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so, winter's over. the teleconnections are a load of old rubbish, the "told you so"ers were right. oh hang on, it's back on again...

If I've got this right (and there's a fair chance I haven't) there's a choice of what we can expect from the SSW - either, cold and potentially snowy nirvana or warm southerly winds and an early spring? Personally speaking, that sounds like a win/win situation to me. An end to wet and windy dross with leaden grey skies gets my vote. Yes, I'm a snow lover but I'm also a lover of t-shirt weather with warm sunshine on my skin too, either one will do.

Biggest easterly reversal for nearly within a decade, nah - it won't do anything, winter is over... Solar Minimum u say.... nah, not having it. MJO blocking leading to this - whats that?? I would bet on stuff changing against the norm between now and the end of March, each to their own..

It’s so cryptic in here sometimes, I’m not sure if it’s because people just like to talk in riddles because it makes one sound clever, or so they can sit on the fence if they don’t spell it out! Odd! Short term, the GFS ups the anti on Tuesday’s possible snow event!

As I said this morning, ECM will not return to the Atlantic ridge and GFS 06z will wipe it out. GFS has basically been 24hrs behind ECM But! I think this mornings ECM is very wrong day 5/6 onward and we will see a new trend toward Atlantic blocking again soon, just at a later date than ECM initially modelled. My guess is that ECM has jumped the shark with its interaction of trough and Azores high and will make big corrections in future output while GFS will continue on the path it is now on but slowly displace the Azores high West in future runs. I think we could see very strong Atlantic ridging suddenly develop after the 20th, rough guess around the 22nd. If this idea has any merit at all such an evolution will likely show up within GFS ensembles first. That is my big call of the year - I will now reinforce my door and go ex directory.

Well this morning’s runs will do nothing to quell the nerves of us long suffering snow seekers. Under more normal circumstances, following on from yesterday, this would have to be considered as a potential trend for the worse. But... these are ANYTHING but normal circumstances. We have a record breaking wind reversal about to take place in the next 24 hours and currently forecast to remain reversed for a stunning 10 days or so. This combined with the highly amplified MJO currently causing havoc to the Nina state in the Pacific and sending waves polewards through the sub tropics. A second warming due in ten days. An already record breaking eddy heat flux. This is fairly exceptional. This is not only going to have a major impact on default weather patterns but right here right now have a major impact on the forecast models. This is unprecedented in modern times, we cannot expect any model to be able to get a firm grip yet. We need to wait at least another couple of days to let the upper warming actually commence and for it to be in the input data. Only then will we, potentially only start to see, how this will start to pan out. To say this is a highly dynamic situation does not due it justice.

With the EC vs GFS saga at the moment, I've seen plenty of members quick to jump on the assumption that we are going to have one of those SSW events that won't benefit us in terms of getting HLB and deep cold this time. However, Easterly mean zonal winds for 10 days+ at 10hpa/65N, see chart below, is pretty phenomenal, probably historic, so I would be surprised, given the likely obliteration of the strat PV, that there isn't a big geopotential height rise to our N or NE by month's end. This no bog standard SSW. This perhaps unprecedented SSW combined with some mixed signal with regards to the MJO wave, RMM plots perhaps not capturing what looks like, as per upper divergence on today's VP200, convection moving into phase 8 too. However, AAM looking a bit meh GEFS AO and NAO clearly tanking from the 20th ... EC still a conundrum though, 12z EPS not tanking NAO until from 23rd, AO goes to neutral. But I'm wondering are any of the models handling all the combined impacts of the SSW + MJO + AAM correctly? Damn hard work trying to fathom out what all these may do if all were modelled right in combo. I think MJO + AAM + La Nina base state are in the driving seat for now, but the impacts from the SSW will ovewhelm the tropopshere towards the end of the month - in a positive way.

Maybe SSW really stands for Strong South Westerlies?!

