Model Output Discussion. 3/12/2022. How cold will it get?

[pdiddy]

51 minutes ago, mathematician said:

I hope I'm very wrong here, but I don't see much precipitation with these synoptics.

 

I'm afraid we will see cold weather, hard frosts but not much in terms of snow.

 

Like I said if I'm proved wrong I'd be the happiest.

models aren't showing much for today, yet in Edinburgh it has been raining on and off all morning.  I think it's one area the models really struggle

[Eagle Eye]

52 minutes ago, Tamara said:

 which in simple terms means that the poleward forcing ammunition within the troposphere is being withdrawn and it is the built-up momentum unstable inertia lag at higher latitudes that is driving the -ve Annular Mode pattern into the medium term. 

 

I feel for anybody reading this and seeing simple terms, it's still not really simple terms but I don't blame Tamara and to be honest I don't understand a few of the words fully but the context is enough for me. So to anybody reading this who may not know that much about teleconnections don't worry, "simple" here probably means simple for somebody of the intelligence of Tamara (hence why it's difficult for me). The trouble is, putting this in simple terms would take a ridiculous amount of paragraphs that no human should be forced to write so instead I'm going to link you to a few documents to help anyone trying to understand here and quote a few of the words.

Poleward forcing within the troposphere - Energy and momentum in the troposphere transferring partly (I suppose possibly fully but I'm not too sure that seems possible) from the tropics and upwards, closer to the pole.

Unstable inertia - Inertia is when it keeps it's existing state unless acted upon by another object. Hence unstable inertia is the transfer of energy is between it's existing state and the 'disturbance'.

This is a very basic view at both though and unstable inertia involves a lot more than that.

-VE just means negative (hence, +VE means positive)

Annular mode (here, meaning Northern Annular Mode)

Avertissement de redirection

WWW.GOOGLE.COM

Some more helpful links

Arctic Oscillation (AO)

Avertissement de redirection

WWW.GOOGLE.COM

North Atlantic Oscillation (NAO)

Avertissement de redirection

WWW.GOOGLE.COM

MJO (basic explanation but further down it has lot's of helpful MJO forecasts, make sure to check the dates as some are out of date, at the bottom has the RMM amplification as well. Phases 6 and 7 are the main help for coldies, 2 and 3 seem to be a more zonal setup)

Avertissement de redirection

WWW.GOOGLE.COM

Atmospheric Angular Momentum (AAM)

I'll once again copy over my basic AAM explanation but I've taken out some of what isn't needed

"

I've shortened a few words because this is the second time writing this after I accidentally deleted the tab first time around. 

AMB - Angular Momentum Budget  

AAM - Atmospheric Angular Momentum 

MT(mountain torque) 

GWT(gravity wave torque) 

FT(frictional torque) 

If AMB increases in the atmosphere it must have been transferred from another source since AMB is always conserved. The sources for AMB are from the Earth, the Oceans and the Atmosphere. 

One major aspect in affecting AAM are torques. A torque is the rotational force in the atmosphere.  

The 3 main torques affecting the atmosphere are: 

Mountain torque (MT) - The turning force applied with the effect of pressure systems on mountains. 

Frictional torque (FT) - Boundary layer dynamics. 

Gravity wave torque (GWT) - Subgrid (local) torque, upward movement and downward movement to do with the buoyancy. 

If there is a net westerly surface wind, the atmosphere speeds up the Earth's rotation and transfers angular momentum to the earth and so there is a net decrease in AAM. The reverse happens with a net easterly wind.

In the NH Winter:

Global MT anomalies are constructed by sypnotic waves that scatter energy across Asia and North America. These sypnotic waves trap the SLP anomaly and push them towards the south. Driven south and east of mountains. Sypnotic wave centres amplify aloft. MT associated with anomaly air parcel transportation in terms of momentum into latitudes its next to. More angular momentum is therefore moves to the 20-20N band. This is where the AAM anomaly appears significant. The anomaly quickly becoming equally uniform leading to a global FT that weakens the AAM anomalies. An anomalous distribution of mass accompanying the MT acting to balance the zonal winds in the 20-30N region. In the mid latitude, Eddy's are the physical link between those two torques.

 The two main torques can be shown in a lag correlation and FT "leads" MT. The relationship related as previously mentioned in the last paragraph. SLP anomalies are related to FT and the coupling with MT.

Some definitions of some words you may not understand

Synoptic is a general summary.

Waves here refers to planatery waves which are propagated by the rotational forces of the Earth and transport energy even if not doing it much themselves and they show themselves in the form of a meandering jet stream.

