chionomaniac

There seems to be a lack of mention to the small Atlantic low pressure seen on the FAX chart above and highlighted below. I suspect that this is critical and is modeled differently in each output. It is not initially critical in the way that it will affect us down the line, but more so in the fact that it shows us how differently each output is in distributing the amount of energy in each section of the jet stream, and how this upstream pattern will have a knock on affect to how the ridge behaves downstream. Keep an eye on this area and even slightly further west on future runs.

Good to see that the pressure on the polar vortex once again extends up into the lower strat - for about the 8th out of 10 runs. maybe the wave positioning is not quite as favourable as we would wish for as this chart from 50 hPa shows. The arrows show the pressure points from the wave two and the red area where heights could rise as a consequence tropospherically. I have seen a lot written about the strat and writing off December to zonal etc and that should not be done. What we are seeing is perfectly in line with similar +QBO/ ENSO states with a building Atlantic November ridge. We are still at a position where the upper levels of the stratosphere are still cooling and the vortex has yet to reach its stable and influencing position on the lower strat - so we are still able to benefit from tropospheric pattern moulding (remember the trop/strat dance). How long this can continue remains to be seen, however, for those touting that an early above average strat vortex will automatically lead to an above average CET this winter may find that that is not the case at all.

Dare I say it but we are getting close to slider undercutting territory there as well - It wouldn't take much.

Worth putting these two posts up to show how short sighted it is to look at just at Atlantic views only. When looking at the larger hemispheric views it is quite obvious that Yarmy is right and there is a lot of divergence in the mid Atlantic wrt to the angulation, strength and precise positioning of the ridge that is forecast for that area. All three have different solutions in this area which will have big impacts down the line. The only common theme is the long wave trough extending into Europe. Edit - just looked at these charts again and tbh the differences are so big as to be noticed in the Atlantic charts really, but the principle still applies.

SK - wrt the 30hPA chart that is what I have been waiting to see and that's like the tropospheric led split that we saw in the other winters - Once we see that in the reliable we know that we are onto something.

Time for a new thread. Please keep on topic - no off topic posts, no gif obsession and please do remember the zero tolerance policy. To start us off here is the 6-10 day NAEFS ensemble mean anomaly. Impressive Atlantic ridge heh? What seems most likely is that the ridge pushes east, flattens and undercuts - the all important southern Europe low heights help this occur- and these show no signs of abating on the 11-15 anomaly charts - though the Atlantic ridge does.

New thread coming soon so don't start any long convoluted posts now!

I constructed that chart back in September - and have been waiting to see if it came into fruition for two months! Also, we have yet to see anything on any 100hPa charts suggetsing a split in the vortex over Greenland. That concerns me as previously that has always been shown by now if something was in the offing there.

.....which could be offering the correct solution, Steve! Also to edit that will be tempered somewhat in the NAEFS full 5 day anomly suite as no doubt some members will be over estimating the blocking as well. However, at least we have something to discuss!

Fwiw, I don't think that it is a toppler but I do think that as we see the high rebuild to the NW it will bang straight back into the polar vortex, so that it is unlikely to lead to a full HLB over Greenland with classic undercutting. More likely that we will see the Atlantic ridge reform bumping up towards Greenland, but not completely enveloping it. And with that we can see some repeated cold shots - not necessarily like some previous year but those in the north west will have a chance of some white stuff - though not the type that lasts for days on end. The NAEFS anomalies highlight this well - the 6-10 day cumulative charts show the stong Atlantic ridge By days 11-15 there is still promise - note the weak anomaly bridge between the Pacific and Atlantic sector (could this grow?) and how the Atlantic sector of the PV relocates towards Svalbard - just not far enough in my opinion. The pattern is most definitely tropospheric led but is not without precedent in wQBO, moderate solar, ENSO neutral years. Here is the composite again for those years - the thing that surprises me is that the formation of the Atlantic ridge for mid month was so predictable. this looks very close to the NAEFS 6-10 day ensemble mean. There is still a window of opportunity for perhaps something stronger to grow into Greenland before the stratospheric influence does become too strong. But for that to occur I suspect that we may want to see a strong Mountain torque, and perhaps a North American one at that, to reinforce the block through lower strat wave breaking - so that will be worth watching. Otherwise the favourable positioned positive AAM anomaly may just fade away. And we wouldn't want that would we?

Just a little reminder - this is the model thread - for model related discussion. (Not for a flood of gif images, not for general weather chat, not for one liners that just add nothing or other none model related chat)

I have to admit that I was expecting to see a wave 1 type breaking event from around mid month, not wave 2, so this is great news because it means that rather than a displacement from the Pacific ridge the vortex will be under pressure in two areas - hence the Atlantic ridge coming into the forecast. If I had thought about it properly I should have guessed that we should expect a wave 2 event because of the Atlantic ridge. Still live and learn! Keep an eye on the MT analysis for the next few days. Oh and Recretos, I agree with sebastiaan - the CW is an early season phenomenom. However, I am interested in the small chance of a wave 2 split SSW later on in the season. We can't rule it out completely!

