Model output discussion - Jan 3rd onwards

[Notty]

GFS 12z ensembles trending lower again after 14th -

https://www.wetterzentrale.de/en/show_diagrams.php?model=gfs&lid=ENS&var=2&bw=1&geoid=48501

[danm]

At this stage we're just looking for trends as any potential deep cold will be at least 8/9 days away. Some encouraging signs from the GFS Para in this regard. UKMO doesn't go out far enough for us to make a call. 

[Tim Bland]

4 minutes ago, Vikos said:

For sure NOT BAD!

And gets better....

[Battleground Snow]

7 minutes ago, Man Without Beard said:

GEFS mean T240 - definitely trending heights further NW, but will be of no use with that amount of high pressure to the south, you'd think

The para brings this in a faster timescale. You would think the low res ensembles would take a few runs to catch up, it is creeping in tho. 06z attached for comparison

Edited January 6, 2021 by Battleground Snow

[Griff]

3 minutes ago, Notty said:

GFS 12z ensembles trending lower again after 14th -

https://www.wetterzentrale.de/en/show_diagrams.php?model=gfs&lid=ENS&var=2&bw=1&geoid=48501

P21 is the winner  

[chicken soup]

2 minutes ago, Tim Bland said:

And gets better....

Just a pity its a complete fantasy and won't happen. 

[Tamara]

51 minutes ago, IDO said:

Latest Met Office 10-day talking about the SSWE and suggesting latest research for the upcoming warming is indicative of a greater chance of SW'lys for the UK! With La Nina it is no surprise that the early direction from the coupling puts the UK away from the cold. I suspect we will learn a bit more from this SSWE as it seems unusual?

As for the 06z gefs, a mixed bag and no real clues away from the overall pattern trend. The op looks like a statistical outlier by d16 (2m temps):

So a run probably to ignore late on.

A seasonal absentee by-stander in all this - but a one-off offering from me.

Its a pity that this post is getting taken apart in some quarters, because hypothetically it *could* promote some interesting discussion if the snow goggle biases were put away for a moment.

This winter has seen a much greater disconnect of the atmosphere to the La Nina base state than anticipated. Intense seasonal bias confirmation processes customarily disguise this, but if one is prepared to stay detached from that, it has been something of a surprise to the neutral diagnostic elements enthusiast. 

What is meant by this disconnect? In simplest terms, much greater poleward rossby wave propagation has taken place than under a more 'connected' and stable w/QBO La Nina  low angular momentum regime in early winter would usually provide. The autumn itself, heading into the first few weeks of winter, saw (overall)  a much more typical EL Nino type presentation, with a downstream configuration that until the festive period did not, mostly apart from a brief period, feature the expected sub tropical Atlantic ridging and instead a configuration of warm air advection processes c/o an amplified Atlantic trough and downstream European ridging. This alignment ultimately provided the feedback catalyst to assist  the wave breaking that has instigated instability of the polar field, albeit reversal of zonal winds are restricted closer to 10mb level.

Interestingly, global relative angular momentum has been slowly falling since the festive period and continuing into the first days of January.

 

 

The Global Wind Oscillation, a phase plot depiction of wind-flow inertia between the tropics and extra tropics has slowly slipped towards the La Nina attractor phases - reflecting greater harmony with the ocean base state.  

 

The effects of falling momentum are to switch greater inertia into the polar jet from upstream. The initial manifestation of this c/o the weakness across the polar field has been for the usual feed of this inertia to proceed eastwards closer between 50 and 60N to be somewhat roadblocked, and instead looped around the pole and create the blocking structures close by to the NNE and linked to the amplification of the more Nina-esque Atlantic ridge.