Shown neatly in this GIF

"

Global Wind Oscillation (GWO) (from the lovely netweather community)

Avertissement de redirection

WWW.GOOGLE.COM

GWO Phases

Phases 4-7 associated with increasing AAM and so theoretically a higher blocking and therefore cold chance (through a -VE AO and/or a -VE NAO typically) later down the line. The rest of the phases, a decreasing AAM and theoretically a more zonal (Atlantic dominant) setup.

Hope this helps at least a little bit.

 

Edited December 5, 2022 by Eagle Eye

[mountain shadow]

50 minutes ago, iceman1991 said:

Looks like March 2013 cold spell from models just dry and cold can’t see much snow from this 

Yeh. There was only about three foot of snow in my backyard.

[Penrith Snow]

40 minutes ago, Bricriu said:

With respect you don't need to be expert on global drivers/ teleconnections to know that blocking is not sustainable indefinitely- if it were winters like 1947 and 1963 would not stand out in memory as they would be quite common. That said if we do get anything beyond  nine days of cold with chances of snow at times i'll be happy enough.

Absolutely, even during winter 1978/79 short mild spells were frequent occurring in early December, just after Christmas, second week in January and last week in February.

Set ups like 1963 or even December 2010 are exceptionally rare.

Andy

[Islander]

12 minutes ago, mountain shadow said:

Yeh. There was only about three foot of snow in my backyard.

Yeh think it was "only" about 2.5ft here

[Bricriu]

29 minutes ago, Eagle Eye said:

I feel for anybody reading this and seeing simple terms, it's still not really simple terms but I don't blame Tamara and to be honest I don't understand a few of the words fully but the context is enough for me. So to anybody reading this who may not know that much about teleconnections don't worry, "simple" here probably means simple for somebody of the intelligence of Tamara (hence why it's difficult for me). The trouble is, putting this in simple terms would take a ridiculous amount of paragraphs that no human should be forced to write so instead I'm going to link you to a few documents to help anyone trying to understand here and quote a few of the words.

Poleward forcing within the troposphere - Energy and momentum in the troposphere transferring partly (I suppose possibly fully but I'm not too sure that seems possible) from the tropics and upwards, closer to the pole.

Unstable inertia - Inertia is when it keeps it's existing state unless acted upon by another object. Hence unstable inertia is the transfer of energy is between it's existing state and the 'disturbance'.

This is a very basic view at both though and unstable inertia involves a lot more than that.

-VE just means negative (hence, +VE means positive)

Annular mode (here, meaning Northern Annular Mode)

Avertissement de redirection

WWW.GOOGLE.COM

Some more helpful links

Arctic Oscillation (AO)

Avertissement de redirection

WWW.GOOGLE.COM

North Atlantic Oscillation (NAO)

Avertissement de redirection

WWW.GOOGLE.COM

MJO (basic explanation but further down it has lot's of helpful MJO forecasts, make sure to check the dates as some are out of date, at the bottom has the RMM amplification as well. Phases 6 and 7 are the main help for coldies, 2 and 3 seem to be a more zonal setup)

Avertissement de redirection

WWW.GOOGLE.COM

Atmospheric Angular Momentum (AAM)

I'll once again copy over my basic AAM explanation but I've taken out some of what isn't needed

"

I've shortened a few words because this is the second time writing this after I accidentally deleted the tab first time around. 

AMB - Angular Momentum Budget  

AAM - Atmospheric Angular Momentum 

MT(mountain torque) 

GWT(gravity wave torque) 

FT(frictional torque) 

If AMB increases in the atmosphere it must have been transferred from another source since AMB is always conserved. The sources for AMB are from the Earth, the Oceans and the Atmosphere. 

One major aspect in affecting AAM are torques. A torque is the rotational force in the atmosphere.  

The 3 main torques affecting the atmosphere are: 

Mountain torque (MT) - The turning force applied with the effect of pressure systems on mountains. 

Frictional torque (FT) - Boundary layer dynamics. 

Gravity wave torque (GWT) - Subgrid (local) torque, upward movement and downward movement to do with the buoyancy. 

If there is a net westerly surface wind, the atmosphere speeds up the Earth's rotation and transfers angular momentum to the earth and so there is a net decrease in AAM. The reverse happens with a net easterly wind.

