Mike Poole

ECM following on from the morning run and looking great at 216 Beaten to it! But I think there's now a good chance that this is the evolution that is going to verify - interesting times!

I had been wondering about this too. The models picked up the SSW ages ago, GFS from well beyond T+300, and the details of the evolution of the stratospheric warming have appeared to me to remain consistent from run to run for some while now. But I guess we need to remember that the stratosphere verifies much better than the weather down here in the troposphere in the models, where we know anything beyond T+96 is suspect. So while there is now little uncertainty about the stratospheric evolution in the model output, what has been very uncertain to the models over the last week is the state of the troposphere at the moment that the warming occurs - that's still subject to normal modeling errors that we see on the model output day to day (FI beyond T+96 say), and which are only now reducing into the reliable.

It looks like it's going to happen now, starting to show on ECM as well (Berlin site) and from the Met Office update, they seem to expect it too, but is it guaranteed for cold in UK is my question.

Strat warming getting closer on GFS - seems like a double warming and a split of the stratospheric PV. A nagging doubt though - a split like this will have significant implications for mid-latitude weather down the line, a 'reshuffling of the deck' so to speak, but if we've already got the cold in place, do we want the deck shuffled?

Everyone to his/her own, of course. But the reason I prefer Meteociel charts over all the others is precisely because of the imaginative use of colour. Most other sites use only pascal shades between green and red or blue and red, by using the whole spectrum of colours it makes the charts much easier to read - if your trying to read them, rather than just looking for extremes. From following this thread for some years, I've learned that the evolution often depends on quite subtle features in the model output and the Meteoceil charts make these clearer in my opinion.

No! 250mb the highest.

It's not borne out by the verification statistics at all, here at Day 5: Very little in it. Of course, he is correct that 'it's the GFS'!

I'm not so sure. Resolution isn't the whole picture. The calculation of the starting position (T0 conditions for the run) is also important, and my understanding is that ECM has a much more sophisticated method for doing this. So increased resolution for the GFS could just result in it calculating the wrong evolution more precisely!

Looks interesting - from -88C to +4C on this chart at the end of the GFS 6Z!

Proper snow in Wantage - did I just write that? 6cm already and it's settling on everything so I doubt there was much if any rain preceding it. And really really quiet outside. Which is a surprise as I was expecting some wind (and, if I'm honest, no snow!) with this slider.

I beg to disagree with this. The reason that these models are being posted (HIRLAM, AROME, ARPEGE, ICON-EU (this one runs 8 times a day)) is because they are at a higher resoulution than the big 3 and run to a shorter time and are hopefully better able to resolve precipitation. GFS is pretty hopeless at this. The reason these have not been trotted out recently is that this is the first time since Mar 13 that a significant snow event is forecast this close in time for most of England. But having viewed output from these models, large uncertainty has remained over the snow risk from the slider event. I think for the last 24 hours we may have been in a scenario where 6 hours more data is no longer useful i.e. The main uncertainty is outwith the models, maybe local conditions that they can,t resolve. So tomorrow becomes a nowcast - good luck everyone!

An idea of the uncertainty on snow for Sunday and Monday from the GEFS probability plots on Meteociel: Probability of snow 24hrs of Sunday: Probability of snow 24hrs of Monday:

For me, the most interesting new tool in our model analysing armoury this year are these Icelandic ECM cluster plots, as often posted (and well explained) by MWB. Although the pictures for each cluster cover rather small area of the globe, at the risk of stating the obvious, more information is provided by the colour of the border. These correlate to the four broad patterns at the bottom of the graphic. The first two are obvious – the others needed Google translate: Blue: +NAO Green: –NAO Red: Fyrirstada translates as ‘obstruction’ – I’m guessing ‘Scandinavian Blocking’? Mauve: Hryggur initially translates as ‘sorry’! But if you get the other meetings, includes ‘spine’ and ridge’ – ‘Atlantic ridge’? The percentages next to these, vetrarmisseri = Winter Term, likur = probability, the middle word doesn’t translate – I guess these are the seasonal likelihoods from climatology.

Worse, many people throw in the word "zonality" when it doesn't even exist.

