Model Output Discussion - mid Autumn

[CoventryWeather]

Anyone saying it's game over should look at ensembles. The GEM, GEFS and even the MOgreps show little support for a collapsing high. The main clusters seem to be a Greenland high, an Atlantic ridge or something close to a UK ridge. The GEM and ECM seem outliers when looking at these. Interesting to see ECM clusters in an hour, and I guessing they'll be nearly identical to what I've said above. 

[MattH]

19 hours ago, Tamara said:

A good summary from Matt. I would very much agree with most of this. The extra tropical evolution is indeed rather uncertain. A GWO Phase 4, currently in progress, back through to Phase 8 would drive a retrogressive signal for the amplification in the Atlantic, and with the polar jet then returning as AAM tendency falls back again in tandem with westerly inertia being scrubbed from the Pacific as tropical convection returns to the Indian Ocean.

The upcoming tropical convection wave through December needs to be watched in respect of its eastward progression and subsequent interaction with potential propagation into the extra tropics, and in turn, how this evolves the relationship between the troposphere & stratosphere.

 

 

Just a quick addition to this one, as there is model data at hand which highlights these discussions well looking ahead...The main caveat is that this is model data and for weeks down the line, so take on that on board first.

However, the CFSv2 plot highlights this next tropical convection wave well, which is mentioned by Tamara here, through December, with an associated signal for a WWB (yellow and orange colours)

The other plot I always note is the EWP zonal harmonics plot for CHI as well. We can see the expected evolution through the short-medium and long-term here, with the initial -ve VP200 anomalies through the Pacific, continuing eastwards into the E Pacific and the W Hem by the end of November. This is what will likely signal another temporary fall in AAM, with the GWO returning to a potential phase 8 or 1, it is through this period, during the end of Nov and into Dec that if coupling of the strat and trop does takes place, then a very unsettled/stormy spell may well evolve as we move into December.

However, notice the signal for the -ve VP200 anoms to return eastwards, in the time, through December. This is the key watch because as we found out last year, any noteworthy MJO event will be important from a strat perspective and perhaps aiding to bring amplification again deeper into December. All are highly subjective, but if the timing is as such, then a Christmas/New Year cold spell *could* evolve.

Cheers, Matt.

[Premiere Neige]

48 minutes ago, sheikhy said:

BINGO!!!!!!!now what i find more interesting is the models tryin to find a bit more amp in the atlantic and the high arching around into scandi at days 5 and 6 more and more in the last few runs!!!we may not get snow out of it but could feel colder and frostier a lot sooner!!lets see if the 12zs keep it going at days 5 and 6!!!

BINGO!!!!!!!now what i find more interesting is the models tryin to find a bit more amp in the atlantic and the high arching around into scandi at days 5 and 6 more and more in the last few runs!!!we may not get snow out of it but could feel colder and frostier a lot sooner!!lets see if the 12zs keep it going at days 5 and 6!!!

To be honest, I'm not expecting December 2010 (or anything like it). I think the main risk of cold will come after Christmas as other, more knowledgeable posters have mused. Anything we get before then will be a bonus so I'm not going to get downbeat about it. If there's something showing at day 4 or 5 in the models pre Christmas then I'll sit up and take notice. 

[ANYWEATHER]

35 minutes ago, CoventryWeather said:

Anyone saying it's game over should look at ensembles. The GEM, GEFS and even the MOgreps show little support for a collapsing high. The main clusters seem to be a Greenland high, an Atlantic ridge or something close to a UK ridge. The GEM and ECM seem outliers when looking at these. Interesting to see ECM clusters in an hour, and I guessing they'll be nearly identical to what I've said above. 

How can anyone say it’s game over for winter, when Winter hasn’t even started? There is no deep cold or anything synoptically to produce early winter weather in the Uk in the latest charts. Yes some cold incursions as the jet stream buckles , but the strong thermal gradient over the Atlantic keeps powering up the jet stream as it often does at this time of year…!

[Mike Poole]

50 minutes ago, CoventryWeather said:

Anyone saying it's game over should look at ensembles. The GEM, GEFS and even the MOgreps show little support for a collapsing high. The main clusters seem to be a Greenland high, an Atlantic ridge or something close to a UK ridge. The GEM and ECM seem outliers when looking at these. Interesting to see ECM clusters in an hour, and I guessing they'll be nearly identical to what I've said above. 

