SqueakheartLW

It is our own UK model so in theory it should be most accurate for the UK shouldn't it?

Now that all of the models that I can find on meteociel have got up to at least Christmas Day it would be a good time to compare them all here right now. I shall begin with the one that has the mild/cold boundary furthest to the north and work southwards. GFS 12z Op As is very typical of the GFS it is the mildest solution as is often the case. It would seem only Scotland has any chance of lowland snow here and with the usual "blow up the low pressure" too much scenario it often plays then this comes as no surprise CFS 06z Yesterday's CFS 06z seems like an age ago now and was a decent run too with easterlies from Christmas Eve right up to at least 6th January. Today's run is a lot less cold and has the cold air very much in Scotland again although with the boundary a little further south then far northern parts of England may get in on the Christmas fun. GEM 12z Very similar to the CFS 06z in where the mild/cold boundary is. Probably a similar outcome to the CFS here with snow mainly in Scotland. ECM 12z The ECM brings the mild/cold boundary a little bit further south than on the CFS and GEM although this is a downgrade for the ECM compared with the 00z run. Very much Scotland and Northern England in for the Christmas snow fun here. A bit too far north still for my area but at least a bit closer than the models featured so far. ICON 12z A very similar mild/cold boundary to ECM. The bit that makes this ICON better than ECM is the more continental SE flow ahead of the low which should bring in more surface cold/lower dewpoints which should increase the snow chances in the boundary zone. NAVGEM 06z Finally the first model that potentially has my area in the firing line for snow chances. With a slack flow and fronts stalled across central UK this means the Midlands and Northern England have the greatest chance of snow here. JMA 12z The mild/cold boundary is just a bit further south again here with the JMA. This puts the Midlands as a more definite snow zone now. Hope the JMA is the closest to the actual outcome for Christmas Day in terms of snow chances for my area at least although others may have their own preferred outcome in a different model shown here. UKMO 12z Finally and last and by no means least we have the UKMO. It is the most bullish for having a cold Christmas Day today and has pretty much the whole UK within the colder air. The snow threat is mostly in the south here and if anyone wants a south of the M4 event then they would want to pray that the UKMO is the correct solution.

That needs to head SE for sure but will it?

GFS even more over the top with the Atlantic low. Even deeper on 12z compared with 06z at 78 hours 06z 12z 965mb on 06z vs 955mb on 12z Unless something strange happens it would at this stage seem 12z is going to be even worse than 06z

Would be better still if the shortwave just didn't happen

Here we go then, GFS 12z is just starting to come out. Brace yourselves for the BIG UPGRADE

If ICON is right then possible snow for central UK for Christmas Day

Cold air coming south between 23rd and 24th on ICON 23rd 24th Looking good for fronts to collide with this cold but where in the UK is the question

The models usually do this. The default pattern is westerlies so if there's lots of uncertainty the easiest thing for models to do is default back to westerlies in their output. All the uncertainty only appears as blocked patterns are not typical conditions so the models struggle to nail down any patterns beyond a few days at most so anything beyond about 3 days at the moment is very much still up for grabs If we were in a default westerly setup and the background drivers all signalled westerlies then certainty in the output would probably be 10 days or more ahead.

Even though the GFS 06z looked rather poor it has to be said the real interest with the GFS is now starting to happen higher up. Maybe those who are downbeat by the 06z tropospheric output should see some of the 10hpa charts that the GFS is now beginning to churn out in the far reaches of the output. Even if the 06z has the right trend for the latest cold spell or cold fail the real interest and possible game changer could now be happening higher up. Here's the two best 10hpa charts I found on the 06z. P5 and P8 Could be prime winter time for mid January onwards if this gains more traction. After all February was predicted to be the coldest month and with an EP La Nina then that would most likely reinforce this signal. However been a coldie I would hope we can get a cold spell towards Christmas and up to new year as well as a SSW and a cold 2nd half to winter on top too.

