Nick B

Are you referring to the -24 core some 400 miles east of Moscow?! (just checking!) :-)

Sorry to hear your news, Fred. I don't post here much, however I am sure that your dad appreciated your support while you were there and that is what matters.

I'm not blue, obviously, but if that pattern were to verify, here's how I would see it play out... That Azores HP is (from that point, I stress) looking to push into Europe. It does not appear to be a retrogressing pattern - there is too much energy coming off the east coast of North America.. However, with a little MJO help, the jet may yet soon afterwards (3-4 days perhaps) buckle underneath into Iberia and allow the HP to build into Scandinavia from that point, while the lobe of PV sitting over Siberia progresses just a little to the east (it may retrogress later with enough jet buckling). With a strengthening Arctic high and a buckling jet assisting by sending energy into the Med, a significant cold pool is then able to flow down through Scandinavia and build into E/NE Europe. That is the only route to a lengthy cold spell I see currently (from that scenario!), apart from transient coldish shots from the W/NW.

Possibly similar discussions in nature to the ones they were having in November 2009, where I guess the background signals maybe didn't agree locally (well, actually for large chunks of Europe?) with their global probability maps? All finely balanced and nuanced, I guess... and at the end of the day they have to carry the can for what they say publicly. We're only covering a small area of the globe. Their model here deals globally, though of course, effectively small changes to the whole can bring big local impacts, meaning much more to those based here!

Found the following site for charts recently, might have been flagged elsewhere but it's an excellent resource for charts. If you don't mind using a translator, you'll find almost every parameter you could hope for (though the key is knowing what to use when... e.g. for general outlook up to maybe 120-212, dependent on dear old Shannon E., standard 500 geopotential: https://kachelmannwetter.com/de/modellkarten/euro/europa/geopotential-500hpa/20171119-1800z.html for the next day, determine whether you might see white stuff, there's a whole host of parameters to choose from, such as 925 temperature: https://kachelmannwetter.com/de/modellkarten/euro/europa/temperatur-925hpa/20171117-0900z.html, probability of heavier precipitation: https://kachelmannwetter.com/de/modellkarten/euro/europa/niederschlag-ueber-10mm/20171117-0000z.html , dew point: https://kachelmannwetter.com/de/modellkarten/euro/europa/taupunkt/20171117-0000z.html etc.etc. Enjoy

I think it's been mentioned before but key to almost all lasting cold setups for the UK as a whole is generally going to involve a lowering of heights over the continent. As soon as the deeper blues on the 500mB charts are modelled as appearing for a reasonable length of time, centred somewhere around N. Italy, S. Germany, Austria, Czech and S.E France, then the UK is in with a much better shout for a lasting cold spell. This will generally hold true whether it's via a Greenland or a Scandinavian high. Situated here in middle-ish Germany, that happens to be what I am looking out for too - UK and Germany will both win when that occurs. As long as the yellow concave shape is showing in any way over Europe, we're on dodgy ground. The recent depth of cold in the ENSO state, somewhat unexpected only a few weeks ago (-0.5 to -1.0 was on the cards, now looking like a solid -1.5, albeit largely on the Eastern side), may throw a spanner in the works but can be overridden if other factors are strong enough (the MJO is not looking like helping us out, AAM will be low). Several factors were working against a cold North Western Europe in the heart of winter last year and right now, we are still in Autumn. I have a feeling we may have to grit our teeth through an extended period of zonal weather, however that does not mean it's necessarily going to be mild all the way. I'd like to continue to see some WAA putting a bit more stress on the PV as well as getting the cold a bit closer to this part of the world. That, for a more substantial return later, rather than a watered-down attempt now (if you'll excuse the pun).

https://www.sciencedaily.com/releases/2017/09/170920100043.htm Gravity waves influence weather and climate Gravity waves form in the atmosphere as a result of destabilizing processes. The effects of gravity waves can only be taken into consideration by including additional special components in the models. (Goethe University Frankfurt)

In fact, purely on verification it ties in this period with UKMO. Maybe worthwhile watching the 12z on each day and see where it's trending...

Wow, trying to work out my daytime temperature from that last chart were something similar to verify. I'm a little way ESE of the bottom right hand corner... That would be a daytime maximum in the negative double figures for me, I think...

Their accuracy can be summed up in the last sentence: 'December 1 marks the beginning of meteorological winter, which lasts until February 1.' I don't think so...

I wouldn't say completely flat as in zonal mush from the SW (not that you did either!). Looking at the air source for the majority of the UK, that wouldn't have been all that mild. Pretty raw in a WNW strong gusty breeze if not gale for many, with frequent showers I'd say, looking at that...

Exactly... must have been 'nuisance' clouds...

This thread had a few chuckles... made me think... Perhaps a new thread should be opened in the Lounge... something like 'Accidentally Funny'. Classics like IB's WTF moment and OTT rants by others would qualify for nomination... at the end of each month there could be a Nobel Prize-type award where the silliest 1-3 posts would be offered their Netweather place of eternal remembrance in a dedicated thread. The rules being that the poster is quite serious and the comedy value of what they post is unintended but obvious to most. Not sure it's entirely fair or PC but could be amusing...

