Model output discussion - Winter has arrived

[Mapantz]

Please keep to model discussion. 

If posts are solely about the MetOffice, please use the general chat/moans/banter thread. 

[Blessed Weather]

There have been a number of posts this evening that are just personal opinion with nothing of substance to back up the statements made. That's fine, but this is not the correct thread for such posts. So if your post is missing it's been moved over to the Moans, Ramps and Chat thread. Thank you.

 

[bluearmy]

15 minutes ago, IDO said:

Isn't the Arctic high a driver of the circulation of the lower-heights on its perimeter, clockwise, east>west moving the chunk of the displaced tPV from Siberia in the direction of Scandi?

This surely will impact negatively on heights to our NE? The op does seem progressive compared to the means in that regard but it may simply be ahead of many ens? Saying that, a d10 ecm chart is really not what it should be these days.

The extended eps do show the arctic high pushing the Asian vortex axis towards nw Russia ...... but I don’t see heights n scand dropping within next two weeks (the odd day excepted) 

[northwestsnow]

Well, this is one of those chosen moments for me to go a little quiet..

At this juncture I'm not seeing much to be positive about.

My worry is the Atlantic not playing ball , and Euro heights building quickly as we move towards mid month.

I see some more experienced guys still feel optimistic, I dont dispute from a NH perspective things look interesting , but that picture can change very quickly ,and  the Atlantic sector remains flat as far as the eye can see really...

Hope I'm wrong !

[Scott Ingham]

3 minutes ago, northwestsnow said:

Well, this is one of those chosen moments for me to go a little quiet..

At this juncture I'm not seeing much to be positive about.

My worry is the Atlantic not playing ball , and Euro heights building quickly as we move towards mid month.

I see some more experienced guys still feel optimistic, I dont dispute from a NH perspective things look interesting , but that picture can change very quickly ,and  the Atlantic sector remains flat as far as the eye can see really...

Hope I'm wrong !

Let the low get into the 120 hours or under range that's at 168 hours and if it still looks flat then worry mate. Until then don't be as downbeat because models especially gfs struggle with strong scrussian blocks and split flow energy

Edited December 6, 2020 by Scott Ingham

[northwestsnow]

9 minutes ago, Scott Ingham said:

Let the low get into the 120 hours or under range that's at 168 hours and if it still looks flat then worry mate. Until then don't be as downbeat because models especially gfs struggle with strong scrussian blocks and split flow energy

Yep,don't disagree with any of that Scott.

Its not just GFS that worries me,the EC mean to me at least, is trending the wrong way, anyway, I tend to go a little quiter when I'm wobbling as I don't wish to clog the thread with it.

Fingers crossed ....

[Scott Ingham]

1 minute ago, northwestsnow said:

Yep,don't disagree with any of that Scott.

Its not just GFS that worries me,the EC mean to me at least, is trending the wrong way, anyway, I tend to go a little quiter when I'm wobbling as I don't wish to clog the thread with it.

Fingers crossed ....

I agree on the ecm mean it is trending the wrong way but even the ECM struggles with this set up. Just not as woefully as the GFS. Let's see where we are after the ECM 12z

[Mike Poole]

Just now, northwestsnow said:

Yep,don't disagree with any of that Scott.

Its not just GFS that worries me,the EC mean to me at least, is trending the wrong way, anyway, I tend to go a little quiter when I'm wobbling as I don't wish to clog the thread with it.

Fingers crossed ....

The issue with the ECM T240 mean from my point of view is the reduction in the trough in Southern Europe, compared to recently:

To my eyes, it still suggests the Atlantic coming up against the block with potential for sliders, look at the kink in the contours upstream and slight elongation towards UK.  What there is though, is a lot more uncertainty than when I’ve posted this chart the last day or two, the spread, again T240:

Which does now allow for the possibility of an Atlantic trough rather than S Europe one, but it by no means suggests a zonal pattern developing, and as others have said there might be a mild spell to sit out in this, a mild spell rather than an Atlantic spell, I would add.

[Catacol]

So - FI is probably at around 120h at the moment, but taking a bit of a gamble this ECM 168h chart is worth a look.

Right now I'm too busy to take a long descriptor to this chart - but suffice to say it is a really good one in the context of background factors such as the MJO progression, momentum cycle and ongoing vortex stress. I would expect NWP products to begin to catch on to it more obviously in the coming days....but I dont think we go flat and zonal from here at all. On the contrary look for the arrival of a block to our north, probably reinforced by a connected ridge through to the Azores which might cause gnashing of teeth for a day or two but in fact is the wave break trigger to something much more productive for cold hunters.

This is going to be a long week as things get mapped out. NWP will struggle, as it always does, with amplified scenarios and pacific momentum spikes. The timing of the next forcing is uncertain in any case - these things don't run to an absolutely precise timetable. But this is decent output tonight that sits within the predicted envelope and all looks good for the last third of the month. Compulsive viewing over the next week to ten days....

