stodge

Evening all It's probably something I've just made up but in model terms Sunday's hope is often Monday's despair. A new week seems to bring a reset away from optimism to pessimism (or realism if you prefer). Let's see if the new week and new models tell a new story.. 12Z GEM: No surprises by the weekend (T+120). The Atlantic LP has two centres - one already over the Faeroes and the other close to the Hebrides. In their circulation showers and rain off a mild SW'ly for England but a change to a PM airmass apparent further north and west. Heights over SE Europe and a new LP developing far to the SW. By T+180, the LP is churning its way slowly towards the British Isles while a ridge builds over Iberia , pressure remains high far to the east while a shallow but extensive trough covers Scandinavia. The PM airflow is gone and a weak HP ridge ushers in a new mild airflow for southern Britain. By T+240, the evolution is getting messy as everything slows. The LP fills and meanders toward NW Britain while heights develop over both Iceland and Scandinavia as well as over southern Europe. It's still mild for most of the British Isles and there's a new Atlantic LP but this evolution has a lot of paths from here. 12Z GFS - after a bit of a nothing run from GEM, what will the Americans offer us this evening? At T+120, slight but subtle differences to GEM. The PM airmass covers the whole of Britain with the complex LP still to the north-west. By T+180, the differences are more pronounced. The original LP is only just to the north of Scotland and secondary features have developed. One has moved across southern England and the LP we saw 60 hours earlier much further to the SW is coming in faster and deeper towards the British Isles. A new mid-Atlantic HP is trying to form at the same time. As expected, therefore, a very different T+240 with the LP crossing Britain and developing over southern Scandinavia as a complex feature. This draws a NNW'ly flow down across Britain which would be pretty cold you'd imagine. Heights from Greenland south to a new HP in mid-Atlantic are under pressure from a new LP coming out of Canada. We get a cold Christmas for a change and by T+324 the HP has finally built in across Britain with a ridge to Scandinavia. LP over Spain helps to support a ridge but clear signs of the PV gathering over its usual place. Nonetheless, the cold evolution does well with the HP heading to Scandinavia and throwing a cold E'ly back across Western Europe. Minus 8 850s suggest the white stuff not the wet stuff. 12Z ECM - well, the GFS OP will have cheered many and the key is how it plays that LP coming from the far SW- Phasing it into the original LP allows time for amplification while a slower approach may not but let's see where ECM goes. T+120 has few surprises and T+168 is the key chart on this output. Note how the LP to the SW has phased in to the circulation of the original LP (as GFS also suggested) and the whole feature looks set to move NE across southern Britain with heights building upstream. The T+240 chart shows how that impacts and we get a chilly Christmas Eve chart with a NNE'ly flow for many parts with the LP over the Low Countries. Much colder sir moving in from the north as you'd expect and it should mean a cold Christmas for all and perhaps a White Christmas for some. Looking elsewhere, the 12Z OP showed the continued strong 10 HPA warming for the period between Christmas and New Year and perhaps a third warming developing from the European side to start 2021. It's all good news for those looking for a disrupted vortex. From an unpromising situation, the 12Z Control ends on a very cold note with a Scandinavian HP and a wedge of -12 850s coming our way. Conclusion - after a bleak end to last week, this week has started with some much more pleasing output for cold fans. It's always helpful to see GFS OP and ECM Master looking so similar and the former (supported by Control) looks a very nice route to something cold. ECM gets to cold but whether it can keep the cold is debatable. GEM is much less convincing and shows what could happen if the phasing of the LPs doesn't happen. We need to LP to the far SW to phase into the main LP and rush through to allow upstream amplification . If that happens, with a weak and disorganised PV in our vicinity, we have a chance to build heights to the North-West. The other option whereby the Atlantic HP transits to Scandinavia also works for those wanting cold. However, caution and patience must be the watch words - we are an eternity away from all this and so much, as we know, can still go wrong. If this is still on the cards at T+24 we can begin to enjoy it but for now, it's nice to look at but that's all.

I'm no fan of Wave 1 warmings from the Siberian side either. All they do is send the PV back to Canada where it can re-strengthen. Tonight's GFS 12Z OP suggests an initial Wave 1 hit followed by a second much stronger attack between Christmas and New Year. It's not enough to split the PV of course but it does weaken it and reduce the zonal wind speeds further which helps in terms of allowing amplification and offering the chance for heights to build over Greenland or Scandinavia.

Evening all One or two crumbs of comfort last evening for those hoping for a break from unremitting mildness and almost unremitting wetness in the next 14-21 days but let's see where tonight leaves us: 12Z GEM: by T+120 (next Friday), a complex LP sits out to the west of the British Isles with a mild SW'ly flow for all areas. Heights over Europe with the main centre way to the south-east. By T+180, the mild theme continues with a secondary LP from the Atlantic developing and running NE to be off the North-West coast of Scotland bringing a further spell of rain for all. A defined HP cell is moving across Iberia while the Eurasian HP is off to the far east but the strength of the northern arm of the jet is enough to keep it at lower latitudes. A new HP is in the Atlantic with a small LP just to the west of the Azores. Now, this small LP is interesting as it sends the HP into mid-Atlantic where it ridges SE to join with the HP over Iberia and to the north where it links with heights over Greenland to produce a new elongated HP ridge running NW-SE from Greenland to Iberia. There's an evolution to something much more interesting from here and there's some colder air over the British Isles by this time. 12Z GFS OP - well, for the second evening, GEM teases and tantalises in FI. GFS OP certainly didn't do that with a T+384 of absolute horror for cold weather fans. T+120 has a few interesting differences in the position and orientation of the Atlantic LP which may be of significance (or may not). By T+180, the initial LP has moved through to the north and north-east of the British Isles while the new LP has passed between the HP systems and has deepened markedly so I suspect this evolution will look very different from the GEM. Well, perhaps not - by T+240, GFS OP and GEM have some significant similarities with both showing mid-Atlantic ridging. GFS has sent the trough into Scandinavia with a PM airflow now over much of the British Isles and heights over eastern Greenland and Iberia. By T+300, it's getting messy - the trough is now over Scandinavia with weak heights over and to the west of the British Isles and heights over Greenland but wr have a new trough coming out of Canada and heading into the Atlantic. Unfortunately, from there, it all goes very wrong for cold fans - the energy in the Atlantic and Scandinavia link as heights rise over central Europe and we end up with a very mild SSW'ly by T+378 despite Greenland heights. Could this be down to the second strong 10 HPA warming now being forecast in FI? I'm not sure but while superficially it looks poor for coldies there's a lot going on behind the scenes. 12Z ECM - not as bad last night as seemed possible but we'll see. No huge surprises at T+120 though the trough perhaps a fraction more accentuated to the south than on GEM or GFS. On to T+192 and the LP from lower latitudes is developing to the south west between the two HP cells though it's not as vigorous as GFS at this time. Yet the evolution to T+240 is much different to the other models as the LP ends up filling as it approaches Biscay and the rig=dge builds behind it in mid-Atlantic while a new LP seems to be heading off the eastern seaboard. Chilly if not cold over Scotland and the north in a slack PM airflow but milder further south. Looking elsewhere, 12Z Control ends with a strong mid-latitude block while the 00Z Parallel is a Christmas present for every coldie with a complex LP moving south through the British Isles and with 850s of -4 to -8, we'd probably not be asking "will it be snow". Conclusion - the question for tonight is will be throw two sizes or will it be, as usual snake-eyes? The amplification forecast across the models at T+240 "could" give us a nice cold outbreak for the immediate post-Christmas period but it's all very tenuous and on a knife edge. The GFS OP shows how it could be a disaster while the morning Parallel shows how it could work so well. I have no clue at this time - I'm also noting the second strong 10 HPA warming suggesting the PV coming under renewed pressure at month end. It all looks very interesting.

