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No need for the sensitivity knocks ...... comment had nowt to do with you ..... was that we could see a northerly or a southerly which isn’t really v helpful as a prediction...... despite your weird fascination with reality and probability rather than fantasy, your contributions on here are valued !

Why all the doom and gloom about F.I.? The trop vortex is showing no signs of getting itself together, The colder 850's are creeping ever closer, And the strat, which is always more reliable in modelling terms, is showing a potential warming event. This only takes us up to the 3rd of December! Give winter a chance, it hasn't even started yet....

Morning . Gfs paints a quiet picture for a few days across the UK and apart from some patchy areas of rain for England and Wales today which could pep up in a line through the wash to Isle of Wight for a time tonight before fizzling out its not looking too bad with some drier spells particularly for Scotland and Northern Ireland but some showery pieces of rain at times. Tomorrow and Tuesday are looking mostly dry for much of the country with fairly light winds so fog could be an issue perhaps exacerbated by wet ground.. GFS.. Some frost too particularly for Scotland where there tomorrow some places in central Scotland may not get above 0c after a very cold night tonight although the rest of Scotland climbing just above before a harsh frost sets in for Northern England and Scotland come tomorrow evening as soon as the weak sun sets. Arpege tomorrow morning.. Tomorrow mid afternoon.. But by Wednesday Atlantic frontal systems will begin to try to push in but only manages to effect the far west and southwest until Thursday night into Friday where they break through the stubborn build of pressure out east or more the block releases its hold on Eastern areas. Wednesday.. Thursday and Friday.. This then puts us in a very unsettled patten next weekend with heavy rain at times pushing north through most areas.. Sunday 24th and Monday 25th.. There will be Drier spells in between. feeling milder and windier too. By Thursday 28th so a long way off and unlikely to verify but Gfs gives us a very windy spell.. Then the extended range so unreliable time frame shows more bouts of heavy rain continually pushing through at frequent intervals with perhaps another very windy spell by the next day Friday 29th and very wet too as depicted by the chart below.. Eventually turning drier towards the end of the run with high pressure building in. I'm simply showing what it shows by no means take the extended range too seriously but the pattern of low pressure close to us remains.. alternatively the block of high pressure to the east may hold the low pressure systems further back to only effect the far southwest for much of the time period of a week or two but currently that looks unlikely. Gfs 10 days accumulated rainfall.. Wettest for Western and southern areas. Gfs synoptic snapshot for the 27th November a westerly regime for the North Atlantic and UK.. Gem still shows a very wet 10 days to come its a very unsettled update with high rainfall totals for England and Wales. Synoptics generally more unsettled too.. This snapshot demonstrates this run well with a much more unsettled model compared to the others.. Mainly very wet due to higher pressure having enough influence out east to keep weather fronts over the country for extended periods of time.. Thursday 21st.. Friday 22nd.. Gem 10 day accumulated rainfall.. Ecmwf a little stronger with high pressure out east so drier for Eastern areas with this scenario. A snapshot below.. Phew took an hour to do this post.

Fine it was just that it was posted following on from my post In fact was mulling over the possibility myself Yes I'm afraid that's a character flaw that I have unsuccessfully tried to eradicate over the years

How about this to wake up to. Best warming in the strat yet,

Evening So whilst its not the perfect set up the continued trending shows a moderate Greenland Anomaly & the PV settling over the Eastern quadrant of the NH was we look down in it - That then followed by a warming in the stratosphere .... Plenty of reasons to feel optimistic then currently..

It is still model output though so surely valid in either thread, sorry though if it is not.

Hi @Decemberof2010 just look at those purples and even blacks heading our way (possibly) on the T850 chart at same time: Exciting times, indeed, but, everyone, there is just that worry, isn't there that come Dec 1st it will all collapse and the zonal mild and wet dirge will somehow rise from the ashes like a wet dead limp phoenix like it usually does. Except that this year I really don't think it will...touch wood.

Have to say I disagree here. The strat is such a crucial element of the story in winter, so what the models are predicting about it cannot be hived off into a separate thread because it is all connected. I think the issue only arose because about 5 of us reacted to the T384 GFS 6z chart in 1 minute, which was the only poignant thing to come out of that run to be honest.