Edited December 6, 2020 by Catacol

[damianslaw]

Reliable timeframe 120 hrs tops, as is often the case, until then we have a rather static picture, in the immediate, cold and showery with low pressure filling in situ, by Wednesday a more active atlantic low will move in, but coming unstuck against Russian heights, so probably deflected on a NW-SE trajectory.

As other have commented it is the second low feature coming out of the eastern USA seaboard that injects more energy into the jet and phases with the incoming low mid-week. The change to a milder atlantic feed if aided by this feature and we see the azores high beginning to build north and eastwards, so no surprise to see the longer output returning us to a SW airflow. 

So all eyes on developments off the USA seaboard, the low pressure might end up being a more shallower feature and may not phase so easily with the main longwave trough, or it may quickly deepen and force its way easily over the UK on a more SW-NE alignment. 

My hunch is for a period of milder atlantic conditions mid month, but I doubt this is the start of a turbo-charged jet, far from it, can see heights quickly building in and over the UK perhaps courtesy of the Azores high, with possibly a scandi trough formation, as hinted by some of the model output beyond the 10 day timeframe, we might then see mid atlantic heights building further north in time.. we shall see.

[Scott Ingham]

6 minutes ago, Catacol said:

So - FI is probably at around 120h at the moment, but taking a bit of a gamble this ECM 168h chart is worth a look.

Right now I'm too busy to take a long descriptor to this chart - but suffice to say it is a really good one in the context of background factors such as the MJO progression, momentum cycle and ongoing vortex stress. I would expect NWP products to begin to catch on to it more obviously in the coming days....but I dont think we go flat and zonal from here at all. On the contrary look for the arrival of a block to our north, probably reinforced by a connected ridge through to the Azores which might cause gnashing of teeth for a day or two but in fact is the wave break trigger to something much more productive for cold hunters.

This is going to be a long week as things get mapped out. NWP will struggle, as it always does, with amplified scenarios and pacific momentum spikes. The timing of the next forcing is uncertain in any case - these things don't run to an absolutely precise timetable. But this is decent output tonight that sits within the predicted envelope and all looks good for the last third of the month. Compulsive viewing over the next week to ten days....

Outstanding example of not taking individual runs at face value. Factoring in background signals (MJO progression) and model bias (this not filtering through yet) Top quality analysis and for anyone new stick to people like catacol for learning the art of reading a chart.

Edited December 6, 2020 by Scott Ingham

[damianslaw]

9 minutes ago, Catacol said:

So - FI is probably at around 120h at the moment, but taking a bit of a gamble this ECM 168h chart is worth a look.

Right now I'm too busy to take a long descriptor to this chart - but suffice to say it is a really good one in the context of background factors such as the MJO progression, momentum cycle and ongoing vortex stress. I would expect NWP products to begin to catch on to it more obviously in the coming days....but I dont think we go flat and zonal from here at all. On the contrary look for the arrival of a block to our north, probably reinforced by a connected ridge through to the Azores which might cause gnashing of teeth for a day or two but in fact is the wave break trigger to something much more productive for cold hunters.

This is going to be a long week as things get mapped out. NWP will struggle, as it always does, with amplified scenarios and pacific momentum spikes. The timing of the next forcing is uncertain in any case - these things don't run to an absolutely precise timetable. But this is decent output tonight that sits within the predicted envelope and all looks good for the last third of the month. Compulsive viewing over the next week to ten days....

Good view, those of  cold persuasion may be advised to tune out and tune back in a week's time, as I fully expect some model outputs to run rampant with either a raging jet, or the bartlett high scenario, conversely expect rogue Greenland highs as well, there will be lots of flip flopping beyond reliable timeframe, making everyone scratch there heads where will things go for the latter third of the month, but as you say, the azores high building and ridging through the uK northwards ia a strong possibility, and some of our best cold spells have come courtesy of such a development, short term mild pain longer term gain.

[Scott Ingham]

7 minutes ago, damianslaw said:

Good view, those of  cold persuasion may be advised to tune out and tune back in a week's time, as I fully expect some model outputs to run rampant with either a raging jet, or the bartlett high scenario, conversely expect rogue Greenland highs as well, there will be lots of flip flopping beyond reliable timeframe, making everyone scratch there heads where will things go for the latter third of the month, but as you say, the azores high building and ridging through the uK northwards ia a strong possibility, and some of our best cold spells have come courtesy of such a development, short term mild pain longer term gain.

Azores high ridging and building through the UK is definitely a good shout mate for me

[Mike Poole]

10 minutes ago, damianslaw said:

Good view, those of  cold persuasion may be advised to tune out and tune back in a week's time, as I fully expect some model outputs to run rampant with either a raging jet, or the bartlett high scenario, conversely expect rogue Greenland highs as well, there will be lots of flip flopping beyond reliable timeframe, making everyone scratch there heads where will things go for the latter third of the month, but as you say, the azores high building and ridging through the uK northwards ia a strong possibility, and some of our best cold spells have come courtesy of such a development, short term mild pain longer term gain.