Evening all A fairly downbeat assessment from me yesterday based on the evening's output but it's another day and some of the background signals continue to offer cause for encouragement for those seeking cold, snow or just some interesting synoptics. 12Z GEM: - by this Thursday (T+120), the first LP has pushed just to the north east of the British Isles and the trough extends back to the main LP far to the west. A SW'ly airflow keeps it mild and with a transient ridge we should be enjoying a fine day. By T+180, there have been some interesting developments. The main LP has cleared to the NE and a PM airflow from the NW is moving down through the country but there's not much happening in the Atlantic with the next instabilities far to the south west and the Azores HP trying to ridge in to Iberia and North Africa so not sure where this is going. However, a new LP develops and swings NE pulling the Azores HP into Iberia so the mild flow remains but there is a pronounced Atlantic ridge behind and heights remain over Greenland so it's a tantalising end to the run. 12Z GFS - GEM hints at a break in the flow and some amplification at T+240 - let's see if the OP is in a similar mood. At T+120 only marginal differences with GEM but perhaps the most interesting is a more defined ridge from the Azores HP through central and southern Europe. By T+180, some differences emerging against GEM - the main LP remains to the NW but with secondary features swinging toward Southern Britain bringing more pronounced periods of rain and strong winds. A further deepening LP in mid-Atlantic adds to the mix with the core of heights over SE Europe. By T+240, we have a PM airflow as the LP moves across just to the north of Scotland with a pronounced trough passing through eastern and southern Britain at that time, Some amplification upstream but not as pronounced as on GEM. By T+312, the Christmas Day BBQs looks safe with HP over France and a mild or very mild airflow with LP held well back in the Atlantic. T+384 is every cold fan's worst nightmare. Perhaps the only positive at the end of FI is another warming setting up which looks more extensive then the warming due at T+192. 12Z ECM - the last chance saloon tonight? It'll be interesting to see if it follows GEM in any way. T+120 looks pretty similar. By T+192, the main LP is just off NW Scotland and the cooler PM airflow is moving in. An LP forming in mid-Atlantic and an HP developing to its north-west are interesting but I suspect it won't help us. To be fair, T+240 is more encouraging than I suspected - the LP is taking a more southerly track with the HP less inclined to ridge NE and could we be seeing the HP building more into mid-Atlantic? I'm not 100% sure where the evolution's going from there. Elsewhere, 12Z Control is a much colder option than the OP and at T+240 isn't too far removed from ECM at the same point. 00Z Parallel ends anti-cyclonic with a impressive cold wave coming out of Siberia but which probably wouldn't reach western Europe. Conclusion: - just a few straws in the wind tonight for cold fans. 12Z GFS OP is a horror story apart from the 10 HPA warmings. Both GEM and ECM tease and tantalise with T+240 evolutions and the 12Z Control wouldn't be wholly unwelcome. One or two mused the reversion to a milder spell might last 7-10 days at most and that's not inconceivable but as always we need all the pieces to drop kindly. One thing in our favour is a quiet-ish Atlantic and a PV which still struggles to show the robust characteristics of some recent winters.

Evening all Not much hope for fans of cold on yesterday evening's output. My fear was the warming from Siberia would simply push the PV back to Canada where it would re-strengthen in situ. There are other factors as well but the trend towards a more Atlantic-based scenario with positive alignment looked increasingly the form horse. Still, another day, another set of output and as we know it can be "all change" as they say on the trains. 12Z GEM: - so to T+120 and the initial re-invigoration of the LP and the dragging of the jet back north has left the LP just to the west of Scotland. A new and vigorous LP has formed over the eastern seaboard while heights remain over Greenland for now. by T+180 that storm has filled slightly but moved ENE to be over or just to the west of Scotland so continuing unsettled and mild for most. Some interesting changes by T+240 - the Greenland heights remain and the next Atlantic LP has developed at lower latitudes but is churning toward us. Heights are low over Scandinavia but rising over western Europe. Again, still on the mild side for most. 12Z GFS OP - this takes us into the Christmas period so FI will be more keenly observed than usual. By T+120, it's a little different to GEM. There is a narrow and elongated trough over the North Atlantic with main centres off the Canadian coast and smaller centres over western Britain and approaching from the west. Slack heights over much of Europe. By T+180 the complex trough sits to the west and north-west with another secondary LP over East Anglia and a ridge approaching as heights build into Europe. Mild but quite unsettled with rain for many. Moving on we do get a colder interlude with a N'ly or NNW'ly as the LP splits briefly with the next system taking its time in mid-Atlantic digging the trough south and forcing the HP over Iberia and threatening a new push of milder SW'ly air. That's pretty much what happens and the Christmas Day BBQ looks safe enough at T+336 with a draw of very mild SSW'ly winds and a deep LP out to the south-west. As expected, the LP pushes NE to the west of Ireland and then turns away NW back into the Atlantic keeping a mild airstream over most of the British Isles. The PV, however, is not the raging beast of recent winters and by the end of the OP run is over the Pole. 12Z ECM - not much hope for cold fans tonight, is there? I'm not expecting anything from ECM if I'm being honest. T+120 not much different to the other models. By T=192 we see the Atlantic LP head NE and the next feature waiting in the wings to the SW. Thr run ends on a cooler note with a PM airflow as the LP heads across Central Scotland and into the North Sea. One crumb of optimism is the PV looks disorganised at this time which you wouldn't expect. The 12Z Control looks pretty mild as did the 00Z Parallel. Conclusion - nothing for cold fans tonight. It's too early to draw stumps on a cold Christmas and GFS OP hints at a brief N'ly interlude but that's all realistically we have to hope for at this time. The PV remains weaker than you would expect but not sufficiently so to drive amplification to give us a break between Atlantic LP. The possibility of anticyclonic conditions remains though we need more to happen for that. It looks a mild and dry Christmas for parts southern and eastern and a wetter one for parts northern and western.

Evening all Another day, another set of model output. Last night's 12Z promised very long-term gain for short or medium-term pain, at least in terms of those wanting cold or synoptically interesting weather. Let's see if tonight's charts tantalises or frustrates (I suspect both and possibly in equal measure): 12Z GEM: - the path through to next week is well set. As it did last night, GEM, by T+120, is developing a secondary LP which looks to be heading toward the Channel except that it doesn't. It absorbs most of the existing LP's energy, crosses Ireland from south to North and becomes part of a new complex LP just to the west of the British Isles by T+180. Heights over Greenland are developing as per previous output but that makes no difference. The LP fills a little and trundles slowly NE as heights rise through Iberia and a new Atlantic LP deepens and moves towards the British Isles with a ridge preceding. A more pronounced mid-Atlantic ridge with a deep LP exiting North America. It's a long way from classic zonality but that doesn't stop the British Isles living on mild street. 12Z GFS OP - this tantalised with a real Christmas treat for fans of snow and cold but will it repeat like a decent parsnip and radish curry? We'll see. BY T+120 the Atlantic LP is looking more complex than on GEM and signs of a secondary feature though not as pronounced as on GEM. Superficially not much change by T+180 but the LP is slightly further south - this is a new feature which has absorbed the remnant energy of the previous feature. BY T+216, it has moved over the British Isles while a new deeper Atlantic LP waits in the wings. T+306 maintains the increasingly unsettled theme bordering on cold zonality with a succession of LP moving on a fairly southerly-positioned jet towards the British Isles. T+384 sees a stormy pattern with new LP just over the British Isles. I don't see a route to rapid cold from this evolution to be honest. 12Z ECM - last night's wet blanket (along with the 06Z CFS yesterday, a real horror show for cold fans). Will it be a new hope tonight? Somehow, I doubt it. Nearer GEM then GFS at T+120. By T+192 not much change though is that jet easing south? T+240 is not far from GEM with perhaps a hint of some amplification and little sign of a raging Atlantic. That said, it's not cold and it doesn't look an easy route to cold. Looking at other things, the GFS 12Z Control ends stormy and unsettled and I'm left to wonder whether, looking at the stronger warming signal on the 10 HPA charts on the 12Z OP, whether we are going to be the big losers from this initial warming. The warming from the Siberian side may well weaken the PV but it sends it back to the Canadian side where it can re-strengthen at the end of the year and into January. Conclusion - I'm quite downbeat tonight. I fear the forecast Siberian warming will re-set the Atlantic and usher in a prolonged period of LP activity leaving us looking upstream for the next amplification. It could get quite stormy at Christmas and that mean higher altitudes get occasional snow but little prospect of sustained cold for many of us I fear.

