snowking

GW, as posted elsewhere previously, the PDO, as with any cycle of such range, will go in peaks and troughs (just as it is claimed the global temperatures do). Even during notable negative periods through the 20th century we would still occasionally see index values returning briefly to positive territory. The most recent values are available here: http://jisao.washington.edu/pdo/PDO.latest And just for ease of reading, here are the values from so far this year: 2013** -0.13 -0.43 -0.63 -0.16 0.08 -0.78 -1.25 Claims of us exiting the overall negative PDO phase are misleading...just as it would be misleading for me to suggest that the slight stalling of global temperature rise in recent years means that global warming has ended. I am always up for having a fair and factual debate, and I realise that some in the no-global-warming camp are guilty of not following through with this, but surely this has to work both ways too? Kind Regards SK

I havn't got much time this morning but needless to say these thoughts still stand this morning, with gathering momentum for some form of troughing close to the North of the UK - though much sooner than I had expected I must say. I suspect, as has been alluded too already by Tamara and others, that the amplification in the pattern depicted by the ECMWF may still tone down somewhat for this period, and adjust to something closer to the GFS solution. However, what is clear is that medium-range NWP is now picking up on the MJO phase 1 signal, and will likely drive with that pattern as a basis through the FI period in the coming 10-14 days. SK

Shorter term it certainly looks like becoming settled and pleasant for much of the UK once again to end the month. Longer term, in terms of the debate on the reliability of the EC32, thats one that could go on for weeks and weeks. What I must say is that I can't disagree too much with its suggestions beyond the opening days of September. Pretty solid agreement on a phase 1 MJO setup: These signals can always be slightly lagged, and indeed I suspect thats what we will see here. But when we look at what phase 1 brings us in to September: So, are there any signs of such a signal yet from the 'standard' NWP as it were? Well, as of yet actually no. I suspect this is a signal that will gather pace in the coming week. We can see some very small signs of a trough digging in to Europe on the NAEFS anomalies this morning: But ultimately its a very weak signal and the trough shown there is far enough East to leave the UK under the influence of the azores ridge instead. Of course we may well end up with such a scenario - those MJO composites are far from full proof, but beyond the 5-7th September as a rough guide, I would be looking for a troughing signal to gain momentum at the moment. SK

First of all SB, congratulations on the information in your signature Completely agree with the above, not too sure about December at this juncture but plenty of signals for the main bulk of the cold to start around the middle of January, with February having looked, for quite some time, like the month with the potential to be the coldest of the winter period - and really rather cold at that! The composite years I have churned up so far using a combination of QBO, ENSO and PDO projections, are 1978/79 and 1990/91 - both cooler winter periods. The biggest thing of interest is the relationship between the QBO and solar maximum state. Somehow last year we managed a rather large SSW with an Easterly QBO under solar maximum conditions, where as the favoured relationship in terms of the BDC is for a Westerly QBO under such solar conditions...so if anything, the chances of an SSW already seem higher (assuming we stick with the Westerly QBO). Anyway...back to the here and now. We seem to be having the carrot dangled in front of us again....it feels like winter already, though this time of course everybody is chasing the warm, settled conditions. We of course await the ECMWF ensembles now, but given recent experience, I would not be comfortable with this showing from the Ensemble mean: For as long as the core of the ridge is shown to be South-West of the UK, you always risk what we are about to experience this weekend, with a 'weakness' in pressure left just to the East, or indeed across the UK, and at this time of the season, with the Jet getting ready to fire up somewhat as the natural thermal gradient strengthens, you cannot afford to leave any gaps in the pattern! SK

Yep as has already been commented upon, big steps towards this mornings ECMWF solution from the runs tonight. The GFS not quite there yet, with enough energy spilling south to develop a secondary low to the South of the UK: But compared to its 0z alternative: Its heading in the right direction. Meanwhile, the UKMO: Holding the energy up to the North-West of the UK, once again promising a drier weekend at least for Southern and Eastern parts. Also for information, I counted 33 of the 51 ECM EPS members this morning, crucially including virtually identical Deterministic and Control runs, backed such a solution. We of course await the ECMWF, but big steps in the right direction for something slightly more settled this evening. SK

