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Had a lovely reversion to childhood afternoon yesterday making the most of the relatively modest product of a very unexpected snowfall (that led rather nicely to the opportunity to change my avatar). Yet another reminder that so many spend so much time by a computer waiting for the weather they crave and then keep on looking for the next opportunity when its waving at them through the window! So, a quick inspection this morning shows that it seems that recommendations (for a few) to read, carefully, the posts from 7th November have been ignored and misleading representations continue. Its been continually emphasised that any evolution to Scandinavian heights, or, alternatively an evolution to flatter upstream pattern is based upon, at least, three things (and in that respect I'm not going to repeat the latest post of the other day which *should* have made all this clear enough anyway) 1) The imprint of tropical convection feedbacks which have shifted over recent weeks to a Pacific led pattern rather than traditional La Nina Indian Ocean based one. I see that Catacol has written quite extensively on this theme very recently. 2) The natural conclusion of the present tropical cycle which will involve loss of atmospheric angular momentum and some de-amplification of the pattern which takes us into the immediate post next weekend period 3) The actual longer term outcome (Christmas but more especially beyond) which is based upon whether the next tropical convection cycle shows intention to replicate another eastward moving pattern back through them Maritimes and West Pacific (and hence emulate the latest cycle in terms of the atmosphere imprinting the very east based nature of this La Nina). This is the cue for a further boost in atmospheric angular momentum tendency and return of the Global Wind Oscillation to Phase 4. It would be this that could very conceivably coincide with seasonal wavelength cycle change (Dec>Jan)and point to height rises to the NE. Tentatively, it could still conceivably happen sooner - irrespective of what NWP *appears* to suggest. The alternative outcome would be for a weak and indeterminate signal based back in the Indian Ocean which dissolves the downstream rossby wave amplification feedback and sustains any mid month flatter pattern. The Global Wind Oscillation (below) would reflect this with a return to the Phase 1,2 and 3 orbits This, absolutely no doubt, would be the "lemming" solution and time to abandon the thread before the usual people flood it with pages of curdled extrapolations of "winters over" out to March. In truth its obvious from reading around the forum a few have even more absurdly already started doing that while we are still trying to seek sensible and well thought answers to where Questions 1, 2 and 3 lead us. - let alone worry about GWO Phases 1,2 and 3... In the present, the updated Global Wind Oscillation still continues a very slow orbit towards Phase 8. Which is completely in line with expectations. The upwards laddering 90 day long term trend in AAM is so apparent from the spider graph. So is the associated and witnessed trend for increased amplification over a reflected period. Its not a coincidence, whatever the small parochial and scepticism element may think. The implications of Phase 8 GWO synoptically were posted the other day, and within a reliable NWP period are well signalled. But its still very wise not to jump the gun in terms of how the upstream pattern behaves the further out one looks. Whilst that interim milder phase is well advertised, and is not unexpected, it continues to be highly unwise to draw conclusions from NWP suites who are themselves still trying to answer Questions 1,2 and 3. Expectations of Scandinavian height rise this side of Christmas on the basis of repeated analysis may prove premature, but so are assumptions about sustained flat patterns based on re-ascendancy of the traditional La Nina pattern (and to yet further repeat - a cautionary book was written about this in the November posts ) The metaphorical virtual computer model brakes and reverse gear are always applicable at any time.. Signals lead models. Repeat, reflect, acknowledge..and then breathe and relax.....

12z GFS op developing a very convoluted upstream flow from day 7 onwards, all courtesy of a temporary extension and retraction of the Asian Jet. Alaskan ridge effectively rips the tropospheric vortex in two. As pure conjecture, 12z would be a heart beat away from developing and easterly flow across Europe.

About those long range model forecasts.. Both CFS and GPC heading for major bust on December (Nov and Dec for GPC / GLOSEA5) in the North Atlantic. Ridges and troughs in completely the wrong places, particularly CFS for December. Pertinent as both models have similar forecasts for January-February periods. Maybe not a tropical lead signal ?

