SnowBallz

I could be wrong here, but doesn’t earth.nullschool just use the raw GFS data to produce wind vectors? I usually see it being used on various news channels whenever there are gale force winds, and they often mislead by presenting it as live data. The only live data I know of comes in from a network of monitoring stations.

Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and major private infrastructure will begin a daily briefing cycle as of tomorrow. To revisit previous post, latest MR output (MOG) resolving to further mute ‘breakdown’ scenario; with continental blocking signal reinforcing through well into March. Atlantic incursions are expected with southerly deflection; considerable potential for extensive and disruptive snowfall as these air masses interact. Short term, ECM:UKMO evolution favoured and considered likeliest; corresponds well with other products and illustrates fair consistency. Small ramp. Next week = mega. SB

I think BA is simply reinforcing the point that it’s not really worth attaching too much credence to current output, where there is clear inconsistencies being exhibited. It really is more about broader trend and the eventual path, whereas the journey to get there remains fluid and undecided. 12z EC could correspond with its peers or it could reinforce its 0z signal and advertise a more subtle path. What I would strongly disagree with, is NWP assertion of a quick return to mobility (or milder weather) That evolution doesn't correspond to mid range products at all, and can quite confidently be discounted as models reverting to type and to some extent underestimating the degree of in situ blocking. This behaviour has been seen previously so reasonable to view a rapid breakdown with scepticism. What an exciting end to winter! SB

I obviously can't speak for Ian, but I'd suggest he's referring to the point in time where there is currently considerable divergence and the general thought is that this is due in part to the models acting upon SSW influence and increasing entropy values. Not certain, but it's a reasonable position. Naturally, as one progresses through time, you would expect convergence as depth of data influences the direction of travel with attentive entropy moderation. I'd still wager on a colder synoptic developing - I don't think the question is so much about that - it's more the degree and duration which retains uncertainty.

And that is a key point which can be overlooked when SSW’s come into the mix. There isn’t so much a guarantee of colder weather, merely a statistically higher chance and which of course is still sensitive to many influences. To some extent, this explains why SSW events also broadly correlate with mid range NWP output displaying higher variance, or at the very least struggle to demonstrate consistency. As things stand, the house is very much in our favour. I wouldn’t necessarily pay too great attention to when a run defaults to benign or mobility, as the warming effect isn't really showing its tropospheric influence in the 10+ day range to the degree which we know it would. That is where meteorologists have to use more than mere computational output, and also where the biggest focus has been of recent years to tune mathematical modelling within GloSea in order to influence that judgement. Some might view this as pessimistic, but shouldn’t. Uncertainties around an outcome doesn’t make it unlikely to happen, it just retains it as a possibility. But within the context of probability, the likelihood of the SSW not bearing significant influence is the least favoured outcome. That’s a strong position to be in. To use a dice analogy, with an SSW to get cold we maybe only have to hit odd or even numbers - not guaranteed, but fancy our chances; however, without it, we must hit boxcars. If we look at trends, and specifically touching back briefly on my previous post, all evidence still resolves towards continental blocking patterns establishing latter part of the month with evidentially plausible continuation into March. Big, repeating and in some parts amplified signal for that. So, no guarantee but good confidence. The daffodils won’t know what’s hit um! SB

Indeed. Stark correlative response from stratospheric influence. This is an interesting one as GS usually ranges a warming signal circa >20 days, so immediacy is unusual which is influencing CF’s confidence re LR synoptic. What is without question is that there has been some quite remarkable perturbations, and strongly balanced towards a very much colder pattern. If downwelling is as rapid as is being considered, it is plausible to see large scale continental blocking patterns dominate for quite an extended period, and very conceivably into meteorological spring. Should see some interesting runs this week, that’s for sure! SB

Ha! They're booting Hall 1 up (fire was in Hall 2) so feeds should hopefully be back online by this evening, tomorrow morning at the very latest