Oh dear oh dear oh dear, Massive change on the GFS at 5/6 days out, amazing how when it comes to cold pretty much an entirely ensemble suite can be wrong. People can roll out the same old cliches but fact is this looks like another let down, and winter is fast running out and we will be left chasing day 10 charts as usual.

Tonights ECM has been cancelled and has instead in true TV style, put on a repeat of a previous winter, unfortunately it could be from any one of the last few winters. In other news, it appears that the three ghosts in the famous Charles Dickens novels can die twice. ECM not impressed by their suggestion of coldie redemption. If this ends up being close to the mark then I will eat my bobble hat with a sprinkling of 7 day old socks. Thankyou

Sorry but that is utter rubbish Ermmmm March 2013

As I said over a week ago, this place won’t be for the faint hearted once it gets underway. Even if we get off to a bad start, it will still be absolutely fascinating to see how this plays out. Many twists and turns to come. ‘If you don’t like the heat, get out of the kitchen’ as the old saying goes. Probably not the best one to use on this forum though...

You'll be back on by tea time and you know it.

You are quite right As was Captain Shortwave observation at the same time about the amplification in the Pacific sector. And that remains the clue, despite suspending usual thought yesterday for good reason. We can all think we are missing something when there are extraordinary things happening at all levels of the atmosphere. But seeing as I have returned to my head attempting to be in control over what is happening, then as previously suspected - its the case that falling angular momentum since the MJO induced Scandinavian ridge of last week, is meaning that -ve zonal easterly winds are lining up again from along the tropics at 30N As repeated a bit like a stuck record by me this season (sorry about that but its based on intended good reasoning) the effect of a return to more La Nina-like type forcing (for the time-being)is to re-boot the sub tropical ridges aligning along 30N. The classic configuration of this forcing this winter has built up the signature traditional default pattern of amplified North Pacific ridge which locks in the Canadian vortex, with increased polar jet energy and further sub tropical ridging downstream pushed to mid latitudes across Bermuda and to the Azores ridge. The -ve zonal wind anomalies supporting these ridges underneath, with the polar jet flow across the top. Very much a +NAO regime. However much members dislike it, that is what the ECM operational keeps modelling each time at the moment into the medium term, and its not hard to see where it is coming from - based on its interpretation of the recent very high amplitude tropical forcing concluding its cycle - and with those -ve zonal winds returning across the 30N as angular momentum falls back ...ahead of the next tropical cycle retuning to the Indian Ocean. If one thinks that the deep amplitude low angular momentum GWO pattern of January helped cement the Canadian vortex at a time when the polar field is typically at its most organised, then as suggested in posts at various times through January (and in anticipation of the latest MJO forcing) it was always going to be a big ask (initially) to change an entrenched tropospheric base state pattern - which in turn frameworks the polar field. I think a weak El Nino forcing, in tandem with eQBO would have created the stratospheric pathway that does not favour amplification restricted upstream in the Pacific and does not teleconnect to a strong Canadian vortex lasting in latter winter and being more resistant to any poleward wave flux that does come from phases of tropical momentum Under a feedback pattern that produces steady background poleward +AAM forcing, and unlike a La Nina regime not relying wholly on tropical convection forcing to boost westerly winds in the tropics as a means to amplifying the extra tropics downstream (the Atlantic and European sector) then this SSW would have taken route 1 - as last weeks +AAM spike produced in terms of the Scandinavian ridge and less upstream energy waiting to return c/o the Canadian vortex. .The SSW would be more likely dealing in those circumstances with a sibling Canadian vortex and parental Siberian lobe - rather than the other way around as we see at the moment, and as very well described by @lorenzo on the stratosphere thread today Its a case in my opinion of the tropical cycle re-setting from the Indian Ocean and angular momentum rising once again. Also I think that March will see the Pacific profile change and warmer sub waters changing to mean that a more sustained +AAM cycle will evolve as a signal that this La Nina is going to fade though the Spring into early summer. So an extension of 'winter' and a cold March does look intuitive on that basis at this stage Before then, however and notwithstanding all said in intended sense as above - its still very much the case to watch this bag of tricks called the SSW . As soon as the parent Canadian vortex shows weakening and the models factor in better the constantly new starting conditions based on the Krakatoa evolving from the highest levels of the atmosphere downwards, then the stubborn tropospheric pattern c/o (weakening) low angular momentum forcing should become less dominant and more easily overridden - especially as wavelengths shorten and assist cold air advection heading into March