However, the difficulty comes with how these blocking structures respond to continued displacement/split processes within the polar field at the same time as angular momentum continues to fall ( *in the shorter term absence of any westerly inertia supplied by tropical forcing)  and much more closely match the underlying base state. This is where the post under reply holds the interest I was mentioning at the beginning and should be treated with better respect

It is perfectly conceivable, at least for a time, for polar jet energy to make greater inroads eastwards at mid latitudes, as the polar field continues to re-organise and as the period of time approaches where zonal winds, at least temporarily, are increased within the lower stratosphere and troposphere boundary. Not to any great levels  by any means, as the overall structures continue to look weak and unstable-but enough to allow a more westerly induced pattern to prevail, at least for a time, with a more traditional Nina-esque Atlantic ridge centred close to the west or south west and ebbing and flowing within the bandwidth of displaced vortexing to the NE.

*The further wildcard is intraseasonal MJO forcing. In keeping with w/BQO Nina-esque regimes, and linked to known periodicity timelines for high frequency activity - it is worth watching out for signs of an eastward convective parcel progression attempting to negotiate the Pacific later in January or possibly into February.    A further variable that could see a sudden and quite dramatic surge in atmospheric angular momentum, tipping the resultant synoptic patterns even more their head.     Impossible obviously to know where and when these may set up hemispherically at this stage - but high impact synoptics are conceivable with very large temperature boundaries across the mid latitudes.

That is all for another time. Perhaps.  Closer to home, putting preference biases completely aside, whatever they maybe - from a neutral meteorological point of view its a very tricky time for numerical modelling ahead which encompasses the ensemble suites and representative upper air anomaly charts . The overriding diagnostic (GWO tropical>extra tropical momentum relationship vs a very disjointed polar field)  susceptible to highly erratic global wind-flow patterns at the tropopause boundaries and creating precipitous jumps in synoptic patterns, at mid latitude,... in either direction.

Falling momentum and weak high frequency MJO activity for the foreseeable future (* above caveat aside ) does weight probabilities towards a more typical sub tropical regime and polar jet flow arcing around this. At the same time and as can be seen, there are very hard to keep tabs of pockets of weak inertia popping op at relatively short notice closer to 60N which quite easily could stall westerly inertia and create subtle eddies within the jet which build very weak 'cold' ridges and derail the movement of troughs from west to east and restrict warm air advection

At present, no outcome is to be discounted or dismissed out of hand, and any discussion should be unclouded by bias preferences and be open minded to the even greater than usual uncertainties. That is not sitting on the fence - its honest objectivity in the face of highly sensitive factors that require a watching brief ,rather than any impetuous call for the sake of wanting to appear confident in appealing to a specific popular outcomes.

[Notty]

3 minutes ago, chicken soup said:

Just a pity its a complete fantasy and won't happen. 

None of the charts we look at will ever happen exactly as it is shown ...

Nothing wrong with a bit of fantasising though

[TSNWK]

3 minutes ago, chicken soup said:

Just a pity its a complete fantasy and won't happen. 

If the charts create it then who are we to question.  Publish and be damned I say.  Trust me in my virtual world every winter since I joined in 2010 has had at least one day 10 January 87 and countless winter 47s in far FI. Im doing ok

[Notty]

3 minutes ago, Tamara said:

A seasonal absentee by-stander in all this - but a one-off offering from me.

Its a pity that this post is getting taken apart in some quarters, because hypothetically it *could* promote some interesting discussion if the snow goggle biases were put away for a moment.

This winter has seen a much greater disconnect of the atmosphere to the La Nina base state than anticipated. Intense seasonal bias confirmation processes customarily disguise this, but if one is prepared to stay detached from that, it has been something of a surprise to the neutral diagnostic elements enthusiast. 

What is meant by this disconnect? In simplest terms, much greater poleward rossby wave propagation has taken place than under a more 'connected' and stable w/QBO La Nina  low angular momentum regime in early winter would usually provide. The autumn itself, heading into the first few weeks of winter, saw (overall)  a much more typical EL Nino type presentation, with a downstream configuration that until the festive period did not, mostly apart from a brief period, feature the expected sub tropical Atlantic ridging and instead a configuration of warm air advection processes c/o an amplified Atlantic trough and downstream European ridging. This alignment ultimately provided the feedback catalyst to assist  the wave breaking that has instigated instability of the polar field, albeit reversal of zonal winds are restricted closer to 10mb level.