Clusters T192-T240:

Clusters 2,3 4 show the Atlantic ridge scenario, with the near northerly - it occurs at slightly different times dependent on the evolution.  I don’t think this has changed much, maybe slightly more of a westerly component, i.e. not directly from the north, but this blast of cold from the north has been modelled for a while, and is increased in terms of number of members.

What there doesn’t seem to be, is any kind of longevity to this - but was there ever?  T264+ shows a variety of outcomes after that but the start of a prolonged cold spell isn’t one of them.

Edited November 15, 2023 by Mike Poole

[LRD]

An interesting little chase this. Still think it favours all this coming to nothing unusual (cold-wise) but there are signs that counter my view. GFS this morning is ridiculous and isn't even an 850s ensemble outlier

ECM op is flat in the later frames, of course, and completely different to GFS over the Arctic. The ensembles are not indicating anything out of the ordinary either

On the Met Office points - of course they don't get everything right. That's completely unrealistic. But good luck to anyone who is prepared to ignore them when they're not seeing anything (that most on here want in winter) when the models (that we see) are seeing something. It's taking a blend of different sources of info, including the pro's, which would be my advice to people that are new to this. But each to their own

Edited November 15, 2023 by LRD

[TSNWK]

1 minute ago, LRD said:

An interesting little chase this. Still think it favours all this coming to nothing (cold-wise) but there are continued signs of something happening. GFS this morning is ridiculous and isn't even an 850s ensemble outlier

ECM op is flat in the later frames, of course, and completely different to GFS over the Arctic. The ensembles are not indicating anything out of the ordinary either

On the Met Office points - of course they don't get everything right. That's completely unrealistic. But good luck to anyone who is prepared to ignore them when they're not seeing anything (that most on here want in winter) but the models (that we see) are seeing something. It's taking a blend of different sources of info, including the pro's, which would be my advice to people that are new to this

nice cluster flatlining around -7/-8 - more of those please in hour

[Anthony Burden]

Morning all,ECM / GFS still showing a pattern change as I mentioned in my previous blog low pressure from the south west / west has for the time being stopped.The debate over temperature will still be the position and orientation of the unexpected high pressure in the Atlantic that could supply a north westerly flow or westerly if the high drifts south.Low pressure further north/northeast could also have an influence on the pattern change but change it is from what we have experienced for months.

[Cambrian]

Mmmm….still not evident that the rotund diva has done her thing on this one.

0z GEM control at day 11 / 12. Some meaty uppers in there too. 

 

A profound split in the PV, Azores to Bering Sea incorporating a polar high. 

0z GFS control at day 11. More energy going into the Canadian Arctic PV lobe, rather than the Eurasian one, a polar low rather than a polar high.

 

0z GFS op at day 11 very similar to the GEM control. Again, some impressive uppers in the mix. 

 

These striking op and control run charts started appearing at the end of the runs around 4 or 5 days ago, so there’s been marginal slippage if any. 

Good confidence on the day 11 spreads for the north Scandinavian trough, southward extent less certain, but the build in Greenland-Iceland heights and the northward extension of the Atlantic ridge is clearly still where the most substantial uncertainty remains. Greatest uncertainty on the ECM surrounds the Canadian PV lobe so a huge amount to be resolved. GEFS / ECM / GEM

  

Because it’s still at day 10+, a cold spell around the 26th is still at the low end of probability overall, but going by this repeated, strong theme coming steadily nearer in the control charts, if anything, possibly fair to say that there’s a slowly growing chance of at least a few days of cold weather on the way. 

We’d expect little more at just the tail end of November, very pleasing at this stage to see so much there to sustain great interest. Far too early to leave our seats, the goosebump arias are still all to come. 

[Downburst]

I'm sure I am not the only one, so I will ask. What teleconnections are likely to produce the day 10 -11 outputs like this

Can anyone keep me sane at this early juncture of year 16 or whatever on here chasing charts. Glacier Point was great sharing the composite maps for a given MJO phase etc., but often in hind cast. Given the current MJO state and disconnect Atmosphere to ENSO and PDO etc, is the above chart explainable with the current teleconnections or not? If not, why should I even consider a possible WWB in late December having any significance

 

Hope that makes sense to someone, or if someone can understand and explain more succinctly

[Jordan S]

Well yesterday was certainly that rare occasion where widespread heavy rain in the south wasn’t modelled well at all. Models hadn’t shown any significant rain crossing through to our south until Monday then with each update I noticed this was edged north as going into France, this was a sure sign that models where picking up on a disturbance that previously wasn’t expected to form and that along with the rainfall radar displaying the rain further north on Monday night than any model was showing, that it would be a much wetter part of the day for at least places south of Cardiff and London. Of course the rain was further north even than this.

