Eagle Eye

Interestingly, weather models not that long ago simultaned increasing AAM suggesting that the +VE AAM state (what led up to this) has an increased chance in Winters going into the future. Only slightly but a slight increase also suggests that significant anomalies should (but not always) slightly increase alongside it. Theoretically strong +VE AAM's lead to more negative NAO's and so the displacement of cold theoretically could be strong. Hence the more extreme events may start popping up. I also read that planets gravitational fields may lead to a leaking essentially of some momentum from the Earth over time so it's sort of a battle between other planets and climate change. I'm pretty sure those are theoreticals but it's an interesting field of study and I suppose in the future can be used to show just how much of an effect climate change is having upon the Earth.

Just before this evening's output, I told my friend who dislikes colder weather that we could see a return to mild and wet beyond mid December and look at the EC46 and long-term updates since A loss for her but who's ever heard of a ginger from the South East that wouldn't prefer cold anyway? She's a coldie at heart I bet.

Interesting, weather right now seems to be defying all odds of the oceanic La Nina state. Wondering if the weak GWO might help lock us in a pattern. Of course, we've got the -VE East Asian Mountain Torque event to think of, it is a possibility that it could re-inforce blocking, towards the normal Greenland or Scandinavia and in my general musings, as long as we are in MJO phases 6/7, I suppose that, that in theory could continue to enforce the -VE AO with the GWO not really going one way or the other. It's been the general trend apart from a few runs to keep the GWO slightly +VE beyond the first dip up until late December and is probably associated with the MJO phases 6 and 7 seemingly being recycled to again and again. We lose some frictional and mountain torque around now but as you can see the effect on the AAM is really just able to be negotiated as we just gain momentum straight after. The effects on the surface are therefore unlikely to be that significant unless the -VE EAMT event props up (or rather flattens) the Atlantic into a more Stormy phase. It's all very interesting going beyond this cold and I will keep an eye on it as I'm not really someone who likes to forecast based off models, there's already many people doing that better than I can (same goes with teleconnections but they're open to a lot of interpretation with less evidence for associated patterns apart from the basic +VE AAM supporting a Nino-esque atmospheric phase and -VE AAM supporting a Nina-esque phase).

Totally agreed. EC 46 just updated and is showing an almost perfect -NAO pattern compared to a -NAO Jan-March average, this is a more of a mid Winter setup we're going into, shows you how incredible it could be. There is no real reason to believe this will deviate from a normal -NAO and so cold is significantly likely and significant cold potential is most definitely in the mix. Oh and there's such a large spread on the Stratospheric zonal winds, anything could really happen beyond this upcoming -NAO spell that we're already dipping in to.

That may be a problem but for the sake of snow lovers let's hope it's not

Back working again

Deep surface cold from this... Don't anyone complain that the uppers wouldn't give Narnia because on this ECM they don't matter as much as they normally would. If you do complain I won't poke you in the eye though, instead I'll just politely disagree.

Crewe Cold seems happy... It's official, the models have officially peaked

Uh oh, @tight isobar is going to be coming after you now

Cheers to the ECM

The absolute collapse of cold... Its a possibility, after all, the GFS is showing it. I don't think it's the most probable outcome at this time range but that doesn't mean it can't happen.

At this lead time it really doesn't matter and if it does happen to come off, with higher resolution models I imagine we should see it get cold enough for snow with uppers like that. Get the cold first and with cold like that and precipitation, snow should follow.

Snowdrifts above the shard

I try and mainly focus on the teleconnection patterns as I know that the basic overall pattern is better until we get within the reliable time frame which for me is about 168 hours but I still succumb to the passion sometimes.

I hate to say it But the next set of runs... Really don't matter unless we see a trend and/or the models converge on one solution. Remember this every time in the future... The weather is finely balanced and small margins come up with big differences the further you go on so unless the models are trending towards one or two solutions don't get hung up on what one model may be showing unless that one model is trending towards that solution in which case it may be picking up something early or may just be a coincidence. Right now, the model trend is the best it's been in December since 2010 (probably not as good as 2010 though) in terms of cold trends so despite the odd on and off model run, we're heading towards the most interesting period (for me at least) since I've joined here.

You know things are good when we're searching down the back of the sofa for one bad run every couple days.