So, it was mentioned earlier in the month that the best chance of a cold outbreak would this month would be from around the back of an Atlantic High and I still think that this hold true. Presently, the current pattern is dominated by a stonking Pacific Ridge aligned to a developing polar stratospheric vortex. This developing stratospheric vortex is yet to fully control the pattern - when the polar stratosphere is still cooling during the early winter, it is prone to strong tropospheric wave activity, however I think that it is unlikely that we will see the local wave breaking over Greenland that we saw in 2010, this year. I don't think that the Atlantic high will be strong enough this year to break the grip of the developing vortex. But that is not to say that we cannot develop a colder pattern during the second half of November, especially further north. Stepping back and looking further afield we have had the AAM tendency drop and then rebound massively. Lowering and negative AAM in the northern latitudes will have the effect of powering the northern ar of the jet stream and increasing the westerly airflow, so ideally we don't want this but want to see any positive AAM deflected poleward. If positive AAM surges around 60ºN then the net effect at this latitude will be an increase of easterly flow. Any easterly flow here will reinforce mid to high latitude blocking - but will the block be in a favourable position to affect the UK. Well looking at the tendency graph above, currently the positive AAM looks too far south to affect our latitude favourably. However, it is likely that the increase in AAM will nudge the GWO into a more favourable position - as suggested below - into phases 5>6>7. Lorenzo, has brilliantly constructed some GWO H5 composite analogues for the phases of the GWO in November. These tend to suggest a reinforcing of the Atlantic block - but will it be far enough north? When we look at the ECM and GFS cumulative anomaly charts then this Atlantic block gains credence. and further afield Tentatively, a suggestion here of a west based -ve NAO, There is very little indication that we will see a major wave breaking event leading to a tropospheric led Greenland block at this point. Back in 2010 when blocking in this area was indicated it was very well supported in the stratospheric models with severe splits in the vortex right up to 30 hPa. There are no such indications that this is on the cards at this time (but we certainly can't rule it out this early in the season). Every year in the strat thread we learn a little bit more about the strat/ trop interactions and this year is no different. I have included a section in the first post that particularly covers how the troposphere can 'set up' a change in the stratosphere that then feeds back and reinforces a change in the tropopsheric pattern - perhaps Steve M missed this when commenting on the thread last night. However, and as ever, if the stratosphere cools to well below average by December then the subsequent strong vortex will influence the tropospheric pattern in the following weeks. Yes, this is simplistic and there may be a chance of blocking before this occurs, but it is disingenious to suggest otherwise when winter is well set. At that point we will need (tropospheric led) strat feedback to break the cycle. But still a little more to keep us interested in the next few weeks regarding cold potential than there has been in autumn so far.

I know that strong ENSO events can feedback into the stratosphere through planetary wave propagation and dissipation. This tends to be reduced in neutral ENSO conditions. When tropical AAM drops through the floor or rises dramatically then I would think that there will be some feedback due to the change in global circulatory pattern and altered wavelengths- the strongest of which we know can affect the strat. Longer term the ENSO state affects the BDC. http://www.atmosp.physics.utoronto.ca/SPARC/SPARC2008GA/Posters/SessionA_P11_A299_Calvo.pdf

The route to cold this November will always be from a northwesterly airflow around the back of an Atlantic ridge and at last this is starting tp possibly show up on the extended anomaly charts. Here is the November expected anomaly composite based on the closest anologue years. The GFS 11-16 day anomaly charts are starting to have a similar look about them - so confidence for an Atlantic ridge can grow tentatively for later in the month. THere is a bit of a confusing signal between the MJO and GWO, but the one thing that I can see omnipresent this winter is already showing. That is the strong Pacific ridge.

On another note we can see that the forecast page has opened on the berlin site. Interestingly the cooling of the strat is not straightforward with the mean zonal mean winds in the middle strat not dipping as one might expect. http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=all&alert=1&lng=eng There is also an omnipresent GFS upper strat warming forecast at T+384 at 1 hPa - the same as last year - eventually it became reality!

If you read a book from the start rather than opening it in the middle then you may find that you need not ask the questions.

Yes, statistically. But the last one in a wQBO was 1980/81 so I wouldn't hold your breath.

I haven't seen 62/63 being bandied around. There was a CW and SSW that winter. However, it was an East QBO year (not west like this year) with lowish solar flux.

Would agree with Nick's assessment here. The forecasts suggest a minor warming downstream from Asia - this is minor and at present hardly affecting the increasing strength that is building in the vortex. At 10 hPa at the end of the 00Z we see a cold establishing vortex for November with any wave activity hardly even 'kissing' the surf zone. The vortex below this wobbles slightly but no great disruption. The forecast shape and position of the vortex is starting to match the November analogue seen in the first post at 30 hPa.

The more criteria you use the smaller the sample size becomes. You will probably end up with a composite of just 1 day, BFTV!

Welcome to netweather, Ethan, and thank you for posting your thoughts and please continue to do so. I would agree with your thoughts regarding about the possibility of a later winter SSW - it certainly shouldn't be ruled out just because we are in a wQBO regime. The analogue years that I have looked at suggest a more 50/50 probability, but when I factor in the increased probability from a slightly above average October snow departure, then perhaps this could be slightly in favour of a SSW occurring. The one thing that I can see omnipresent this winter is a -ve EPO regime and only once the stratosphere conditions change will this move, decline or migrate westwards - that is consistent with the wQBO chart that you have posted. I suspect that the reason that you mention the more poleward 0 u line is that wave activity can be reflected more towards the polar stratosphere, though there is evidence that this line is currently retreating between 10 and 50hPa to well south of 30ºN as the wave 1 activity declines. Anyway, back to the present and the vortex is set fare to crank up and I suspect even with the increase of positive AAM around 60ºN that this will serve to reinforce the midlatitude ridges and the vortex will continue its strengthening especially to the north of the UK. - a lovely 4 wave pattern but the anomalies the reverse of what cold lovers would like to see this winter!

Trees starting to come down around here looking at the local travel info. http://www.theargus.co.uk/li/traffic.in.Brighton/

Winds really picked up since a squall line went through. Stronger than an average autumn gale, hopefully this is as strong as it gets.

I would be quite concerned for anyone who wished for death and destruction whatever the cause, Gary. But the point I was making was that no true weather enthusiast is wanting that. But I am wondering what point you are trying to make other than trying to disrupt a thread that is full of weather enthusiasts enjoying their passion.