The longer term Ecm 0z ensemble mean is mild & unsettled which it has been for days..seriously, I think cold expectations are too high and we need a reality check!!

Oh dear. Oh dear. Oh dear! There's nae much sign of a PPE (purple people eater) paying us a visit, any time soon...On the contrary, the future looks orange! Never mind...it ain't even winter yet!

The North Atlantic 500mb and surface analysis and sat image A cold rather nondescript day today with some trailing fronts bringing cloud and patchy rain to some areas, mainly north Wales and England with showers continuing down western coasts of Wales and Cornwall. Elsewhere dry with sunny intervals. But in the North West Atlantic rapid cylogenisis is again taking place with the formation of another intense extratropical cyclone Tonight many areas will be clear with frost by morning with the movement of the fronts confining the cloud to east and south east regions A cold start to Monday, particularity in Scotland with quite a severe frost, but then a fine. if cold day, is on the cards. The exception being the east coast where it will be quite windy courtesy of a wave that has formed in the east and drifted into the North Sea. The old front will continue to bring some rain the far south east. Meanwhile the deep low is making it's way across the Atlantic Some rain in eastern regions at first on Tuesday courtesy of the fronts associated with the north Sea low but this should clear during the day. But out in the central Atlantic the low is slowly filling and continuing to drift east and the associated occlusion will bring rain the western regions during the afternoon. Ergo most areas quite sunny Over Wednesday and Thursday the east bound energy hits the buffers of the block in the east bringing the longitudinal movement of the low to a halt albeit the fronts do manage to cross the country and thus periods of rain interspersed with sunny intervals

Hi Folks. Regarding the posts being made in this thread that are entirely or predominantly about the stratosphere. Whilst it can be argued that strat charts are still model output, we have a specialist Strat thread that is intended to capture ongoing stratospheric developments during the season. This is very useful in following seasons when folk might want to look back and see how the SPV developed in a particular year. If strat charts are continually posted in the wrong place that benefit is lost. It’s fine in this thread to include some strat charts as part of a wider post discussing implications for 500hPa model output, but 'strat only' or ‘predominantly strat’ posts will be moved to the Strat thread. The Mod team felt some clarity was needed and I hope everyone is OK with this guidance. If you wish to discuss this further please pm any of us or raise in Contact the Forum Team thread. Many thanks.