Evening all With a disappointing (for cold fans) 06Z GFS OP prompting toys to be thrown out of prams aplenty, let's see if sanity or even hope can be restored by the 12Z output. 12Z GEM - the initial journey little changed with the Atlantic LP originating at lower latitudes swinging NE and invigorating the main LP to the south of Iceland by T+120 and triggering a positive alignment but this isn't a normal zonal winter so far and while part of the energy forms a secondary feature to the south which heads SE into Europe, the main LP withdraws west into the Atlantic as heights continue to build through Greenland in the absence of any significant vortex. The complex LP begins to move east toward and across the British Isles as a new area of LP exits North America. It remains on the mild side but the heights continue to build over Greenland. I also note the strong ridging from the Pole but it's looking like a west-based negative NAO which won't end well for cold fans in western Europe. Potential but in all the wrong places. 12Z GFS OP - a poor 06Z for cold fans but let's see. by T+120, the LP is a bit deeper than GEM but otherwise not too different as you'd expect. From there, the parent LP extends the trough over the British Isles but fills in situ maintaining a slight positive alignment as heights build to the north and north west. Heights also rising to the SW as the Azores HP tries to ridge in at T+180. By T+240, the jet is clearly moving south in response to heights buildinf to the north west and the next LP has filled but moved in over or close to the British Isles maintaining a mild but unsettled theme as we enter Christmas week. By T+312, the Atlantic LP has become and elongated feature aligned SW-NE across northern Britain and into Scandinavia. Heights have built over Europe but the focus of heights is south from Greenland. As we reach Christmas, the low finally sinks south as pressure rises from the NW and an anticyclone develops from the cold Greenland HP first to the north of the British Isles and then to Scandinavia with an ESE'ly flow to finish the run on Christmas Day with -8 850s for most so we'd be looking at snow IF we et any precipitation but the HP is building into Scandinavia. The 10 HPA hints at a warming from Europe at the very end of FI. 12Z ECM - well, a Christmas gift of sorts from GFS OP and cold it would be if perhaps not white. Will ECM be the thorn in our side or the slap on our back? I'm not expecting much to be honest - more hints at what might unfold beyond T+240. At T+120 no surprise at all but it then gets quite messy by T+192 with shortwaves aplenty and perhaps an attempt to build heights over the British Isles. However, by T+240 it all comes to naught as a new LP takes over and heads NE and I'm left wondering about the Azores HP ridging NE into Scandinavia as the next step. Not much hint of anything cold from that chart. Strong heights over the Pole and perhaps the PV starting to move west into Canada, Looking elsewhere, 12Z GFS Control would be a very snowy Christmas for many but not from the 00Z Parallel which shows how even a strong Scandinavian HP AND a strong Greenland HP can leave the British Isles mild. Conclusion - this is a time to hold nerve and be patient. We know there's going to be a milder interlude which could well last 7-10 days at least but there are plenty of positives beyond that. The strong polar heights help and it looks increasingly as though ridging from the Pole into Greenland will keep the PV far enough into Canada to allow amplification and slow the jet. The Greenland heights push the jet south which is another help. Cold fans are still very much in the game tonight but the next few days will try everyone's nerves I suspect.

Evening all Before I begin my look at the models, just a comment on those who argue posting T+240 or later charts is pointless because said charts never verify. It's Model Output Discussion - we're not discussing actual forecasts but looking at directions of travel - not what WILL happen but what WOULD happen if such and such a synoptic evolution occurred. We're discussing trends and I'm well aware these change and as the output changes (as it does every day) so will the discussion. Those who want to deal in detail are happy to stick to T+96 or earlier but if we all did that it would get very boring. We all want to be the first to spot the trend, see the sign, appreciate the nuance. That said, and with a definite milder interlude on the way, let's see where tonight's speculation takes us: 12Z GEM - not much obvious change at T+120 as the LP from lower latitudes gives an energy boost to the main LP as kicking the Azores HP into southern Europe - the result is the trough re-aligns positively and it;s seasonal SW'lies for us into the weekend. Note the weak heights to the north. By T+180, the evolution is getting messy and fragmented - the original LP has filled and moved only slowly north and a secondary feature has deepened markedly as it approaches Ireland. Note the more defined heights over Greenland - symptomatic of a weak PV - the Atlantic isn't powering through either. T+240 shows that even with a Scandinavian HP and a Greenland HP it doesn't work out for the British Isles in terms of cold. I mean, there's plenty of cold air nearby - just not where we want it (at least not yet). 12Z GFS - I'm expecting a more progressive Atlantic-driven run from this model. As you might expect, nothing unremarkable at T+120 and by T+192 the LP has more or less filled in situ. A weak LP is over southern Britain with a hint of troughing into Europe and heights remain over Greenland with another Atlantic feature moving slowly out of the Canadian Maritimes. The two LP systems join and oddly enough the pre-existing feature re-invigorates and eases back fractionally to the west by T+240. The SW'ly flow continues over the British Isles but this is a long way from a zonal Atlantic. On to T+312 and the jet has eased south as heights continue to persist over Greenland and the LP are now crossing close to or just to the north of the British Isles bringing a more unsettled spell. Christmas Eve sees an unseasonal N'ly with a secondary feature moving towards the SW. 850s are heading in the right direction as well - could it be? The 10HPA continues to show a distinct warming but it's a long way off a strat-splitter. 12Z ECM - as expected, GFS keeps the Atlantic in charge though it tantalises with a nice bit of eye-candy at the very end. Will ECM be the icing on the cake or the fly in our soup? T+120 brings no real surprises - it looks very similar to GEM. BY T+192 a small secondary feature has crossed southern England into the North Sea and swung north to create a complex trough. Mild enough for the SE but more unsettled elsewhere. Heights have returned to Europe though not strong at this time. Yet by T+240 the evolution has switched stride - the trough has moved south into Iberia creating a new LP which comes north to be over southern Britain with a light E'ly further north. Heights over Greenland and Iceland and the trough over Scandinavia all combine to give us chart a sense unlike many we have seen in recent years. Away from the output I've already discussed, the 12Z GFS Control ends very stormy whereas the 00Z Parallel was very anticyclonic. Conclusion - there are always those who, if they don't see storm force E'lies and -20 850s heading directly for their part of the world proclaim the model output to be "dire" or even "dyer". We may not "get lucky" again this winter - that's life. However, the charts on offer tonight are not what I've seen at this time in recent winters. The Atlantic is more docile, the jet weaker, the PV less intense and all that gives us a chance and it's only that. GFS OP ends with a wonderful chart for fans of snow and cold but it is where it is and the key remains, as it often does, for the dice to fall favourably. Intense HP over the Pole looks helpful as does a disorganised PV but as GEM T+240 tonight shows, the 850s aren't quite playing ball yet.

