Eagle Eye

There have been a lot of "what if's" in the past and let's hope this doesn't become another one. The Azores low offers a lot of difficulty going ahead but it doesn't change the fact that this is arguably the best chance for early Winter proper cold since 2010.

Like others have said, it's not all bad. Downstream effects of the retracted East Asian jet seem to be good for us but that's still in FI for now. Remember, it's only a couple runs and not all models are showing it as 'bad' as people are saying. The 18Z runs may offer a bit more insight but I fear we will see the same thing again with a model split. Any 1 solution is unlikely to be sorted out anytime soon, me thinks .

3 all. Penalty shoot out anyone?

I could write an English essay on the juxtaposition of this thread for my GCSE'S

Physics . That is not the chart I would expect to see from the initial setup. It's impressive how much difference is between the models as to their setups especially.

Just a joke, realise it's a bit off topic but surely we can just extend Florida and it won't affect the UK? Edit, just seen a brilliant BBC comment

AAM and GWO backing up what I've been saying recently Slightly +AAM input keeping the unbalanced inertia and -VE AO in place for now but it's very difficult to tell how it'll evolve from there. Clearly, there is a lot at stake here and it won't be solved by one CFS run of 4 members but there are sign of increased AAM input around the 17th onwards perhaps associated with a +VE mountain torque or +VE frictional torque event with a 6 day correlation cycle of the torque. We obviously cannot keep this going for all of Winter as we'd have to be extremely lucky(or unlucky) for that to occur especially within a La Nina Oceanic base state year. Eventually, the MJO phase 6/7/(8) repeating pattern should wane and we see a weakening of the AAM downstream. A SSW may be possible with the increasing Eddy Heat Flux pushing upwards and the split troposphere but I'll keep off that for this post for now. The event doesn't necessarily matter that much but it's the movement after the event that interests me with a slight increase in southwards momentum transport hence the circumglobal troughs. That southwards momentum transport would end up helping us because it increases the temperature gradient in the area between the tropics and us. This temperature gradient increase just north of Africa draws up Eddy energy fluctuations and transfers them upwards hence the potential for blocking. The relatively stationary high over North Africa could get 'drawn up' with the Eddy Heat Flux hence the main blocking potential is around Scandinavia going through mid December as well as the -VE East Asian Mountain Torque (EAMT) Eurasian feedback although that will probably start waning and we see a separate energy dissipation and that's seen with the Pacific/North American Pattern going positive eventually. Having different downstream effects however we'll probably only deal with that fully when it happens.

Thank you for the insightful view to December 1981 and how that evolved. I'm going to quote myself from yesterday in the model thread to hopefully help you all a little more... " 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 Avertissement de redirection WWW.GOOGLE.COM Arctic Oscillation (AO) Avertissement de redirection WWW.GOOGLE.COM North Atlantic Oscillation (NAO) https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=0CAMQw7AJahcKEwiIjKX2yOL7AhUAAAAAHQAAAAAQCA&url=https://www.climate.gov/news-features/understanding-climate/climate-variability-north-atlantic-oscillation&psig=AOvVaw26Xvy7Pu8AqqyAd4bXNDGJ&ust= 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. 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. "

Jet retraction across East Asia from the -VE East Asian Mountain Torque (-VE EAMT) scattering energy across Asia and North America could mean extra amplification input downstream into the North African high aided by MJO phase 7/8. The Eurasian feedback to the -VE EAMT allowing for a strong Eurasian block shown on a couple recent runs. This could aid the development of a Scandinavian block in the mid term. On the other hand, the energy scattering could help aid the Atlantic depending on how the Pacific/North American Pattern evolves in response to the jet retraction and the timing of the amplification of symoptic waves. Its clearly going negative for now but a return to more nuetral mid month may be possible but I think that's more from these synoptic waves leaving than anything. In which case, we could be on course for a Scandinavian blocking further down the line potentially intensifying the cold but for now, the response to the jet retraction remains hard to tell. The timing of the Eurasian feedback and the synoptic wave train as the unstable inertia balances out, the driving of the -VE AO pattern may wane and as well as that, the amplification of tropospheric Eddy's may decrease alongside it so we may need to get a slightly quicker timing of the Scandinavian high and Eurasian feedback if they do pull it off but I wouldn't worry about that for now. That's how much the cold pattern continues though, the initial cold pattern just keeps getting upgraded. A more moisture rich but still cold easterly route potentially being favoured and maybe a channel low could form depending on shortwave movement therefore the chance of snow has increased on the latest few runs but we still need to keep an eye on if it evolves into an actual trend. Mixing of uppers with the SST through North Sea convection may warm the uppers as they approach but considering the starting cold of the actual feed, we don't necessarily need to worry about that causing too much of a problem yet.