Good answer - I'll chip in on these 2. @Northern SkyThink of the strat and trop vortices as ballroom dancers. Who leads who? Friction helps transfer the "lead" circulation....so take a jug of water and use a teaspoon to circulate the upper levels of the water only. After a few spins of the spoon frictional transfer of that energy means the lower levels of the jug also circulate. Very simplistic analogy but might help. Early season the upper layers of the stratosphere cool over the arctic, and the temperature differential between that increasingly cold air over the pole and warmer air towards the midlatitudes begins nature's attempt to equalise those temperatures....doomed forever to fail because solar energy continues to warm the mid latitudes while the pole stays dark....but that attempt creates the circulation. But returning to the dancer analogy - is it always the growing power of the stratospheric vortex that leads the dance? No. There are times when patterns within the troposphere can hold their own, and times where tropospheric events produce a forcing via intrusion of warmth into the stratospheric vortex that disrupts the need to equalise temperature and therefore slows the vortex down. Ways in which warm air can hit the stratosphere are complex, but again in simple terms warm air can bounce off mountain ranges or indeed strong tropospheric high pressure ridges can cause movement of air in a column that also disrupts the temperature profile way up high. So - the tea spoon stirring the upper layers can find itself working against factors from the troposphere which prevent simple "connection" between the circulation. Bear in mind this is simplistic - in reality there are multiple layers of the atmosphere all interacting at once. If it was as simple as 2 layers operating in a binary fashion the models would never be wrong....but we are dealing with a fully 3D process here which is massively complex. However conceptualise with 2 layers in your head and you'll be on the right track. Right now we have a tropospheric pattern which is causing such disruption. A strong Siberian high, another strong high anomaly over Europe and pressure patterns over the north pacific are all combining to disrupt the spoon. Go and read up on the science behind the Aleutian low / Euro High combination - or simply take it as read that this combination works to disrupt the vortex. The longer it hangs around the greater the disruption. And with the upper vortex strong (as of last week) we want the disruption to continue as long as possible and are hoping it can create a forcing via warm air injection into a cold stratosphere big enough to completely shatter the circulation at the top of the atmosphere. You can imagine what happens if the opposite goes on - if tropospheric patterns SUPPORT the westerly bias of the upper vortex then the spoon spinning the water finds support from the bottom of the jug, and a strong connected circulation occurs which frankly can be the end of the winter season in terms of blocking. There are a multitude of other factors that can impact on the strat/trop vortex relationship, the biggest probably being the ENSO impacts on atmospheric momentum budgets....but now things are getting really complex and I'd leave reading into that until you can conceptualise the dancer relationship-analogy properly. This answers point 3. The vortex wont strengthen if there is no temperature gradient. Essentially this is what helps drive the jet stream, and at our latitude what we really mean by "tropospheric vortex" is the passage of the polar jet, the boundary between warmer sub tropical air and colder arctic airmasses. Being right on the boundary between the two for most of the winter season we get all kinds of variations. Very cold winters happen largely when that jet is able to drive south, under conditions perhaps when sub tropical warmth dictated by the latitude of sub tropical Highs eases south....and conversely when the sub tropical highs ridge north the jet rides north too and we end up under mild conditions. But even that is simplistic because it assumes a direct west/east passage of the jet and that "flat" passage is never guaranteed. NW/SE bias or SW/NE bias can greatly impact the source of the air that rides over the UK. Hence we spend a lot of time discussing the ridge/trough pattern and the upstream influence of the power house which is the pacific ocean, and the temperature gradients produced as air travels over the US. Ultimately we get what the US gives us to an extent, though conditions in our own atlantic sector can moderate the flow, especially the location and strength of blocking highs. So - getting to your last point above - to get an SSW we need conditions favourable to injecting warm air into the upper vortex, and then we need friction to cause that upper disruption to "downwell" to lower layers and therefore put a brake on our jet stream pattern, encouraging the growth of more high pressure blocks. Helps massively if the pacific pattern is in line with this, and some luck with things like the solar context and the passage of the QBO (another complex variable) also matter. This season, certainly by January, the solar context and the QBO pattern will be working to help with any potential disruption of vortex/jet westerlies and will support any cold blocking pattern that might emerge. I'll stop now. This kind of post could keep going and going....but hopefully that adds some flesh to Mike's answers.

6Z as others have posted, does provide a serious warming i the strat .. I will happily endure a few more weeks of waterboarding if we hit the jackpot later on..

Well it looks like game on in the strat, GFS 6z at T384, might have teeth this one!

The warming appears to be initiating around 27th November, so that's a date to keep an eye on. The peak of the SSW (if it does happen) is outside of 384 at the moment so we're not able to see it's full strength yet. The mornings 6z is still continuing to show a potential strong warming, actually even stronger than the 0z. 252 312 384 I wouldn't put too much money on the GFS having this nailed, however it did forecast last years warming quite well, albeit that the result was that we never really felt its effects on the ground (certainly not the effects most on here crave!). Looking at the 6z running at the moment, there does appear to be a gradual tightening of the PV as we head into December, which is to be expected. 324 For those of the cold persuasion, this is going to be a game of patience (when is it not!?). My personal belief is that we won't see anything notable cold wise before mid December at the earliest, but never say never!

Back to looking at 10 day charts and beyond which never verify,in hope for something colder. Usual setup coming to fruition as we head into the actual winter months again,lol

Hello all for another year. So it’s that time of year now where I am needed to go cherry picking. So here we have the GEM control run at just 16 days out. Exciting times!!!!

Yes, we will need to see at what point the warming subsides, will it do enough damage to the vortex, no sign yet other than an (unfavourable) displacement but the warming hasn't finished, we need it to continue to strengthen post T384 then hope somehow we can get it followed up, you don't often see those charts in late Nov / early December so not bad at all, by about this time next week we will have a fair idea if there is any chance of something significant for xmas or not.

Strat warming getting stronger by the run white Christmas anyone.

Yes the channel of cold could be a bit further East but a pretty good run...