Certainly agree on the last part but to me UKMO and ECMWF are actually fairly different in terms of their eventual outcome for the UK - adding even more to the confusion! The UKMO far more keen to push the influence of the trough in across the UK, signalling a rather unsettled day on Saturday for all, where as the ECMWF holds the trough further North-West, with Southern and Eastern areas escaping with a mostly dry day. Here's the synoptic setup with precipitation overlay: So I think its becoming a case of whether its an all UK rainy bank holiday special, or whether we can hold off the worst of the conditions for some. As for the GFS and its yo-yo'ing, it's safe to say I'm not paying too much attention to its operational suggestions right now SK EDIT: And as I waffle on, the ECM ensemble mean giving good support for the operational suggestion:

The longer range model outputs this morning look to be reacting to a phase 1 MJO signal, and whether you look at such a signal for either August or September, the result looks the same: Still a lot of uncertainty in both operational and ensemble outputs at the moment, but a lengthy heatwave such as that experienced through July hasn't really looked odds on if you had stuck to using ensemble means and of course the now famous anomaly charts. However, beyond a few blips a mostly settled end to August does look on the cards the further South you head across the UK. SK

It might just be worth holding off on temperature projections until we get a clearer idea of the actual surface flow, with that shortwave causing some serious issues akin to something of a winter-time drama on here. The current ensemble mean projections for London: Certainly pleasant, but nothing absolutely exceptional showing as of yet away from the operationals. ECM ensemble mean pretty similar: The general rule of thumb I use is that the ensemble means tend to underestimate the eventual maximum temperatures by around 2-3c, but there is no guarantee of this always being the case. So for now face value outputs suggest warm, but not exceptionally so (which I must say suits me just fine). Dependant upon the eventual orientation and location of the shallow trough to the SW in the longer timeframe, this could well change. SK

Same here. Saw the settled spell coming but didn't expect the temperature profile that accompanied it, and it was longer in duration than anticipated. But overall I have been happy with the QBO/ENSO blend for composite years I used - the key details were the three main settled spells of the summer forecast - Early June, Mid July, and Late August. So far its sort of 1.5/2, hoping to make that 2.5/3 as this settled spell develops later next week (making of course the huge assumption that it does so!). The most significant part of the Autumn forecast for me remains the story carrying over from the very early thoughts based around the summer composite years - and this is of the continuing strong signal for a very settled October. After an unsettled start, it looks as though it will be high pressure dominated. Taking it further beyond that, and the other strong signal seen over the last 6 months is for a very cold February - something that I know Roger disagrees with based on his preliminary thoughts. I do agree with him about the mid-January spell though, certainly a signal there based upon the composite years....February still looks the main month though for me. SK

Its GFS vs ECM again into the medium range These two charts may only look to be showing subtle differences: But in reality we are seeing quite a big difference at the surface, with the ECM mean keener on a trough solution (consistent with its upper forecast), whilst the GEFS suggests something flatter with the azores high influencing things quite a lot more in around 10 days time. The 8-10 day mean charts today could be rather deceptive in terms of their absolute suggestion of an upper trough across the UK, with days 8 and 9, when separated from the mean, in reality exhibiting something more akin to the GEFS mean day 10 output with some influence from the azores high. I still agree overall with the sentiment in here of a general continuation of the status quo, but always best to be a little cautious with calling the pattern out towards day 10 when we have the unusual situation of the ECM being the more keen of the two on a slight trough solution! I would still back the ECM mean every day of the week over the GEFS, but perhaps just a glimmer of hope for further temporary ridging at times - I think it will be restricted to just temporary spells though - amongst the less settled pattern that looks set to dominate. SK

Unfortunately a little further North of there into Glasgow... So it would appear to me for the UK as a whole average will best describe the conditions all around really, with perhaps the better of the conditions further South. We're not talking summer of 2012, but rainfall and temperatures closer to the seasonal average (which will be a bit of a relief for trying to sleep!). SK

Hi BA Perfectly aware of that. I'm looking at where the signal is heading SK

Looks like winter is about return from the North... In all seriousness, it will be a welcome relief for me personally...with perhaps the worst of the humidity yet to come. Its been very difficult trying to sleep...and I like sleep. ECMWF ensembles pointing towards the sharp decrease in temperatures: And with Chio suggesting earlier it might be wise to watch for a re-emerging MJO signal: The kick in tropical convection leading us seemingly somewhere towards phases 8/1, neither of which look particularly inspiring: Recent increases in AAM too sending the GWO on a quick progression through phases 5-8, and into phase 1.....all of which suggests a more dominant upper troughing, rather than ridging, scenario. So we do finally seem to be nearing the end of this very fine spell of weather (it feels like we have been saying this for about two weeks now!) but one thing is for sure, this has certainly defied my expectation in terms the strength and longevity of a spell that in my LRF for summer looked likely to be a 10 day settled spell between the 10th and 20th, sandwiched in between two less settled spells of weather. Its been both a pleasant surprise, and a pain in the backside! SK