Evening all A thoroughly cold and bleak day here in downtown East London though the early mist lifted up more than I had anticipated. The journey to a milder evolution seemed set in the short to medium term yesterday - longer term signs of a rise of pressure in the vicinity of the British Isles but lots of options as to location and orientation from traditional Bartlett to mid-latitude to even some promoting high latitude blocking. The models may not like Mondays, those who discuss them may be more ambivalent - let's go.. 12Z GEM: - the opening salvo proceeds with the incoming Atlantic LP again shifting SE as it comes up against the weight of the Eurasian block but by the weekend (T+120) the trough and the Azores HP are aligning more positively suggesting a milder regime on the horizon. Indeed, that's what happens as the invigorated LP spins round for a while but by T+192 it has split and started to fill. Heights remain over Europe with the hint of a new storm coming off North America. However, we're not in a typical zonal environment by any means - there is no strong jet and PV to propel the storm across the Atlantic flattening every thing in its path. Instead, the LP starts to shift ESE and it meanders towards us by T+240 and heights are showing to the north of the British Isles and we end with an E'ly over the north of Britain and the evolution far from clear. 12Z GFS OP - while the GEM has given us a bit of a poser with its evolution, can we rely on GFS to play the old zonal game? by T+120 not too different from GEM as you'd expect - the second LP is developing nicely and set to re-invigorate the first to the south of Iceland and re-align the trough positively. I also note the Azores HP is weaker and further south than GEM with the lower heights over Europe more pronounced. By T+192 it's starting to get interesting - heights far to the north are holding the LP just to the west of the British Isles where it is going nowhere slowly. A mild SW'ly flow for most but we're not talking a long fetch draw from the Caribbean by any stretch - also unsettled with rain and showers. On then to the T+258 chart for the end of next week and the heights are over Greenland but also building from the south west - the Atlantic isn't anything like as strong as you'd expect with weak systems moving erratically across the British Isles. By T+336m HP is in charge with a cut-off LP in the Atlantic and a new HP developing between Iceland and Greenland albeit with signs of renewed PV activity. Instead, and this becomes apparent by T+384, the jet is forced far to the south. It looks as though the core of the PV is moving from Greenland to Scandinavia - I'm not sure what to make of it in all honesty. Both GEM and GFS have dished up some fascinating midwinter evolutions this evening and while neither guarantee cold for the UK, both would offer much more likelihood for cold than we've seen at this stage of winter for several years. Can ECM be the showstopper or will it be as dull as today's weather? Let's see. By T+120 it makes more of the elongated trough across the UK and into Europe with heights over Scandinavia but the second LP is in mid-Atlantic and you'd think would re-align the trough positively as the Azores HP pushes into Europe. That's pretty much what it happens and by T+240 it's a fairly familiar winter chart though the evolution from there would be interesting. Looking elsewhere, 12Z GFS Control is superb for cold weather fans so I won't bother posting any of those as I expect it's been analysed to death already. This morning's 00Z GFS Parallel was also worth a look. It seems very likely we will have a milder interlude next week but the stress seems to be on the "interlude" - plenty of evolutions suggesting nothing more than a 3-5 day break before the possibility of more amplification. GFS OP doesn't quite get there but Control does in some style. GEM is the pick of the medium term output once again while ECM keeps it mild to T+240 but we'd expect that. The truth is the next amplification is still just over the hill and it may not happen but the PV looks much weaker and less organised than normal and if the decrease in zonal winds forecast comes to pass the opportunity for amplification increases. All in all, a highly interesting few days of model watching ahead - the next fortnight may not inspire but there's a chance we'll be in a better position for some colder and perhaps snowier conditions as wr approach Christmas - we'll see.

Evening all Some thoughts on tonight's main models into mid month and beyond. 12Z GEM - model of the day yesterday but GEM flips around a lot so we'll see. The early stages this week are well set and by T+120 signs of another south-east disruption of the Atlantic trough in the face of persistent heights to the east and north east. The Azores HP negatively aligned and ridging into North Africa rather than Iberia. However, this promising evolution is quickly undone by a new and vigorous Atlantic LP formed as a result of a drop of cold air toward the eastern seaboard of the US. This new LP swings NE and re-aigns the main trough positive and drags the Azores HP up over Iberia and France introducing a much milder SW'ly air flow for the British Isles by T+216. The run ends mild or very mild with the HP centred over north Africa but dominating most of western Europe. Not quite sure the NH profile is as bad as it looks but it's not promising at this point. 12Z GFS OP - swept into the mild camp yesterday and with GEM going the same way tonight, I'm not hopeful. By T+120 one or two subtle differences with GEM. The trough is aligned less favourably but oddly enough the Scandinavian heights seem a little stronger. By T+192, the new Atlantic feature has invigorated the original LP and it has now developed into a large slow-moving feature just off the south west of Iceland with the trough extending to the British Isles. Heights have risen to the south but not strongly at this time. By T+240 it's all getting a bit messy - shallow areas of LP form close to the British Isles as the Azores HP edges NE and the more vigorous Atlantic features stay well to the west. BY T=312, HP is dominating southern Britain but a vigorous complex LP is moving NE albeit well to the north of Iceland on what looks a strong northern arm of the jet. The final T+384 chart has HP firmly in charge across Europe and a hint of continental air moving into southern England but the jet has too much energy to the north to allow for northern blocking at this time but the Atlantic doesn't look active to any extent. The signal for a brief but strong warming remains in FI. 12Z ECM - it's going to need a miracle to save us from a milder spell and I don't think ECM is going to provide it. T+120 looks much closer to GEM than GFS but note the small LP to the SW of the main larger feature - that's the spoiler for cold fans. The journey is fairly predictable from there with the Azores HP raising heights across Europe but I'm not seeing a hugely active mobile Atlantic at T+240. Just to add 12Z Control ends with a strong anticyclone over Northern Poland and a push of frigid air into central Europe. The last vestige for cold fans would be the 00Z Parallel. Conclusion - the switch to a milder more Atlantic-driven weather pattern looks inevitable from the end of this week but how long it lasts and what form it takes is far from resolved. Plenty of signals for heights to become more influential over Europe and the chances of some form of mid-latitude block look reasonable but whether that would be in a position or orientation to bring cold to the British Isles is doubtful at this time. I think we need to get the block in place first - what I'm not seeing is the zonal express of deep LP crossing west to east and in fact the Atlantic looks unseasonably quiet past mid month. It may well be we will have to just wait for the next amplification and while the NH profile isn't brilliant, I've seen a lot worse and all the models keep heights over the Pole. I'll leave those looking at other factors to judge the situation but while the overall picture doesn't look inspiring in the short to medium term it's not what we've seen in recent winters.

Afternoon all I'll comment more specifically on the 12Z output this evening but just a couple of thoughts from me as we await the next offerings: 1) The route to very cold often starts from very mild and those who look at the Azores HP ridging through as a bad sign miss the point that some of our most noticeable cold spells have occurred because the Azores HP (or a lobe of it) has pushed NE into Scandinavia and we've advected the chill air from the east. What normally happens when you have a strong PV is the northern arm of the jet is so powerful it keeps the HP at mid-latitude so we get the block over Europe (hello, Mr Bartlett). It's perfectly possible for the HP to transit NE and become a higher latitude block. 2) HP over the UK is a mixed blessing - if you want cold it can be great as long as there isn't too much cloud trapped in the circulation (and that can be a problem given we are surrounded by water). Inversion is king in mid-winter and an ice day is perfectly possible if fog and frost persist. Ideally, you want the HP over Scotland to advect the chillier continental air in but the easier path is not a straight E'ly but an ESE'ly or SE'ly. HP doesn't last forever and normally it either sinks south or withdraws east (the latter keeps the cold for longer). Just occasionally and again a disrupted or weak PV is a big help, we can get the holy grail of retrogression. Now, that's what the cold and snow fans really want as that opens the door to the N'ly or (and this is the real gold star) the NE'ly from Scandinavia. It's an evolution we see more in spring oddly enough and coincides with the final warming. 3) The Greenland HP is cited as the "Holy Grail" and of course it's a big help but it needs to ridge either directly south into the mid-Atlantic (the N'ly) or SE through Iceland (the NE'ly). If it ridges SW toward Canada, it triggers a west-based negative NAO and Mr Mild comes knocking at our door - that's essentially what happened in both January 2011 and March 2018 to break down the severe spells so I don't and wouldn't rely on a Greenland HP - a Scandinavian HP is much more durable and helpful. 4) As long as the PV is weak or disorganised or over Siberia or central Canada we have a chance at cold - it's NOT a guarantee of cold by any stretch but it's a shot we don't have with a strong PV over NE Canada/Greenland in most instances. An SSW may help but again it's no guarantee - the 2018 SSW was a thing of rare beauty and power and the way it shredded the PV and opened the door for the cold air was remarkable and well forecast throughout late February. I'm not a fan of Siberian warmings as they often displace the PV back over the Canadian side and we then have to hope the PV doesn't re-strengthen in situ which can happen. We almost never see a warming from the Canadian side and it's been interesting to note warmings from both Siberia AND Europe being forecast in GFS FI. The combination of such warmings may well have an impact but I'm sceptical of an SSW because even if it happens it's no guarantee we'll end up on the right side.