All OK if it stays there mate! This model watching is all getting quite exhausting and I've yet to see a snowflake, although some close by did last week, so where are we in ten days time? Well the models say this, ECM, GEM and GFS: The uncertainty is huge isn't it, but perhaps the least uncertain part of it is the location of the trop vortex. So as far as the hunt for cold is concerned, which doesn't have it's own thread so I'll use this one, we currently have two irons in the fire, a meridional tropospheric pattern that could, possibly at quite short notice, morph into a UK cold/snow scenario, or a route to an early SSW which would lead to a lottery that we hold two thirds of the tickets for. We will see...

Anyone not doing anything over the next 4 days? ECMWF will be live-streaming their workshop on “Stratospheric predictability and impact on the troposphere” during 18th to 21st November 2019 and it's open to all with no registration or login required. There's some big names taking part including Amy Butler and Simon Lee. "The topics will include understanding and diagnosing stratosphere-troposphere interactions, improved parametrizations and numerical schemes, the role of water vapour and ozone, observational evaluation and data assimilation." Link to live-streaming: https://www.ecmwf.int/en/learning/workshops/workshop-stratospheric-predictability-impact-troposphere

No....................... Or is there????

...for most on here, these changes in surface conditions really do not deliver the nirvana of a cold plunge. The differences are more to do with how rainy it will be. I do not see any changes to the NH cold flow and bearing in mind the great synoptic this month and the total absence of FI "boom" charts, it does suggest that no matter what small changes occur with the main pattern, cold is elusive. The models are very inclined in FI to show us some cold and snowy charts (with the right back story), so the lack of such, is telling IMO.

According to the gfs major troughs continue to track across the Atlantic during the next five days until they hit the buffers but the process does, as usual, promote down stream ridging which results in a build up of pressure in southern Greenland;and that links to the strong European ridge Thus continuing unsettled and quite windy at times but not as cold as of late

Pub run T186: Like it

Jetstream profile forecasts for rest of the month would suggest low pressure being steered in a direct course for the UK, which will no doubt result in plenty more rain, and heaviest totals not just reserved for northern parts as tends to be the norm, given the more southerly position of the jet. Also becoming a bit flat which suggests troughs may now be able to move further to the east. Temperatures overall preety close to average certainly nothing overly mild for the time of year, nor conversely anything particularly cold. No sign the jet will align on a more northerly path anytime soon, which gives every chance for something colder to develop in time from the north, so not surprised to see some of the models showing a northerly in the outer realms of model timescale. This certainly looks like going down as a trough dominating November, with barely any high pressure on the scene. The pressure pattern for the month will show a very deep trough direct over the UK, strong heights to the east and to the north. Suspect for many sunshine levels will be very below par.

Quite a big difference at T168 ECM (left) and GFS (right) ECM opens the door to a ridge into Greenland here.

Maisie Report Another modest increase (this time of 55K Km2) has been recorded, mainly by virtue of a Kara(-41K) drop. This was part of a push back in the Atlantic front, which also saw drops of Barents(-2K) , Greenland(-2K) and Central (around Svalbard) which dropped by -7K, caused by the switch to westerly winds.. Elsewhere the Pacific front was steadily being dispatched back to where it belongs with Beaufort(+6K) and Chukchi(+27K), and even the ESS joined in today with (+13K), Baffin added another (+13K), and Hudson Bay 'burst through' with (+38K). All the western coast is now iced over in Hudson and it looks like it will maintain a high rate of freeze now. The minor areas all made steady gains with Baring(+5K), Baltic(+2K) and SOO(+2K). With regard to Hudson this is the 3rd consecutive year that the refreeze has started earlier than the seasonal norms (though not as early as last year), and is exemplified by all the polar bears moving back onto the ice. Apparently there is a 'bear count' of these animals, held in Churchill, and the locals use this to determine the start of winter (when the mother bears take their cubs onto the ice). Also, in N America the refreeze has started early in the Great Lakes, with the northern lakes of Lake Superior, Lake Michigan and Lake Huron all icing on the northern shores. Temperatures are forecast to remain low all week here - so it likely that the ice will continue to grow. A weather forecasting service in the USA has just reported that everyone of the North American continent's states (except Florida) now has warmings of ice or snow. Apparently the earliest that this has ever happened. So as KW has been reporting, the cold in N America is (in addition to be becoming some of the coldest ever recorded), is now extending its grip to cover the whole continent. MIA

Enough, now. I have said to PM me with any concerns. Back to the models now, please?! And just to be clear on this, as it seems some are not reading my posts correctly.. I haven't once said that no one is allowed to post about the strat in here. I have said twice now, strat chat is fine if you're mixing it in to musings around standard model discussion, it's exactly the same as our guidelines for tweets/met office, which has always been the same. Stop stressing and continue as normal - there's no issues at all here.

