Glacier Point

Copycat! In essence we agree that little has changed since September so why not a much above return. The SSTA reanalysis late '60s vs 2000s clearly major differences there, most notably all of the Atlantic, most of the Pacific and the polar region. The western Atlantic is notable because in terms of differentials, the situation is not as different compared to say the Pole - we have replaced cold water anomalies with neutral ones whilst the warm anomalies have become increasingly stronger north-east of Newfoundland more particularly in the last two years in this area. A crude inference from this would be that most CETs should follow the warming suit although sudden and often dramatic reversals in CET over the last two years stand as anomalies to this uniform warming. If October followed the predicted outcome, I for one would not be that quick to draw conclusions of Nov - Dec- Jan - Feb following the trend. If anything, I think it would inspire some quiet confidence in at least one of these months producing a big turnaround. This I think is where the real skill in the CET trophy will be displayed - sucessfully predicting that below average month.

I'm taking my comparison spread over June to Oct so even whilst 1969's September was reasonably warm of its time, the following October was way above - this is the 'similar course' folowing the summer of '69. The prime factors of similarity for me are the current AO, QBO, PDO and developing weak El Nino signature. The summer reanalysis is interesting in terms of its fit to 1969 pattern in terms of 500s anomalies, SSTA and temp (allowing for elevated global values). I'll hopefully verify my summer forecast which will carry these comparisons, but as ever, no single analogue will ever be the same but it's particularly useful in identifying possible anomaly patterns from at least the QBO / AO / El Nino combo within the context of a similar SSTA profile.

September and Octobers are very often matching pairs so without hesitation, it's got to be an above average month, but how much - that is the question. The three key influences for me this month are the Artic Oscillation (AO), the developing El Nino and SSTAs in the northern Atlantic. The AO is statistically more likely to be neutral-positive for October. 77% of all Octobers since 1950 were in this state whilst the westerly phase QBO makes this even more probable with 82% of analogue months following this course. Of late there have been some height anomalies at upper levels suggesting a -ve phase AO: http://www.cpc.ncep.noaa.gov/products/prec...hgt.ao.cdas.gif although faced with the QBO, and plenty of tropical depressions, I fancy this to be forced back positive as October progresses. This leaves the door open for SSTs and El Nino to really assert their influence within the context of peak tropical depression activity. The northern Atlantic continues to favour a western ridge-eastern trough scenario with downstream ridging over central and western Europe: http://www.cdc.noaa.gov/map/images/sst/sst.anom.seasonal.gif We now start to see quite a reasonable sample of Sep - Oct - Nov analogues for a developing weak El Nino. These favour a striking anomaly for low pressure either to the west or directly over the UK. With the SSTA, I would favour this to be slightly further west giving rise to a strongly SW or even S'ly draw. The composite anomaly for temperatures suggests only 0.5 above the 1968 - 1996 average: although I would favour a value much above this to reflect the SSTA and recent monthly returns with a neutral or +ve AO (i.e. June, July and September). This makes a record breaking October very much a possibility, especially with the night time minima likely to be quite high from a SW'ly flow off the Atlantic. We are also following 1969 very closely at present which recorded a very warm October. My judgement for October 2006,12.9 C. GP

Some valuable research there which would appear to support the composite anomalies suggesting a strangely more clear signal from a QBO (w) / solar maxima flux compared to the QBO (w) / solar minima: I'm not sure about the poleward shift being less apparent during the solar minima though as the composites at sea level suggest the opposite: Overall from punting a LRF, I would still be faced with this:- Record of DJF QBO westerly vs easterly phases 35% of Decembers witnessed a -ve AO with QBO in the westerly phase compared to 38% for the easterly phase. In terms of AO+ve, 35% of Decembers with a westerly QBO had an AO+ve compared to 26% of QBO easterly phase. 30% of Januarys witnessed a -ve AO with QBO (w) compared to 50% with QBO (e). Slightly at odds with the early breakdown of the polar vortex theory. 26% of Jans with AO+ve were associated with QBO (w) whilst only 19% of QBO (e) resulted in AO+ve. 50% of Februarys witnesed a -ve AO with the QBO in its westerly phase compared to 51% in the easterly phase. For AO +ve, 32% of Febs with a westerly phase and 21% for the easterly phase. In short, a westerly phase QBO is always more likely to be less -ve and more +ve compared to an easterly phase. Not a great statistical sample I acknowledge, but given the choice, which would you favour ? GP