Interestingly, global relative angular momentum has been slowly falling since the festive period and continuing into the first days of January.

 

 

The Global Wind Oscillation, a phase plot depiction of wind-flow inertia between the tropics and extra tropics has slowly slipped towards the La Nina attractor phases - reflecting greater harmony with the ocean base state.  

 

The effects of falling momentum are to switch greater inertia into the polar jet from upstream. The initial manifestation of this c/o the weakness across the polar field has been for the usual feed of this inertia to proceed eastwards closer between 50 and 60N to be somewhat roadblocked, and instead looped around the pole and create the blocking structures close by to the NNE and linked to the amplification of the more Nina-esque Atlantic ridge.

However, the difficulty comes with how these blocking structures respond to continued displacement/split processes within the polar field at the same time as angular momentum continues to fall ( *in the shorter term absence of any westerly inertia supplied by tropical forcing)  and much more closely match the underlying base state. This is where the post under reply holds the interest I was mentioning at the beginning and should be treated with better respect

It is perfectly conceivable, at least for a time, for polar jet energy to make greater inroads eastwards at mid latitudes, as the polar field continues to re-organise and as the period of time approaches where zonal winds, at least temporarily, are increased within the lower stratosphere and troposphere boundary. Not to any great levels  by any means, as the overall structures continue to look weak and unstable-but enough to allow a more westerly induced pattern to prevail, at least for a time, with a more traditional Nina-esque Atlantic ridge centred close to the west or south west and ebbing and flowing within the bandwidth of displaced vortexing to the NE.

*The further wildcard is intraseasonal MJO forcing. In keeping with w/BQO Nina-esque regimes, and linked to known periodicity timelines for high frequency activity - it is worth watching out for signs of an eastward convective parcel progression attempting to negotiate the Pacific later in January or possibly into February.    A further variable that could see a sudden and quite dramatic surge in atmospheric angular momentum, tipping the resultant synoptic patterns even more their head.     Impossible obviously to know where and when these may set up hemispherically at this stage - but high impact synoptics are conceivable with very large temperature boundaries across the mid latitudes.

That is all for another time. Perhaps.  Closer to home, putting preference biases completely aside, whatever they maybe - from a neutral meteorological point of view its a very tricky time for numerical modelling ahead which encompasses the ensemble suites and representative upper air anomaly charts . The overriding diagnostic (GWO tropical>extra tropical momentum relationship vs a very disjointed polar field)  susceptible to highly erratic global wind-flow patterns at the tropopause boundaries and creating precipitous jumps in synoptic patterns, at mid latitude,... in either direction.

Falling momentum and weak high frequency MJO activity for the foreseeable future (* above caveat aside ) does weight probabilities towards a more typical sub tropical regime and polar jet flow arcing around this. At the same time and as can be seen, there are very hard to keep tabs of pockets of weak inertia popping op at relatively short notice closer to 60N which quite easily could stall westerly inertia and create subtle eddies within the jet which build very weak 'cold' ridges and derail the movement of troughs from west to east and restrict warm air advection

At present, no outcome is to be discounted or dismissed out of hand, and any discussion should be unclouded by bias preferences and be open minded to the even greater than usual uncertainties. That is not sitting on the fence - its honest objectivity in the face of highly sensitive factors that require a watching brief ,rather than any impetuous call for the sake of wanting to appear confident in appealing to a specific popular outcomes.

Thankyou. Fantastic post ! It will take me about a week to read and translate it (via Google/Wikipedia) as I am a complete ignoramus.

[swfc]

6 minutes ago, Tamara said:

A seasonal absentee by-stander in all this - but a one-off offering from me.

Its a pity that this post is getting taken apart in some quarters, because hypothetically it *could* promote some interesting discussion if the snow goggle biases were put away for a moment.

This winter has seen a much greater disconnect of the atmosphere to the La Nina base state than anticipated. Intense seasonal bias confirmation processes customarily disguise this, but if one is prepared to stay detached from that, it has been something of a surprise to the neutral diagnostic elements enthusiast. 