So what precisely is the point of the Strat thread then and equally, the point of this one?. And if the argument is that they are connected so it is legit to post in here then surely any strat post needs to show a direct connection to current model output, not just woolly speculation Personally I agree with Jordan Smith above

Hi @Northern Sky, I don't think anyone has answered these specifically, so I'll have a stab... 1. As of now, yes, the trop vortex is disorganised and the strat vortex is strong. 2. This is quite difficult to answer, the reason the strat is forecast to get weaker is actually because of stuff going on in the trop - the Scandi high, Aleutian low combination is helping this. So it is kind of all connected, but as winter proper starts you would expect, all other things being equal the two to trend towards being coupled, but all other things aren't equal this year in my opinion. 3. I would look at this question the other way round. What would not cause the trop vortex to gain strength? Because, unfettered it will going into winter...one reason is that the jet stream doesn't play ball and blocking patterns occur that prevent it gaining strength, but that's kind of like expecting to roll a dice every week and throw a 5 or 6 every time. Or an SSW should one occur and downwell favourably, this can marmalise the trop vortex completely. 4. Yes, the last two SSW events illustrate this perfectly. The Jan 2019 warming, caused the strat vortex to split into three and the trop response was slow and unfavourable for UK cold. The 2018 warming, however, split the vortex completely into two, and the trop response was rapid and favourable and led quickly to the Beast from the East in March. This whole event was fascinating with a narrative over two months from the precursors to the SSW, the event itself, and what happened after, all with some real predictability, which is why it is worth trying as best one can to understand this aspect of winter weather. 5. An SSW, specifically a strong one, after a couple of weeks delay, should impact our weather for 4-6 weeks. So I guess it depends which months of the cold part of the year one would want that to happen in...but if the trop pattern was already favourable for cold, an SSW could mess that up and be the last thing you'd want. Hope that helps, and also helps answers the questions by @weathergeek and @mushymanrob too. Regards, Mike

A few FI jaw droppers on the GEFS

Eeeeee up...it's a one-man Mexican standoff: barbecue in one hand, sledge in the other...? Possible unseasonal warmth followed by our first blast of real winter!?Or wishful thinking!

It would appear my hope of the Euro heights taking over and drying the UK out have nosedived over the last 48 hours. EC 144 looked OK potential wise But ends with very poorly It would have been nice to see a cold high during November, one of my favourite months..clearly,that ship has sailed.

The ext EPS has the vortex over Franz Joseph Island, suppressing the declining European ridge, with an extension aligned to northern Canada wiith the energy running south of this, and the Greenland ridge, to a mid Atlantic trough, both of which have evolved during the evolution. Thus a more unsettled zonal flow over the UK to a toasty Europe

Morning all, quite a change in the latest UKMO run. Gone is the full Atlantic flow as the low hits the buffers and looks to slide. Maybe the next attempt will break the deadlock but the trend seems to be putting back in the medium term time scale. GFS run looks to progressive post 144t and GEM goes for Greenland height rises with an eventual Northerly .

It really has been an incredible spell of weather - going back to the second last week of October here. Driest, least stormy (gales/severe gales) coldest and sunniest November (so far) in a long time for this location. (Be interesting to see the Metoffice stats at the end of the month) Just keeps on going - cold and sunny today and then Monday and Tuesday are baltic yet again/well below average temperatures continue. Not even Winter yet... @Benvironment absolutely stunning pictures! You are living the dream!

Another clear frosty start to the day, I've now lost count of how many that's been this month. Very different from what many of our more southerly cousins have been experiencing.

It's got to be In The Bleak Midwinter for me. Winter/Christmas Eve of 1981, I was in Young Farmers, we were booked to do the rounds of local big houses, carol singing for charity, the only way we could get around was on skis. I'll never forget the surreal sight of coming out of Great Tew church (in the Cotswolds) after midnight mass and seeing rows of skis stood up against the church. Snow had fallen, snow on snow, it lasted for weeks, cut villages off, it was like middle England had turned into the Austrian Tyrol. For me, still the best winter ever.