Just to update everyone on what the ECM and it's ensembles are showing in terms of height anomalies through the lead up to Christmas Day as well as a snapshot of beyond this too. Christmas Eve Well if you are after a -NAO Christmas Eve you have got your wish here, all 51 options are a -NAO. What is important however is where the high and low pressures are located here. Option 1 - (Top Left) This one is very much battle lines drawn right through the centre of the UK with the cold air coming down from the north hitting the fronts and low pressure to the south. The snow zone here is very likely to be Midlands/Northern England on option 1 Option 2 - (Top Middle) This one is still battle lines drawn but with a different placement of the block and the troughs it is more of a north UK battle zone instead with more of central and southern UK in the milder air unfortunately Option 3 - (Top Right) This option is the southern battle zone option as it is clear the troughs are weaker here and the mild/cold boundary is clearly more in southern England here. Christmas Day Yet again 3 options on the table and like Christmas Eve they are all -NAO again. Option 1 - (Top Left) Battle ground continues through central UK in particular on this option with that weak trough in the south of the UK and no doubt a front stuck to the north of it. Cold and dry in the north, rain to the south. Option 2 - (Top Middle) Cold option. This option clearly shows the general N to S flow here with cold air flooding right down to the south of the UK. Snow showers a threat here, especially towards exposed coastlines. Option 3 - (Top Right) Southern battle zone. This one could either be a continuation of the southern battle from Christmas Eve or the central or northern UK battle zones pushing down to the south. Either way a snow risk in the south, fairly dry and cold elsewhere with a snow shower risk towards exposed coastlines Whatever option we get here it is clear that overall the ECM favours a cold Christmas Day with a snow threat somewhere in the UK depending on how things fall at the time Boxing Day Very much cold options for all 3 options showing up for Boxing Day but variations on a theme showing here. 2 of them continue with -NAO, the other more of a mid Atlantic Ridge option. Option 1 - (Top Left) Cold with snow showers a risk in N and C parts. The south could see more persistent snow from that small trough showing up to the south of the UK but risk is fairly small here Option 2 - (Top Middle) Generally just cold everywhere with a snow shower risk in exposed locations Option 3 - (Top Right) Similar to option 1 but the snow threat greater in the south as the trough is a bit deeper than in option 1 29th December (+240 hours) We are starting to see a general split in the ensembles here. Option 1 - (Top Left) Despite a -NAO here it is getting too far west based so things are turning milder again here with a general W or SW wind flow over the UK. This is looking like a general breaking down of the colder pattern and unfortunately this is the favoured option at present. Option 2 - (Top Middle) This is the colder option and has a potential snow threat to the UK too with that trough right over the UK in a general mean flow from Arctic regions but even this option has a more flimsy block and looks like it will soon become milder here too. 3rd January (+360 hours) We see a 3 way split in options by the time we get into the new year. Very much shows up how much uncertainty there is later on in model output and the differences in the options couldn't be so big as they are here. Option 1 - (Top Left) Back to normal, Atlantic zonality is ruling here as the +NAO returns and unfortunately it is currently the heavy favourite option to happen. Hope for a big shift in the output before this time. Option 2 - (Top Middle) A potential beast from the east precursor option here with blocking getting going to our NE here and plenty of WAA showing up just to our west too. Option 3 - (Top Right) Continuation of the -NAO but with southerly tracking jet stream and consequently troughs too. A potential snow risk on the northern side of these troughs. Least favoured option but is there so there's a chance anyway.

Wonder if this could be playing a part in the reducing signal for cold at present. The EP La Nina is getting too strong That is well and truly in strong La Nina territory now and isn't far away from super Nina territory now in region 1+2

This was today's 00z OP at the end of the run. A bit stretched out I must say A few of the 00z ensembles also caught my eye too

How does 25th December 12z GFS mean compare with the 06z 06z 12z Although the -5C isotherm at 850hpa doesn't look to have moved much it is the mean SLP that has altered somewhat with the pressure slightly higher to our west now could be the crucial factor that allows the colder air to come further south come the big day.

I know it's the CFS but who wouldn't want this stretch from just before Christmas Eve right until the 6th of January to verify for the cold especially but also the snow chances at various points throughout. 23rd December Christmas Eve Christmas Day Boxing Day 27th December 28th December 29th December 30th December New Years Eve New Years Day 2nd January 3rd January 4th January 5th January 6th January Now this is what I like the models to show for Christmas right through to early January. I'll BANK this latest 06z CFS run even though there's very little chance it will verify as shown but nice to look at.

