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The UKMO & GFS are all alligned now with a potent Northerly bringing ~-8 air in, which moderates to -4/-7 depending on your proximity to the source of air- Then a slight subsidence of the cold which still needs to be finalised however the -5 line is unlikely to receed any further East than the central point of the country before being pushed back west as the NE / E flow builds- Post that 1 undercutter seems very likely, then some more atlantic influence could well bring so more widespread rain & snow with tricky forecasting parameters .... Optimal areas for snow- ENE & E Scotland transferring further south past day 6... Looking very seasonal- Stratospheric forecast in the 'means' now down to 2 M/S on the 00z GFS for 20th December indicating a high probability for a cold Christmas- to put this into context the climo means for christmas week ( ironically the least probable chance of snow in winter ) is 38 M/S .... very rare times - 1962 & 1965 Had December Warmings... *** Update The MERRA data which runs back to 79 indicates that the weakest strat zonal for this current week is Dec 81 @ a negative 2 M/S - hence why Dec was cold that year ***

Whilst the gist of the extended GEFS and EPS looks credible (+ve height anomalies centred Hudson Bay), there's any awful lot of white space across the rest of the Northern Hemisphere. Suspect that modelling remains too progressive w/r/t Scandinavian ridge demise, and, possibility that we will retain some weakish +ve heights to our north in the run up to Christmas. My punt of technical strat warming date would be 26th December.

12z GEFS 10 hPa mean is a heartbeat away from a technical strat warming event.....(closer than 00z)

The GFS is still refining the current situation at ~96-120 West & North which deliver better blocking ~144 Note the marginal changes here- New run on the right Note the height of the yellow 552 Line on the second chart V 06z top chart. What the model is resolving as we transition 144> 96 is the finer points of the long & shortwave pattern - The longwave pattern is becoming ever more amplified with increase in jet returning SW through Scandi & as that increases the force acting on the atlantic allowing it to bend further & further away from the UK. ^^ This is exactly why sliders often migrate south & west when we go from 96 > 0 in the models as they are reducing the NE component of the jet replacing it with increased SW component looping back around the High pressure Worrying about the 12z operational to me means that people have learnt nothing about models & their capabilities / nuances over the last 5 - 10 years....

Coldies can breathe a sigh of relief, according to the latest models, next week is set to become much colder with frosts, ice and wintry showers with snow in places..much better extended update from exeter too (at least away from western areas)...signs are good for netweather coldies!!

Guys stop panicking about the atlantic pushing through- * ITS A MODEL BIAS * Wait for another 48-72 hours & then see what it shows in terms of the block holding strong-

Hehe - you make me laugh. Not at all concerning for anyone who is reading the signals and understands what is going on. The growth of the Scandy High is the product of the MJO phase just gone, and until we get the interaction of frictional/mountain torque we have a short period of waiting for further enhancement. The fact that the atlantic makes an appearance is hardly a surprise given the fact that its December. From here on this image I would expect to see the high wobble a bit, but then be reinvigorated by the impact of the next torque cycle. Interestingly the "down" slide of the current pacific phase has become steep as westerly momentum is scrubbed out, particularly around 30N But to be honest AAM has sat so high, and I've been musing over that for many days, that a drop like this helps restore some faith in conceptual understanding of momentum budgets. But what goes down....must go up - and this leaves room for a decent jump back up in mountain torque in the next few days. Given decaying pacific wave at present this is likely to be a moderate event...but enough to provide the bump necessary to reinvigorate the Scandy High and draw it a bit further west. Timing is +/- a few days because it rather depends on the exact timing of the uptick in torques - but I'm expecting these within 72 hours and that would mean a strengthening of the pattern about 10 days later - so maybe Dec 18? From there it gets really exciting.... Ventrice plots suggesting another fairly strong MJO phase on top of a vortex event of good proportions. So - anything that happens next week in the run up to mid month is simply the breadstick prior to the starter....bruschetta perhaps round about Xmas

Don't know what all the worrying is all about especially as the ever reliable CFS is forecasting this for valentines day ;-). Already said to the wife roads will be treacherous so no fancy meal this year frozen pizza job I'm afraid.