Surely the right thing to do is that when a model favours us coldies they're the best in the world whereas when they don't they just don't exist anymore

Trying to be a bit more serious here... My attempt to make sense of everything at midnight, what could possibly go wrong? The AO has already started to decrease and with the reinforced Greenland blocking helping split the tropospheric vortex as shown by the 3D vortex at 180 hours, we should see the associated -NAO and an increased chance of cold coming our way as shown by the recent model outputs in the mid term that are starting to get towards a reliable(Ish)time frame. This split vortex from the Greenland blocking should help to decrease (and reverse) the zonal wind and therefore...easterlies. Once again, that is shown in the recent model output. So we're getting into a timeframe where it's not about these individual teleconnection patterns but instead about surface to troposphere localised conditions. I'm not going to discuss them for now but the significant negative AO and -VE NAO likely stems from the +VE AAM which was helped by the MJO values in the Western Pacific with the lag correlations of phases 6 and 7. The La Nina state of the ocean seems to not be affecting us too much as of yet, perhaps the ocean and the atmosphere not well coupled which I think has been said before. I think it's the best setup for cold since I joined (except maybe the SSW but they are more delicate evolutions for them even to occur, increasing recent energy trains across Asia roughly and wave-1 amplitude increasing in the lower Stratosphere may help and/or be the products of increase trop-strat coupling and may lead to a SSW but for now I'm not going to stick my neck out) because the easterly stems from actual teleconnection backgrounds and the possibly significant -VE NAO state suggest that, for now, this may take quite a long time to recover. Alternatively, we could see a quick return to a +VE NAO due to the sped of which the -VE NAO happened and the thermal recovery process theoretically occurring quicker due to that speed. The AAM is being forced into a more neutral state but I'm not sure of the dynamical processes involved with that so for now I'll say that I simply don't know. At a total guess, I think localised dynamics more associated with shortwaves may be what ends up at play here. The zonal wind shouldn't really recover amazingly quickly as the strength of the weakening looks to be fairly strong and stretched out so we may end up seeing a lengthening of the -NAO state but it just depends on what happens with the Greenland high movement and whether the La Nina oceanic state has more of an effect and for now I don't think it's worth mentioning that much. Long-range forecasts are quite difficult to interpret from this but purely based off the oceanic La Nina base state I think a flatter and therefore more Atlantic influenced theme going into late December and January but we cannot rule a SSW off the cards just yet so that's interesting to add to this increasingly complicated equation. A possible bottom up split evolution if a SSW does occur with large deviations around the Greenland area away from the zonal mean and so the Stratosphere is in asymmetry and there is a large deviation away from the local thermodynamic equilibrium (LTE) and to be in LTE the zonal wind weakening is transferred back down to the theoretically already split Troposphere. So it's not really a typical SSW evolution but you essentially get the same results. Anyway, went off on a tangent there. The GWO doesn't really help with matters amazingly here but along with recent trends of the GWO, it looks like we should eventually move towards phases 2 and/or 3 associated with northwards momentum transport with the loss of AAM and so an increasing southwards drag and possibly eventually a more circumglobal ridging pattern with a stronger westerly flow and so Atlantic dominance is the main variable here I would suggest. Decreasing amounts of meanders in the jet stream with the increasing westerly flow meaning a flatter sypnotic pattern. It's still quite far out but you'll see what it seems to be associated within your read further down. If we look at the MJO forecasts, eventually we should move our angle of attack towards phases 2 and 3 but then a re-entry towards phases 4 to 7 is quite a quickly moving weak MJO setup. The weakening of the AAM over the next couple days seems to be associated with the dip into -VE RMM values and the West Hem and Africa areas as the roughly 14 day general lag correlation makes sense here. So I would suggest getting close to phases 2 and 3 here help prop up the weakening of the AAM but the general stability comes from the fact that the RMM values aren't really that amplified in either direction so the weather synoptics are probably going to be on a knife edge throughout December. That re-entry into the increasing RMM2 values should get us back into a (fairly weak) +VE AAM so that's a positive from mid to late December but how strong that +VE AAM could be will probably fluctuate a lot run by run. I think the next month or so will be balanced between the +VE and -VE AAM so dynamical recovery processes of a -VE NAO state and significantly negative AO state will matter quite a lot here beyond this cold we're being forecasted at the moment. So, what about the closer timescale? ECM Vs GFS Vs CMC (GEM) Significant differences deriving from whether the NAO is west based or not but for now I'm going to be boring and say... More runs needed.

Just for fun, perturbation 17 and 24. The GEFS mean. I'm not going to say it... Nope... Alright fine, BOOM!!!

Yay, my point seems to have been proved here.

Mean at 168 vs operational (I think) at 168. Ironically, the mean is showing a better angle of attack from the cold to defeat the low and a differently angled low, the mean much better for it to not block out the easterly so much. Think the operational (or whatever it is at this point I don't know) will prove to be an outlier among it's own ensembles.

Looking at the risk alone for the 18Z run and the first potential around the 4th is actually looking fairly good. -5 and below (850's) Risk of snow (24 hours) And that's just the taster for the potential main event.

Don't worry, the GFS likes to do random things, sometimes it gets it very right, sometimes it gets it very wrong. Let's hope it gets it wrong here but even if it gets it right it feels like it's just denying the inevitable. I'm not saying it's definitely going to happen, I'm saying that I have officially joined the excitement of the easterly express. As Ozzy Osbourne said "I'm going off the rails on a crazy train".

The easterly express to leave the station soon...

And seeing as I was 3 for the 2010 business, could end 15 years of December hurt for me, if we do get that lucky, I might enter the lottery, might ask out my 'crush', might run for prime minister. Could be the best December for years lol. But we need to get it first.