In the NH Winter:

Global MT anomalies are constructed by sypnotic waves that scatter energy across Asia and North America. These sypnotic waves trap the SLP anomaly and push them towards the south. Driven south and east of mountains. Sypnotic wave centres amplify aloft. MT associated with anomaly air parcel transportation in terms of momentum into latitudes its next to. More angular momentum is therefore moves to the 20-20N band. This is where the AAM anomaly appears significant. The anomaly quickly becoming equally uniform leading to a global FT that weakens the AAM anomalies. An anomalous distribution of mass accompanying the MT acting to balance the zonal winds in the 20-30N region. In the mid latitude, Eddy's are the physical link between those two torques.

 The two main torques can be shown in a lag correlation and FT "leads" MT. The relationship related as previously mentioned in the last paragraph. SLP anomalies are related to FT and the coupling with MT.

Some definitions of some words you may not understand

Synoptic is a general summary.

Waves here refers to planatery waves which are propagated by the rotational forces of the Earth and transport energy even if not doing it much themselves and they show themselves in the form of a meandering jet stream.

Shown neatly in this GIF

"

Global Wind Oscillation (GWO) (from the lovely netweather community)

Avertissement de redirection

WWW.GOOGLE.COM

GWO Phases

Phases 4-7 associated with increasing AAM and so theoretically a higher blocking and therefore cold chance (through a -VE AO and/or a -VE NAO typically) later down the line. The rest of the phases, a decreasing AAM and theoretically a more zonal (Atlantic dominant) setup.

Hope this helps at least a little bit.

 

I think I need to go and lie down now, but seriously thank you for taking the time to explain it all to dumbos like me.

[MATTWOLVES 3]

31 minutes ago, Eagle Eye said:

I feel for anybody reading this and seeing simple terms, it's still not really simple terms but I don't blame Tamara and to be honest I don't understand a few of the words fully but the context is enough for me. So to anybody reading this who may not know that much about teleconnections don't worry, "simple" here probably means simple for somebody of the intelligence of Tamara (hence why it's difficult for me). The trouble is, putting this in simple terms would take a ridiculous amount of paragraphs that no human should be forced to write so instead I'm going to link you to a few documents to help anyone trying to understand here and quote a few of the words.

Poleward forcing within the troposphere - Energy and momentum in the troposphere transferring partly (I suppose possibly fully but I'm not too sure that seems possible) from the tropics and upwards, closer to the pole.

Unstable inertia - Inertia is when it keeps it's existing state unless acted upon by another object. Hence unstable inertia is the transfer of energy is between it's existing state and the 'disturbance'.

This is a very basic view at both though and unstable inertia involves a lot more than that.

-VE just means negative (hence, +VE means positive)

Annular mode (here, meaning Northern Annular Mode)

Avertissement de redirection

WWW.GOOGLE.COM

Some more helpful links

Arctic Oscillation (AO)

Avertissement de redirection

WWW.GOOGLE.COM

North Atlantic Oscillation (NAO)

Avertissement de redirection

WWW.GOOGLE.COM

MJO (basic explanation but further down it has lot's of helpful MJO forecasts, make sure to check the dates as some are out of date, at the bottom has the RMM amplification as well. Phases 6 and 7 are the main help for coldies, 2 and 3 seem to be a more zonal setup)

Avertissement de redirection

WWW.GOOGLE.COM

Atmospheric Angular Momentum (AAM)

I'll once again copy over my basic AAM explanation but I've taken out some of what isn't needed

"

I've shortened a few words because this is the second time writing this after I accidentally deleted the tab first time around. 

AMB - Angular Momentum Budget  

AAM - Atmospheric Angular Momentum 

MT(mountain torque) 

GWT(gravity wave torque) 

FT(frictional torque) 

If AMB increases in the atmosphere it must have been transferred from another source since AMB is always conserved. The sources for AMB are from the Earth, the Oceans and the Atmosphere. 

One major aspect in affecting AAM are torques. A torque is the rotational force in the atmosphere.  

The 3 main torques affecting the atmosphere are: 

Mountain torque (MT) - The turning force applied with the effect of pressure systems on mountains. 

Frictional torque (FT) - Boundary layer dynamics. 

Gravity wave torque (GWT) - Subgrid (local) torque, upward movement and downward movement to do with the buoyancy. 

If there is a net westerly surface wind, the atmosphere speeds up the Earth's rotation and transfers angular momentum to the earth and so there is a net decrease in AAM. The reverse happens with a net easterly wind.

