kold weather

Yeah, literally been on this site half my life. I waa 14 when I first started here, back in those bleak 00s year where even getting a below average month felt borderline impossible (we went nearly 2 years without one at one point!) @Sheldon Cooper keep at it as others have said, you maybe young but that doesn't mean your contributions are worth less, and indeed you may view things from a different point of view which may end up being correct.

Whats worth noting is just how much faster the models have been making this sytem. It was originally due to come overnight, now its basically clearing the channel by 9pm! Does make some sense since a weaker system will have less of a fujiwara effect with the main low and so will be more prone to swing faster and further south around that parent low.

Ends up giving 5-10cms to the far east of Kent. Have to say I didn't spot many attempts at that set-up in the ensembles from the 06z runs mind you. Far more were way north of the M4 for example than gave that set-up from the 12z GFS op. Still could be a trend, you never know.

I'd say that based on all the models/ensembles that I've seen the mean would be somewhere around that area. Of course the 12z suite may well change that, we will have to see.

12z GFS operational looks basically the same as the 06z, small area of snow for the far south. As I noted earlier, there is still WIDE range of options on the ensembles, I looked through well over 100 ensemble runs from various models earlier and honestly there was still plenty of scope for movement, though I do personally faovur a more southerly track, if purely based on history.

Yeah, the upshot though is that its a sideway sweep on Thursday, so there is alot more room for error compared to the set-up on Wednesday. So confidence is higher with that set-up at the moment thankfully, especially for the north of England.

I think regardless of any shifts, we aren't going to be seeing those amounts now! Just to note though, remember there is equal chance Thursday's shift eastwards. In much the same way as channel lows shift southwards, typically set-ups where fronts come down the country adjust eastward closer to the time. On the upside, they did a decent job with todays area of precipitation. Not saying that will happen, but one to keep an eye on...

Both years had northern blocking at a similar time of year, I may well be thinking of Feb 2005! Though Feb 2006 also did have similar flows to what we are forecasted to see: Neither were exactly that impressive, though March did end up pretty cold and at times snowy in 2006.

I'd not be looking beyond tomorrow anyway yet to be perfectly honest. Just to give you an idea on the ensembles just how much uncertainty there still is, here is two runs from the ARPEGE ensembles. I could find similar extremes from the ECM and the GFS ensembles as well: Yes on that second one its down in CENTRAL FRANCE. This is just 36hrs out and there is still a very wide range of option. Hopefully the 12z runs will firm up a little more, gotta hope in a positive way.

Its pretty borderline looking to me, the 850hpa temps are pretty tame it has to be said...however to be fair to Daniel SST's are higher than they would have been back in the 80s, so it may well be we don't need to go quite as cold to spark convection (though on its own its not all that impressive I admit). Less certainty but there does look like there is some weak wave action in the north sea that may help to create some instability in its own right, something the ensembles have been hinting at. Put the two together and I suspect there will be convection around. My bigger concern would potentially be the air just isn't cold enough. It looks to me like a wintry mix type set-up, where heavier precip turns to snow, but as soon as it eases back to sleet/rain. any settling snow probably for higher ground or overnight. The airflow as modeled reminds me of the Feb 2006 spell, plenty of falling snow but little in the way of accumulation apart from any overnight stuff.

Just taken a deep dive through most of the models and ensembles (35 ARPEGE, 30 GFS, 50 ECM, plus all the high resolution models) that we have access to and again only backs up my viewpoint that there is a heap of uncertainty regarding Wednesday. I can see why the Met office has kept the warnings up for now. The models may well yet shift north or south and there is enough within the ensembles suggest that this is possible. I'd say though purely based on the ensemble weighting the more numerically likely option is a shift somewhat to the north. Maybe not hugely, but more likely than any adjustment to the south. However its likely to end up being a nowcast situation anyway.

Look how fast it is as well! Thats WAY too fast. Its basically 3-6hrs ahead of any other model! Only one that is close is the equally far south Euro4. So we have an interesting battle here where nearly all the high resolution models are to the south, where as the globals and the ensembles are somewhat further north. I'd probably put more weight onto the high resolution, it fits with the normal southward trend and it should be entering their zone so to speak, however there is alot of uncertainty yet and I'd not feel confident until it comes onto the radar. I suspect UKV/Euro4 is too far south because of how fast it shoots it eastwards.

Well good luck trying to come to any conclusion about tomorrow evening from the last set of runs. 00z ECM op was on the southern end of the ensemble suite (most are a little further north at least) and a little weaker as well. 06z GFS op is pretty much inline with its set of ensembles - there are a few that go south, but more are to the north of the GFS op. Plenty of uncertainty from other models, AROME and Euro4 again are more on the southern end of the suite of models. In theory they should be reaching the time where they are more accurate but even they are prone to wild swings at this point in these types of set-ups where even small differences in depth of the low will shift it pretty drastically.

