Met4Cast

Better mean at 144, block is more expansive and slightly further south putting more pressure on those lows. I honestly wouldn’t be surprised to see the slider lows correct so far south they miss the UK entirely..

BOOOM. Best run of the season so far by a country mile.

Being picky this is ringing some alarm bells 12z det at the bottom end of the envelope by boxing day but still a fairly significant number of members remaining on the milder side through the Christmas period, perhaps a little more compared with the 06z run.

Will never understand this forums of shutting down threads just because there's a lot of pages, don't see what difference it makes but there we go. 12z ENS are an improvement, more amplification on the high and a better NW>SE alignment of the energy in the Atlantic. With the UKMO shifting towards the ECM (albeit not quite fully making it), momentum towards a cold and potentially snowy Christmas period is picking up.

KA-BOOOM! Hello there, 12z GFS..

It’s a figure of speech f f s. The trend is going in the right direction, anybody unable to see that/not excited about that really should get a different hobby.

The latest update from the Swedish Met is well worth a read, very bullish on the idea of blocked conditions continuing into January with an increasing influence from southerly tracking low pressure systems, seems they're also going with the ECM. Far more bullish than the Met Office would ever be. Tonights EC46 update will be interesting to see whether we see a continuation of Mondays forecast, Så blir vädret i december och januari - Klart.se WWW.KLART.SE Vinterkylan kommer tillbaka lagom till jul och nyår, men hur kallt och snörikt kan det bli efter det milda vädret denna veckan? Nedan hittar du väderutvecklingen vecka för vecka hela vägen fram till mitten på januari.

Expecting all the ensembles to agree 8-9 days out will always lead to disappointment

Are we looking at the same suite? - Increased number of members going blocked/cold - Less Atlantic influence There’s lots to be excited about, all trending in the right direction.

If I had to put my neck on the line this is what i’d suggest; - Turning much colder Christmas period - Low pressure attempting to move in from the SW will fail, cold air will win out - Wintry in the east - Potential for frontal snow S/SW as lows slide underneath the block Christmas > New Year Less cold air will eventually get into southern parts of the UK, colder air most likely clinging on further north, i.e further snow risks. GFS is probably wrong re: collapsing high, ECM closer to the mark but probably too extreme in terms of the block.

Bit of an uptick on the latest MOGREPS with an increasing signal on that model for low pressure to begin becoming more influential to the south-west. Albeit notice the split in 2m temperatures, some bring milder air in across southern counties and some disrupt the low and keep the cold air in place, the colder ones could be potentially rather snowy.. Heck of a lot of uncertainty going forward into Christmas.

Likely having some impact on the MJO area which is why models are struggling, ECM should in theory have a better handle on it. The block hasn’t collapsed yet, it’s currently sat over us, models are just trying to resolve a few complicated drivers hence the wild swings between outputs.

Subtle changes towards the ECM in the shorter range, this is what the GFS does, it’ll rarely switch straight over but inch over run by run until the momentum tips. ECM I would argue is on the extreme end of possibilities, but can’t be rules out.

Ensembles for the north: Ensembles for the south: Note a much wider spread across southern areas vs a more tightly packed ensemble for the north. The milder members make more of the lows coming in from the west, the colder members are more disrupted and slidey. Until models resolve exactly where the high goes, looking into detail re: 850hPa temperatures is a pointless endeavour because much of that depends on how the lows disrupt against the growing block of colder air. Disrupt further south = Colder, but frontal snow risk less Disrupt further north/deeper low = Wider snow event for northern areas, less cold air into the south.

The ECM ensemble trajectories paint the direction of travel rather well, moving increasingly towards a -NAO with Scandi block regime, perhaps moving towards a Scandi low/-NAO later in the period. I.E. UK/NW Europe becoming increasingly cold. ECM mean at 192 & 216 showing the increased signal for slider lows underneath the ridge to the north, models struggle on how to resolve this energy so expect further swings in outputs going forward. Any cold/snow lover not happy with these charts probably needs to significantly lower their expectations, we're in a very good position.