Evening all On we go then and whether there's a Deal with the EU I don't know but a Deal with GFS, ECM and GEM seems much more elusive. Clear signs last evening of a perhaps brief return of Atlantic conditions but let's see where the 12Z output takes us: 12Z GEM: - by T+96, the weekend trough is over the central Mediterranean and the next Atlantic system is approaching but this seems to be positively aligned with the Azores HP trying to ridge in from the SW. Despite that, the trough elongates and disrupts SE through the British Isles with the thrust of the energy NW-SE into Europe. Another unsettled and wet weekend beckons. The big development from here are heights around Iceland which serve to push the jet south and the Atlantic LP systems weaken and pull to the south by T+216 and by T+240 there's a weak but defined E'ly across the British Isles. 850s a -4 for many so cold enough. 12Z GFS - well, the GEM was a distinct plus for cold weather fans but I suspect the GFS won't come to the party given its history for Atlantic "resets" in FI. Let's see. As you were at T+96 but a very different profile by t+156. The LP is just to the south of Iceland and the British Isles is completely under its influence so bands of rain or showers, but I note the Azores HP moving in toward Iberia suggesting heights are going to rise through Europe and the Russian HP has been pushed back so not looking promising for cold fans. By T+240, a very different profile from GEM with an Atlantic regime in charge yet there are signs of weak heights to the north and the block holds on to the east. By T+342 however the Atlantic is back in charge with the jet heading north and the PV looking to be back where it should be. However, pressure is rising over southern Britain and perhaps a hint of something drier and more settled and by T+384 the Azores HP has moved NE and the prospect for cold and dry (as distinct from cold and snowy) is still very much there. As we know, mid winter HP can being fog, frost and low daytime maxima. It's worth noting the PV is more over Canada which would help a Scandinavian or European block. 12Z ECM - so, it's 1-1 so far tonight with GEM scoring for cold and GFS equalising for mild. By T+120, some interesting developments with the Scandinavian block keeping the Atlantic trough negatively aligned through the British Isles. By T+168, the block through Scandinavia is even more defined and there's a light ENE'ly flow over much of the British Isles but the Atlantic hasn't gone away just yet and the evolution is far from clear. The journey from there to T+240 is complex. A weak LP is over Iceland but pressure has risen over the British Isles as the Azores HP has swung NE to be just to the east of the British Isles and it's worth noting a number of cold spells have originated from this movement of the HP NE from the Azores to Scandinavia. The question is whether we'll get the advection of colder, drier air off the Continent if the HP continues to move NE. While 12Z GFS Control is very stormy and unsettled, it's worth noting the 00Z GFS Parallel wasn't a million miles away from tonight's ECM and showed what can happen if the Scandinavian block is augmented by the Azores HP moving up from the SW. Conclusion - fans of cold are still very much in the game tonight. However, we can't ignore the GFS evolution which brings back the Atlantic though it's a long way from the "zonal express" to Russia. The GEM evolution, while positive for cold fans, doesn't look the form horse but the notion of the Azores HP moving NE and linking with the Scandinavian HP to produce a stronger block after T+240 is one to bear in mind when considering possible evolutions.

Evening all For some, it seems, winter has arrived with a vengeance and if you've had or are having snow, kudos. As expected, nowt but cold rain here in lowland East London but there's more than a hint of winter about. :Last evening's output wasn't inspiring to my eyes suggesting the Atlantic would be back in the coming week but let's see where tonight takes us. 12Z GEM: - by T+96 the trough is still very much with us. An LP forming off the German coast deepens and moves NW across the North Sea to the north of Scotland while the trough extends south into Europe. The Atlantic doesn't inspire confidence for a prolonging of the cold spell at this time but the block is edging into Scandinavia. Initially, the Atlantic LP does draw up a milder feed but by T+168 the LP is stalling and filling and the bulk of the enrgy is now heading SE with a secondary feature crossing southern England. By T+240, we end in a messy situation. Strong heights are developing to the north and north-west and the jet is heading south with a new LP slowly heading towards NW Europe. I note the cold pool over Scandinavia which is something we may (or may not) be able to tap into down the line. 12Z GFS - again, the Atlantic showed its hand on this model last evening. T+96 looks similar to GEM with the LP heading NW towards Scotland and maintaining the cold and unsettled theme. Things then start to get interesting as the next Atlantic LP splits with the main energy heading SE and developing quite a potent feature crossing southern Britain at T+156 - you'd think the Pennines and the Peaks might get some snow from it. By T+240 not much has changed - a succession of shallow LP head across southern Britain and again the northern hills might do well from that. There's a potent little storm in the Atlantic and heights to the NW. Unfortunately for cold fans, the Atlantic LP stalls and all it does is ridge the Azores HP north east so back come the SW'lies but by T+330 there are signs of disruption once again as the block to the east remains in situ. We end with renewed heights to the north of Scandinavia and a shallow feature over Germany providing a weak E'ly facing a renewed Atlantic push leaving the British Isles in a col. Signs again of a warming at the far end of FI at 10 HPA but I'm not convinced. 12Z ECM - let's see where this goes. The T+96 is fairly familiar but by T+168 the Atlantic looks set to take over despite the lowering of heights over Europe - or perhaps not. Once again, the bulk of the energy slips SE and we have an active LP crossing Southern England at T+240 with the trough negatively aligned through the British Isles into central Europe. Heights remains over Scandinavia and the enormous active PV of recent winters not really evident with heights over the Pole and in Russia. 12Z GFS Control looks very different to the OP in all fairness. Conclusion - 3-5 days of cold and unsettled weather before a brief return to the Atlantic but we aren't talking deep LP barrelling past northern Scotland to Russia by any stretch. The "slider" still seems the form horse and GFS in particular plays this well. The tendency of that model to "reset" the Atlantic pattern cautions reading too much into FI but there seems a strong signal for heights over the Pole and into Russia offering the possibility of an increasingly frigid pool in Scandinavia. The problem for us is it may just be too far away and the trough sits across us so more rain though snow for northern low ground and higher elevations can't be ruled out as we move past the middle of the month.