Looks like P14 on the GFS is the first member to have a go at bringing the colder air in at +84 hours

You would think they would have realised this by now after 15 years and done something about it. Then again better to wait for all of the ensembles to come out and see what the average comes out at

Just a catch up from me. Had a look at the ensemble mean charts for GFS 18z and GFS 00z for Christmas Day It seems to be an upgrade between 18z and 00z as it shifts everything a bit further south 18z 00z Hope the 06z pushes things a bit further south still to put more of the UK in the colder air for the big day itself.

Just using GFS 12z 850hpa temp charts for my examples shows how much uncertainty there is for a potential snow event next Thursday 23rd. I roughly picked out 4 groups within the big majority of the ensembles that show a battleground of some sort 1 - The approximately Midlands battleground (Op, P12, P19, P24, P25, P26 and P29) 7 of 31 options This first group for me personally is the one I hope comes off as it has the maximum snow chances for my part of the country although others on here may want to pick one of the other groups for their best chances. 2 - The Scotland / Far N of England Battleground (Ct, P03, P05, P13, P16, P17, P18, P21 and P27) 9 of 31 options The largest cluster of the ensembles currently has the battleground further north around Northern England or Scotland but as these events have a tendency to correct southwards come the day then this gives hope that the Midlands is in the firing line when the time comes. 3 - The Southern Battleground (P07, P10, P23 and P30) 4 of 31 options You could almost call this the rare "south of M4 event". Now we know how rare these snow events are south of the M4 but if this cluster comes off then it will very likely end up a "south of the M4 event" and this would please a few coldies who live right down there. Couldn't correct any further south or we would all miss out entirely. 4 - Too Far North Battleground (P11, P22 and P28) 3 of 31 options These are very much the horror show options where the boundary between mild and cold is so far north that basically only Shetland has any chance of any snow here and this is a push too with some of these charts. Now we would definitely want corrections south here. The other 8 ensemble members The remaining 8 ensemble members were very much not applicable to the potential battleground situation. They were either mild with westerlies dominating or were under mild or cold uppers with high pressure stuck right over the UK.

Today's GFS Extended run Why only have one beasterly when you can have: 1 2 3 .... yes .... 3 BEASTERLIES for the price of ONE BOOOOOOOOOM !!!

Don't know if anyone had posted this yet but this doesn't look so promising as it did with that sudden collapse of the MJO back into COD territory. Is this the signs of the La Nina interference setting in now and over the next few days the rest of the forecast will also drop back to COD? No wonder the cold signal is reducing somewhat from the back end of next week onwards

I like the recent trend with the GFS runs in the last day Yesterday's 12z GFS Using just the ensemble average and the long term mean we see the mild spell to come, although with high pressure in charge it may not be as mild as these uppers suggest. The transition from mild to cold uppers appears to begin around 23rd on this run and the transition to colder is complete by 27th The change is from average 850hpa temps of a high of 6.5C to 7.0C to the colder -3.0C by the end of the run. Yesterday's 18z GFS Now this appears to be an upgrade to the 12z. The mild spell is still there but the main thing to take away here is how we have a more defined switch from mild to cold now and it takes place on the 22nd, an upgrade compared with the 12z which had a delayed transition between 23rd and 27th The 850hpa temp averages now drop from a peak of around 6.5C to now a new low of around -5.0C by the end of the run, a cold upgrade. Today's 00z GFS A slight downgrade on the 18z unfortunately but not by a lot in terms of when the transition from mild to cold is likely to take place. A definite switch around the 23rd. The 850hpa temps are the disappointment here as they have become a bit less cold later in the run, averaging at around -3.0C by the later stages of the run. Today's 06z GFS It would appear we have upgraded somewhat again compared with the 00z. The transition from mild to cold has come back forwards again to the 22nd before a well defined below average period now shows beyond that. The 850hpa temps are also a slight upgrade on the 00z too, dropping down to an average of -4.0C now compared with the -3.0C on the 00z.