What is meant by this disconnect? In simplest terms, much greater poleward rossby wave propagation has taken place than under a more 'connected' and stable w/QBO La Nina  low angular momentum regime in early winter would usually provide. The autumn itself, heading into the first few weeks of winter, saw (overall)  a much more typical EL Nino type presentation, with a downstream configuration that until the festive period did not, mostly apart from a brief period, feature the expected sub tropical Atlantic ridging and instead a configuration of warm air advection processes c/o an amplified Atlantic trough and downstream European ridging. This alignment ultimately provided the feedback catalyst to assist  the wave breaking that has instigated instability of the polar field, albeit reversal of zonal winds are restricted closer to 10mb level.

Interestingly, global relative angular momentum has been slowly falling since the festive period and continuing into the first days of January.

 

 

The Global Wind Oscillation, a phase plot depiction of wind-flow inertia between the tropics and extra tropics has slowly slipped towards the La Nina attractor phases - reflecting greater harmony with the ocean base state.  

 

The effects of falling momentum are to switch greater inertia into the polar jet from upstream. The initial manifestation of this c/o the weakness across the polar field has been for the usual feed of this inertia to proceed eastwards closer between 50 and 60N to be somewhat roadblocked, and instead looped around the pole and create the blocking structures close by to the NNE and linked to the amplification of the more Nina-esque Atlantic ridge.

However, the difficulty comes with how these blocking structures respond to continued displacement/split processes within the polar field at the same time as angular momentum continues to fall ( *in the shorter term absence of any westerly inertia supplied by tropical forcing)  and much more closely match the underlying base state. This is where the post under reply holds the interest I was mentioning at the beginning and should be treated with better respect

It is perfectly conceivable, at least for a time, for polar jet energy to make greater inroads eastwards at mid latitudes, as the polar field continues to re-organise and as the period of time approaches where zonal winds, at least temporarily, are increased within the lower stratosphere and troposphere boundary. Not to any great levels  by any means, as the overall structures continue to look weak and unstable-but enough to allow a more westerly induced pattern to prevail, at least for a time, with a more traditional Nina-esque Atlantic ridge centred close to the west or south west and ebbing and flowing within the bandwidth of displaced vortexing to the NE.

*The further wildcard is intraseasonal MJO forcing. In keeping with w/BQO Nina-esque regimes, and linked to known periodicity timelines for high frequency activity - it is worth watching out for signs of an eastward convective parcel progression attempting to negotiate the Pacific later in January or possibly into February.    A further variable that could see a sudden and quite dramatic surge in atmospheric angular momentum, tipping the resultant synoptic patterns even more their head.     Impossible obviously to know where and when these may set up hemispherically at this stage - but high impact synoptics are conceivable with very large temperature boundaries across the mid latitudes.

That is all for another time. Perhaps.  Closer to home, putting preference biases completely aside, whatever they maybe - from a neutral meteorological point of view its a very tricky time for numerical modelling ahead which encompasses the ensemble suites and representative upper air anomaly charts . The overriding diagnostic (GWO tropical>extra tropical momentum relationship vs a very disjointed polar field)  susceptible to highly erratic global wind-flow patterns at the tropopause boundaries and creating precipitous jumps in synoptic patterns, at mid latitude,... in either direction.

Falling momentum and weak high frequency MJO activity for the foreseeable future (* above caveat aside ) does weight probabilities towards a more typical sub tropical regime and polar jet flow arcing around this. At the same time and as can be seen, there are very hard to keep tabs of pockets of weak inertia popping op at relatively short notice closer to 60N which quite easily could stall westerly inertia and create subtle eddies within the jet which build very weak 'cold' ridges and derail the movement of troughs from west to east and restrict warm air advection

At present, no outcome is to be discounted or dismissed out of hand, and any discussion should be unclouded by bias preferences and be open minded to the even greater than usual uncertainties. That is not sitting on the fence - its honest objectivity in the face of highly sensitive factors that require a watching brief ,rather than any impetuous call for the sake of wanting to appear confident in appealing to a specific popular outcomes.

Great Post thanks. 