Evening all Well, if you like cold rain and the day getting dark at 2.30pm, you'd have loved Thursday December 3rd 2020. A thoroughly bleak day in lowland East London and if you've had some of the white stuff, whether it's settled or not, good on you. So to the evening models and the journey deeper into December with Christmas Day just three weeks away tomorrow. 12Z GEM - the current LP heads away SE into Europe and the next Atlantic system, a relatively weak feature, starts to slide SE across Ireland and south-western Britain at T+96. By T+150, the LP has moved down into Europe and the British Iles is in a col between pressure systems but the Atlantic looks close at hand and the alignment suggests a return to milder conditions. As might be expected, after a brief struggle, the Atlantic wins out and by T+240 it's a fairly familiar picture of a vigorous LP over Iceland and a ridge across Iberia so perhaps not long-fetch but a milder SW'ly flow as the Eurasian block is pushed back NE. The NH profile doesn't look brilliant either. 12Z GFS OP - well, a disappointing start for cold fans from GEM but let's see if the Americans can come to our aid. The T+96 chart isn't too far removed from GEM though the angle of alignment looks slightly steeper to this observer. By T+168, a more interesting evolution with the next trough also tilting negatively across Ireland and south-west Britain into the continent in the face of what looks a weak but extensive block to the NE. The Atlantic profile is different from GEM with the Azores HP suppressed well to the south. By T+240, the Atlantic is starting to wind up with a complex and vigorous LP to the south of Iceland so a draw of SW'ly winds but these won't be too mild I would guess. The thing is, the LP spins round in the ocean and then fills and the following weaker system doesn't do much better and starts to slide SE to the west of the British Isles as the focus of heights shifts to Greenland with the main PV still over Siberia. It's a mild and unsettled SSW'ly flow for us though as heights build over the far south-east of Europe. The NH profile at the end of FI is fascinating with a strong HP over the Pole ridging into Greenland and the PV not looking good with one lobe further to the west over Canada. Once again, hints of warming in the 10 HPA but at the very end of FI. 12Z ECM - the GFS OP evolution is atypical of many recent midwinters though the GEM evolution less so. We've heard talk of an Atlantic return but that such would not last long and GFS seems to confirm that. What then of ECM? Differences start at T+96 with a very different profile. The LP is more concentrated to the SW rather than an elongated trough as the other models suggest. However, any hope for a continuation of the chilly conditions soon get swept away and by T+192 milder Atlantic air has pushed back in with the trough aligned positively over Iceland and a long-fetch SW'ly though we're not looking at a traditional zonal scenario by any means. It does seem the PV is back over Greenland with a vengeance. The T+240 NH chart doesn't look inspiring. As we see with the GFS, it may be a brief Atlantic period will be the gateway to another period of amplification. 12Z GFS Control is also less than stellar into FI though again I've seen worse over the years. It all seems a million miles away from the GFS 00Z Parallel which certainly was much better on the eye. 12Z ECM COntrol ends quite interesting as well. Conclusion - after the current chilly and wet spell, it looks as though the Atlantic will return by mid-month in some form but the duration of this next Atlantic spell is far from clear. With the PV perhaps not as dominant as recent years, it may be it will be a pause before the next amplification. We'll see.

Evening all Is this the start of the countdown to a winter wonderland this weekend? I suspect not - I'm not expecting any snow in lowland east London - just a good soaking of cold rain. Some may get a little sleet and snow and kudos to you if you are in such a fortunate group but a widespread national snow event - nope. Anyway, the models churn on as they always do and after some interesting evolutions last evening let's see where this evening's offerings take us: 12Z GEM - by the end of the weekend (T+96) the LP still sits over us with weak heights to the NW and NE. By T+150, the enxt Atlantic feature has swung SE through Ireland and the south west of England and is sitting over western France but it's a complex trough with a residual centre over northern Scotland so the unsettled and cold theme remains very much in evidence. Clear signs of positive alignment further west but there's still a weak ridge coming north from the Azores HP. The trough quickly splits as pressure rises from the SW and there's a return of an Atlantic-sourced flow as a new deep Atlantic LP develops but is that a renewed negative alignment in the face of the block to the east at T+210. To a point, yes but the trough fills in situ over or just to the west of the British Isles by T+240 and the block looks to be extending into Scandinavia at the same time. 12Z GFS OP - it's been the model keenest to bring back the Atlantic and with GEM having more of an Atlantic influence tonight, I suspect that's where the American model is heading. At T+96, perhaps further south than the GEM and a more defined ridging to the north but that's nit-picking. The next Atlantic feature duly heads SE but by T+174 we have a complex but shallow trough from central Europe through southern Britain to the mid-Atlantic with a new vigorous LP coming off the Eastern Seaboard. However, that soon fills and just joins the weak trough - heights over Greenland don't look strong but it's a weak or non-existent PV so the block can force the Atlantic systems south and there's a broad but shallow LP covering much of northern Europe by T+240. However, the next LP changes everything - it pulls down a lobe of very cold air into the Atlantic which drops the trough south and encourages a new LP to form around the Azores. The response is to push the HP east into Europe and draw up a mild SW'ly over the British Isles. There's also signs of vortex energy moving back towards Canada and there's little warming on the 10 HPA so some ominous signs for cold fans. 12Z ECM - so we're 2-1 down with 20 minutes to paly, can we force an equaliser? Possibly the cleanest drop of the trough through the British Isles by T+96 and the most defined height rises to the north so an encouraging start. That comes to little as the second Atlantic also swings SE and fills into Europe but the Atlantic looks in a mean period by T+192 albeit with quite a defined ridge of the Eurasian HP into Scandinavia. That's significant as we see by T+240 which is as good a chart as many cold fan would want to see from this evolution. The HP is moving into Scandinavia and the block is forcing the LP to disrupt SE once again. As we've seen, the 850s don't float everyone's boat but the block is looking promising. Moving beyond the models I've already mentioned, 12Z GFS Control ends with a real stand-off between an active Atlantic and HP over both Scandinavia and Greenland. It doesn't work well for the British Isles in terms of cold . Conclusion - a step back for cold fans this evening. While it may be the next 7-10 days will be cold and unsettled and possibly just on the wrong side for snow, the hope that might draw some colder air over us looks misplaced this evening. The block to the east looks resilient however and it remains to be seen if it can force the bulk of the energy SE into Europe which will always give us a chance to import some frigid air. It all looks very knife-edge to this observer and the medium to longer term trends suggest a return of the Atlantic as PV energy seeps back over to Canada and re-invigorates the jet.

Evening all So it's winter at last - 90 days of watching every nuance and every indicator and even though the Netweather Forecast suggests it will be wet more than white, the atmosphere doesn't know or care. On then to this evening's procrastinations from the 12Z models: 12Z GEM - the LP hangs about like Christmas turkey on New Year's Eve and it looks a thoroughly cold and miserable weekend especially for England. Unlike some other modelling, GEM splits the trough -part of the energy heads back NE towards Norway while the rest heads south and leads to the formation of a significant LP in the Mediterranean. A brief ridge over the British Isles is soon chased away by the next LP which duly shifts SE down across Ireland but then fills and dissipates in situ as heights build strongly to the north so where is our E'ly? The Azores HP is ridging in so it all gets to be a bit of a mess with heights over Greenland and northern Scandinavia and a slack LP across Europe. It should be better and the 850s are okay but no more - not quite sure what to make of the evolution. 12Z GFS OP - this was perhaps the most disappointing of the output tonight threatening a rapid return to Atlantic conditions albeit a fair way away from Bartlett HP and long-fetch SW'lies. Not much change from the GEM at t+96 though it looks like a cleaner shift south from the LP. Unfortunately that's deceptive and by T+156, not only is the original LP still around over Scotland but the next Atlantic LP has slid SE as a bit of an "undercutter" so we have a complex trough over the British Isles. By T+216 the LP is still around Scotland and while heights have lowered over Europe the Atlantic looks poised to return but in a deceptive evolution this too turns out to be wrong. The block to the east and north east doesn't look substantial but if you have a weakened vortex and jet it doesn't need to be and we see the trough disrupting over the British Isles with heights to the north east. There's some frigid air getting into Scandinavia by the end of the run but can we tap into any of it? Once again there are hints of warmings from both Siberia and Europe in far FI. 12z ECM - the slap on the back or the knee in the groin tonight? T+96 looks pretty much as you'd expect though I'd like to see more heights to both east and west. By T+168, as with other output, the LP hasn't eased away south but has returned north but with heights rising toward Iceland, it still looks reasonable for cold fans. There's an old expression about saving the best to last and the T+240 chart isn't without its attractions tonight. There's a wedge of heights to the NW with a ridge down through Iceland which is helping to send the trough SE past SW Britain into central Europe leaving most of the country very much on the cold side. There's also a growing pool of cold air with the -4 850 covering most of the British Isles. Just to note beyond the output on which I've commented, 12Z GFS Control ends with a strong Scandinavian HP and a light but cold E'ly airflow but ECM Control is less inspiring with a return of the Atlantic. Conclusion - the journey to and through the weekend is set and it seems increasingly the weekend's LP doesn't want to leave us too quickly. This helps the Atlantic slide SE into Europe and this looks the form horse. The ECM evolution to T+240 would be ideal for cold fans but GEM is not without its merits. GFS is much less inspiring into FI but it's hardly a return to full-blooded winter zonality and the PV remains weak and disorganised and as @Tim Bland wisely opined last evening, a weak vortex is always open to renewed amplification.