Also ,ECM slides the low at 144t. So the Atlantic put back again. That trend continues. No good really looking past 144t at the moment.

@CatchMyDrift agree about the fish and chips in Oban, although being a Fifer I will say that there are plenty of good fish and chip shops here too

Who is "she"? Any chance of an explanation for us divvies?

@CatchMyDrift - can't help you with the distant mountains, agreed re the concrete thing, it looks hideous, but your photos are works of art... 'the clouds, oh my god look at the clouds dad' I remember oldest young HC a long time ago at nacreous. I was in the co-op earlier and there was father showing his toddler boy the xmas goodies. Nearly 20 years since I last had the fun of doing that - anyone out there who has wee children now, just enjoy the time cos it doesn't last.

Nope. Nasty wind, don't like windiness, takes all the heat away... (Home has no double glazing and work accommodation is draughty too!) @CatchMyDrift - lovely picture of oaks there - they keep the leaves well into autumn and they have such texture as well as colour. @Mr Frost - he's after your nuts! (Sorry) A milder day today on the Black Isle and overcast. We did see some mergansers on the firth and they were abruptly joined by a grey seal which is an unusual sight here. There were also some cute little ringed plovers on the shore pretending to be pebbles. I'll get round to looking at my holiday snaps soon - there must be hundreds of Icelandic waterfalls... and this was 11th September, albeit at about 800m. Does Iceland have weather, does the bear crap in the woods?

I have indeed But not as much as I'd like in winter, if I'm honest. Still, what few times I've done it, it's been memorable! Yesterday might not have had camping but it was still pretty glorious in Perthshire tbh The cover would go quite quickly in any mild spell but it's still really nice to see in November. Long may it continue!!

Horrible non-day here. No sun, no rain, no wind. Nothing but grey. But at least I did come across the most incredible fungi 'flower' on my walk. At least something is enjoying this weather.