Or indeed match 0z runs with 0z runs (or 12z and 12z) over a reasonable time period, 3-4 days minimum to get some idea of trends, staying within perhaps 144hrs to discount the noise (though of course keeping an eye on any consistencies between runs for further out in time). Try it with hemispheric patterns too if you can. That way you can separate out what are model vagaries from the likely developing trends.

Perhaps 'Noctilucent clouds'? https://en.m.wikipedia.org/wiki/Noctilucent_cloud

A quote from Carinthian from the same day last year... "Another cloudless morning dawns. Sunshine and warmth all the way until 17/18th of this month. The picture below shows only snow on 3000m plus peaks." Polar opposite, if you'll excuse the pun...

I'm not sure that's entirely fair! Ian needs no defending in here from the likes of me, my observation has been however that he states his opinions which are inevitably backed up with reasoning. No-one can be in possession of all the facts with something so mobile. I think it's obvious that Ian goes into details which may risk being proved wrong by subsequent events, however he does this in the full knowledge that this can and will happen - always. My impression is that when he issues a forecast, in a sense it is a marker stuck in the ground, so that as events unfold the forecast can then be measured in order to gain further understanding of the factors influencing real events. This is open, courageous and humble and, in particular, is a wholehearted scientific endeavour. Hence his entirely correct reasoning for his change in position recently.

I think the move in this direction is one to be looking for if you're searching for lasting cold. Lasting cold for the UK as a whole will be unlikely without reduced heights over Western/Central Europe. As I logged on while reading this page it opened up the first page in the thread... where folks were discussing the likelihood of 30C being reached. Not very long ago...

From my understanding, one of the key possibilities will be a transition of the main lobe of the PV albeit briefly through Greenland eastwards to Scandinavia/Northern Asia. I would hazard this absolutely cannot happen without this part of the globe being subject to Atlantic-sourced weather for a period of time. However, the potential benefits down the line for those seeking colder weather would then be heightened (with the caveat that it would be required that the lobe positions itself where the air mass arriving in the UK is once again sourced from a N/NE direction, only this time with more venom).

Very nice indeed... Constable would have returned with his easel and paintbrushes...

Super Typhoon Nepartak about to slam into Taiwan. May well make landfall as Cat 5 equivalent within only a few hours. Despite the very strong winds this beast is packing, it's the 300mm+ of rainfall coming in the next 36 hours which will be of most concern, causing likely flash flooding and landslides. https://weather.com/storms/typhoon/news/tropical-storm-typhoon-nepartak-pacific-east-asia

Can confirm it was quite something, in terms of lightning and thunder... it looked like it was dying out as it approached my town (about 5okm north of Frankfurt. It finally arrived properly from about 00:30, putting on a reasonable show at first with plenty of IC and the odd CG thrown in for good measure, though nothing unusual. Then, some time after I'd gone to bed and the heavy rain had died out a bit, we had several CG's very near (averaging less than half a second between lightning and thunder). Not sure what time that was - by then too sleepy to care much, am as a rule not woken by thunder but these were like a cannon going off.

"You were only supposed to blow the bloody doors off..."

Exactly. Not so much the "failed perturbation" as he put it, more the trendsetter (along with chiono!).

I would have thought that if an atmospheric wave is analogous to an ocean one, then there is more to this. With an ocean wave, its propensity to break is surely based on the interplay between between the wavelength, the amplitude and the thickness of the available medium through which it is travelling? i.e. a wave with a higher amplitude in relationship to its wavelength would break more readily when the medium is constricted (I'm imagining an ocean swell as it approaches the beach). Is this why a low amplitude wave can only make minimal impact through the lower part of the stratosphere and at most may cause slight displacement and wobble of the PV for a short period of time before it strengthens once again? Whereas a real monster of a wave 1 with a big amplitude colliding with a PV is going to break through a very large percentage of the stratosphere, dissipating its energy in many chaotic directions, causing it significant disruption. Some speak of wheels with sticks placed in the spokes, or spinning tops etc. but I'm not sure they're the best analogy. I think everyone has seen a whirlpool in a round bowl, however, and that might be the easiest to grasp (although not perfect). In fact, if there are any sediments in the water (they are denser than the water), you could see they will usually find their way to the centre - analogous to the denser cold air being trapped at the heart of the PV. Set up a whirlpool first (by spinning the water and then leaving it a little while) - then the core (of the whirlpool) is the PV. Disturb the flow very slowly over a minimal depth and a small cross section, i.e. a little finger near the edge of the bowl and the core of the whirlpool survives - in fact is hardly troubled at all, just maybe displaced temporarily. You would see very little effect on the sediments - the cold air stays where it was within the vortex itself. Do this less slowly, nearer the middle of the vortex, with four fingers and allowing them to penetrate through more of the depth of the water, introducing a little flick to provide a 'wave' and the vortex will have real trouble surviving, and your sediment - the cold air, is forced outwards from the vortex in all manner of chaotic directions. However, given time, due to the net movement of all the water, the vortex will of course reform. So I think how and where in the stratosphere the wave breaking might occur is dependent on: 1. the amplitude of the wave; 2. the wavelength; 3. the strength of the PV at the time. If you want to trouble a raging PV, it had better be a big wave 1 to begin with, followed by further waves 1 and 2 mixed to offer it minimal chance of re-establishing too quickly.