Oh John, don't make coldies reach for the Prozac. If it wasn't for the MJO heading into 'colder' phases, as Nick Sussex has kindly reminded us through the CPC update, I think I would be waving the white flag for a return of cold the rest of this month after the expected bout of milder more mobile weather indicated to take over next week. With the MJO already in phase 7 and expected to move through into phase 8, with the associated area of upper divergence moving east across the tropical Pacific will likely induce further poleward wave propagation over the N Pacific and a return of a strongly +PNA / -EPO ridge later this month, as is being highlighted by the 00z EPS. Couple this with an east Asian mountain torque event, working with the trop ridging to induce wave breaking over the N Pacific, which will continue to keep the strat PV displaced from the pole to other side over toward N Russia. For now, we are probably seeing the lagged effects of the MJO movement of phase 6 as we see the models extend the influence east of the Canadian trop PV and enhance the Azores high toward western Europe as the Euro trough declines eastward, a composite of mean monthly 500mb heights for December in phase 6 produces this: similar look to what's shown by GEFS mean next week: However, move on to a phase 7 and 8, remember there's a lag of 10-15 days, we could be looking at a pattern change to more blocked look for later this month. Ridging signal building to the N and NE with 7 and 8, with troughing over eastern N America and the polar front jet extending east on a more southerly track (-NAO) as a result. This could be the way forward, but, in reality the actual patterns often don't play out like these composites, which at the end of the day, are means over several years when the MJO is in certain phases. So although the model guidance is all pointing to a more mobile, milder and maybe even zonal outlook as we count the days to Christmas, there is room for optimism given the MJO signal for a pattern change upstream. However, there is the caveat that a pattern change away from the likely increasing influence of the trop PV over Greenland and Iceland may not transpire until after Xmas. As with all longer range predictions using drivers such as the MJO and ENSO, they aren't an exact science, with their influence perhaps more muted this side of the northern hemisphere than over N America, so there is the possibility that we may stick with a more mobile and milder pattern to the end of the year if the trop PV to our NW proves resilient to expected re-amplification upstream from the wave propagation over the N Pacific.

Interesting MJO update from NOAA which doesn't match the current longer range outputs apart from the GFS 06hrs run which is the first to hint at the MJO possibly bringing in another pattern change. The CPC velocity potential-based and RMM-based MJO indices indicate a MJO signal with the enhanced phase approaching the Western Hemisphere.  This envelope is forecast to continue eastward over the next two weeks, although the propagation may be masked somewhat in the RMM index by a competing easterly signal in association with a Kelvin wave approaching the Indian Ocean at present. Equatorial Rossby wave activity in the Central Pacific may further muddy this perspective.  The MJO is favored to continue propagating eastward over the West Pacific (Phase- 7) for the majority of Week-1, before progressing into Phase-8 during Week-2.  An active MJO over the West Pacific suggests a colder solution from the Northern Plains through the East in approximately two weeks. As the MJO envelope shifts into the Western Hemisphere, lagged impacts over the U.S. become less robust. The above suggests the return of troughing to the east/ne USA with a dig of cold there, depending on the amplitude of that we could see high pressure to the sw pulled further west/nw and colder conditions in western Europe. They're suggesting that the RMM index might be incorrect and the models might be having problems picking up the correct signal. Its notable that the forecasts had originally wanted to take the MJO into the COD for about a week before strengthening it once again with movement into phase 7 , yesterdays shortened the time in the COD. Operation Save Christmas given a further lift but a long way to go yet!