Looks like good news for coldies overall with several members of the 12z GFS, 12z GEM and the last few CFS runs all going for colder than average from around the Christmas period but especially after Christmas. 12z GFS As can be seen here a fair bit of scatter but the trend is undeniable as we head from above average now down to around average near Christmas before the average line heads below average right at the end. Even better news is that the Op run was generally above the ensemble mean more or less throughout so we can take some comfort from that at least. There's some real decent looking cold charts by the end of the run however like these examples below The one thing they all seem to have in common is not beasterly but generally high pressure out to the W or NW nearer Iceland or Greenland so this is a very plausible evolution after Christmas. 12z GEM Just like with GFS we see a similar trend of declining 850hpa temps as we head towards Christmas and beyond and similar to GFS there is a lot of scatter. Hope we can remove some of this scatter and focus more on a definite direction soon. Some decent cold options within the GEM ensembles too. Unlike the GFS the GEM is more keen to give us a beasterly over a Greenland or Iceland high solution but which of these two models has it correct. Maybe we can go to the all famed CFS to decide the outcome. CFS - Yesterday's 12z, 18z and Today's 00z and 06z One thing I have definitely noticed with the CFS in recent runs is how all have pulled the UK high up to the north around or just before Christmas Day to various locations between Greenland, Iceland or Scandinavia. Friday 17th December CFS 12z CFS 18z CFS 00z CFS 06z All here are dominated by the UK high and although there are tiny differences between each run they all basically have the high pressure smack bang over the UK with about average UK temperatures Monday 20th December CFS 12z CFS 18z CFS 00z CFS 06z Although slight differences all of the runs are very much in agreement here for the UK high to start retrogressing and moving up towards Greenland and Iceland, preparing us for the colder air to come. Thursday 23rd December CFS 12z CFS 18z CFS 00z CFS 06z All of these charts look decent for cold lovers, especially if it is a white Christmas you are after. We are pulling the colder air in now and I would hope the most recent 06z is the closest to the correct solution as it appears to have the strongest block to the north. Saturday 25th December CFS 12z CFS 18z CFS 00z CFS 06z I won't be complaining at all if any of these options came off for Christmas Day. All are cold with northern blocking of some variety and snow is a risk on the majority of these runs on Christmas Day. Maybe yesterday's 18z the driest of the 4 of them. All 4 runs keep the cold and blocked theme going after Christmas for a short time at least but anything beyond New Years Day could be taken with a pinch of salt at this stage.

Happy New Year Coldies !!! Here's P24 from today's GFS Extended How's this to see in the new year. I'd take it BOOM !!!

How are we doing in regards to Christmas Day today on the GFS 06z as well as what the signals are for 384 hours away too to give us an idea of the trend up to New Year High pressure location Options for Christmas Day Option Members Percentage UK Based Op,01,03,05,07,12,13,16,21,22,23,24,27,28,30 47% SE (Euro) 04,06,08,09,10,20,26 22% NW (Greeny/Iceland) 02,17,18,25,29 15% SW (Azores) 11,14,19 10% E (Sceuro) Ct,15 6% NE (Scandi) 0% As you can see, a strong signal here for a UK based high pressure for Christmas Day so minimal chances of snow it would seem. As for location of the UK high it seems a position more to the SE is favoured with the Euro high signal a bit stronger than the Greeny High option. This would bias things slightly towards a milder than average Christmas Day unless we can get under an inversion This is how the model mean shows up and very much confirms the UK high signal too Now how does this compare with the signals for 384 hours away? High pressure location Options at 384 hours away Option Members Percentage % Change from XMas Day UK Based Op,01,02,05,09,11,12,14,19,23,24,27,30 41% -6% NW (Greeny/Iceland) 03,16,17,18,22,25,29 22% +7% SW (Azores) 04,07,08,13,28 16% +6% SE (Euro) Ct,10,21,26 12% -10% NE (Scandi) 15,20 6% +6% E (Sceuro) 06 3% -3% As before the UK high signal is the dominant one although less than before but is there any particular increase in signal for any of the other areas for the high pressure to head towards It would seem a Greeny or Iceland high is the favoured place for high pressure to drift towards with the highest percentage below the UK high option It is looking unlikely we'll end up with a Scandi High or a return to the Azores high even though their signals increase a bit. The average of the members very much reflects the uncertainty A weakened UK high signal as reflected above in the data but with patches of high pressure dotted around this very much reflects the uncertain picture after Christmas. The main thing to take away however is the reduction in the low pressure signal over the Atlantic which to me would mean a reduced risk of zonality as we end the year which is something coldies can at least put their hope on.