Ok so Wednesday will looks *highly* uncertain. On the face of it the nodels have reshifted back south again, and has sped up. Both things are obviously bad for snow chances. However the GFS ensembles on the 06z are basically all giving S.England some snow (might 1-2 runs that go south). The ECM ensembles also have a fairly decent percent that give some snow to at least the far south. ICON 06z also giving some snow to the far soth as well. Meanwhile Euro4 still remains totally on the southern edge of the suite for where it goes, so much to see. Its highly likely to come down to a nowcasting situation. I agree with others who say these things usually trend south, but it does remain to be seen...

ECM ensembles are all over the place out to 240hrs, there really isn't a huge amount of support for any solution in particular. If anything there does develop stronger agreement lat into the run for a more +ve NAO developing but that really can't be depended upon given how the stuff before hand is very up in the air. GFS ensembles on the 06z look a little more in agreement. There is a definate trend to towards LP attacking from the SW which at the least we will see some warmer air try to come up from the south, but lots of time for that to shift around.

I think that may have been in January 2006, I can't remember that well since nearly every cold spell form that era got downgraded to some extent I also remember Feb 2005 which at one point was basically modeled like those big 80s cold spells. Whilst we did have a cold spell, it was kinda like this week, very marginal. We did briefly tap into deeper cold and there was a somewhat ok snow event right at the start of March, but yeah, it was nothing like it was originally progged to be. Locally back in S.Essex I did quite well thanks to several Thames streamers that set in, and actually it had quite a long stretch where somewhere got snow in the UK, but it was most known for a terrible bust with a LP that came in from the north sea. The models quite widely went with snow, but the front came in weaker than expected and basically dissolved into a drizzle sleety mess - I remember being out in it and it was raw and unpleasant.

I'd also perhaps add late Feb 2006-Mar 2006. That had two pretty sustained cold spells and was on for a sub 4C month until a warm spell came along for the last week. (indeed it took till the 25th March to record a day over 15c showing how cold that first 20 days was. Interestingly it had the same CET as March 2018 as well. Though definitely not in the bracket of March 2013, I'd say for its bursts of cold it was still noteworthy, especially at the time, but its been rather forgotten as frankly, better has come along since then.

Euro4 has shifted a bit further north on its 18z for Wednesday: Its still somewhat south of some of the other models but its a decent shift up from the 12z, which at the same point was decently into the channel. I'd personally still like it somewhat further north, but its a good start.

Based on the airflow, my guess is that might be a snow-rain type event, at least for the SE/EA, its very good the further west you go though.

So just worth noting what @bluearmy said earlier today on the 12z EPS, there are a number of GFS ensemble runs that take much longer to break down the riding to our north to allow a northerly as per the OP. Some don't ever. So what happens on some runs is we ingest milder air, at least at 850hpa from the ESE, though for quite a few runs its temporary. Probably would be a fair risk of a snow event in that type of situation, though obviously the further north any area like that got the more a snow-rain risk increases for the south. However that really is out in lala land, lets get the 120hrs into the 72hrs range, still time for this to go very wrong, regardless of how good the background set-up looks at the moment.

Yeah we had a big snow event towards the end of Decemb er which almost served as a major primer. From that point the surface cold just stagnated further and further. To the point that like Dec 10, even in airflows that don't look that cold, it was frigid! I think at this point a reasonable worst case set-up probably would be the upper high being a little too close to the UK between 120-168hrs and then retrograding but not enough to draw in a proper cold feed. In that set-up we probably stay in a elongated easterly which probably will go northerly anyway once we get another trigger low coming down. Something like P21 on the GFS ensembles. It still remains cold throughout.

The key time period is between 96-120hrs. There is a little bit of energy that crosses to the north of the upper high, if it comes in too hot it could at the least delay the set-up a little (though I'l be honest given background conditions, it'd be a delay rather than stop) Of course if it develops once east of that area, it may in fact help to strengthen that high and speed things up.

Just looking through the first 10 days of Jan. Needless to say if that run was correct we'd be below 0c CET for the first 10 days, and easily the coldest at that time of year since the Jan 10 cold spell.

Looking through the 18z ensembles upto 168hrs and its fair to say that the op run is certainly one of the more aggressive runs with how it evolves the pattern. Some do keep the HP much close to the UK for longer, however nearly all have a set-up that will mean the HP will retrograde towards the NW at some point. My guess is that there will be some runs that take longer to get there, but I think most will, and pretty much all remain cold, or very cold. Also one word of caution, still ALOT of different solutions out there, they all go cold but I'd like to find some consistency first.

Probably be close to a sub zero first half IF the 18z came off. Of course the 18z is probably somewhat on the extreme end of the options. The parallel probably is more reasonable in terms of timings. As @Catacolhas just said, going to take something pretty major to shift out of the cold spell now. IMO the only real risk is whether or not this shifts too far west too quickly. So in a funny sort of way, the HP taking a little longer IMO reduces this risk a little. Given the background pattern we'd be very unlucky to not get some decent northern blocking. Whether or not the HP will hang around a few extra days eventually is not going to make much difference, and will keep us cold regardless.