Just to put this one to bed: SST's are still slightly below where they should be for the time of year - hence the recent cloudy mornings for Eastern areas under the NEly flow SK

This sums up the likelihood of next week for me perfectly: The UK riding the boundary between ridging to the West, and Troughing to the East. This mornings outputs generally favour more of an influence from the West than the East, but I think the overall theme will be something a little fresher (thank goodness!), temperatures moving back to around average values, and perhaps a little more in the way of precipitation potential towards Northern and Eastern areas in the form of showers. ECM ensembles pointing in the same direction too: SK

Very kind words and thank you very much MJO and GWO obviously only have a limited use (i.e. where BA points out above obviously that below an amplitude of 1 the links to composite climatology are limited) but part of what drives my medium range outlooks is the projection of those signals beyond day 10. Match the expected progression of either the MJO or GWO (for which composites are less convincing at present - the Recretos composites will prove very handy in years to come) to ensemble mean forecasting, and confidence in a forecast can improve drastically. I had sat in frustration for 10 years trying to find a complimentary technique to use alongside ensemble means just to give an indication of how believable their signals are, and in the last two or three years (thanks to the guidance of GP and countless others, not of course forgetting those over on the stratosphere thread) i've found this method to produce some pretty good results for anything out towards 30 days - and then more recently i've been dabbling in longer range stuff, but thats a whole other story.... Anyway, thanks once again! SK

I suspect the GFS is, once again, picking up the correct solution, just bringing it in a little too early MJO forecasts now heading straight for phase 7 (i had suspected a phase 5-6-7 transition instead), from the UKMO (MOGREPS): And the bias-corrected ECMWF: Given the <1 amplitude for the next 7-10 days not much offer of help from either the MJO or the GWO, but a stronger signal for MJO phase 7 (very similar to phase 5 - trough dominated upper pattern as opposed to recent ridging) also reflected in the mean height anomalies today: With a pretty flat looking upper pattern towards days 8-10, and troughing perilously close to the NE of the UK. We're not talking deluges here, but it looks to be headed back to the more typical pattern for the summer so far - unsettled, sunshine and showers type - by day 10. The ECM postage stamps today, having been so consistent in the lead up to this settled spell, are also now showing in 3 clusters - two thirds of which promote something more low-pressure dominated. The ECM Glasgow ensembles help to illustrate this too: Shown above are Tmax and Rainfall projections from the last 3 ECM ensemble runs - a pretty consistent picture of temperatures returning to average values, whilst precipitation amounts also increase towards average. Birmingham ensembles also displaying similar characteristics. We may end up with a North/South split, but I think there is an inevitability into week 2 that most of us lose the settling influence of the Azores HP, and return to something we have become more accustomed to in recent years. SK

Yep and I think the other point to make on that in fairness to the NW team is that it looks to be based mostly on the CFS - which even they would acknowledge i'm sure, doesn't have the best of track records (the same can, of course, be said for any number of LRF forecast models, similar reports for the ECM and EUROSIP seasonal models too). As for the FI outputs, the ensembles clearly a little split in the medium range, but an overall trend for lowering SLP The EC32 update which SS just posted is not hugely unexpected. Still awaiting the EC32 MJO update, but I suspect we will perhaps be looking at either phase 5 or 7 eventually given the T2m ensembles shown above. Some very pleasant weather to look forward to though for the next 7-10 days before we have to worry about any of that SK

Absolutely, the hints are all there from the current medium range ensemble means, with a likelihood of some form of troughing just to the North and East of the UK, still a difference in timing as Tamara illustrated earlier, the current difference in the mean height anomaly outputs around day 10-12 for a transition from the ECM, and around days 13-14 for the GEFS The biggest thing now will be whether we will see sufficient AAM to drive us towards GWO phase 4, or whether we are left meandering around phase 3. If we are left in phase 3 then we may find very little coherence in the medium range - this is the sort of time we could do with the analogues Recretos was looking to create, set against various ENSO states too. All ensemble suites at this stage though do point towards a decrease in T2m, and an increase in Precip, which once again would tally with MJO phase 5 or even 7. True, although much of July 2012 was spent under amplitude <1 conditions, which doesn't always offer a coherent signal . SK