Okay because some are still struggling.. the reason i'm binning the 6z GFS is as follows. 120hrs the low is a weak area of low pressure leaving the Eastern Seaboard 144 it's deepened fairly rapidly, (gfs left) note UKMO (middle) and GFS(P) (right) are both much shallower than the GFS at the same timeframe GFS 180, the low has deepened extremely The run then goes on to sit the low there and spawn secondary lows from it into the UK, blasting the block away as if it didn't exist. This is a very known GFS bias, one that does appear to show up on the 6z more than other runs for some reason. Lets take a look at the ensemble mean Yep, shallower and more inline with the ECM/UKMO/GFS(P). Control run? Also shallower. GFS op has no support for the rapidly deepening low nor does it have any support for blasting the block away the way it does so. So. A few of us aren't "binning it because it doesn't show what we want", we're binning it because it's unrealistic, it's a known and understood bias within the model and it doesn't have support from any other models. Hope that explains things a little better.

180 shows a nice snow event across the UK with energy moving SE - Wont take long before its all going SE - & the block will remain in Situ...

Hi, not sure how they work these charts out from over 50 years ago, but I remember the night of 19th January 1963. Think it was a Saturday night and the coldest I can ever remember from a wind chill prospective. I lived on the family farm in Cheshire and kept a weather diary. At 10pm snow was blowing about in a very strong NEly and noted a temp of 17f . My dad ran home from the local pub about 2 miles away and he told me he had never been so cold in his life. Before I went to bed , I had a bath and the steam froze on the inside of the window. No central heating in those days. The following morning a foot of powder snow had fallen with drifts of 6 feet or more down our lane. What a winter that was. C

Plenty of cold wintry weather on the way next week according to tonight's Ecm 12z ensemble mean..here are my highlights!

Many a time I say this - but always worth looking at the Jetstream profile forecasts, for idea on where low pressure may decide to position itself. Today's run shows a southerly tracking fairly moderate zonal jet for all of next week, becoming a bit more diffuse and erratic -shredded is the word as we enter the following week (but that is a long way off). The GFS 6Z run doesn't tie in with the profile - as it suggest a SW-NE position, no strong heights to our north - contrary to what the jetstream forecast is showing. The main player next week looks to be strong heights to our north east, the extent of height development directly to our north is key, there are signs a ridge could extend out from the main feature to our north and head towards Greenland, if this occurs, then expect a much weaker shallower low development feature which will attempt to encroach SW part of the country, but quickly sink into France - thus we will maintain a cold continental SE flow. If the ridge doesn't develop strongly, then the next plausible evolution would be heights to sink slightly SE into eastern europe which would open the door to a more concerted atlantic attack - but equally a set up dispositioned to trough disruption with heights building to our north and possibly NW. Either way, the theme of 2018 looks like continuing - no atlantic zonal onslaught, instead fine lines between something much colder and wintry, or perhaps akin to what we have now as we enter the run up to christmas. Longer term - further atlantic derailment and hitting the buffers looks very likely.

Actually thinking here that there will be two, possibly discrete episodes of ridging to our NE depending on the extent of Atlantic incursion on the back of this. The first being reasonably modelled but probably too progressive in its break down / eastward displacement and a second phase around the 21st - 23rd December.