The cauld rain eventually turned to snaw overnight Fri into Sat and gave us a covering by dawn on Sat before more cauld rain and sunshine dispensed with it. Then headed off to Glenshee. Cracking conditions. Wind today was 'brisk', but superb and bright. Bonus flock of snaw buntings were skittering about, too. Back here tonight and there's been a further snaw shower today which has left some flakes stuck to the pavements, roads and bin tops. Currently 0.1C/-4C. The stealth winter of 2017-18 continues...

@Hawesy I’m still waiting for my predicted 5 cm despite the occasional snow(ish) shower ... currently snow lying on car only.... perhaps Tuesday will be the day? Anyhow... Hawesy you got to let me know Will it rain or will it snow? If you say that it will rain I'll be ‘ Oh no not again!’ So you got to let me know Will it rain or will it snow? You always tease, tease, tease You're list of guesses always aims to please One day it's fine and next it's cack So if you want me off your back Well, come on and let me know Will it rain or will it snow? Will it rain or will it snow now? Will it rain or will it snow now? If it rains there will be trouble And if I snows then I’ll want double So Hawesy you gotta let me know Will it rain or will it snow?

Well here’s +0 hrs it’s on like donkey kong! So models may start getting a better handle on things soon! I urge patience, usually we would be waiting weeks for a trop response, this time not the case. Come late March there could be a few wishing it never happened lol

It’s best to remember that Chinese proverb! A bad chef can make a rubbish dinner with 5 star ingredients ! Regardless of how good the strat reversal is what counts for coldies in here is the weather on the ground . The SSW does increase chances but we still need some luck with where any blocking sets up and also where any Euro low heights are located.

But I don't want back edge snow, i want full frontal middle and back edge snow please lol.. ?☺

So the chance of cold weather more than a week away is gone because the models, which are useless more than a week ahead at the best of times, don't show cold for that time period. Forgetting the highly complex situation of a SSW that is only just getting underway. Watching people fret about this is ridiculous.

Indeed, the Ecm shows an early taste of spring, the polar opposite of the background signals, you could say the Ecm has gone teits up in a manner of speaking!

As I have said many times in the past. It doesn't matter how good the background signals are, it means absolutely nothing if these aren't translated into decent charts in the model output at a sensible timeframe. If the ECM is right then my word we still have so much to learn!

Just model discussion please. I’m aware that the SSW is the topic of the hour but has anyone checked out what’s happening in the ‘reliable’? And has that output been affected? I said the same yesterday morning, let the SSW happen and then start worrying about the detail - the models are producing a whole range of possible outcomes, none of which will be bang in and at this stage I don’t think there is any merit in writing off any of the solutions. There’s also no point in getting emotional at weather that’s being modelled for 10 days time off the back of an event which hasn’t concluded yet. If you do want to ramp or doom monger; there’s a special corner of Netweather to do it in the moans and ramps thread. Please remember there will be lots of new and guest posters reading, driven here by the SSW chat. Let’s not put them off for life eh? Be nice. ta.