MJO really is all over the shot at present, my current best estimation would be heading somewhere towards phase 5 (after a quiet spell with <1 amplitude) temporarily before probably meandering back through the, lets call it the MJO zone of death, into phase 7 to end July, then into phase 8 for August. At the same time we will see AAM ramp up a little in the coming days which should push the GWO towards phase 4 - this would teleconnect well with MJO phase 5 and 7 composites. The ECM has been about the best quite in recent weeks, and the EC32 update tonight might well prove once again to be fairly useful to give us a guide SK

From a completely selfish point of view I'm pretty happy with that - temperatures were looking far too warm (and still may be) for my liking, especially at night. A decent breeze and temperatures into the mid 20's is fine by me! Longer term, the ECM ensembles have now been quite consistent in sometime around the 14-15th being the transitionary phase, with ensembles showing declining Tmax values, and increasing Precip totals: Nothing drastic, but signs of a transition to something less settled into the following week from the North-West - ensemble mean products also pointing in a similar direction, although GEFS means this morning holding out until around day 13 before collapsing the ridging signal. So a 10 day decent spell of weather looks in order - not to be sniffed at set against the background of recent climatology SK

I have just started putting together some new analogue years for the preliminary Autumn forecast - the two years that still carry over from the previous years are 1955 and 1962 You may remember me mentioning from the analogue years for the summer that there was a very strong signal that October could end up being the best month of the year. Well, heres the latest result.... SK

NOAA engineers new solution to improve GFS's performance - give it some acid Just a quick one RE: FI developments, the eventual Sceuro trough dropping through is the favoured outcome given MJO expectations (likely move towards phase 5 eventually) and my personal expectations from the summer forecast...but as Tamara pointed out earlier, it does seem to be a case of the models being a little progressive in bringing this feature through, just as they have been in FI in recent weeks with other such features (including, initially, the upcoming settled spell). We look pretty safe for much of the working week next week, and I would, at this juncture, suggest into the following weekend too. Beyond that? Well the LRF signal for this spell (initially looked to be from 10th-20th, so a little earlier than expected) was around 10 days. Realistically we are looking at this spell taking shape over all of the UK around the 6th, so expectation would be for the conditions to continue through until the 16th, give or take a day or two (in reality, it may end up being the 18th before we see any significant change) - MJO progression through the latter part of phase 2 and into 3 lasts around 10 days too. A few mentions of storm activity potentially too - I would urge caution with this. We saw during the mini-plume type development back in June that as the energy progressed North out of France, the cooler sea temperatures rather downgraded the energy by the time it made landfall over the UK, so I would take projected CAPE and LI at present with a pinch of salt SK

Unfortunately not necessarily the case - its more of a bit of an urban myth. Certain posters on here agree with the sentiment after their own research, others do not, its very much a grey area But in terms of cold hard facts well currently the 6z is one of the better verifying GFS run through days 5-8: Its a case of taking each model run as it comes, and analysing it vs. what is shown elsewhere, as well as against verification stats, to decide how reliable a particular run might be. It would be far easier if we were to know exactly which runs to disregard, but where would the fun be in that eh? Regards SK

Not entirely unexpected: http://www.ukweatherforecast.co.uk/wp-content/uploads/2012/12/July500mb.png That was the projection for July as a whole from the composite years - with the added stipulation in my summer forecast of a likely settled spell around the middle third of July. Whilst the absolute reality of the situation will likely differ from that above picture with the positive height anomalies to the West a little further East, the above correlates well with an MJO phase 5 projection: Just where the ECMWF (which in recent months has been head and shoulders above the rest in terms of its MJO forecasting) hints towards us heading: With the bias corrected ECMWF Mean taking us there a little quicker: And the bias corrected EC32 also true to form: It's this signal that I suspect the very end of the ECM 0z mean is beginning to hone in on. The difficulty is going to be in determining the absolute details in the longwave pattern, given the likes of the GFS et al. all floundering around with their projections, meaning that we are left only really with the ECM ensemble mean pointing us in the expected FI direction - what i'm getting at here is, don't be following NAEFS means in FI too closely for the time being. GWO headed for phase 3 in the 10-15 day period, before a likely progression to phase 4 given a continued signal for low AAM. Phase 4 would suggest an overall fall in pressure hemispherically too. So I suspect, just as it has done in the past few weeks, the ECM ensemble mean is picking up on the eventual signal (certainly the sort of pattern I would expect during the final 10 days of July), but delivering the final result just a little too early. Once the Sceuro trough sets up, expect it to be a little bit stubborn into August too SK