You weren't kidding about P19 Let's hope that somehow all of the models start to trend towards this (unless you want your energy bills to stay within the bounds of numbers)

Let's have a look at the GFS mean... I think that's called a decent run "Siri, show me a negative Arctic Oscillation pattern" (half stolen joke but my goodness me is that quite the chart)

Away from the UK on the ICON, slight amplification of the low pressure centre from the retraction of the East Asian jet amplifying the jet oscillations downstream in the Pacific Ocean, good signs that further down the line and the Scandinavian blocking potential is increased. An increasing thermal gradient enlarging the amplification of thermal eddy transfer further along the line. So downstream we have increased jet amplification meeting with the Eurasian feedback of the -VE EAMT. The only real way for the thermal eddy's to transfer is up towards a Scandinavian high. We could still see a less favourable jet retraction response but right now the Icon is showing a fairly decent initial response to the retraction so as a coldie(ish) I'm going to back this ICON run. Oh and the ICON over the UK isn't half bad either .

I'm not sure but I don't think it's great it's just that it's good signs. Thank you, wasn't sure what it was much just had a general idea.

Deep -VE AO and -VE NAO signal going into week 2 on the EC46. Very good signs for coldies.

Upgrades are more likely (in my opinion) with shortwaves, lake effect snow (possibly) and maybe a few more fronts showing themselves up as we go through the cold spell. Uppers could upgrade as well with the high resolution models showing the more local cold uppers. There can be a lot of snow hidden even a day or two before the event starts.

I don't think you are the only one, you're the only one brave enough to make the call though

AO continues to tank, I don't think I need to say too much else. No real need to over analyse at the moment except the general long term trends as the variation in the Atlantic especially is way too much to look at anything other than the initial start of the cold episode.

My two penny's worth on the longer term discussion. It's clear that the MJO is moving back towards phases 5/6/7 with the latter two being of the most help for us. The strength is relatively weak but it should help to amplify the jet stream's oscillations further along the line. The timing of this is important as the anomalous energy distribution scattering from the -VE East Asian Mountain Torque (EAMT) helped retract the jet (I think) towards Eastern Asia and with the slight amplification aloft of the low pressure centres, downstream amplification towards Europe may be possible. The area of amplification is important though as it clearly should be fairly amplified although by the time of the lag correlating with MJO phases 6 and/or 7 the Eurasian feedback may be waning. The general dynamics for the downstream amplification mostly correlated with the MJO phasing as the -VE EAMT's downstream effects will be dampened away from the typical Pacifc/North American Pattern response area with its main response being in the zonal wind and we simply don't know yet how that will evolve. The best evolution as mentioned above but it could also 'associate' itself with the weakening AAM and increase Atlantic downstream influence, just depends in the exact extension of the jet and how the energy scatters itself.

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.

Main mode almost has to be convection apart from a couple fronts based off what is showing at the moment but that may dump a lot of snow near the coasts depending on the timing and the area. The further north and east you are, the better chance you have off the North Sea but an increased chance of fronts further north and/or west (as far as I can tell as a general trend, not sure what these last couple runs are showing though).

I think the effects of shortwaves, Atlantic bias and the effects of the -VE East Asian Mountain Torque event along a +VE AAM and the varying Eurasian feedback strength are the main reasons for all of the spread, could go both ways really but I'd say a Scandinavian high is favoured along a strong Eurasian block from the -VE EAMT feedback but I simply don't know for now as it could get blown out by a shortwave in it's early development phase.

Just don't let this be the well known Met Office curse (or for the sake of heating let's hope it is, I don't mind which end of the spectrum you are from). Just look at that wording, 90% chance of severe cold weather and icy conditions between the 7th and the 12th.

Low confidence medium to long term now, will try and make sense of it all when the GWO and AAM forecasts update on the site I use as they haven't updated since the 30th of November hence no real long-term forecasts since then. Models clearly have little confidence in one setup beyond this week stemming from their handling of shortwaves and the -VE EAMT, leading me to think that we're on a tipping point for medium to longer term being generally colder and we won't know for a long time me thinks .

True and don't forget they underestimate the effect of subgrid gravity waves on the ability to affect the troposphere so more localised snow showers are going to be missed by the models, especially the lower resolution ones. The higher resolution ones can pick up on this effect more but I find them to be quite inaccurate at this range still.

The GFS has been in the pub for a long time in that case