Definitely a disturbance that slipped through the “fine net”. 

 

Anyway not the only feature models are having trouble with, the low for tomorrow obviously still quite uncertain for the computer models although they are converging, but previous most likely chart I showed in my previous post from the Gfs run on Saturday looks like being close still.

So then yet more heavy rain over southern England and Wales tomorrow, there is a chance that this rain makes its way through north Wales and the central northern Midlands I would say 25-40%. 

15-30mm of rain widely with rain lasting for 9-12 hours in places and more on high ground and to lower levels where the bands pivot, this looks to be over parts of southwest England and southeast Wales. 50mm could accumulate here in places. Rain will also likely be very heavy for a time as it moves though places south of the M4 west to east where 50mm or so could accumulate in a few areas. More widely 20-40mm So some flooding is likely in a few places. 

Arpege..

Then we have those strong winds across the southwest and parts of the south coast. Likely to gust to 40-50mph perhaps 60mph in a few places here, but a more concerning risk of another area of stormy and potentially damaging winds moving through the Channel Islands and perhaps the northern tip of France, with gales and potentially damaging gusts to 60-70mph for a time, but as north to northwesterlies! So given the weakened structures and trees from violent storm ciaran a couple of weeks ago and given the strongest winds could be from an unusual direction they could potentially cause even more damage and problems than a southwesterly would do at the same strength, so definitely not as strong or as problematic as violent storm Ciaran for the Channel Islands but it will still likely pack a meteorological “punch”.

One thing to note is if the rain tomorrow reaches north Wales and the midlands 25-40% chance then some potentially locally damaging north to northwesterly wind gusts of 60-70mph could effect parts of the exposed south coast and far southwest of England. Though emphasis really is on the rain for mainland. Still turning windy inland with gusts to 30-40mph for many south of the Midlands and potentially 50mph in some areas. Winds will be southeast then turning easterly and then north and northwesterly over much of the southern half of the uk in association with still storm system.

Comparing my previous look into next week and beyond, great thing is there’s not a whole of difference so no need for much of an update for now, only thing to highlight being the increased potential for more overnight frost and fog in a few areas, probably mainly over more southern areas at times next week as the unsettled weather continues to some extent over Northern Ireland and Scotland with the potential again of snow to lower levels in Scotland and possibly high ground of wales and northern England.

About the early December look, One thing that I do want to mention and while it does still look like high pressure will influence the uk with frost and fog into early December it really does look like this will be a few day thing before very unsettled weather returns from the west or southwest, heralding milder weather but of course not a definite.

Take care, stay vigilant if you live in the Channel Islands tomorrow. Weather won’t be extreme or anywhere near as bad as 2 weeks ago but will be problematic and potentially severe for a time if those 60-70mph do materialise, which is fairly likely.

 

Will update tomorrow or Friday. 

[tight isobar]

20 minutes ago, Cambrian said:

Mmmm….still not evident that the rotund diva has done her thing on this one.

0z GEM control at day 11 / 12. Some meaty uppers in there too. 

 

A profound split in the PV, Azores to Bering Sea incorporating a polar high. 

0z GFS control at day 11. More energy going into the Canadian Arctic PV lobe, rather than the Eurasian one, a polar low rather than a polar high.

 

0z GFS op at day 11 very similar to the GEM control. Again, some impressive uppers in the mix. 

 

These striking op and control run charts started appearing at the end of the runs around 4 or 5 days ago, so there’s been marginal slippage if any. 

Good confidence on the day 11 spreads for the north Scandinavian trough, southward extent less certain, but the build in Greenland-Iceland heights and the northward extension of the Atlantic ridge is clearly still where the most substantial uncertainty remains. Greatest uncertainty on the ECM surrounds the Canadian PV lobe so a huge amount to be resolved. GEFS / ECM / GEM

  

Because it’s still at day 10+, a cold spell around the 26th is still at the low end of probability overall, but going by this repeated, strong theme coming steadily nearer in the control charts, if anything, possibly fair to say that there’s a slowly growing chance of at least a few days of cold weather on the way. 

We’d expect little more at just the tail end of November, very pleasing at this stage to see so much there to sustain great interest. Far too early to leave our seats, the goosebump arias are still all to come. 

IMO definitely an-El-nino frequency response- and corresponding reasonably well - to boot. The final 3rd of November is gonna get very interesting I think!!

Edited November 15, 2023 by tight isobar

[ItNeverSnowsInWindsor]

We need to see the snow row show interest in subsequent ensembles if we’re to see anything wintry later this month.