So - here we go. Vortex split, reversal to occur in the next 24-36 hours. Depth of reversal significant, length of reversal significant, vortex shard placement and progression a bit uncertain - but set to leave the UK in no man's land between the 2... surely providing a rich context to height rises to the north... maybe NE (my best guess) or maybe N to NW (as per some model runs recently..) Either way - height rises. Still looking also for the storm track generally to drop south, though this has not been hugely noticeable in model runs in the last few days. Are the algorithms able to deal with a split vortex on top of an extended and deep reversal with a pacific context of high amplitude MJO and ongoing impact of east asian MT promoting the kind of poleward wave activity as posted so well recently by Masiello on twitter? And warming of the Canadian vortex shard on the horizon also? No. NWP will model all this far worse than usual. Wild swings will occur I think - with some awesome charts interspersed with downright ordinary looking ones. GFS just now churning out good ones - and this image here for medium term illustrates my thinking pretty well. There have been some wise words in the last day or so, urging caution. They are right. Caution in weather forecasting is the name of the game - I suspect I have been guilty of being rather bullish in some recent posts. But at the same time - let's be clear. We havent seen a split and reversal like this in the modern record. Amy Butler has tweeted today that eddy heat flux has just broken the modern record and will be making a mess of vortex shape as I type. Sustained reversing strat winds for around 10 days are not something we have seen before - but are forecast. End result is that we have preconditions for something special. To be honest - if we cant be excited now (coldie excitement that is) then frankly we never can be.

Since we dropped the term precipitation and replaced with blob or sausage my hit rate is 100% ?

The SSW does look to be of historic magnitude and we should expect to see some pretty extreme output from the models methinks. Of interest is the broader 45-75N zonal index. It shows the historic reversal of winds. As this is an unknown situation for the models, it'll be fascinating to see how they handle it in the coming weeks! The ride is just beginnig!

I have already thought of some alternatives to what SSW means.

very scientific, your posts are sometimes just a touch off the mark, cheers!

Just in time for the new thread then! A post to go with lassie upcoming spring!

Liking the look of Tuesday morn Ideally christopher blanchett is indicating the size of stick you'll need to measure snow

I've seen group therapy sessions less depressing than some of the posts on here this morning. It's true, the OPs are about as exciting as Theresa May popping round on a Wednesday afternoon for a cuppa, but many are acting like it's a done deal and that she's already on the bus heading over. I said a couple of days ago that the GFS/ECM ops were probably being too progressive with the initial ridge and getting the Easterly in, it hasn't been "wiped out" it's just been pushed back, which again isn't really a complete surprise. ECM Clusters long term still have the scandi high ridge signal The signal clearly grows the further out you go, which ties in with the idea of the models being too early with developments. The ECM ensembles whilst admittedly don't scream bitter cold Easterlies, have shown that the ECM Op has been consistently at the top of it's own ensemble suite for the last few runs. The GFS Ensembles have plenty of cold runs We are on the verge of record breaking zonal wind reversal, a fully fledged SSW and a coming off the back of a high amplitude MJO. Double whammy on the vortex. Relax. Stop taking every run as gospel, that includes the cold ones. Take a step back, get off the rollercoaster if you're feeling a bit woozy. Were in a good place, the models are toying with different ideas/solutions.

Guys. Come on. The models are topsy turvy and swinging one way to the other but don’t get disheartened yet. The SSW isn’t underway yet and until it is I don’t think any models will have a proper handle on how things might progress. Ride it out and wait for the runs tomorrow onwards xx

You have to have a wry smile...over a week after ssw and ecm gives us......the mildest chart of the winter! IF this does turn out to be correct it could finally end the teleconnections debate for good!

Just let the cat out, I didn’t expect to see this. Checked the radar, it’s a shame it won’t last long.

I think people forget how cold it can get in March. If you're saying first 2 weeks of March is too late then you should also be saying last 2 weeks of December is too early. The reality in both cases is a Scandinavian high will be bitterly cold. .

last time i checked, the 21st of feb was still winter. i could post the earlier charts which lead to this if you like? in fact, here you go- the 144 chart with the ridging underway which leads to HLB.

GFS much more in tune with what we would expect to see in any transitional phase around Day 7

light snow now

7th lot of snow falling this winter.. brrrr with even the hens saying sod this.

Pyeongchang eat your heart out! #WinterOlympics #Ayr2022

Can I just say quite blatent - the SSW will wipe the la nina base state off the map. It wont matter if theres a pacific ridge when theres downstream ridging blocking the canadian vortex. Anyway - Have a good night all*

Nothing to see here.