In the NH Winter:

Global MT anomalies are constructed by sypnotic waves that scatter energy across Asia and North America. These sypnotic waves trap the SLP anomaly and push them towards the south. Driven south and east of mountains. Sypnotic wave centres amplify aloft. MT associated with anomaly air parcel transportation in terms of momentum into latitudes its next to. More angular momentum is therefore moves to the 20-20N band. This is where the AAM anomaly appears significant. The anomaly quickly becoming equally uniform leading to a global FT that weakens the AAM anomalies. An anomalous distribution of mass accompanying the MT acting to balance the zonal winds in the 20-30N region. In the mid latitude, Eddy's are the physical link between those two torques.

 The two main torques can be shown in a lag correlation and FT "leads" MT. The relationship related as previously mentioned in the last paragraph. SLP anomalies are related to FT and the coupling with MT.

Some definitions of some words you may not understand

Synoptic is a general summary.

Waves here refers to planatery waves which are propagated by the rotational forces of the Earth and transport energy even if not doing it much themselves and they show themselves in the form of a meandering jet stream.

Shown neatly in this GIF

"

Global Wind Oscillation (GWO) (from the lovely netweather community)

Avertissement de redirection

WWW.GOOGLE.COM

GWO Phases

Phases 4-7 associated with increasing AAM and so theoretically a higher blocking and therefore cold chance (through a -VE AO and/or a -VE NAO typically) later down the line. The rest of the phases, a decreasing AAM and theoretically a more zonal (Atlantic dominant) setup.

Hope this helps at least a little bit.

 

Classic mate...you said you would sum up Tams very intelligent post which would have taken her forever to sum up in layman terms....and I reckon that post must have taken you longer than it did Tamara! 

Gr8 explanations though..from you both...

[winterof79]

24 minutes ago, mountain shadow said:

Yeh. There was only about three foot of snow in my backyard.

Yes it was a shocker,,

[winterof79]

1 hour ago, mathematician said:

I hope I'm very wrong here, but I don't see much precipitation with these synoptics.

 

I'm afraid we will see cold weather, hard frosts but not much in terms of snow.

 

Like I said if I'm proved wrong I'd be the happiest.

Dense slack cold pool by weeks end....Warmer sea = you do the maths.

[Lord Baltimore]

1 hour ago, Tamara said:

And so the same prognosis moves into another day and starts to firm up the timetable for the first half of December. The short to medium term consolidating the cold theme for NW Europe (and very wet but equally at least very mild/quite warm down here)

The interest beyond that remains how long the weakness at the tropopause/stratospheric boundary can sustain the -ve AO/NAO pattern. Most all of this has been driven through the remarkable longevity of tropical forcing during the second half of autumn and programme of poleward +ve AAM anomaly eddies propagating from the tropics into the extra tropics and creating the highly amplified tropospheric pattern to forge the weakness at the boundary to the lower stratosphere.

As stated previously, tropical forcing is now heading into a periodicity timeline cyclical lull - which in simple terms means that the poleward forcing ammunition within the troposphere is being withdrawn and it is the built-up momentum unstable inertia lag at higher latitudes that is driving the -ve Annular Mode pattern into the medium term. 

This, to stress again, is not sustainable indefinitely.

While a trickling seeping away of angular momentum and consequential attempts to inject renewed polar jet energy downstream will initially interact with the upper tropospheric weakness and 'roadblock it - as time goes on in the absence of renewed poleward momentum c/o tropical>extra tropical forcing, then the upper tropospheric levels will stabilise, and more organised vortex layers higher up should descend and turn the Arctic Oscillation increasingly less negative.

This implies the polar jet being less and less disrupted and 'roadblocked' and returning on a flatter downstream path and with the jet stream returning incrementally northwards - through the attritional processes discussed in many previous posts.

It underpins my own scepticism expressed a few times about SSW potential. There is no top-down mechanism whatsoever here and, at present, there is no tangible sign or route to one. Falling angular momentum persisting well into December and towards New Year most probably wholly focussed on a slow but sure battleground focus heading from south to north over time.

It all becomes highly speculative beyond that and with a lot of winter remaining and renewed westerly winds stirring in the Indian ocean perhaps attempting another poleward tropospheric lead on the atmospheric circulation.  Before that though, while finely balanced, it could be that the coming couple of week sees peaking coldest and potentially snowiest peak for NW Europe before the last third of the month and into the New Year sees a relaxation from the south and milder air making inroads from the SW. For my part of southwest Europe, a distinctly wet period looks to remove further the severe drought issues of over 12 months - before with luck a more settled period arrives as pressure rises with the jet stream heading northwards, bit by bit.

Rain in the Iberian peninsula is very much needed.