[TSNWK]

I might regret this post - but for now I'm liking the cut of the 06z Jib at Day 8 - looks better towards Greenland than the 0z and that was good run.

[TSNWK]

19 minutes ago, TSNWK said:

I might regret this post - but for now I'm liking the cut of the 06z Jib at Day 8 - looks better towards Greenland than the 0z and that was good run.

I regret it - look better at Day 8 and then went wrong - so much to learn 

Edited November 15, 2023 by TSNWK

[Downburst]

28 minutes ago, tight isobar said:

IMO definitely an-El-nino frequency response- and corresponding reasonably well - to boot. The final 3rd of November is gonna get very interesting I think!!

ECM weekly temp anomaly pretty much matches your chart. That somewhat odd signal over NE Canada toom warmth surrounded by cold and the cold to our NE too.

[sheikhy]

21 minutes ago, TSNWK said:

I might regret this post - but for now I'm liking the cut of the 06z Jib at Day 8 - looks better towards Greenland than the 0z and that was good run.

Moves towards ecm!!!!flat thereafter!!!some posters have mentioned winters over!!nope its not over cos it aint even begun lol!!!im just commenting on the output at the moment and just pretty much predicting what the most probable outcome shall be from my perspective taking into account my years of experience on here and analysing charts/posts from the biggER boys and girls on here!!so far my post from 2 or 3 days days ago has been spot on!!northerly watered down and also aint getting any closer as always!!!now over the years i would throw my toys out the pram but last couple of years no way!show me a cold snowy chart at 120 or 144 hours and wer in!!

[ItNeverSnowsInWindsor]

No Atlantic block on this one or any retrogression.

Having the block to the South ensures milder but dry weather.

Least it’s looking drier after the deluge recently! 

16 minutes ago, sheikhy said:

Moves towards ecm!!!!flat thereafter!!!some posters have mentioned winters over!!nope its not over cos it aint even begun lol!!!im just commenting on the output at the moment and just pretty much predicting what the most probable outcome shall be from my perspective taking into account my years of experience on here and analysing charts/posts from the biggER boys and girls on here!!so far my post from 2 or 3 days days ago has been spot on!!northerly watered down and also aint getting any closer as always!!!now over the years i would throw my toys out the pram but last couple of years no way!show me a cold snowy chart at 120 or 144 hours and wer in!!

Rather see December delivering something a bit more snowy than last December!!!!

Edited November 15, 2023 by prolongedSnowLover

[joggs]

20 minutes ago, TSNWK said:

I regret it - look better at Day 8 and then went wrong - so much to learn 

Interesting to note the arctic high.

[Met4Cast]

On 27/10/2023 at 18:16, Met4Cast said:

15 days on from this post and things have progressed mostly as expected. Unsettled conditions are likely to prevail as we go into November with the potential for some very unsettled periods of weather with further named storms looking likely. 

Meanwhile, the MJO continues its slow but likely progression into phase 8, I'm not seeing any abrupt pattern changes for the next couple of weeks however we may begin to see high pressure strengthening to the north/NE towards the middle/latter part of November. WWB in the Pacific have somewhat faded although importantly no long term return to easterlies around the dateline so I don't personally anticipate the AAM falling too considerably. We have, as expected seen a gradual rise.

So.. unsettled for the near and medium term with the broadscale tropospheric pattern likely developing into something capable of producing wave 1 activity into the stratosphere through November. I mentioned a potential battle between lows over the UK and high pressure to the NE and that still seems to be the broad direction of travel. 

As air cools to the NE and with seasonal wavelength changes, late November could be *potentially* interesting..

I like to go back & check how previous forecasts have faired. Not too bad - We have indeed seen a pretty unsettled first half to November as expected albeit heights to the NE haven’t materialised largely down to the lower than expected MJO amplitude, so a bit of a bust there. Some stirrings now appearing for the final part of the month, albeit probably not quite as exciting as it could have been with the MJO not playing ball. 

I had hoped a more amplified phase 8 would coincide with the rising AAM tendency but that hasn’t happened with the MJO remaining in a low amplitude orbit  

The AAM has now risen into +ve territory following a strong WWB event, as this begins to wane though I’d expect to see AAM tendency fall away quite sharply again so unlikely to be sustained, this recent AAM uptick is probably responsible for the Atlantic ridging we’re expecting to see circa 20th-26th.  