re the Met O model seasonal outputs. I have no axe to grind one way or the other, but I do like to be as constructive as possible about forecasts. The link below allows anyone to see these predictions back a long time, certainly to this time last year, I've not looked beyond it. https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/glob-seas-prob My professional days are long gone and meteorology and models have moved on way beyond anything I dealt with so I do not feel able to comment. One thing, mentioned by jvenge, I think, is that average or above average does not mean the same every day. So an above average forecast of 2 m temperatures can be correct over a 3 month period but still allow a cold spell much as we are having. For instance my own weather data shows an T of 0.1 C for the last 4 days, the average for the first 12 days is 4.4 C. I hope helps explain how quite large variations in averages/values over differing periods can occur. My forecasting is limited to 10-14 days, sometimes I'll go out to 20 days. Nothing specific but using what I consider are the necessary tools to provide an overview in the 5-20 day period in the upper air. For shorter times scales then the 3 main models and my own experience as a forecaster. Sorry to clutter up the thread but I hope this post helps some of you.

i've been watching this over the past few years and this year in particular has seen a very steep rate of decline in solar output. solar minimum is due in 2020 but i believe we will hit minimum numbers before the end of 2018. both prediction scales have been steadily adjusted downwards all year. there is a lot of scepticism regarding solar output. some seem to view the sunspot count in the same way as tea-leaves and seaweed. the fact is, that solar output affects the stratosphere (i won't go into detail as this is a bit off topic). the last solar minimum was 2009, our last 2 coldest winters came straight off the back of that. frost fairs on the thames occurred during the dalton minimum. its certainly not 'mumbo-jumbo' as some might think...

Whilst watching the model output in the next few days, it would be worth bearing in mind John Hammond's updated Blog, updated sections in bold published this morning. https://weathertrending.com/2017/12/08/on-the-horizon/amp/?__twitter_impression=true

It would be rare for Hammond to go out on a limb too, so I expect the opinions of other experts are similar to his. I rarely post in here because I'm not an expert but I can reassure the younger members here that this winter has a long, long way to go. In 15 years of model watching it's rare that a cold spell is picked up beyond +180hrs and arrives as predicted. Watching each new output and reaching conclusions about the next 3 months is somewhat pointless and does not make for enjoyable or informative reading on this thread.

You might also want to look at Arctic summer snow cover, which was the highest for over 10 years this June and July, and the highest for nearly 20 years this August https://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=nhland&ui_month=8 Also Arctic ice volume which is still up if anything since 2011 http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/cryosat_piomas_awi_ts.2011.2017.Oct.png How can you be sure high sea surface temperatures around Svalbard aren't a release of heat (cooling), rather than a warming? Bear in mind that the North Atlantic at 0-700m depth is still the coldest for 15 years despite an upturn this year www.climate4you.com/SeaTemperatures.htm#North%20Atlantic%20(60-0W,%2030-65N)%20heat%20content%200-700%20m%20depth Not wanting to go off topic either, just trying to add some more pieces to the jigsaw in understanding how it's still possible to get severe cold despite longer term warming.

The transfer occurs at T264/T300 the remnants of the typhoon get into the base of the ridge at the very end of the run so the two are unconnected looking through the ens gives me the feeling that unless we see a sudden acceleration of patters, we are looking at the approach to new year to be of great interest - of course there is the possibility that the build of heights the other side of the NH just pushes the vortex this side further and further south which could see us becoming very unsettled/stormy under v low heights. I just don’t see a long spell of zonal westerlies/sou’westers

Yes Ed. I do believe we have something relatively concrete (Alaskan ridge) to work from here.

-9c this morn, currently 5 below. Bonnie sunrise, lovely pinky/purple light filling everywhere. Southern softie media has excelled itself again the last couple of days.. standard hysterial winter blabbering from them ???. Hints at a mild Christmas are disappointing, hope it all changes. Few random pics from this morn

Some pictures from Sunday and Monday in Ashridge forest near Dunstable

In the aftermath of widespread snow, the coldest day in 7 years and the coldest night of the year, are we in danger of treating Wednesday night / Thursday slightly casually? I still think further ahead the scatter is HUGE. When that happens it means (to me) that upstream signals are not clear cut and a number of permutations are possible. All to play for still and I wouldn't be surprised to see some cold operationals appear over the next few days: Scatter gun:

Most of the algorithms I’ve looked over keep it fairly simple: precipitation intensity over time period = rough depth calculation. I’m yet to see any model which introduces soil temperature feedback to calculate an accurate melt rate, and therefore a modifiable depth (assuming further snow was within the forecast) UKV has an experimental field [water_equiv_lapse] which tries to establish this but I wouldn’t say it’s conclusive, reliable or widely used within output. SB

@Tamara hints this morning that some members may be starting to view the models without blinkers on... obviously never any guarantees but using the 'thinking outside of the box' method, i'm expecting to see an improved version of this- at around day 10. if the models have a climatological bias, they will be playing catch-up as predicted background signals unfold. it should be stressed that to get to this pattern, we have to transition through a more 'zonal' pattern. the risk of course, is that during this transition, 'zonal' overpowers the meridional flow but with a weak vortex, this hopefully won't happen.

Clear and calm nights and surface cooling with enough water vapour in the atmosphere in order for saturation to occur at dew point. The more water vapour present the higher the the dew point basically. This time of year the surface cools quite quickly so condensation readily occurs at lower levels. More so currently with cold ground temps. A link for you https://en.m.wikipedia.org/wiki/Fog I hope that helps.

100% accurate i would say, it has a small patch of green right over my house, amazing accuracy

or whether the southern arm of the jet pinches the Alaskan ridge off allowing for a faster retrogression.

Not good news for coldies re the overall winter patterns, looking at the latest computer output from UK Met. What the discussions will be in their Ops room trying to marry this output with what we have had and the possibilities according to some on the longer range models we see would be interesting to be able to eavesdrop! https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/glob-seas-prob

How I would love to be proved wrong because the 06Z certainly does give some hope towards Xmas. As Nick says we need to hope this trend continues on the 12Z and isn't an outlier. Just add to Tamara I hope some of your comments were not directed at me. My approach to the models in this thread is simple. I comment on what the models are showing and how based on past experience they might be wrong.

All the proof we need, so as to really know that 'winter proper' is now well-and-truly 'underway'!

For' once a deep limpit canadian/alaskan vortex 'may' be a ball player!?? Thats an' obvious ACE card player. Trop/strat interfere'.. And key for vibrating the jet... And bullying the Azores hp. Loads on offer via n-hemispherical.. After the mild blip!! @butterfly effect

Looking at the latest MJO forecasts, disagreement between the GEFS and ECM, we've been in phase 7 then a brief entry into the COD. The ECM brings the signal out quickly into phase 7, the GEFS into phase 6 taking a few extra days to go into 7. However the GEFS has a large increase in amplitude in phase 7. The ECM a slight increase. The EMM which includes climatology has a big increase in amplitude in phase 7. For those interested we have a further MJO update out this evening from the Global Tropics Hazards outlook which goes into more detail. For newer members the amplitude of the signal is important: That's the GEFS so the further the signal is away from that inner circle the stronger it is. There are other factors that can mute out the MJO but you have a much better chance of a NH pattern change with a stronger signal. PS The COD which you often see referred to stands for circle of death! basically the signal isn't doing anything and won't have any impact.

Five new pages of posts since 10.00 pm last night? And no significant snow in the forecast? Something must be afoot.... Ah yes, a spell of milder weather awaits us just before Christmas.... This is how the main models currently depict the scene in six days time (18th December): UKMO ECM GFS GEM Reasonably good agreement that milder Atlantic sourced air will be on our doorstep by the 18th. Only the GEM appears not to be on the same page regarding the extent of the colder uppers pooling over Europe. This would be a predictable return to normal or should I say average conditions which are common in the UK at this time of year, and it is not unsurprising that the models are taking this direction. When the next cold spell is going to show, and how we get to it, is yet to be known but given the great start to this winter I am sure it just waiting around the corner, out of sight! My own feeling is that early in 2018 we are going to see another snowy event - most of the coldest events in UK weather occur in January after all.... In the meantime, for those enjoying wall to wall snow and ice today, spare a thought for the farmers and their livestock who cannot take a day off and still need to find food so that milk and other farm produce can be in the supermarkets when we look for it.....