Evening all On the cusp of winter so we can probably expect raging zonality, a large European HP and long-fetch SW'lies with temperatures well above average. It often happens early in December but will this year be different? Last night's 12Z output was far removed from that but the evolution from the weekend trough disruption was far from clear. Some were complaining at what looked a less-than-stellar E'ly while hints of a returning Atlantic as a response to a Siberian warming were also evident for mid-month. What of tonight - seasonal or just "teasonal" ? 12Z GEM - the trough collapses south on cue and is quite an unpleasant figure by T+96 bringing plenty of cold rain and some wintriness to higher ground. We don't get the clean shift to the south we've seen on other outputs leaving the LP to fill at first in situ and by T+144 it's over the northern North Sea. However, the next Atlantic LP duly slides SE to or just over Ireland before easing further south as heights build nicely to the north of the British Isles. By T=240 pressure is rising over Scandinavia with 1035 MB over Norway and a strong ridge west across Scotland to the Azores HP ridging north. Signs of the PV over NE Canada however and the notion of battle to be joined between the conflicting airmasses. Again, there's no especially cold air over the British Isles at T+240 but Scandinavia is becoming increasingly cold which will help block durability. 12Z GFS OP - by T+96 the LP is centred more or less over my house (well, east London) so may be a day to stay indoors and stay dry. The next 72 hours sees the LP try to extend south into Europe but retreat back into the North Sea remaining as the dominant feature so keeping most of the British Isles cold and unsettled. By T+240, the evolution has changed. A new LP centre originally forming over eastern Spain has finally pulled the trough into Europe and a weak narrow ridge of HP has developed across the British Isles between the Azores HP and Scandinavia but the Atlantic trough is now showing signs of positive re-alignment and two small LP centres are over Iceland and heading NE. By T+312, an Atlantic LP has crossed Northern Britain with a strong NW'ly flow to its southern and western flanks but signs of cold are fast disappearing with the PV now looking to be back over Greenland and NE Canada. At the end of FI, LP is over northern Scandinavia and between that and the Azores HP, we have a WNW'ly flow - nothing remarkable to be honest. As an aside, the 10HPA stratospheric forecast continues to suggest weak warming from both Europe and Siberia in FI which might explain the re-consolidation of the PV over Canada. It's also fair to say Control goes a very different route. 12Z ECM - the fly in the ointment or the partridge in the pear tree? No surprises out to T+96 and as with other models the trpugh becomes a complex feature close to the British Isles by T+144 before re-forming over or just to the east of Scotland briefly before finally clearing away. However, the evolution to T+240 is messy and the final frame leaves us many more questions than answers. Is the LP over Iceland going to slip SE through the British isles into Europe? The PV looks nowhere near as strong as on GFS so could we see more amplification in the Atlantic? Control sends it south before building the HP close to Ireland by T+240 so the airflow remains from the north west or north. Conclusion - I can't help but feel it's a step back for coldies tonight. GEM is good albeit with little cold air. GFS hardly screams zonality but the Atlantic and the PV are back and we are relying on enough residual heights over Scandinavia to encourage negative alignment. ECM is similar but a notch better and it may be this pattern of the trough sinking through the British Isles may be something we'll see for a while and that's not wholly discouraging. The mid-Atlantic build of heights is much less pronounced tonight on ECM and GFS but there's still plenty of interest.

Evening all Another day, another set of 12Z output to consider and certainly plenty to comment on yesterday so let's see where we are at the start of a new week and almost at the official beginning of winter: 12Z GEM - yesterday this was very much in the negative alignment with the block to the east forcing successive LP systems SE over or just to the west of the British Isles. On then to tonight and by T+120 the LP has shifted south on cure and become a complex feature with multiple centres over northern and central Britain. The complex trough fills in situ with the next Atlantic feature - a shallower LP - sliding SE over Ireland. Clear pressure rises to the NE and perhaps a hint of a rise of pressure in mid-Atlantic and the latter becomes a key development by T+240 as the Azores HP ridges North and North East with the LP settling over the continent leaving the British Isles in an E'ly airflow. Unremarkable 850s at the time with the air source further south than some might like but the Eurasian bloc is very much in charge at this stage with the Atlantic moribund. 12Z GFS OP - perhaps the pick of the output last evening with a classic route to an E'ly - some similarities to what tonight's GEM is showing - but with increasingly cold 850s as we approach mid December. The initial trough disruption south means by T+108 a defined and quite deep LP over North Wales with presumably plenty of rain, strong winds and hill snow. It doesn't clear fully to the south but fills slowly over or just to the east of the British isles as pressure rises to both east and west. Moving further into FI and we find a bit of a stalemate developing with pressure rises to the east and west slowly squeezing out the residual trough which has by T+264 headed south to a core position over Corsica. Ultimately, as you might expect from GFS, the Atlantic re-asserts and by T+384 there's quite a familiar look but the LP still aligns negatively. The NH profile suggests a new but shallow PV re-forming over Canada and the 10 HPA profile in FI is very interesting with warming first from Siberia and then from Europe putting a lot of pressure on the vortex so it's an interesting scenario if not perhaps quite as positive for cold fans as yesterday. 12Z ECM - better last night than Friday I thought. As we see with the other models, the LP sinks south and by T+120 the centre is over northern Britain. By T+168, the LP has moved further south to Biscay but there's no rapid build of pressure behind initially as the next Atlantic LP is already sliding SE further to the west of the British Isles and by T+240 the LP is off the west of Iberia and there is a clear pressure rise to the west and North west while at the same time the Eurasian HP had extended a ridge into Scandinavia. I'm struggling to see the very cold 850s but I'm not seeing a raging Atlantic either. I'm seeing a disorganised PV suggesting an anticyclonic set up is very much on the cards. Where are we then this evening? The initial evolution is clear but there remains a lot of uncertainty as to how the LP exits to the south and where it goes and whether we will see the build in pressure behind it. Both GEM and ECM suggest we will see this but GFS is less clear and defaults back to an Atlantic-led scenario deep in FI (well, the OP does, Control is if anything even messier suggesting a lack of clarity in the medium to longer term).

