jvenge

Seasonal models dont worry about weekly detail and instead focus on likely synoptics over a season and then play percentages. For example, I think atlantic driven is most likely as we enter December. ECM EPS and GEFS might disagree on some detail, and both may be wrong, but that doesn't change the most likely influences come December. If during that time its south westerlies, polar maritime or a more zonal flow, a seasonal model doesn't care.

Did anyone check if the building blocks and cherries are safe and well?

It's not really worth dwelling on the run details, especially in the later frames. Sufficed to say, it keeps the UK quite toasty and a certain squirrel is likely coming over quite faint now.

From Weatherbell. Note: Any maps, images or charts from ECMWF (License) may never be posted or re-distributed (except for WMO-Essential). All other maps, images and charts from other models may be shared in moderation under the following conditions: The images may not be used for any commercial (revenue generating) purpose including, but not limited to, ad-supported websites or private consulting. Any images must be attributed to WeatherBell Analytics. The teleconnections doesn't fall under WMO essential :-) The WMO essential consists of some stuff related to the det run and some from the EPS, but mostly heights, anomalies, 850 temperatures, etc. Nothing that someone else doesn't receive quicker from Meteociel or somewhere else.

I'll send you what I'm looking at in private, since they aren't too happy about posting ECM stuff publicly.

Quite true, but as it has come closer, it does seem that the ECM has been shortening the duration of that negative NAO. In the interest of balance, it is worth saying that the GEFS see it going on for much longer, but I'm not really convinced the value it is predicting, even if it verifies, will be of too much use. I think the UK still has a reasonably good shot of something interesting in the next two weeks, but I can't really say that is reflective in model output at the moment, unless you live at a quite high altitude.

The ECM EPS, although never quite sold on a deeply negative NAO, is sending both the AO and NAO to neutral and then onto slightly positive conditions around the 25th or so.

I say this in the kindest of ways, but there is no back tracking if people were ever looking at anything over than det runs and isolated runs at that. Still, there still remains a period of opportunity over the next two weeks for the UK. Models have been known to come up with surprises ;-)

Surface and 850 mean anomalies from the GEFS.

Not that I care either way, but having looked at the EPS mean, I remain rather confused why it is the saviour of coldies this morning. To me the uppers on offer are not nearly cold enough and it seems to be the model most in a rush to let the atlantic in towards the month end.

Although at the last few frames it looks like the UK wasn't invited to the after party with the other guests. Still, best not to obsess over det runs. To the ensembles....;-)

For those wanting a visual between the 00 and 06z means from the GEFS.

Seems a good time to post the NAO forecast, then. I don't think I'm allowed to post the ECM one, but it is a little different in it sends things neutral/positive towards the end of the run and it doesn't send it as negative as the GEFS.

That term, building blocks :-) The only building blocks getting into place are for an increased atlantic westerly influence towards the end of the month and early December. Until then, at least, the UK still has a very good chance of experiencing some unseasonably below average temperatures and possible snow as a result. Not guaranteed, not nailed on, but there is model output to support that. Towards the end of the month those atlantic westerly building blocks are the most likely....that's not really model output though.

Control from the ECM is quite encouraging for those looking for cold all the way out to T360. The ensemble mean suggests that the control is not among a majority favoured evolution, though.

EPS weekly should be interesting later tonight, since it is the first one that will be reflecting the recent move away from a negative NAO.

In that case, the CFSv2 is planning a Spring ice age for the northern hemisphere.

Better here, considering how sensitive they are in the output thread. Over the weekend and continuing today, the ECM and GEFS have shortened the duration and depth of the negative AMO. This means that likely by the end of the month there will be an increase in a westerly regime. Still a long way out, but thats what one would expect from the current La Nina.

The EPS46 just isn"t seeing a prolonged or strong - NAO. The control is giving brief cold shots, but nothing prolonged. The mean is so weak after day 13 I'm not sure it is worth anything without being able to see the 51 members. Based on the 0z from yesterday, which was different from the 12z. If someone was hoping for a strong signal, the EPS46 is not the place to seek it.