Extended eps show a continuing trend of troughing over nw Europe and generally low slp over w Europe as a whole ....... if the block puts up a decent fight at the outset then week 2 could be a lot more interesting than currently looks likely as the lw trough disprupts in our vicinity

Ok lets evaluate.. In a nutshell.. Wave action..and forcing'momentum.. Have us firmly into the the notable sector!!!.. 10hpa forms are MORE THAN OF NOTE-as we gain and responces are forceful. @raw data situs..are also of wake up synops.. And have the momentus-evos at clear structure- pressure points. Taking the p-stamps at face value...and decipher the blocks-.. ! And formats are both terrific/significant!!.. As an overal assumption.. Thus... Raw data in real time...=ops/supports are fraught with miss align..'somewhat' -deception!.. But will engage-the outer forms as indeed WE GAIN-..and oceanic forces also commit!!.. Taster...coming up.... Full meal deal...2 follow.... Im salavating...right now!!. For phase and note...lets see where the gfs 18z suite...throws evo!!! Ssw..territory..being flagged!!! Edit..forget to throw the julien oc- in also.. 'Courtesy ecmwf'.... @of large note-...4 decipher.

Tend to disagree with this statement Nick. Mike Ventrice's plot shows increasing depth VP centred east Indian Ocean / Maritime Continent week 2: These tend to under represent anomalies in the week 2 range, so an increase in depth of the -ve VP anomaly is significant (and this increased from yesterday's plot as well). So whilst the RMM values might be weak, the angular momentum tendency signal will be increasing once more. The eastward propagation of this will lead to an increase in total AAM as well weeks 3 -4 through the Pacific. So whilst the +AAM signal through 30N will decay, new inertia off the tropics will hold up the global AAM budget to elevated Nino levels. The real fun and games start when that signal begins to decay, and should coincide with the MJO in phase 8.

I don’t know why folk are so downbeat....about a week ago most were resigned to weeks of Atlantic zonal mild be it from the models or or extended outlook. Now we have the expected much better outlook and already folk are breaking it down before its arrived. I expect the cold, I anticipate it to ‘relax’ a bit but not nationwide and then a resurgence of the true kind last 3rd of Dec. I could make a call to Darren Bett and arrange for 3000 mile SW’lies BFTP

Lots of worry over it not being cold enough.... -7c uppers , likely sub zero dew points (air sourced from east) and one of shortest days of the year ....

From a coldies point of view, the Ecm 00z ensemble mean makes very pleasant viewing!!..a much colder week than this week awaits and some of us will see snow!!

Gone a bit mad in hear this morning lol . Everyone chill out . We all know how the gfs can be very erratic , remember Ian f saying it a while back . The ECM is rock solid . Add to that the very good METO update . Winter is coming . ECM the pick of the bunch this morning and the UKMO looks a lot better than yesterday 12z . Ps - where’s @Spanish Dani gone

Morning all, ECM run certainly pick of the models regarding our hunt for cold. Remember in the post above sent this time yesterday , I did mention formation of a Upper Low showing over the continent .It looks like ECM has also picked this up as well and likely to move towards the Southern part of the British Isles with an associated area of lower 850 mb height temps. So snow starts to come into the equation for your part of the world from the period 168T. Its still along way off but our outer perimeter snow forecasting model may soon pick this up. Will talk to the experts later this morning with their updated single model run to see if the this threat is still an on going feature. c

To those asking where other members are.. could I request you send them a PM, or make a status update. Asking in here will generate replies and stray off of the desired topic. Cheers!

If you're a coldie which I assume everyone in the hunt for cold thread is!..there's lots to like about what the Ecm 12z shows for much of next week which is much colder than the current mild dross, windchill factor, widespread frosts with icy patches, wintry showers with snow in places and even some freezing fog where winds fall light...winter proper!!

GFS has a tendency to overblow Atlantic lows too much, so not sure I buy the progressiveness of the 06z op in pushing back the block and moving in Atlantic upper trough close to the west. 06z GFS 500mb heights profile quite markedly lower over the NW Atlantic than the 00z GFS and 00z ECM, with lower heights/deeper troughing meaning the Atlantic more bullish in pushing in from the west. I think GFS bias of pushing away blocks to easily at work here!