Evening all Well it seemed to work all right last evening - ignore what everyone else has said and look at the model output itself so I'll try that again. 12Z GEM: - a decent run last evening for fans of cold with a lot of disrupted troughs and negative alignment. Okay - the LP starts to sink south on cue more or less over the top of the British isles by T+144. The trough heads south into the Med setting up a decent LP centre over Italy and leaving the trough line through the British Isles with hints of pressure rising both to the NE and NE so overall another decent effort. 850s are uninspiring however albeit with quite a push of cold air into Scandinavia. 12Z GFS OP - again a decent show for fans of cold yesterday evening. The LP disrupts south on cue but on this output the centre passes just to the east of the British Isles with a chilly N'ly for western areas at T+138. Unlike GEM, GFS OP keeps the LP in the North Sea before moving it east with a second LP setting up further south in Europe. The elongated Atlantic trough is much more prominent and the next LP duly follows the negative alignment moving SE first to the west of the British Isles and by T+240 moving slowly in over the British Isles from the west before sinking south allowing a lobe of the Azores HP to ridge to the north and put the British Isles in an E'ly flow by T+300. Further into FI the air mass becomes progressively colder as more of a continental feel becomes established. In all, another interesting run for fans of cold. 12Z ECM - the life and soul or a party pooper? There were aspects of last night's run I didn't like but I think I was in a minority. I'm looking to see any sign of the PV heading back to Canada in response to a Siberian-based warming. All good early on with a right Alan Partridge centred over Norfolk - sorry, couldn't resist. It sinks away to the south though not entirely cleanly and the next Atlantic LP, albeit quite a shallow feature, is close on its tail so no opportunity for ridging so nearer GFS than GEM. The next LP heads SE over the west of Ireland and the block is building through Scandinavia to keep the negative trough alignment. We're relying on that as the NH profile, while suggesting a disorganised vortex, doesn't have any sign of heights over Greenland. However, all the energy seems to be on the other side of the Pole at this time so raging zonality it ain't. Where are we then this evening? The trough disruption promises a cool and wet spell for many through into next weekend but there still remains a lot of doubt beyond that. GFS offers a classic path to an E'ly and perhaps quite a lasting one while both GEM and ECM provide the Eurasian bloc but not yet with any real frigid air. If we can get the bloc to the NE and a weak vortex, an extended period of negative trough alignment could work very well for fans of snow in northern and eastern areas as the air flow would be ESE'ly and the continental airflow would soon become much colder as we move toward mid-December and beyond.

Evening all For a change tonight, not reading anyone else's contributions (invaluable as they no doubt are) and ploughing straight into the output: GEM - pretty decent for cold weather fans with clear negative alignment of the trough which sinks SE over or just to the west of the British Isles. The blow from T+168, T+228 and T+240 All FI of course but the wedge of heights across Scandinavia and toward Iceland holds increasingly frigid air and that "block", insubstantial as it seems, is enough to send the LP away SE and with a renewed pulse of WAA over western Greenland, will we see the Mid-Atlantic ridge develop? GFS - OP The 06Z OP backed off disrupting the trough through the British Isles completely so what does the 12Z OP offer? Well, disruption is back to a point - at T+168 we see the trough elongating into a shallow but extensive feature running north through the British Isles from a main centre close to southern England. By T+204 the LP has developed into a classic "Genoa Low" with heights starting to build in response over Scandinavia and that block forces the next trough to align negatively and dive SE across Ireland at T+240 so not a million miles from the GEM above at the same point. From there, an element of traditional GFS re-set kicks on but there's no long-fetch SW'lies and a raging jet on offer. Indeed, the trough continues to align negatively. I'll conclude with the T+384 NH overview and simply say I've seen a lot worse for mid-December. ECM - will this be the fly in our soup or the cream on the cake? First thing is to get the LP and trough to disrupt down over the British Isles and at T+168 we have something that aligns nearer to GEM than GFS but would bring a nice bit of cold rain for many - 850s are 0 to -4 so I'll yield to the experts on dew points and the like but there should be something wintry for high ground you'd think. The trough never quite disrupts fully and becomes a complex feature and though there is a defined centre over Europe it's the one to the west of the British Isles which develops as the next significant LP and moves in by T+240. It draws in milder air from the south-west. The two routes for the LP are NE or SE. The other concern for cold weather fans is the PV energy seems to be leaking back across the Pole to northern Canada. This is a typical response to a warming from the Siberian side - I'll be honest, I'm really worried the warming will allow the Strat and Trop coupling to occur and it will be game over for the bulk of midwinter but I hope I'm wrong. GFS has backed off the warming a little but it's a real worry and emphatically NOT what we want to see - if it were from the Canadian side that would be different but they are as rare as hen's teeth. In conclusion, looking like a chilly and unsettled start to December and we could be looking at an extended period of negative trough alignment which would be good news for fans of snow especially in the north and east. We need to see the block develop and hold over Scandinavia and what we don't want is anything to send the PV back over to the Canadian side which would fire up the jet, smash the block and reset the pattern to something with which we have had to become accustomed too often in recent years (though I suspect it's been the default pattern for millennia).

Evening all Interesting model output has naturally produced a surge in comments and there's little point repeating what others have said (though that's not stopped me before). My perception is the models have struggled with the forthcoming evolution to some degree. That happens when conflicting signals are at play and naturally at this time of year we always hope the dice will fall kindly in terms of cold and, dare one say it, snow for the UK. Needless to say, GEM 12Z has provoked plenty of comment. The LP disrupts just to the south of the British Isles leaving us on the cold side and while the 850s aren't too exciting, it's still the kind of chart we want to be seeing and the key point is the Atlantic is moribund. ECM doesn't quite play the same game. The LP disrupts but then splits to the east of the British Isles - with one segment heading north and the other south leaving us in a chilly col: Over to GFS 12Z OP: That works out pretty well for the British Isles as the trough heads SE and pressure builds behind it leading to several days of cool, if not cold weather with a NE'ly flow setting up for southern and eastern areas. It's not as wonderful as this morning's 00Z pre-Parallel GFS which is a thing of beauty for fans of cold and snow. The main thing into FI is the PV remains over northern Siberia. I'm not sure where this is going - some form of disruption of the Icelandic LP SE into the British Isles looks certain but where and how that disruption occurs and where that leaves us is far from resolved. The likelihood is pressure will build from either the NE or NW but whether that lasts or we see a reset to a more traditional synoptic pattern I don't know.

Evening all I'll put down my personal winter favourite which isn't snow (get over it) but a good old traditional anticyclone centred just north of Birmingham (1050 MB) going nowhere for 10 days. Serious inversion - daytime temperatures around or just below freezing, plenty of fog and frost, wonderful. Anyway, before the Mods reprimand me, the key factor in this evening's models is how the LP coming out of NE Canada next week is modelled: Starting with ECM, GEM and GFS OP 12Z at T+144: Slight variations in the theme as you'd expect but all have a powerful storm close to southern Greenland flattening the ridge building in front of it. On 72 hours and it goes in three different directions: So that's three models and three very different evolutions. ECM swings the LP away to the NE dragging the jet north and encouraging height rises across the British Isles. GEM holds the core of the LP between Iceland and Greenland and that potent little LP is a secondary LP which developed in the flow and ran NE to the British Isles so rain and strong winds. Finally, we have GFS OP which fills the LP as it slides SE down across the British isles and note the heights building to the north which is the precursor to an interesting FI. The end of the month conditions seem to depend on which (if any) of the three evolutions is correct. The MetO line for a colder, drier December would be supported by either ECM or GFS - different paths to the same outcome in truth. GEM looks the outlier (but GFS Control looks similar).

For what little it's worth at this very early stage, my initial thoughts are it's going to be a long wait. I don't see much in the way of cold (the odd PM blast notwithstanding) until February but then I think the "fun and games" will begin. Anyone who thinks we will get 90 days of cold from early December to late February is deluding themselves. Most "memorable" winters consist of either a 7-10 severe spell or a cold "month" at most. The fact older members on this forum speak of the 1962-63 winter with such reverence shows its rarity. December 2010 was the coldest month in over a century yet who remembers January and February 2011? The short severe memorable episodes define the British winter - March 2013 and March 2018 for me for example. There's a clue perhaps the winter is starting later and staying later but that's a discussion for somewhere else.

By any sense, an extraordinarily powerful storm for this stage of the "season". 917 MB in November is matched only by the 1932 Cuba Hurricane and I fear the damage and loss of life from this will be considerable. This has developed from almost nothing in six days. Let's just hope it's not as destructive as Mitch was back in 1998 - the damage then was caused by days of uninterrupted rainfall from a slow-moving storm.

Evening all Well, it's all been said, it would seem. The GFS 12Z OP and Control are certainly heading in a very different direction and if GEM went beyond T+240 it could be very interesting. ECM at this stage doesn't want to know and the build of heights into Scandinavia at T+192 just isn't sustained as the Russian HP is too far to the north and east. This looks to be the critical point - T+216 tonight - so really still very much FI and reliant it seems on the continuing disconnect between the stratospheric and tropospheric vortices.