[SLEETY]

Wow there's your SSW effect in fl, be rivaling 1987 for depth of cold and snow depths, yes we know its fl but ties in with the 70% chance of bitter cold winning out, let's see more of this in future runs, please 

[Battleground Snow]

8 minutes ago, Tamara said:

A seasonal absentee by-stander in all this - but a one-off offering from me.

Its a pity that this post is getting taken apart in some quarters, because hypothetically it *could* promote some interesting discussion if the snow goggle biases were put away for a moment.

This winter has seen a much greater disconnect of the atmosphere to the La Nina base state than anticipated. Intense seasonal bias confirmation processes customarily disguise this, but if one is prepared to stay detached from that, it has been something of a surprise to the neutral diagnostic elements enthusiast. 

What is meant by this disconnect? In simplest terms, much greater poleward rossby wave propagation has taken place than under a more 'connected' and stable w/QBO La Nina  low angular momentum regime in early winter would usually provide. The autumn itself, heading into the first few weeks of winter, saw (overall)  a much more typical EL Nino type presentation, with a downstream configuration that until the festive period did not, mostly apart from a brief period, feature the expected sub tropical Atlantic ridging and instead a configuration of warm air advection processes c/o an amplified Atlantic trough and downstream European ridging. This alignment ultimately provided the feedback catalyst to assist  the wave breaking that has instigated instability of the polar field, albeit reversal of zonal winds are restricted closer to 10mb level.

Interestingly, global relative angular momentum has been slowly falling since the festive period and continuing into the first days of January.

 

 

The Global Wind Oscillation, a phase plot depiction of wind-flow inertia between the tropics and extra tropics has slowly slipped towards the La Nina attractor phases - reflecting greater harmony with the ocean base state.  

 

The effects of falling momentum are to switch greater inertia into the polar jet from upstream. The initial manifestation of this c/o the weakness across the polar field has been for the usual feed of this inertia to proceed eastwards closer between 50 and 60N to be somewhat roadblocked, and instead looped around the pole and create the blocking structures close by to the NNE and linked to the amplification of the more Nina-esque Atlantic ridge.

However, the difficulty comes with how these blocking structures respond to continued displacement/split processes within the polar field at the same time as angular momentum continues to fall ( *in the shorter term absence of any westerly inertia supplied by tropical forcing)  and much more closely match the underlying base state. This is where the post under reply holds the interest I was mentioning at the beginning and should be treated with better respect

It is perfectly conceivable, at least for a time, for polar jet energy to make greater inroads eastwards at mid latitudes, as the polar field continues to re-organise and as the period of time approaches where zonal winds, at least temporarily, are increased within the lower stratosphere and troposphere boundary. Not to any great levels  by any means, as the overall structures continue to look weak and unstable-but enough to allow a more westerly induced pattern to prevail, at least for a time, with a more traditional Nina-esque Atlantic ridge centred close to the west or south west and ebbing and flowing within the bandwidth of displaced vortexing to the NE.

*The further wildcard is intraseasonal MJO forcing. In keeping with w/BQO Nina-esque regimes, and linked to known periodicity timelines for high frequency activity - it is worth watching out for signs of an eastward convective parcel progression attempting to negotiate the Pacific later in January or possibly into February.    A further variable that could see a sudden and quite dramatic surge in atmospheric angular momentum, tipping the resultant synoptic patterns even more their head.     Impossible obviously to know where and when these may set up hemispherically at this stage - but high impact synoptics are conceivable with very large temperature boundaries across the mid latitudes.

That is all for another time. Perhaps.  Closer to home, putting preference biases completely aside, whatever they maybe - from a neutral meteorological point of view its a very tricky time for numerical modelling ahead which encompasses the ensemble suites and representative upper air anomaly charts . The overriding diagnostic (GWO tropical>extra tropical momentum relationship vs a very disjointed polar field)  susceptible to highly erratic global wind-flow patterns at the tropopause boundaries and creating precipitous jumps in synoptic patterns, at mid latitude,... in either direction.