My source for the EPS 46 didn't update yet. But the last run showed some intermittent periods of colder shots (last Monday)

Sometimes chasing the furthest reaches of the output one can miss what is coming up in the near term. ECM this morning showing a cold start to next Monday for the UK, with temps just above freezing for much of the country and parts of the North West and parts of Scotland seeing temps just below freezing. Snow for the north west of Scotland. Sorry, the little disclaimer on the site I use says I can't take images from there in regards to the ECM. I'm missing meteociel this morning, as it tends to be the easiest way to see what the GEFS is showing. But, as a visual, how the GEFS mean 2m sees it for Europe for the next few weeks. And it is seeing things differently to the ECM EPS and it is likely more worthwhile to focus on the 7-10 time range at the moment, rather than focussing too much on the further reaches of the GEFS output. It seems realistic to say that at times the UK will experience below average temperatures for the next few weeks and at times comfortably below average. The EPS 46 should be interesting next run to see what the ECM decides it is doing with the NAO. GEFS are keen to send it negative from mid month. Seems Weatherbell is having issues with its teleconnections page. A lot of outdated stuff there.

Of course it is, but how much is it lying? ;-) By the way. Anyone else noticed that blocking has a new definition on the output thread? It seems to have become "high pressure somewhere where we want it", no matter what that then does and for how long.

I'm not Tamara and I'll also try to keep this model related somewhere along the lines ;-) The 2010 start to winter saw a disconnect between the enso state and atmospheric circulation. This was caused by the amplitude of the MJO in October that year. This cleared itself out and the regular La Nina like conditions resumed. I've read Tamara's explanation of this quite recently and she puts it much more eloquently than me. There isn't a sign of that this year (yet). As the winter progresses, the UK is likely to come under the influence of warmer atlantic air and this is most noticeable come February. In December, the influence is less, but as the month progresses it will likely manifest itself as well. All things being equal, which they rarely are, the UK should be looking for the first half of winter to get what they crave in terms of cold. I do note that some US forecasters are thinking that an amplified MJO is possible based on various analogues they use. That's way beyond my level of knowledge though, but it does seem that forecasts for a cold Western Europe are actually assuming this is going to happen. Who knows. In cold winter La Nina years (for the UK), there has been something to dampen the La Nina effect. And now, to try and keep it model related (sorry mods), there isn't any sign that the enso state is being suppressed based on the output. Some of the later November and early December charts are very La Nina like and although I personally don't care too much for longer range models, they are pretty much reading the enso state.

I don't take too much notice of the theory, as although it is built on something real, I just don't think it is enough to change more important drivers (ENSO, QBO, Solar) and so the situations where it might be useful are few and far between. That said, before people trash the theory and the guy, have a detailed read of http://www.aer.com/science-research/climate-weather/arctic-oscillation and understand exactly what his thinking and logic is for this coming season. Just to be sure you don't misunderstand where he is actually sitting on this season.

Not to be a party pooper, but just a quick reminder to those looking at analogues. La Nina is not ideal for prolonged cold in the UK. Yes, there are winters such as 95/96, but you really need to look into detail to see what dampened the "normal" La Nina effects in those winters. A weak El Nino would be the most favorable, as it would make extended blocking conditions more likely and potentially cut off the atlantic lows. No guarantees, even with that :-) Other conditions such as low solar and EQBO are favorable. 08/09 is a good example of a fairly average winter, that could have been so much more if a weak to mild El Nino was on offer, as opposed to La Nina. Just to keep in mind, average is by no means warm and a washout. I'm also not saying there are no chances of prolonged cold, just that what is on offer presently doesn't really favour that for the UK as a strong candidate. I also don't think anything particularly mild (last two years) is likely. And as always, understand how averages and anomalies come to be and what happens in between to arrive at those.