Long post coming…. OK – here’s my winter forecast for 2019/20. My rationale is simple – I want it to be accessible in plain speak but technical enough to tweak some interest. I’m a snow hunter so have written it largely from a snowfall perspective (and make no apologies for that purpose). Finally I do see 2 quite clear possible routes, with the potential direction of travel hinging on the extent of vortex disruption in early January. I am not using any analogs. If you want to see forecasts hinging on analogs there are plenty on sites over in the US at 33andrain. I have become less and less convinced by the relevance of analogs, though acknowledge they make for interesting reading and pattern matching. Drivers Both via observation and technical paper reading there are clearly core drivers that impact the pattern over the UK. In some kind of approximate hierarchy these are: 1. ENSO forcing that impacts global momentum budgets and, as a result, likely pressure patterns. Central to this in winter is the extent to which the sub tropical high pressure belt is supported in a northerly direction by circulation at the pacific equator (including convection patterns mapped via the MJO), but also the extent to which surges in momentum can create blocking at higher latitude. The UK sits right on the boundary between the sub tropical (Azores) High and the polar jet, and torque events either over North America or East Asia can have a significant downstream impact on the ridge/trough pattern that leaves us either on the warm or cold side of the flow. 2. Vortex strength from the top down, but also the extent to which impacts from the bottom up can either disrupt the vortex or alternatively encourage a coupling of the upper and lower layers. Once coupled the vortex is a tough beast to break. The tropospheric vortex naturally strengthens through November and into December before beginning a slow decline through January and more especially through February, and this is an important precondition to keep in mind. 3. Sea Surface temperature anomalies in the North Atlantic and the extent to which the jet can be affected by this. 4. Snow cover, ice extent and the issue of arctic variability which can impact on the Siberian High in particular. Perhaps also impacts the vortex in terms of tropospheric ridges in the arctic causing disruption. 5. Solar variability. Much disagreement here amongst forecasters and interpreters, but the balance of the argument suggests that times of low solar activity encourage higher than average ozone levels in the stratosphere with a greater chance of vortex disruption, but also reduces the overall strength of the jet, encouraging more “wobble”, often described as a more meridional pattern. 6. Finally its worth acknowledging the natural waxing and waning of the wave pattern, and therefore shifts of wavelength and movements in the peak/trough pattern are inevitable. Observationally I have come to see these as working in thirds of months, with occasionally a standing wave situation creating less movement. We are in one such standing wave situation now with the trough fixed over the UK for, I would think, two thirds of the month. With such a neutral ENSO background state I wouldn't be surprised to see static periods of wave activity repeat. The Driver Context in 2019/20 1. ENSO impacts are expected to be minimal this season, with an essentially neutral position currently. The MetOffice forecast sees the weak Nino focused in the central pacific but a context further to the west of a very positive IOD and cooler waters which, in theory, promotes more of a Nina pattern. Much further to the east the pacific is cool, once again suggestive of Nina impacts. This “Nino Sandwich” is a tricky one to call, but the signature is so close to neutral that impacts will probably not be substantive. However – and this is important – the global atmospheric momentum signature is rising and has been rising for several weeks. This is indicative of Nino forcing in the pattern (as well as nature's desire to try and return momentum budgets to zero....), and so it looks possible that the tropical cycle through the winter may become more of a factor later on, particularly if GLAAM hits positive values as it rebounds. Given the elastic nature of GLAAM the upwards trend looks likely to continue for at least a few more weeks with a likely peak in January. Whether the upwards trend continues beyond that is a tough call – but more Nino style impacts increase the chances for stronger late winter blocking patterns. More commentary later on this in the monthly descriptors. 2. The stratospheric vortex is currently strong, but just beginning to feel the impacts of a well known tropospheric combination of low pressure over the Aleutians and High Pressure over Eastern Europe and Scandinavia which encourages warm to be fired into the upper vortex from opposite sides of the globe. This is providing early stress on the vortex, helping prevent the upper and lower layers from properly coupling, and this is a process that may be being enhanced by the background low solar context. Given expected lag times, the impact of this wave 2 attack may take up to 4 weeks to see real tropospheric change given any stretch/split/displacement needs to work its way through the layers (assuming the atmosphere is receptive to frictional downwelling…and we all know that last year it wasn’t…) meaning end of December or early January for maximum downwelling effect. As we move towards December the signs of vortex stress in the modelling are increasing, though these values vary a bit from day to day and model to model. There is broad agreement, however, on an unusual trend towards a weak vortex by end of November and probably beyond. 3. Sea Surface anomalies currently favour a slightly south of normal jet projection. Warmer than average water around Greenland, if maintained, may help to further support any anomalous ridging in that area, and a jet firing beneath weak heights to the north, and over cooler waters, is a tendency we have already seen this season and one which ocean temperatures suggest may continue. Low solar may also strengthen this signal. The CFS forecast going forward for the season sees warmer waters to the north, and cooler do the west. To me this strengthen the possible undercut signature with favourable conditions, especially late season, for continental high pressure to nudge west. 4. Snow cover is high, and ice regrowth on the atlantic and Siberian side has been robust, much more so than around Alaska in the pacific sector. This may well help create a very strong Siberian anomaly for this coming season, and this is a consideration for the second half of winter when atlantic firepower starts to drain away. 5. The sun is quiet, and looks