Falling momentum and weak high frequency MJO activity for the foreseeable future (* above caveat aside ) does weight probabilities towards a more typical sub tropical regime and polar jet flow arcing around this. At the same time and as can be seen, there are very hard to keep tabs of pockets of weak inertia popping op at relatively short notice closer to 60N which quite easily could stall westerly inertia and create subtle eddies within the jet which build very weak 'cold' ridges and derail the movement of troughs from west to east and restrict warm air advection

At present, no outcome is to be discounted or dismissed out of hand, and any discussion should be unclouded by bias preferences and be open minded to the even greater than usual uncertainties. That is not sitting on the fence - its honest objectivity in the face of highly sensitive factors that require a watching brief ,rather than any impetuous call for the sake of wanting to appear confident in appealing to a specific popular outcomes.

Did you see the snow in parts of Iberia coming this week? 

Thanks for the post

[Tim Bland]

Para show how you don’t need extensive northern blocking for cold and snow in January, just a few wedges and lower pressure over Iberia will do the trick 

[Tim Bland]

Nice to see the mean heading back below average after mid month now...

[SLEETY]

So turning a bit milder next week before we get to see how the SSW will effect us after next ten days, could be some insane runs being throw out, over the next week and more! 

More runs already going below minus 10 upper air on latest gfs ensembles

 

 

Edited January 6, 2021 by SLEETY

[BARRY]

2 minutes ago, SLEETY said:

So turning a bit milder next week before we get to see how the SSW will effect us after next ten days, could be some insane runs being throw out, over the next week and more! 

More runs already going below minus 10 upper air on latest gfs ensembles

 

 

It's gone from a week of mild now 2 days lets give it a couple of days and the mild may have disappeared all together 

[Fourty Point Three Degrees]

Shouldn't really pin too much hope on getting any cold.  Isn't the current SSW a displaced event and not a split event? The SSW of 2019 was displaced that gave us record warmth in Feb following a moderate cold spell in early Feb, while 2018 was really a split event. 

[steveinsussex]

26 minutes ago, Tamara said:

A seasonal absentee by-stander in all this - but a one-off offering from me.

Its a pity that this post is getting taken apart in some quarters, because hypothetically it *could* promote some interesting discussion if the snow goggle biases were put away for a moment.

This winter has seen a much greater disconnect of the atmosphere to the La Nina base state than anticipated. Intense seasonal bias confirmation processes customarily disguise this, but if one is prepared to stay detached from that, it has been something of a surprise to the neutral diagnostic elements enthusiast. 

What is meant by this disconnect? In simplest terms, much greater poleward rossby wave propagation has taken place than under a more 'connected' and stable w/QBO La Nina  low angular momentum regime in early winter would usually provide. The autumn itself, heading into the first few weeks of winter, saw (overall)  a much more typical EL Nino type presentation, with a downstream configuration that until the festive period did not, mostly apart from a brief period, feature the expected sub tropical Atlantic ridging and instead a configuration of warm air advection processes c/o an amplified Atlantic trough and downstream European ridging. This alignment ultimately provided the feedback catalyst to assist  the wave breaking that has instigated instability of the polar field, albeit reversal of zonal winds are restricted closer to 10mb level.

Interestingly, global relative angular momentum has been slowly falling since the festive period and continuing into the first days of January.

 

 

The Global Wind Oscillation, a phase plot depiction of wind-flow inertia between the tropics and extra tropics has slowly slipped towards the La Nina attractor phases - reflecting greater harmony with the ocean base state.  

 

The effects of falling momentum are to switch greater inertia into the polar jet from upstream. The initial manifestation of this c/o the weakness across the polar field has been for the usual feed of this inertia to proceed eastwards closer between 50 and 60N to be somewhat roadblocked, and instead looped around the pole and create the blocking structures close by to the NNE and linked to the amplification of the more Nina-esque Atlantic ridge.

