means of the extra tropical wind-flow budget playing its part in the overall correction of relative and total angular momentum. Especially so given future lack of organisational MJO activity. NB: I do not deal in uncertainties of long term MJO forecasts but most especially given the inhibiting factors as revealed by the underlying diagnostic.

The Global Wind Oscillation, a plot depiction of global wind-flow comprising both tropics and extra tropics, has trod a highly impressive quasi-stationary high angular momentum orbit for some time. Taking into consideration the weighting of -ve inertia to come, then a break in this +ve AAM (El Nino attractor phasing) has to be anticipated.  Therefore, a breakaway GWO Phase 8.0,4 sequence sets up an intriguing passage for NWP to interpret synoptically- and certainly against so much amplified eddy inertia left within the global circulation at the same time as the polar jet attempts to return but potentially derailed by a tropospheric>stratospheric roadblock which, like any granite substance, takes time to splinter & fracture and without knowing where these fragments will disperse across the NH.

An attempted musing sees me point to the remaining pockets of -ve zonal winds in the troposphere/stratosphere layer orchestrate with rarified retrogression of the substantial blocking structure to Greenland as inertia across the Pacific weakens (becomes more coupled to base state). Highly likely that this retrogression will eventually edge further east towards Canada (and try and evolve the pattern more -NAO west based) Before this however, a cyclonic envelope over my part of Iberia migrating northwards to bump up against the increasing CAA across more Northern and Western parts of Europe. This accords with a circa Phase 8/0 GWO signal as angular momentum retreats. Clearly a defined thermal boundary of very different airmasses setting up somewhere across these parts of Europe with large amounts of Atlantic moisture sourced from more southerly waters mixing with much drier, denser arctic sourced air. This clearly implies high impact weather event potential - no such detail can be given at this time as to where or when these will be.

Further out, an attempt at reload is conceivable with the GWO en route back to Phase 4 and renewed rises in angular momentum tendency. However, heading back to the starting discussion of this post, there is great uncertainty about this - based on the said reasoning for tropical correction to re-assert a further active cycle. The chances are equal that this might not materialise/be delayed.

So to reiterate, at least from my viewpoint, a lot of caution and restraint in over expectations of wholesale stratospheric destabilisation around the end of the year. At this stage, if it is to happen at all, closer to the mid-winter period seems more feasible. However, there are plenty of advanced pitfalls that can be foreseen, notwithstanding it is a ridiculous time period ahead to try to speculate.

De nada. Os melhores cumprimentos. Ciao.

Edit: For what it is worth, the ICON 12z shows a very 'clean' step up of returning polar jet energy. One of a myriad of solutions based on the tropopause zonal wind state which will not be modelled accurately from one output to the next and one computer model to the next. Yet another reason, as usual to not over analyse each and every roll-out (What is new about that)

 

 

Edited November 29, 2022 by Tamara

[Skullzrulerz]

16 minutes ago, bluearmy said:

Icon run isn’t great over the polar field and certainly missing amplification over Greenland 

let’s hope it’s not a portent of the 12z suites …..

I really hope this isn't the start of a unravelling...

[Ross Andrew Hemphill]

So far so good on the GFS?? High even looks a little stronger 

[IDO]

I think we can call the Iberian low out of the game as a spoiler in the reliable:

 T108> 

So, we get that slack easterly and a cold pool from D3. However, the low never really dissipates and will rebound in the medium term, but initial worries now relinquished.

[Mark wheeler]

GFS 108 is that conductive for snow , looks like -8 uppers with a cold pool incoming ?  bit kinky over the southeast.

Edited November 29, 2022 by Mark wheeler

[Ali1977]

The GFSP looks wintery on Sunday. 

[Rain All Night]

4 minutes ago, IDO said:

I think we can call the Iberian low out of the game as a spoiler in the reliable:

 T108> 

So, we get that slack easterly and a cold pool from D3. However, the low never really dissipates and will rebound in the medium term, but initial worries now relinquished.

There are certainly some interesting options for it to "rebound" among the ensembles...

[Lord Baltimore]

22 minutes ago, Tamara said:

 

Boa tarde e todos.   Excerto publicado da semana passada.

There seems to be some belief, not sure what it is based on (beyond hope?) that the tropics are inextricably set to repeat a further active Pacific orbit later in December- both assumedly as means to keep (or reload) an anticipated cold pattern for NW Europe and as means to initiate a festive season SSW to set the path for winter 22/23 on an ice-age of yesteryear.

Personally, at this time, I would very much question this based on empirical knowledge of tropical convection/MJO periodicity timelines. Active cycles, particularly seen during transitional ENSO phases (in this case a weakening Nina base state) follow an upwards of 60 to 90 days timeline recurrence for intraseasonal active progressions of the 'mini ENSO cycle'. The autumn has seen prolonged active cycling within the tropics focussed on West Pacific convergence, propagating +AAM anomalies to the extra tropics and carving out the very amplified downstream hemispheric patterns that are being seen.