Ok I lied ? I'm not taking a break nice point to that high pressure and angle of attack .

Another collection of strat charts from various places looking at the next 24 hrs in terms of reversal for u wind to start with - then the warming progress within the stratosphere and also the vorticity plots to look at what is going on at various levels first of all, then down through the atmosphere at a couple of points following the SSW. Zonal wind plots Hannah Attard at 60N and 65N View from NASA Site Berlin Temperature Charts 10hPa in motion - of continued interest at day 10 the impact of the warming on the canadian vortex lobe Potential Vorticity - in all plots note the reconnect of the Siberian daughter vortex with the parent Canadian one, this was initially separated for longer 48 hrs ago but toward verification time scale the merge of the vortices has become quicker, possibly diluting the solution for a clean blocking evolution. Roughly 144 - 168 hrs. 500 - c 50hPa 600 - c 30hPa 800 - c 10hPa - this plot to me shows the real crunch dynamics coming on line at day 10 A look at Sat 17th and Tuesday 20th coming down through atmosphere - to take a view of proceedings following the vortices amalgamating again. The lower we go, clearly gets to be a messier picture. Given the strength of the vortex over Canada, by strength I mean ( what's left of it #tilted ) the transition of the weaker segment over the blocking locale, the monster action at 10hPa circa day 10 , would not expect to see any modelling get hold of this. That's just a snapshot of now, imagine what other chaos theory we can factor in once the real event takes hold with the next 24 -96 hrs seeing the main stratospheric anticyclone push pole wards see 10hPa temp plot.

I think what were seeing today is the start of a QFR (Quick Forum Response). FWIW the GEFS look broadly similar to what we have been seeing in recent days (ignoring the earlier run). Plenty of better options with the majority going easterly. I suspect we will get an easterly, but the real question is around what type of easterly and that's the bit I'm far from convinced over.

If this is the outcome, I don't think I'll bother monitoring the stratosphere next winter.

Best to bin today's output, I think by Wednesday the models should have a more accurate idea of what is to come and if they reflect today's output by them, best bin winter too, in fact bin everything.

Glad to see more milder air appearing again on the ECM this morning for next week as this frequent cold & wet weather is playing havoc with my asthma.

Today and tonight The low and fronts associated with yesterdays bad weather have scooted away east leaving the UK in a a strong, unstable, north westerly airstream. This will mean frequent wintry showers of rain, sleet and in particular snow in N. Ireland and western Scotland. The showers will initially be confined to these areas plus Wales and the western coasts of England but increasingly further inland as the day progresses and the snow showers may well slip further south as well. Some reasonable accumulations could occur. There is always the chance of more persistent precipitation with the odd trough embedded in the flow. The showery activity will continue overnight, but perhaps more confined to northern areas with the wind backing a tad, but with ice an added danger Monday morning with a widespread frost. Feeling very cold in the strong wind Monday another day of sunshine and showers, these confined to the west, but not feeling as cold as the wind abates. But by 12 a deep low 971mb is south of Iceland with associated fronts lying N/S west of Ireland and by Tuesday 00 they have tracked east to be over Ireland backing the surface wind over the UK to a strong south westerly accompanied by a band of rain. This is probably going to be another marginal affair with snow on the higher ground to the north. The band of rain/sleet/snow clears to the east by 1800 Tuesday leaving the UK in a transitional weak ridge with showers in the west but there is an occlusion out at 20W associated with a deep depression 954mb south east of Greenland that is poised to move track east, which it duly does, and by 1800 Wednesday has brought more rain and strong winds to the UK. At the moment it would appear unlikely to bring snow apart from perhaps on high ground in Scotland. Once cleared the UK is back in and unstable westerly with frequent wintry showers in the NW once more. The Atlantic is dominated by the cold upper trough but changes are afoot with the Bermuda high pressure beginning to amplify and surge north in the western Atlantic but there we must leave it. This is of course according to the gfs. Having had a quick glance at the ecm for the purposes of this thread no significant difference to the gfs. I say no more. .