In my opinion we haven't been seeing wild swings in the output in recent days. Actually the models have been consistent in bringing us a return to milder SW,lys. Personally I think members should forget about the predicted Scandi HP and focus on just what the models are currently predicting. The reason I say this is because even towards the latter stages of the GFS we couldn't be further away from an E,ly via a Scandi HP if we tried. If anything any future cold spells in distant F.I are more likely to come from a NW/N,ly.

Even at day 10 the Atlantic zonal jet fails to make significant in roads into the British Isles. Yes, most models going for a milder phase but the outcome for type and how mild still open to doubt in my thinking anyway. C

Intriguing from Mr Hammond - increasing number of models showing mild westerlies won't last. Let's hope the METOs super computers show some different to the last few GFS FIs. Anyway, another cold shot from the north on Fri could bring yet more snow and frost, and with about 50 percent of England getting snow over the last few days, and -13c all before mid Dec - that's pretty darn good so far in my eyes !!

EC Weeklies Week 1 (12-18 Dec) UK is under control by a Euro/Scandi low and an Atlantic ridge. Week 2 (19-25 Dec) UK is under ridging anomalies, with ridge extended well into Atlantic. Week 3 (26 Dec-1 Jan) UK is under troughing anomalies for the Inter Holiday period, with troughing across the Atlantic. Week 4 (2-8 Jan) Still troughing anomalies over Atlantic, extending over the UK. Summary: AO is rather neutral/slightly negative for Week 1 & 2, but goes towards a more -AO setup in Weeks 3 & 4. UK troughing on Weeks 1, 3 & 4. -EPO/+PNA present through to Week 3.

Mines going a treat

perhaps we need reminding that the low res gfs is, in effect, quite often a gefs member plucked at random from the previous suite. Never to be taken too seriously, whether showing blocked or mobile, mild or cold.

Tonight's ECM is one of those if only it were summer runs

Some Crazy looking NH profiles looking at some FIs on the GEFS - still v interesting model watching. A few Scandy highs and split PVs among them. some of the more interesting below

This Alaskan ridge is a banker going forward how it affects downstream is unknown we are now beginning to see more Atlantic amplification around day 10 (the 12z gem looks of interest)

Yes certainly better ridging from the Azores high.If this trend continued we could start to think surface cold under quiet conditions, especially away from the far north. No upper cold like we have just had but it would feel more seasonal at least with frosts,maybe freezing fog.

Morning all. This mornings GFS run holds back the full throttle mild invasion into the UK again. Looks like not giving up its cold hold without a fight, Chart below keeps cold surface flow at day 10 .