However, the difficulty comes with how these blocking structures respond to continued displacement/split processes within the polar field at the same time as angular momentum continues to fall ( *in the shorter term absence of any westerly inertia supplied by tropical forcing)  and much more closely match the underlying base state. This is where the post under reply holds the interest I was mentioning at the beginning and should be treated with better respect

It is perfectly conceivable, at least for a time, for polar jet energy to make greater inroads eastwards at mid latitudes, as the polar field continues to re-organise and as the period of time approaches where zonal winds, at least temporarily, are increased within the lower stratosphere and troposphere boundary. Not to any great levels  by any means, as the overall structures continue to look weak and unstable-but enough to allow a more westerly induced pattern to prevail, at least for a time, with a more traditional Nina-esque Atlantic ridge centred close to the west or south west and ebbing and flowing within the bandwidth of displaced vortexing to the NE.

*The further wildcard is intraseasonal MJO forcing. In keeping with w/BQO Nina-esque regimes, and linked to known periodicity timelines for high frequency activity - it is worth watching out for signs of an eastward convective parcel progression attempting to negotiate the Pacific later in January or possibly into February.    A further variable that could see a sudden and quite dramatic surge in atmospheric angular momentum, tipping the resultant synoptic patterns even more their head.     Impossible obviously to know where and when these may set up hemispherically at this stage - but high impact synoptics are conceivable with very large temperature boundaries across the mid latitudes.

That is all for another time. Perhaps.  Closer to home, putting preference biases completely aside, whatever they maybe - from a neutral meteorological point of view its a very tricky time for numerical modelling ahead which encompasses the ensemble suites and representative upper air anomaly charts . The overriding diagnostic (GWO tropical>extra tropical momentum relationship vs a very disjointed polar field)  susceptible to highly erratic global wind-flow patterns at the tropopause boundaries and creating precipitous jumps in synoptic patterns, at mid latitude,... in either direction.

Falling momentum and weak high frequency MJO activity for the foreseeable future (* above caveat aside ) does weight probabilities towards a more typical sub tropical regime and polar jet flow arcing around this. At the same time and as can be seen, there are very hard to keep tabs of pockets of weak inertia popping op at relatively short notice closer to 60N which quite easily could stall westerly inertia and create subtle eddies within the jet which build very weak 'cold' ridges and derail the movement of troughs from west to east and restrict warm air advection

At present, no outcome is to be discounted or dismissed out of hand, and any discussion should be unclouded by bias preferences and be open minded to the even greater than usual uncertainties. That is not sitting on the fence - its honest objectivity in the face of highly sensitive factors that require a watching brief ,rather than any impetuous call for the sake of wanting to appear confident in appealing to a specific popular outcomes.

So Atlantic based lows and ‘normal winter conditions’ more favoured....

 

disappointing news 

[steveinsussex]

18 minutes ago, SLEETY said:

Wow there's your SSW effect in fl, be rivaling 1987 for depth of cold and snow depths, yes we know its fl but ties in with the 70% chance of bitter cold winning out, let's see more of this in future runs, please 

70% said who?

[Weather-history]

Bonkers ensemble at just 54hrs!  Actually GFS 12z ensembles for that date have colder 850hpas than the 0z run 

[Stu_London]

16 minutes ago, Tim Bland said:

Nice to see the mean heading back below average after mid month now...

pretty cold at the surface up to the 12th / 13th also

[Griff]

17 minutes ago, SLEETY said:

So turning a bit milder next week before we get to see how the SSW will effect us after next ten days, could be some insane runs being throw out, over the next week and more! 

 

 

 

 

11 minutes ago, BARRY said:

It's gone from a week of mild now 2 days lets give it a couple of days and the mild may have disappeared all together 

BARRY took the words right out of my mouth... 

[Walsall Wood Snow]

6 minutes ago, steveinsussex said:

So Atlantic based lows and ‘normal winter conditions’ more favoured....

 

disappointing news 

That's not the impression I got. Maybe for a time but I think uncertainty is the word I took away most of all with a number of outcomes possible?

[cheshire snow]

11 minutes ago, steveinsussex said:

So Atlantic based lows and ‘normal winter conditions’ more favoured....

 

disappointing news 

Well I read it as neither options to be discounted  as Tamara states in her last paragraph 

C.S

Edited January 6, 2021 by cheshire snow