[Bats32]

The "Azores hurricane" is forming https://twitter.com/NHC_Atlantic/status/1599768945380454400?t=6lYfOi3TofNfPeLJTdsJjg&s=19

[SizzlingHeat]

I have to admit that I havent been on this site now for some time and I no longer follow the weather models like I used to, however I heard on the radio that there has been a cold weather alert issued by the met office. So, with this in mind I had a look, for the first time since the summer at the GFS, ECM etc but am a little perplexed to what they are showing. Yes, its going to get colder everywhere, but it does seem very dry with limited precipitation anywhere aside from exposed coasts. I am also very underwhelmed by the forecast 850s, which barely drop below -5/-6c for the duration with occasional increases to -4/-3c particularly across the SW. This doesn't seem like it would be that cold surely and any precipitation would be mostly cold rain rather than snow? Perhaps my lack of enthusiasm with weather and waning knowledge of the models has me doubting a lot more now. I remember cold spells from the past with -10c air entrenched over the UK for days, with occasional outbreaks of -15c but this seems very watered down and dry given such hype and excitement from a lot of members on here. Perhaps I am looking negatively, but I cant fathom too much excitement from a very dry cold spell with a few days of overnight frosts/little snow? 

Regards

Edited December 5, 2022 by SizzlingHeat

[Light Without Heat]

50 minutes ago, Penrith Snow said:

Absolutely, even during winter 1978/79 short mild spells were frequent occurring in early December, just after Christmas, second week in January and last week in February.

Set ups like 1963 or even December 2010 are exceptionally rare.

Andy

79 was my last year at primary school and is what got me into weather. That was one crazy winter never forget it.

[Updated_Weather]

10 minutes ago, Bats32 said:

The "Azores hurricane" is forming https://twitter.com/NHC_Atlantic/status/1599768945380454400?t=6lYfOi3TofNfPeLJTdsJjg&s=19

They don’t seem to think it’ll do that much

[LightningLover]

ICON 12z on it's way!

[Teun Voskamp]

6 minutes ago, LightningLover said:

ICON 12z onderweg!

Model Timeline

MODEL-TIMELINE.NETLIFY.APP

 

[Snowboy111]

1 hour ago, mountain shadow said:

Yeh. There was only about three foot of snow in my backyard.

We had 15ft drifts

[Blessed Weather]

Model Output discussion please folks. Thanks.

[bluearmy]

16 minutes ago, LightningLover said:

ICON 12z on it's way!

Approaching day 6, you’d expect it not be as ‘good’ as the 00z run by the time it ends …

[Battleground Snow]

Scandi high, Genoa low?

Hopefully Atlantic low heads south further on.

[Alexis]

20 minutes ago, SizzlingHeat said:

I have to admit that I havent been on this site now for some time and I no longer follow the weather models like I used to, however I heard on the radio that there has been a cold weather alert issued by the met office. So, with this in mind I had a look, for the first time since the summer at the GFS, ECM etc but am a little perplexed to what they are showing. Yes, its going to get colder everywhere, but it does seem very dry with limited precipitation anywhere aside from exposed coasts. I am also very underwhelmed by the forecast 850s, which barely drop below -5/-6c for the duration with occasional increases to -4/-3c particularly across the SW. This doesn't seem like it would be that cold surely and any precipitation would be mostly cold rain rather than snow? Perhaps my lack of enthusiasm with weather and waning knowledge of the models has me doubting a lot more now. I remember cold spells from the past with -10c air entrenched over the UK for days, with occasional outbreaks of -15c but this seems very watered down and dry given such hype and excitement from a lot of members on here. Perhaps I am looking negatively, but I cant fathom too much excitement from a very dry cold spell with a few days of overnight frosts/little snow? 

Regards

Most of the big events in the past, especially in the South West, have occurred with hardly spectacular 850s as mild air clashes with the cold. 
I think -10+ entrenched over the UK for days is a bit rose tinted  It's only early December anyway - you're more likely to get the really low 850s in late January into February.
Simply too early for much evidence of this spell being dry or wet yet. We'll know more on Wednesday.

[Snowy L]

Benelux ridge... going to make it difficult for Atlantic low to slide, hopefully another diving Svalbard low to put some pressure on it later?

[LightningLover]

Low is struggling on the latest frames, can't tell if it's going to slide or be forced northwards by that ridge though...

[Skullzrulerz]

ICON low looks to push through, bringing the cold spell to a close...

[frosty ground]

1 minute ago, Skullzrulerz said:

ICON low looks to push through, bringing the cold spell to a close...

Looks like the low is struggling to me leaving a battle ground across the U.K.