set to remain quiet. No pepping up of a flat jet is a decent bet for the coming season, and indeed already I think the seasonal models have been blindsided by the angle of the jet as encouraged by the more meridional flow than expected. This is a context that will be with us all season. Monthly specifics December Current patterns have demonstrated a very resilient Scandy/East Euro block that has acted as a solid barrier that any amount of atlantic fury has failed to crack. Watching the first 2 weeks of November carefully has been instructive in this, and for snow lovers the sight of atlantic lows hitting this block is mana from heaven in terms of adding weight to vortex disruption. The MJO pattern through late November is also supportive of blocks at higher latitude. As a result a trough has remained as a semi permanent feature over western Europe, unable to move, dropping copious amounts of rain in England (less so Scotland with the southerly displaced jet) and temperatures have undercut model predictions. However, this pattern looks set to fade. The MJO will reenter the Indian Ocean shortly. In addition, the tropospheric vortex continues to be on an upwards curve seasonally, reinforced in all probability by growing cyclogenesis caused by colder than average temperatures in the US, and into early December a flatter pattern looks likely. A neutral ENSO signature overall is not going to significantly disrupt this seasonal trend. In this scenario the vortex disconnect will remain in force, as tropospheric impacts on the stratosphere disrupt the stratosphere while at the same time the atlantic becomes more dominant tropospherically. +NAO setup will be the end product for the first two thirds with an increasingly +AO in attendance. However, by month’s end downwelling impacts of vortex distress, and possibly even vortex disintegration, will begin to be felt, and the next ENSO cycle will bring the MJO back close to phase 7-8-1 and more support for blocking. A wet first two thirds, with temperatures average to slightly above average will be replaced by a drier final third, greater presence of frost and a pattern shifting towards less mobility. January Timings tough to pin down here, but two possibilities broadly. Possibility No 1 rests on major vortex distress and a downwelling that impacts significantly. If GLAAM continues in an upwards direction, elastically turning positive on the current upwards curve, then torque events may enhance this phase. Lag time, and likely MJO cycle and associated torque increases, suggests mid month for any potential reversal pattern as the AO drops swiftly, and much will depend on where residual shards of the vortex may land. With the axis of attack sitting between Alaska and Siberia we may expect energy displaced to east Asia and Canada, so a burst of atlantic energy initially via a +NAO followed by a swift reduction and a reversed pattern with a -NAO taking over. Best guess here therefore is for greatest cold impacts mid month, maybe final third. Blocked, cold and snow potential at that point. Possibility No 2 rests on the vortex resisting the predicted assault, stretching and reforming. This may be assisted by a transition back to a lower GWO (low GLAAM state) as the ENSO signature fades and the MJO returns to the Indian Ocean. In this circumstance again a stormy first third to January, perhaps with a Scandy High in attendance due to vortex stretch, and a slight relaxation into a default westerly regime by mid to late month. A close but no cigar event for snow hunters. Southerly jet predisposition may keep temperatures around average, perhaps marginally below, with rainfall above average. The angle of the jet wont totally rule out snow at times, but widespread and durable cover difficult in this scenario. February Being honest, if the vortex collapses in January then I think February could turn out very cold. Shortening seasonal wavelengths, as the tropospheric vortex continues its slow decline, encourages retrogression of the wave pattern, and the generally cold and blocked January could lead to a period of significant continental influence as the Siberian High edges west. It is beyond my gift to predict with any reasonable accuracy the likely progress of the month from start to end, but years of observation would suggest that, as the month ends, any cold pattern would begin to relax. First two thirds very cold, final third relaxation as inevitably a degree of late season vortex reforming returns. However the likely passage of the MJO later in the month may help to sustain the blocking throughout, and any relaxation would be relative. Dry overall, with temperatures below average. If the vortex reforms its shape in January then a second opportunity for cold blocking arrives in the latter half of February as the troposphere makes one final stab at vortex stability. January mobility will produce more wave breaking and another assault on a much weakened vortex, and the knock out blow may arrive with the final ENSO pacific cycle of the season towards the end of February. Chance of late season cold in this scenario – but no guarantee. A non descript first two thirds, certainly drier than January, with temperatures perhaps above average as the Azores High makes an appearance initially, before a colder final third as blocking appears to the north, and intrusion of further cold into March. Temperatures overall around average as the cold end cancels out the relatively mild beginning. So – there it is. I’m going to plump optimistically for possibility No 1 through January (though possibility 2 definitely remains on the table), and summarise my overall spread as: December: Broadly +NAO, wet, average temperatures but more blocked final third. January: Stormy first third under renewed +NAO, then strongly negative -NAO mid to end of month and continental influence. Widespread snow potential. Temperatures overall slightly below average, rainfall overall average. February: Largely -NAO regime, especially first two thirds. Temperatures below average throughout, relatively dry. I hope this reads coherently. Bear in mind we all have limits to skill levels, and the truth behind most forecasts is that they are as much hopecasts and guesses as anything else. However I'm interested to see how the season works out in relation to the level of understanding that has created this moment of crystal ball gazing, and ultimately I post for enjoyment more than anything in looking for cold weather patterns. If we get a cold December with snow, and a mild January/February with no ice in sight I won't mind one bit - a cold December would cancel out any disappointment at inaccuracy and, in any case, we are all learning all the time. I'll do a review in Mid March once the winter has lost its edge.