Joe Levy

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=187&y=178 (South West England) http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=234&y=1 (Northern England) A bit more agreement on next weekend amongst the ens, trending colder than the 0z. There is considerable scatter after that point, however there is not much in the way of prolonged cold until much further into FI. In spite of this, it is worth remembering that all of this is still quite some time away meteorologically speaking, so there is a lot of time for change.

I think I didn't communicate myself correctly! Basically I am trying to simplify what you have just said! But my understanding of thermodynamics and physics is limited so perhaps think of a shortwave as many many specific "circumstances" as I called them. My point is more that tiny factors can change a lot and so in spite of what is being shown now, the outcome could be very different indeed.

We will, inevitably, at some point get a westerly this winter. It could be after the Northerly that is predicted for next weekend, however not necessarily. I could be wrong, but if I remember correctly a westerly has been progged several times in the last few weeks and I must admit, the outcome has been far from mild, at least in how it feels outside. The models' different versions of events rely on a specific set of circumstances occurring and the further from the present we get, the more those specific circumstances result in huge deviations. However, if one of those circumstances suddenly changes, such as the positioning of a short wave, or the angle of the jet, then it can change completely. So we may lose our Northerly for next weekend, but if we don't we may also increase the chances of prolonging cold. This is why model watching is always interesting because just when you think everything is set in stone, something slightly changes and the whole pattern starts altering in response!

I couldn't help but chuckle to myself reading this. I was thinking the same thing when I saw the charts, but only you could express it in such a fabulous way!

Anyone who has ever studied geography and tectonics will know that continental drift can mean something completely different if we need tectonics to get cold air then we have no chance...

Clear skies and long nights, combined with cold surface air and snow fields in places means that frosts will be inevitable. Obviously clear skies are needed for this to happen EDIT - Glenn for some reason it didn't quote your whole post but I hope you get what I was directing my remark at haha!

That was a very good run of the ECM and more than I would expect at this time of year. As a child of the mid-late 90s and early 2000s, 3-4 days of cold would be mega long in my books if it were not for the last 4 or 5 years, so these charts are exactly what I am looking for this winter! Even in the last chart there is long term potential as high pressure ridges into Scandinavia

The wintry weather continues at 192 hours! Lovely!

A lovely cold northerly with -6 uppers covering the whole country and -8 uppers just touching the south coast. This is exactly the sort of chart us coldies have been hoping to see maintained in the charts

Yes - in the low res section at 204 hours away. On this run maybe, but far too far away to be assertive about anything. Besides, let's not look at the collapse of the cold spell, when it hasn't even started yet!

Looking better to me at t150, but we shall see what happens later. Anything could happen!

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=188&y=177 (South West England) http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=258&y=2 (Northern England) The ensembles show a huge amount of spread from the 5th with plenty of very cold options and some milder (but very few actually mild) options too.

Ensemble mean at 228 hours. There are a variety of options available, some closer to the op, but most not. This could go down to the wire potentially

I feel like people are jumping to conclusions based on one run! In the same way that we must not assume that one cold run is correct, we must not assume that one wet and windy run is correct. There is plenty of time left for things to change in either direction. It's a dangerous game to play if you allow yourself to be swayed by one piece of evidence and not the full picture. This particular run is very bad for cold and snow, but that doesn't guarantee the same for the next. Look for trends and key triggers that will affect the outcome of this spell of weather.

I don't understand the pessimism. Firstly, this run hasn't finished. Secondly, it is only one run. Sure, it's not as clean or as clear cut as some of the previous runs, but that is to be expected. Patience is a virtue that might come in handy at the moment!

No, we are just waiting to see what happens before we decide if it's a downgrade or not. In my mind, though it's slightly delayed, it seems a bit better as there is more energy in the Scandinavian trough but I could be wrong

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=186&y=177 (South West England http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=250&y=5 (Northern England) The 12Z GEFS shows that the ensembles are coming to a bit more of an agreement about the prospects for cold weather late next week, with a spell of a few days the most likely outcome at the moment. However, even after that spell there is still potential for the cold to return but this would not be guaranteed to show up all the time on the models as that is very deep in FI. So some exciting prospects for the nearer term, with still a degree of uncertainty, and other things to consider for FI.

The contrast between the 12z and the 0z on the GEM is quite extreme at this point - that low pressure to the south-east of Greenland is massive... In any case this is one run and not a run that fits with other models, on this particular detail at least

Correct me if I'm wrong, but the 12z GEM hasn't finished running yet. At least on meteociel it hasn't

In spite of the eastward shift on this run, I believe (though I could be wrong) that the outcome will be more or less the same from this run, just slightly delayed. When I say the same, I don't mean identical, just the overall idea of a cold northerly should be the same. But we shall see!

This lovely chart from GFS but in FI of course!

Interestingly, as Frosty has just inferred, some of the key building blocks, if you like, to us receiving cold weather over the next couple of weeks are now falling into a much closer time frame and so there can no longer be the same argument that this is all in FI. However, stay alert for anything that might scupper our chances, such as shortwaves. Equally, keep an eye out for anything that might prolong the cold. All options are still possible but currently, the way things stand, cold weather is becoming increasingly likely.

Whilst this run of the gfs has provided us with some fantastic looking synoptics, it's worth bearing in mind that it doesn't give us very cold uppers! However, it is one run of the gfs, and this all takes place in FI. Let's get the pattern in place first and then consider the uppers! I am having this discussion with myself of course, for reassurance purposes...

It doesn't matter that it's FI - we're looking for trends and this is a trend that has been repeated again and again (hence I have called it a trend I suppose!). When we talk about FI, it's more that we should ignore the details in FI. However, the broad pattern being shown on this run is an improvement, and actually many of the causes upstream are visible in the short range. It's about looking for signals in the short range which can lead to trends in FI.

Also there are slightly lower heights over Southern Europe, indicated by that area of green over Italy