Which is a very fair assessment. I touched on a few days ago that various products were resolving towards colder outcomes and whilst this broadly remains the case (some moderation in parts, albeit not material) the key uncertainty remains around timing, which I believe is what Ian is also keen to emphasise. In my view, some products appear to accelerate transition towards mobility faster than others, and in a blocking synoptic such as we see it is often wise to take a step back and consider plausibility; is it really likely that there will be sufficient energy within the Atlantic to displace an anchored pattern, or is it more likely that the incumbent synoptic would amplify and deflect (hence reference to advertised battleground scenarios) Very interesting output at present and there really is no strong reason to call any particular outcome. If you're a coldie (as I am) there is plenty reason to maintain interest and see where the models begin to favour with confidence. SB

This. For me, it's a case of micro and macro analysis; I personally find trends are easier (ha!) to identify and analyse when considered within a wider gamut, otherwise I find that you can become lost within the noise and data scatter of intra-run variance - something which I pay little close attention to. There are various techniques which can be adopted and one of those is time benchmarking (comparing 12z to 12z, etc) Lastly, GFS gets a fair bashing on here, but what I would reinforce is that its output is absolutely considered within MO, albeit within the context of holistic NWP output; it isn't the case that it is ignored, more that its output is considered against other more locally sensitive products. WRT such products, without dangling any carrots, there are signs of some confidence around a colder signal - but the timing of this remains less certain. Again - and to reinforce the analytical approach - this is something of an emerging trend, and is probably better described as a moderation of confusion, following a period where no particular outcome held greater confidence. I wouldn't go buying sledges just yet, mind. It is vitally important to see whether such an aforementioned trend consolidates in future runs, or whether it remains rogue and undecided. As a coldie, I am obviously favouring a colder outcome! As you were... SB

2nd this Please keep posting, @DIS1970 I find this a very inclusive forum (I recall how members have supported a couple of other posters over the years, which was nice to see) Quantity does not always equal quality and a pithy comment can be of equal value to that of a thesis! As John says, best wishes with your continuing recovery.

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

That isn't strictly true, John. Whilst you are correct in respect to how thermodynamics are considered primary drivers in NWP, various other factors and variables need to be introduced to account for regional variation and idiosyncrasies, in order to improve accuracy. The difficulty, is that the layering of variables increases error rate by an order of magnitude, and therefore models require tuning. It has been observed many times over that some NWP models are predisposed to resolving certain patterns or outputs more favorably than others, and there is no real explanation other than how the underling mathematical weighting has been written. Does that constitute a bias? In terms of its output, possibly - but it is entirely intentional, and in any event anomalously recurring patterns are generally synthesized out (ensembles are particularly sensitive to this) SB

I think people are subconsciously managing their own expectations, as well as that of others. Many observers on here have years of experience and have literally analysed thousands of model runs, so it's an informed and reasonable position to take, in my view. The earlier GFS run was, as others have noted, quite exceptional. On the balance of sheer probability, it is more than likely that the outcome will at least be tempered in the 12z's - but the question really is, to what degree. But yes, I agree that there is some background signals which do - to more or less of an extent - support cooler phasing, so the evolution witnessed on the 6z's shouldn't necessarily be discounted out-of-hand. In my view however, and again in that of many others, it is a little bit extreme. Definitely one of the more exciting 12z's coming up, because if it's anywhere near comparable with the 6z's, then eyes shall definitely be raised

Indeed, not so much an outlier but very much a member with little support. What's most evident for me is a couple of things: the level of noise within the signal into the new year, which is clearly dispersed across a wide range of outcomes, and secondly that the mean - whilst acknowledging the noise - does actually trend downwards. I think we'll see a moderate cool down, but nothing notable as such. Sledge remains on stand-by

I have to admit, space weather isn't my forte! Leaves me very Some intriguing signals popping up in the seasonal modelling; I wouldn't say it's decidedly different to previous, but more a meander towards something perhaps a little cooler. Whilst that is no doubt something to observe on the horizon, there is very much more immediacy - and focus on - our current dalliance with the wet stuff.