You can see the increased spread towards Christmas on the ECM ensembles across the south as they tried to resolve how far north any Atlantic influence will get. Members that send the lows further north introduce milder air, further south & they stay cold. Lots of uncertainty.

Lots of "booms" and I tend to agree with them. The broader picture of the ECM, UKMO and GEM are the same (UKMO pick of the bunch at 144 for me), high pressure becoming increasingly amplified towards the Christmas period with much colder air undercutting the high. Now.. specific details re: snowfall, low pressure tracking, exact high placement are all up for debate and will produce very different surface conditions. A 200-300 mile shift south of the low on the ECM for example leads to heavy snowfall piling into eastern/SE England over Christmas. A shift further north pushes the less cold air further north. These are tiny changes in terms of the entire global circulation so given the timeframe we're dealing with here, it's pointless to ride the up and down rollercoaster if one run has -10c and snow over your house and then the next run has 2c and rain. Tiny shifts in the overall pattern lead to big shifts in the weather we see above our houses, until the broader pattern is resolved, these micro details will continue to change. What do we know? - It'll turn increasingly cold across the UK leading up-to and over Christmas - High pressure will amplify northwards, most likely towards Iceland/Greenland The trends today are very, very good, despite a very underwhelming 00z set, todays runs have trended back towards the colder solutions. Get the cold in, snow will follow..

Pointless even looking at that kind of detail given the huge scope of solutions still on the able, the low being a little further north would make a huge difference to how far south the coldest air is - Models will not be handling the split flow well, it's essentially showing a retrogressive pattern against climatology, models are trying to resolve the impact of the typhoon on our part of the world & how the jet splits over the Atlantic. People should only be looking at the broad picture, not whether or not -8c 850hPa is sitting above their house, far too early for that detail. I agree..

Far less Atlantic influence overall on the 06z mean compared with the 00z. ENS certainly a shift back towards more blocked conditions, but with such wild swings between the outputs it's very difficult to pick out a single in either direction. This run should keep some happy for now though and perhaps settle some nerves.

Improved ridging northwards on the 06z mean so far, be interesting to see the full line graphs in a short while, would expect to see a shift back towards colder solutions. I did tell you to strap in.. this is going to be a bloody nightmare to forecast/predict.

Baring in mind models underestimate blocks & overestimate westerly momentum at longer lead times, I think we should dampen the cause for concern at the moment & turn off the big red flashing lights until we have more data.. Steady now.

Absolute beaut of an inversion next week. Always odd to see temperatures increasing with altitude rather than decreasing.

A few comments re: seasonal models posted here a short while ago. It's entirely possible they are still factoring in a more central based La Nina during the initialisation, hence the more typical La Nina prediction of a +NAO/+AO during the second half of winter. What we're actually seeing is more of an east based La Nina developing, this combined with the -EPO/-PDO tends to favour a slower, more blocked jet stream during the later part of winter, so it's not necessarily all doom & gloom. Having said that, the MJO looks likely to become less influential during January, before that though we're looking at 14-20 days of blocking potential from the 22nd onwards. Huge shift northwards on the latest EPS..

The SPV still needs to be fed into the forecast so the model would never "ignore it", but in forecasting the disconnect you'd expect to see models suggesting a slower tropospheric pattern overall, i.e no trop vortex which is broadly what we're seeing in the NWP outputs anyway. That's not to say a disconnect = bitter cold and snow of course, it just means the strat at least at this stage and potentially going forward isn't running the party so to speak.

"Locally mild" Honestly baffled by that forecast. The EPS suite is showing a very clear period of below average temperatures within that forecast period above. I know the Met often sit on the fence and don't tend to actually forecast much beyond complete vagueness at that range, but that's taking it to the extreme even for them.