Who needs model output? Dr. Cohen’s latest AO blog is hilarious. In it he presents the winter forecasts from various models (NMME, CFS, ECMWF and UKMO), which are all screaming mild – junks the lot and in his AER forecast goes for cold right across Eurasia, to quote: ‘multiple weeks of severe winter weather across the NH’. It’s quite a call – either he’s wrong or the models are. Well worth a read after the rather mixed model output this morning: http://www.aer.com/science-research/climate-weather/arctic-oscillation

At this stage I am optimistic that we may get a more interesting winter this year than the last four. I reason this as follows. Although the long range models should be taken largely with a pinch of salt this far out, there is some good news in that whereas they were pretty much screaming +NAO full stop a couple of months ago, CFS is now starting to move towards some high-latitude blocking. Will be interested to see if GloSea5 does so too when the October runs are out. I also think that with the easterly QBO and reducing solar activity, it is unlikely we’ll go the full three months without some blocked periods. Once concern I have is with the warm temperature anomaly that exists pretty much across the globe at the moment, will half decent synoptic patterns which would normally deliver snow, lead only to marginal 850 temperatures? A concern for the south of England anyway.

Well, this looks extraordinary for the UK. We appear to be off the scale into 'black hole' territory on the GFS 06z CAPE chart. Pretty close to my location too. Suspect nothing will happen but you never know.

Something about the chart below bothers me. It is the tercile probability plots from GloSea5 for the summer months for 500 hPa heights: I accept that these probabilities are derived from a large number of model runs and averaged over a 3 month period, but without being able to see the individual evolutions, I find the plot is hard to interpret. It seems to depict a rather extreme position, with higher probability of higher than average heights over pretty much the entire globe. Does anyone know what might be causing this – is the averaging process masking everything but significant seasonal drivers? – is this rather extreme-looking position a hangover from last year’s El Nino, for example? Finally, a few posters have expressed concern that we may be headed for a 2007/12 type summer – the plots aren’t available for 2007, but for 2012 the corresponding plot from GloSea4 (as I think it was in those days) is as follows: It couldn’t look more different to this year’s. GloSea5 clearly sees this summer very differently to how it saw 2012 at the same time 5 years ago, so I see a repeat of 2012 as rather unlikely.

Things continuing to fall in place for a decent summer - here are the May GloSea5 predictions for the summer months from the Met Office (2m Temp and 500 hPa height):

For the first time in perhaps a decade, I’m looking forward to the summer weather with a sense of optimism. It has seemed that since 2007, for some reason, the dice have been rather loaded against prolonged hot spells in summer in the UK – that’s not to say there haven’t been any (July 2013 springs to mind) – it’s just that they have been less frequent than previously. This year, the Met Office contingency planners forecasts have been suggesting warmer than average, the long range models that I have looked at also suggesting high pressure more likely. In fact, high pressure close to the UK seems to have been a factor in the weather for much of many months now, and while Sod’s law would suggest this will change in the run up to summer but there’s nothing scientific about Sods law! So my money’s on a hotter than average one, and if that transpires I think I’m about 60% hot, humid and thundery, 40% hot and dry. Time will, as ever, tell.

Thanks, that question being my 16th post seems to have solved the problem then, as if by magic I now seem to have permission.

Hi folks, I don't seem to be able to post in the 'serious discussion' section, although I can most everywhere else, is there any reason for this? I'm only an occasional poster but wanted to reply to something posted about the election and found I couldn't. Thanks Mike

Unfortunately the Met Office only quote the probabilities for the categories for the Dec-Feb period in their Contingency Planners update, which are fairly average masking a forecast cold start and mild end to winter. So I overlayed a grid of squares to calculate the probabilities for the December only probability distribution graph on Figure 2T on the link Matt quotes (presumably this information comes from GloSea5 runs primarily), and got the following: Warmest category - 7% Second-warmest category - 11% Middle category - 16% Second-coldest category - 22% Coldest category - 44% As someone who uses probabilistic modeling in another (non-weather context), this looks to me a very strong signal compared to climatology (each category 20%) for December.

Yes, Here it is (for France - they didn't do UK charts in those days). http://www.meteociel.fr/modeles/archives-gfs/28/6/2012/0/cape-et-lifted-index/3h.htm

My take on Summer '15 from Oxfordshire. Plus point - it was largely dry - I organise a big rounders competition over the summer months and we've had little in the way of problems with the rain. But other than that - where was the heat???? Few hot days around 1 July and another on 22 August - apart from that it might have been late spring or early autumn. Still, I was staying in Bournemouth the night of THAT storm!!! Oh well, roll on winter...