Yep - I'm never one to be pessimistic when it comes to seeing cold on the horizon....but it is worth pointing out that a really really special spell of weather in March was turned into a special one only, precisely because the extreme nature of the reversal had a feed from Siberia to Canada the wrong way, and it moved the block so far west so quickly that we got an unexpected warm undercut from Portugal that rather spoiled the epic party. It created some unbelievable scenes here in the SW where we had an inch of frozen rain sitting on top of 5 inches of snow....and houses were caked in the same frozen rain - but it brought that spell to an end around a week earlier than was expected. So we do have to be a bit careful when looking and predicting the impact of an extreme type vortex shredding event (assuming it arrives in the first place....) I think CreweCold referred to it in the strat thread as "buying a ticket" - we have certainly got a ticket here.....but we cannot be sure exactly what the show is going to be. Ideally we want blocking to the NE and NW to oscillate in between Greeny and Scandy under conditiions driven by the high impact tropical wave present at the moment and the impact of reduced westerlies and even possibly a reversal up above. But these are fine margins. A bit too much to east or west on that oscillation and warm air will be sucked in occasionally/regulary....and the atlantic will not go completely quiet in winter. So dont expect wall to wall cold. Be realistic and accept that all weather types are still on the table and likely at stages over the next 3 months. I'm clutching my ticket and hoping for the weather equivalent of Muse in Concert....

On the subject of missing members : Anyone heard from TEITS / The Eye In The Sky aka Dave ? Always valued his input, he loves an easterly so not like him not to be posting ?

Yes Daniel Just to assist any newer people more ( not sure if anyone interested ) Heres the FV3 156 6z V 12z ( Second ) Note pic 1 shows the atlantic pushing East & the cold air boundry moving back into the continent where as 12z the blocks more upright & the cold is held in situ as the jet is bent away from the UK

I hear that SSWs can 'knock us out' of a cold spell. However, I think what has to be understood is that this is most likely when we already have Greenland blocking running the show. SSWs basically set the (upper) zonal flow into reverse which means that if Greenland blocking has already taken hold, a west based set up becomes more likely (the high retrogresses even further). What we're seeing at the moment is a pretty perfect base for a SSW to occur as one would expect Scandi heights to become Icelandic-Greenland heights with time (reading between the lines I think this is what GP is expecting). Cold-cold, winter-winter. Allied with Siberian heights that keep popping up, we could actually be in the game for a holy grail set up where we end up with one big conveyor belt of heights transferring between Scandi and Greenland.

Hi Final location doesnt matter as much as the angle & spread of the advection ahead of it - in that respect 18z is better & slightly more amplified even though the low is slightly further East then overall scenario is that the run is more amplified - If you look close at 12z right v 18z left ive marked the top of the ridge ( 'the wave height' ) you will see 18z is further north ( check against faroe Isl ) & the allignment is more vertical plus atlantic alligned more NNE as opposed to NE S

Still perplexed by some of the doom and gloom merchants, on this thread. I don't know about anybody else's but my calendar tells me it's 5th December!! I'm 63 years of age and, as I stated the other day, only in a handful of those Decembers have I seen any substantial pre-Christmas snowfall, in my location of S.E.Lomdon/N.W.Kent. Notably 1981 and 2010. But on this thread, it's the same every Winter, a case of knee-jerk reactions, to every frame of every run. Or as the French would say, "Plus ca change, plus c'est la meme chose!! For pete's sake, RELAX. If come late Jan/ early Feb, we're still chasing favourable synoptics, then have a moan but its way too premature for some of the "toy throwing", that's taken place!! Regards, Tom.

anniversary of 'that ecm' today, Wed 5th Dec

Ah Stewart - I can almost taste your desire to reveal your Jan/Feb thoughts. Not seen you post this often in years. I'm not sure we could pick a better date for the start of a warming event than last week December given potential lag impacts over the following 60 days. The question is - will wave 2 warming shred it completely, or do we get a much weakened but displaced vortex under primarily wave 1 forcing? 50hpa vortex very stretched at the end of next week on the Attard plots Could do with a killer Wave 2 punch at this point. Current forecast perhaps not quite sufficient for that? Next MT cycle and pacific jet extension peaking circa 15 Dec perhaps to deliver this around 10 days later - hence 26 Dec?