To me, this suggests sustained Atlantic blocking isn’t likely & due to the MJO not playing ball, blocking is unlikely to transition into the high-latitude type many here crave. With the possibility of a trop/strat coupling it looks like a continuation of unsettled weather into December. 

The hunt for winter proper continues. 

Edited November 15, 2023 by Met4Cast

[Cambrian]

I’ll be a bit quieter for a while after this post - it can get a bit heavy banging on about the same set of trends!  i.e. trends in the changes being modelled (the change between two particular days or valid times in the outlook) and changing trends in the modelling of the same period between different base times.

Just wanted to pair up yesterday’s weekly heights anomalies with the today’s EPS heights anomalies. 

ECM weekly heights anomalies chart for 20-27 November, first chart here from Monday, compared with same for the same period from yesterday’s 12z, just a day later. 

 

Even on a run when the ECM op and control both went notably flatter, note the steeper NW-SE orientation on the Atlantic heights and the appearance for the first time of the southward extension of the Scandinavian trough through the Mediterranean (and then some!) and the base of the trough (going by the contour lines), if anything, is further west on the latest chart, particularly relevant to the UK and Ireland. 

0z EPS at days 8 and 10, (23rd and 25th) to show the trend during the middle of the same week.

 

Westward movement of heights, withdrawing from Iberia, consolidation of the Scandinavian trough down through Europe into North Africa, with the UK and Ireland very much on the cold side of the trough, as above in the weeklies.

As ever, we would expect inter-run variability of ops and controls. There has, however, been a firm trend in the means, getting stronger, towards Atlantic ridge / Euro low for much of next week.

Any tangible trends for the period further on from that, say from day 13 onwards, as this year and this autumn in particular have repeatedly shown us, probably haven’t even begun emerging yet.

Have a great day. 

[NewEra21]

It’s still not a bad set of ensembles from the 06z, despite how fickle they can be. The OP amongst the mildest members throughout the period of interest.

 

[TSNWK]

1 hour ago, Cambrian said:

I’ll be a bit quieter for a while after this post - it can get a bit heavy banging on about the same set of trends!  i.e. trends in the changes being modelled (the change between two particular days or valid times in the outlook) and changing trends in the modelling of the same period between different base times.

Just wanted to pair up yesterday’s weekly heights anomalies with the today’s EPS heights anomalies. 

ECM weekly heights anomalies chart for 20-27 November, first chart here from Monday, compared with same for the same period from yesterday’s 12z, just a day later. 

 

Even on a run when the ECM op and control both went notably flatter, note the steeper NW-SE orientation on the Atlantic heights and the appearance for the first time of the southward extension of the Scandinavian trough through the Mediterranean (and then some!) and the base of the trough (going by the contour lines), if anything, is further west on the latest chart, particularly relevant to the UK and Ireland. 

0z EPS at days 8 and 10, (23rd and 25th) to show the trend during the middle of the same week.

 

Westward movement of heights, withdrawing from Iberia, consolidation of the Scandinavian trough down through Europe into North Africa, with the UK and Ireland very much on the cold side of the trough, as above in the weeklies.

As ever, we would expect inter-run variability of ops and controls. There has, however, been a firm trend in the means, getting stronger, towards Atlantic ridge / Euro low for much of next week.

Any tangible trends for the period further on from that, say from day 13 onwards, as this year and this autumn in particular have repeatedly shown us, probably haven’t even begun emerging yet.

Have a great day. 

Nice Post and thank you..  here's to a  stonking set 12z suite

[ItNeverSnowsInWindsor]

GFS 6z outlier or trend setter ? Take your pick!

 

The snow row also heading the wrong way!

Edited November 15, 2023 by prolongedSnowLover

[damianslaw]

The ensembles are important to look at especially when we see swings from run to runs, as the case with GFS 6z. Sometimes these swing runs can be major outliers, sometimes they are not..

I often notice the model op runs when change quickly are just showing broadest range of extreme options and usually the end product is something in the middle of each intra run.

With this in mind, my hunch is we will see a mid atlantic ridge build through next week, but not far enough north to block the atlantic, and not far enough west to pull in colder uppers from the north, but I think the ECM output is rather too flat, the trough to the NE looks set to be deep driving cold air advection to our east, and a degree of warm air advection to its west - end result probably a drier chillier spell with frost, not sustained but it won't be mild or a very blink and miss affair.

Thereafter, signal is for heights to collapse eventually but whether we draw in a typical zonal atlantic start to winter or something more meridional with lows tracking more NW-SE, quite plausible given the dense cold air that will have bedded in to our NE remains to be seen.

Its all very average late autumn fayre.