Yes this is absolutely my view too at the moment, nothing much has changed with respect to the trop vortex being in disarray, and it probably still will be when any mild spell is past, models at T144:

But it’s not even certain there will be a mild spell yet, the existing scrussian block may have a say.  

Edited December 6, 2020 by Mike Poole

[captaincroc]

I think the spirit of Sheiky is still with me....

 

Sharper slider/attack on the 18z Icon

12z

18z

[Allseasons-Si]

20 minutes ago, Scott Ingham said:

Azores high ridging and building through the UK is definitely a good shout mate for me

Yes Scott and some of the EPS clusters(only six tonight) show this then build north...hopefully.

the ICON has a more neg tilted trough(less rounded)

120 v's 126.

just to add,i did go up to the peak district this morning,first time i have been out for a long walk in ages,most of the snow had melted but there was still a bit up there

 

Edited December 6, 2020 by Allseasons-si

[captaincroc]

2 minutes ago, Allseasons-si said:

the ICON has a more neg tilted trough(less rounded)

120 v's 126.

 

 

Yes, plus look at in 6 hours (from the last run) a fully developed low has just disappeared from view.  Just shows the massive differences at such a short range.

[Scott Ingham]

11 minutes ago, Allseasons-si said:

Yes Scott and some of the EPS clusters(only six tonight) show this then build north...hopefully.

the ICON has a more neg tilted trough(less rounded)

120 v's 126.

 

Yes mate this second bout of forcing will in my opinion happen further west over the UK and could (although the majority of stratties) believe it will be at a 3rd bite of the cherry could split the strat from the bottom up! Also just to back up musings from myself Steve Murr Catacol we can see from the icon shorter term the extra amp being fed in the closer we get and that low slider ever further west

Just to add beautiful pictures mate!

Edited December 6, 2020 by Scott Ingham

[damianslaw]

3 minutes ago, Donegal said:

Following on from the above posts and overall view, if we are to get a cold spell in the not too distant future is it more likely to come from the North or the East?

Initially probably east, but then north.

[Mike Poole]

6 minutes ago, Donegal said:

Following on from the above posts and overall view, if we are to get a cold spell in the not too distant future is it more likely to come from the North or the East?

I think east.  Either by Russian high backing west, or scandi high developing possibly from an Azores ridge?  I don’t see an obvious route to a Greenland high (which would bring winds from the north) at the moment.

[Griff]

18 minutes ago, Allseasons-si said:

Yes Scott and some of the EPS clusters(only six tonight) show this then build north...hopefully.

the ICON has a more neg tilted trough(less rounded)

120 v's 126.

just to add,i did go up to the peak district this morning,first time i have been out for a long walk in ages,most of the snow had melted but there was still a bit up there

 

 

2 minutes ago, Mike Poole said:

I think east.  Either by Russian high backing west, or scandi high developing possibly from an Azores ridge?  I don’t see an obvious route to a Greenland high (which would bring winds from the north) at the moment.

Scandi looks interesting given how all the talk has been about encroaching from the Atlantic, is the east being underestimated? Presumably the models particularly GFS have an inbuilt Atlantic bias, given the usual default? 

[Daniel*]

1 hour ago, mulzy said:

Outer reaches of the extended EPS - best of the winter season so far - high heights to the north and west as previously advertised; low heights to the south and finally low heights showing up over Russia.  Is this the start of a trend?

The continuity in the blocked theme is encouraging the Ural blocking is set to verify and seems to be very persistent,  this has been something models like CFS has been forecasting for December for a long time. PV in serious trouble this month methinks. 

[Mike Poole]

Just now, Griff said:

 

Scandi looks interesting given how all the talk has been about encroaching from the Atlantic, is the east being underestimated? Presumably the models particularly GFS have an inbuilt Atlantic bias, given the usual default? 

Yes, my experience is that the models especially GFS are over-confident about how easily blocks can be broken down.  And especially now, when there is hardly a zonal train racing across the Atlantic.  I’d expect more resistance from the block than the models are showing.  In this instance though, it may not bring us any closer to snow, because of the lack of cold air, but that will come with time...

[Kirkcaldy Weather]

Just now, Griff said:

 

Scandi looks interesting given how all the talk has been about encroaching from the Atlantic, is the east being underestimated? Presumably the models particularly GFS have an inbuilt Atlantic bias, given the usual default? 

Over the years its been a common theme with the models (I wouldn't say only the gfs doing it) where the strength of blocking high pressures get underestimated yes, usually during cold spells associated with big blocks like 2010, BFTE the models tend to be too quick with the breakdowns. 

[Scott Ingham]

6 minutes ago, Griff said:

 

Scandi looks interesting given how all the talk has been about encroaching from the Atlantic, is the east being underestimated? Presumably the models particularly GFS have an inbuilt Atlantic bias, given the usual default? 

Its a well known bias mate yeah especially so with the GFS. Its why it's frustrating to read people believing a 168 hour chart. Steve Murr has spoken about this for years and we still see people getting downbeat at the Atlantic breaking through a huge Russian block that is almost certainly being under estimated