ECM Is definitely the pick of the bunch today! Here is the snow fall by next Friday from ECM

Well well well.. GFS has effectively put the Atlantic on hold and told it to naff off, blocking further West and the first signs of energy disrupting South-Eastwards.. look at the isobars to the W of Wales and SW England.

Well 5/21 of the GEFS showing a technical SSW this morning, 6 if you count the one that just hits the line...the signal grows stronger.

Really surprised at some of the comments regarding the ecm those uppers from the continent will produce snow and temps just above zero for me a great start to the winter

In all fairness it is unusual to get uppers colder than around -8c, especially down south. Not every cold spell brings -12c uppers - you do not need them! -2c and a slider will deliver more snow than -12c and wishbone showers. Get the cold in first and then like Christmas, the surprises will show up!

Well sorry but thats not accurate at all..(imho) Here are the 850s from 192 onwards, add to that Dew points will be sub zero for most..

The evolution is very very plausible and anticipated. I will go further to say, any relaxation....which there may be but not nationwide, is to do with the shift to produce/ settle heights to North and NW with a potential serious winter outbreak come Christmas. I’m waiting for members to jump on my side of the fence as I look up to you...... BFTP

I’m going to be the person who’s trying to be level headed so here goes. We could be in a much worse position this time of year. It’ll be nice even if we get a chilly Christmas.

Ecm still sticking to it's more amplified guns in the mid term before agreeing with the other models on a return of the Atlantic. Very much along the lines of the meto updates. It is incredibly rare to get an extended cold spell in the UK during December, even during the classic winters. Any cold incursions tend to be transient in nature as it is just too early in the season. I'm sure I am not alone when I cast my eye to the end of December as there seems to be something brewing Some on here are miffed about the ecm at day 10. All I will say is look west - that is a very impressive high pressure cell being pumped up towards Western Greenland. I think it looks like a fantastic chart going forward. I said earlier in my post about transient cold spells. I should correct that - I actually feel that it will be the mild spells that will be transient in nature. I think cold will be the dominant player. I leave you with the ecm day 10 chart. Not so bad is it? Look west

Terrible language on Meteociel

ECM Op certainly joined the cluster we didn't want it to join then! I also see the "winter is over" folk have come running out of their caves in excitement over it, too! Given it's day 10 and uncertainty is still present as soon as day 5, I'm not too concerned re: what a single Det run shows, though it did have support on the 00z EPS.

ECm showing a big snow event @216 especially more N & E you go...

Actually day 6 ECM looks even better than UKMO with more Atlantic troughing heading se. with that evolution continuing at day 7.

The good thing about those clusters is there isn't any significant signal whatsoever for any strong heights to the south and any true zonality

That NH plot at day 10 is superb for wintry prospects .... the vortex has moved to the Asian side and the Azores about to pump up a another Atlantic ridge with upstream jet looking abject for the time of year and no Canadian vortex to invigorate it that won’t verify but the broad scale pattern is expected note that the gfsp goes awol with the undercut phasing too far north (eps cluster 30% yesterday so not to be dismissed) and gem is awol for the second consecutive 00z run one final thing that has caught my eye is gfs and gfsp end week two are both consistently generating a TS in the nw Pacific whilst it won’t be a sig feature, will be interesting to see it interact with the vortex over there if it recurves n ...... seen complete hemispheric splits from features like that acting as a a catalyst before

FWIW ECM raw maximums for London: Monday 10th: 7C, Tuesday 11th: 6C, Wednesday 12th: 6C, Thursday 13th: 4C, Friday 14th: 3C. A case of it getting colder through the week - by Friday it will bitter everywhere with snow in places.

120 144 UKMO makes a move towards EC!!! Winter begins next week..