Joe Levy

The fact that all the models today are even showing a chance of wintry weather in the short term is exciting enough for me, but perhaps living in snow starved Exeter has informed that... None of the models are showing anything I would call rubbish this morning. The prevalence of high pressure is extremely promising since that should mean we won't get the same degree of flooding nationwide as last year. However, where that high pressure sits will make a huge difference to our weather, which is even more exciting! Place your bets now people...

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=188&y=179 It is pretty irrelevant me pointing this out, since the details change so frequently, but I am intrigued at how far south the snow risk extends on the ens. Whether or not it transpires in this manner ultimately, November snow in the far south of England is undeniably unusual, even if it does occur from time to time. A very cold set of ensembles and I notice that in the North of England, the mean is a rather bitter -8 for a fair while! http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=254&y=2 A cold set for the whole country. Just one set, but interesting nonetheless and I am intrigued as to whether this will be reflected in other runs and models or whether in fact it is an anomaly.

The 18z seems to be reflecting how uncertain the forecast really is at the moment. We can be pretty sure it will get colder, but how much? It would be marvellous if a chart like this became reality, but given how different it is to some of the charts we have seen today, it's anyone's guess! It's all good fun guessing though and if this sort of weather came easily to us regularly, we would not have nearly as much fun following these sorts of charts in my opinion!

It has taught me to never taking anything for granted weatherwise! I pride myself in not having an opinion on what will happen to the weather over the next few weeks, as from my assessment of the model output and different people's theories, I can see quite plainly that noone actually knows what will happen either, which tends to be normal with the weather lol! It is fun to speculate, but I am not prepared to tie my emotions to the pretty colours of a cold chart haha!

I completely agree with you. One of the key problems is that we instinctively look for absolutes. We want definitive answers to questions that do not have definitive answers! I remember how pleased I was that March was so cold, and when that enormous low looked like it was going to hit the South West, it was very exciting indeed! But a slight alteration of its course completely changed that and we got almost no snow from it in Exeter! So even if we do get cold synoptics, that does not mean we will be lucky with the specifics. Equally in reverse, not so cold synoptics can bring surprises. Last October, late in the month I believe, higher parts of Somerset got up to 3 inches of snow because of evaporative cooling and a cold surface flow on the back edge of a weather system.

See this sort of thinking is exactly what is needed! Long term trends carry more value than small details when we are looking at anything after t72. We can start looking for wintry specifics when we get nearer to the time, but right now things are heading in the right direction. But that depends how impatient we are!

Thanks... I think I've never been compared to anyone's wife before!

If anything, the fact that the models keep changing is reassuring, as it shows that a pattern shift is under way, whatever that may be. I suppose it's quite fun to think of all the different runs and charts as parallel universes! The further out from the present you go, the more vastly different the options become, because small differences now mean big changes later! It is these small differences that are currently evolving that are giving us and the models a headache!

But the BBC would be much wiser to wait until there is greater consensus and consistency in the models, a piece of advice which we should all pay heed to as well! The model output at the moment is not great for cold, but it is not dire. We are not talking a bartlett or wall to wall zonal. I wonder how people will then react if we get extremely cold charts tomorrow, and then less cold charts the day after... will they forget that this day ever happened?!

Regardless of specifics, which are nigh on impossible to predict, it is the re-occurrence of charts like this that explain my optimism. Clearly the models want high pressure to form somewhere in the North Atlantic, reflected in the height anomaly charts. It's where exactly that makes the difference. The issue is that tiny details can overcomplicate matters and so this is why trend spotting is a more intelligent idea rather than losing all sense of reality every time a chart is not so good for cold, or equally if it is fantastic for cold. We must use our heads and our experience!

A chart cannot have optimism. It is how you read it that determines whether it seems positive or not. The general theme of building high pressure further north than one would expect for the time of year means that even if this particular event does not bring bitter cold to the UK, it still presents opportunities further down the line. Given that many people on here are finding optimism in the current charts, it is possible to be optimistic about them. I suspect that we are all inflicting our own wishes on the weather, which is really out of our control haha!

My view is that if things have so dramatically changed in the last 12-24 hours, we still have several more periods of the same length for things to dramatically change in either direction! So don't despair because of today's runs - see what they do tomorrow and the day after etc. until we get to a time frame where we can have a little bit more certainty! The modelling of shortwaves that appear later on will also be crucial, and many of them won't have been picked up yet.

So synoptically, to my eye the ECM looks a lot better, but then we have the issue of uppers, which are not nearly as cold. However this is a detail that could and probably will change, like everything else!

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=186&y=177 These are the ensembles for Exeter. The scatter of the ens is quite substantial during the period of time when cold weather is most likely. Some only dip to about -1/-2 while others dip as low as -8/-9 which makes a huge different in the kind of weather we will get, especially when there is forecast to be precipitation about. I suspect that many areas of the North are fairly certain to see something wintry, the area of contention though is at what elevation and how far south will the effects be noticed. The time is drawing closer and if anything I am less clear on what I think than before!

Yes that's a good point! Also I keep forgetting that many of the major developments are still 4-6 days away and in forecasting terms a lot can change in that time! Last winter was testament to that for us all...

Do you think this is a good or a bad thing? I mean clearly we want the high to be propped up sufficiently if we are looking for any wintry prospects, but at the same time we don't want the high to topple. Would I be right in saying that there is a fine balance here?

If I was going to create a chart that had as many different types of weather as possible this would certainly be a candidate! There are sliders, a strange high clinging to the coast of South East Greenland, a northerly from a section of the pv and the western edge of a Russian high. All we need is a hurricane and this map would be complete...

So now at 144 we have three different solutions... but ukmo and gfs are a lot closer to each other

I thought I might have a crack at being the first to comment on the 0z gfs output at this ungodly hour (essay writing for my degree...). Considering how close we are to the actual beginning of this cold snap/spell, it seems remarkable how different the 0z is to the 18z. Firstly, as is noticeable in this chart for 144 hours, the very cold uppers never make it very far south and as a consequence wintry precipitation would be very marginal. I am personally not convinced by gfs at the moment. One moment it throws out a very cold and snowy run, the next it throws out a quite cold and wet run. Be careful about being too excited but also be careful about being cynical! This period of model watching is showing how small differences can exaggerate consequences in our weather the further into the future you go! I shall reserve my judgment for the exact nature of this cold weather until it enters the 72 hour period. http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=187&y=176 Rather annoyingly, in the crucial time period for cold weather, the spread of the ens treads precisely that fine line that can make the difference between snow and rain. These are for Exeter by the way, since that's where I live but also in the South West where gfs has been indecisive about precipitation. Some of the ensembles on -6 850hpa would be more likely to produce snow, but one or two are at around -2. These are in the minority but in any case it will be a case of looking out the window next Tuesday and Wednesday, not staring at the ens as I am now!

It's not that clear cut. It would struggle to sink easily given that the euro trough is still being fed by splinter lows (not sure of the technical term) that keep undercutting the high

Also the angle of the high is notably different to the same time frame on UKMO, even if it is roughly the same shape

But that may be because on the previous run (at least on meteociel) the time after that is about 12 hours ahead. Too early to say for certain

The snow was very heavy at one point and settled readily on the grass and some other surfaces, however now that the rate of snowfall has dropped, any lying snow has melted very quickly

Stopped snowing here, but judging by the radar it's only a brief respite, as the next blob moves towards us! EDIT: aaaaaaaaannnnd it's starting again...

Same here in Ealing! I was only expecting a few flurries today and maybe a temperature of 4C, but it feels much more wintry than that!