Key point indeed... and you'll notice today that teleconnective comments are absent because we await exactly what you ask for here - real data rather than forecast data. A few things we do know for sure - the GWO orbit is holding up and the CPC report on the MJO published today (it is updated each week) is quite bullish about the current renewed and observed MJO cycle and observed enhanced convection over the western pacific. The same report also suggests a slow moving MJO cycle from here, at the lower end of the expected rate of transition, so probably holding longer in the 7/8 orbit. We can also see from NH charts that a trough/ridge pattern close to the Himalayas is currently in place and is likely to provide a spike to east asian mountain torque in the next few days... a point made earlier by Masiello on twitter. We know we have an ongoing wave 1 moderate level hit on the vortex keeping it pushed over towards the Asian side with no great coherence to vortex influence currently on tropospheric patterns. We also have a fast climbing temperature over the north pole at 30mb - an old fashioned tool over on JMA that has always seemed to me a handy guide on the state of things over the pole for those (like me) who struggle to visualise the entire complexity of the many layers of stratospheric vortex activity. We know also that ensemble forecasts from both EC and GFS have swung in the last few days towards a flatter pattern, elimination of the mid atlantic ridge but also an increase in height anomalies to the NE. What more would I like to know tonight? I'd like to know exactly where the AAM budget sits... the trend over the last few days... and the actual situation regarding frictional torques. This data has not updated today. Conclusion? Today's bullish MJO report from CPC and visible east asian torque with associated lag has me firmly fixed to a strong belief in the return of amplification in the medium term. Lack of vortex intensity supports this. Tie into GP's key knowledge on composite data (something I have as a 2018 target to improve on myself....) pointing strongly at a Scandy ridge evolution on the back of the observed GWO orbit and current observed state of the MJO moving slowly through 7/8 and it seems a very good bet that this amplification will produce the aforementioned scandy high. Timing? Well - not for the first time of stating.... there's the thing. Lag impacts are uncertain - and I wouldnt want to make a timing prediction at this stage. Our atlantic is not being driven by a rampant vortex this year - indeed I am beginning to wonder if the vortex is going to remain weak for a sustained period now especially with IF tweeting about Metoffice sense of ongoing warming and disruption. A sluggish atlantic makes it difficult to predict how much westerly momentum might gather through next week. Are the models built around a westerly bias that may overcook this signal based upon "normal" climatogical impact of the winter vortex? The models continue (by observation) to underestimate the orbit and direction of the MJO - underestimating first of all the impact of the 5/6 transition but now equally underestimating the move to phase 7... and as such are they failing to pick up an amplification signal for Xmas week? Laying my cards on the table (admittedly without the data update today...) I think amplification will return more quickly than the ensembles are seeing following a short to shortish period of westerly influence of around a week.

When I got to T+240 I did think that FI would show that. Building blocks.....

Haha. Here's a pic of our disruptive snow from Sunday, it was horrendous!

Just a comment on the GFS continually suggesting snowfall in the next two days. The model (and every other one too it seems) thinks that most of England is currently under snow cover. They are wrong. It seems from a quick question on the SE regional thread that most of the M4 south is snow-cover free. This discrepancy is surely going to lead to errors in the localised modelling in the immediate short-term, as the models will surely be making wrong assumptions about temperatures in localities where snow is not actually laying.

Just had a quick peak at the GFS 12Z - and there is far more amplitude in this run in the Atlantic and Europe, as opposed to the flatter 06Z run.

Took these shot of frost growth from overnight..

I have an ice volcano in my birdbath. I assume that it's due to the water freezing at the edge first and so the only place for the rest of the water to go is inwards and upwards where it has frozen and exploded! Well I know what I mean and if it was at all possible for this techno-twit to post a picture........I would! ? Beautiful morning, though. ?

Above the snow line on Reigate hill...

Lovely morning after overnight min of -1.8C. Glad I don't have to venture out this morning onto the ice rink normally known as a road! The satellite image is interesting this morning and shows up the lying snow across the UK with Wales and the Pennines doing best. For our Region the demarcation line between snow or not can be seen roughly following a line just to the north of the M4 - although you can also pick out the exception - the high ground of Surrey. Also a north/south split in East Anglia.

Totally agree. We are really cold at the moment, renewed cold shot come weekend. I strongly suspect we will start to see different solutions developing during the week. Yes westerly/Atlantic influence is likely to come but how it comes and how long before more cold interaction? It’s been a pretty decent start to winter and more cold interest still to come before one needs to think about ‘westerly’ incursions. Let’s give it a chance at least to play out.....as this winter imo will have several chances of real wintry weather BFTP

Yes the blog is from 4 days ago, but he Tweeted a link at about 07:45 this morning stating he has updated it with the bits in bold. So the bold bits are from today. https://twitter.com/weathertrending/status/940490098197528576

What a night! We had very loud thunder cracks directly overhead as well as around half a dozen lightning bolts, I was really frightened and on top of that it was snowing at the same time and the light looked really odd in the snow! It looked like the air was about to catch fire. Its the only time I've ever seen that in my entire life! Snow is everywhere on the ground now.