However, cycling of tropical forcing phasing, irrespective of long-term base state trends, both waxes...and wanes.

A 'waning' of the sustained Nino-esque interference with the ENSO state is becoming increasingly overdue based on the periodicity cycle and suggests that the autumn of strongly a-typical high angular momentum decoupling of the atmosphere cannot continue indefinitely for yet further weeks to come. Ergo a fall /correction in angular momentum must be viewed within a lens of time 

........................................................................................................................................................

Some further thoughts to this discussion through the lens of the GSDM (Global Synoptic Dynamical Model) :

 

Tropical convection steadily fading in line with upper layer tropical waves. The convective impact on SST's will be to cool the surface -  further underpinning the periodicity/timeline lag for future active tropical convection. Therefore, I would maintain any further significant convection less likely for a 6-8 week timespan allowing for a more coupled ocean/atmospheric signal than the highly destabilised regime of the past several weeks.

Frictional torques lead mountain torques and with the former -ve c/o re-emerging trade wind inflection increasing across the tropics (as convection weakens) this implies that a tumble in mountain torque is signposted as means of the extra tropical wind-flow budget playing its part in the overall correction of relative and total angular momentum. Especially so given future lack of organisational MJO activity. NB: I do not deal in uncertainties of long term MJO forecasts but most especially given the inhibiting factors as revealed by the underlying diagnostic.

The Global Wind Oscillation, a plot depiction of global wind-flow comprising both tropics and extra tropics, has trod a highly impressive quasi-stationary high angular momentum orbit for some time. Taking into consideration the weighting of -ve inertia to come, then a break in this +ve AAM (El Nino attractor phasing) has to be anticipated.  Therefore, a breakaway GWO Phase 8.0,4 sequence sets up an intriguing passage for NWP to interpret synoptically- and certainly against so much amplified eddy inertia left within the global circulation at the same time as the polar jet attempts to return but potentially derailed by a tropospheric>stratospheric roadblock which, like any granite substance, takes time to splinter & fracture and without knowing where these fragments will disperse across the NH.

An attempted musing sees me point to the remaining pockets of -ve zonal winds in the troposphere/stratosphere layer orchestrate with rarified retrogression of the substantial blocking structure to Greenland as inertia across the Pacific weakens (becomes more coupled to base state). Highly likely that this retrogression will eventually edge further east towards Canada (and try and evolve the pattern more -NAO west based) Before this however, a cyclonic envelope over my part of Iberia migrating northwards to bump up against the increasing CAA across more Northern and Western parts of Europe. This accords with a circa Phase 8/0 GWO signal as angular momentum retreats. Clearly a defined thermal boundary of very different airmasses setting up somewhere across these parts of Europe with large amounts of Atlantic moisture sourced from more southerly waters mixing with much drier, denser arctic sourced air. This clearly implies high impact weather event potential - no such detail can be given at this time as to where or when these will be.

Further out, an attempt at reload is conceivable with the GWO en route back to Phase 4 and renewed rises in angular momentum tendency. However, heading back to the starting discussion of this post, there is great uncertainty about this - based on the said reasoning for tropical correction to re-assert a further active cycle. The chances are equal that this might not materialise/be delayed.

So to reiterate, at least from my viewpoint, a lot of caution and restraint in over expectations of wholesale stratospheric destabilisation around the end of the year. At this stage, if it is to happen at all, closer to the mid-winter period seems more feasible. However, there are plenty of advanced pitfalls that can be foreseen, notwithstanding it is a ridiculous time period ahead to try to speculate.

De nada. Os melhores cumprimentos. Ciao.

Edit: For what it is worth, the ICON 12z shows a very 'clean' step up of returning polar jet energy. One of a myriad of solutions based on the tropopause zonal wind state which will not be modelled accurately from one output to the next and one computer model to the next. Yet another reason, as usual to not over analyse each and every roll-out (What is new about that)

 

 

You could be right, but I haven't got a scooby about what you have written. 

[TSNWK]

6 minutes ago, IDO said:

I think we can call the Iberian low out of the game as a spoiler in the reliable:

 T108> 

So, we get that slack easterly and a cold pool from D3. However, the low never really dissipates and will rebound in the medium term, but initial worries now relinquished.

still a risk of back door route to - that was not there on 06Z?

[Captain Shortwave]

The precipitation that was modelled for Sunday is now more a wintry mix than all out rain now. There will be uncertainty in regards to the placement of any disturbances but obviously there is the chance of snow falling even to low levels by the end of the weekend and into the following week.

GFS/Parallel and UKMO are all decent in terms of upstream amplification (especially compared to the ICON).

Edited November 29, 2022 by Captain Shortwave

[Ali1977]

The GFS building that Greeny high nicely by day 5, unlike the icon thankfully. 

[Uncertainty]

UKMO 144

Stunning chart… Slack easterly flow,  really quite cold! 

[TSNWK]

UKM 144 looks ok to me with build of heights towards Greenland

[sheikhy]

Much better ukmo this evening up to 144 hours!!cold aswell!!