This is the really crucial one. For major stratospheric warmings, read blocking or negative phase AO. Timing, as in all aspects of life, will be the crucial thing here. A westerly QBO continuing throughout the winter into next Spring will signifcantly reduce the probability of -ve AO (greater +ve leading mode) which will in turn force the NAO to a +ve leading mode regardless of what the SSTA looks like. If the QBO phase shortens markedly and say we observe a neutral value in December, then that is a totally different ball game - deep cold pooling in December over the Pole followed by two months of -ve AO conditions displacing this cold air southwards - dream scenario. Since a very weak duration of the QBO in the 1950s (possibly related to strong solar activity), the length of the westerly QBO has been around 7 - 14 months, average 11. That woud be close but no cigar for us. Just as an aside, analysis of the QBO / AO has, since April, called the AO correctly 4/5 times so it would appear to be running true to form so far this cycle. It didn't call June correctly but this was strongly positive perhaps consistent with the stratospheric cooling associated with westerly QBO.

One thing that the UKMET may also be hedging on in their latest seasonal outlook is the transition of the westerly phase Quasi Biennial Oscillation (QBO). http://en.wikipedia.org/wiki/Quasi-biennial_oscillation http://www.jisao.washington.edu/data_sets/qbo/ Right now this high altitude Kelvin wave pattern is in a positive or westerly phase which started last April: http://www.cdc.noaa.gov/Correlation/qbo.data Westerly phases of the QBO are more strongly associated with a strong polar vortex, indeed, there is a deal of published research suggesting that the QBO has a direct influence on the stratosphere by helping to propogate aerosols and Ozone resulting in a cooling of the upper atmosphere forcing the leading mode of the Arctic Oscillation (AO) positive. The composite anomalies for positive phase AO for the winter months look this: http://www.cpc.ncep.noaa.gov/research_pape...DJF.z500.ao.gif with low pressure over the pole and higher pressure bands shifted northwards delivering milder weather for the UK. The composite anomalies for all westerly phase northern hemisphere winters (DJF) confirms this trend with positive anomalies for pressure in the Atlantic: leading to pretty average temperatures for the UK and western Europe. A crude analysis of AO and QBO westerly winters suggests that: 1) Decembers tend to be split between neutral, +ve and -ve phase AO; 2) Januarys favour slightly +ve AO and neutral conditions; 3) Februarys are notable for the bias towards -ve AO conditions. This is in contrast to easterly phase QBO winters where -ve AO conditions are more strongly favoured throughout. The QBO is also related to the solar cycle. Right now we are at the lowpoint of Cycle 23. http://en.wikipedia.org/wiki/Image:Zurich_..._since_1750.png You might think this was a good thing - less incoming insolation, less warmth ? Wrong. The combination of westerly phase QBO and solar minima tends to exagerate the impacts on the AO and there have been no breakdowns of the polar vortex (blocking) during westerly phase QBO winters during solar minima. The composite anomalies for westerly QBO and low solar cycle winters looks like this.... Not great for cold prospects at all. But there is some hope there for the cold lovers. February for example looks to be the one month where the likelihood of an easterly shot looks most favoured: whilst the timing of the westerly phase may end anythime between January and April next year. If the QBO were to turn easterly during January or February, the prospects of some quite juicy wintry weather would be increased considerably as this has often been associated with some of the most severe winters Europe. So it's not just El Nino that needs to be watched closely over the coming months. The QBO should be followed in detail to give a clue to our winter prospects, more particularly that January / February period. GP

Have you tried 1969 ? Perfect match-up on the Summer pattern thus far and seems to be tracking the September and likely October warmth quite well. Only problem is that this was a peak solar cycle year (quite opposite to now)hence my problems with placing too much store in single year analogues. In so far as El Nino, is that cold water I see off Peru ? http://weather.unisys.com/surface/sst_anom.html GP

Thanks all for your comments so far. The one thing I would like to point out is that my earlier post was not intended as a forecast. There is much time for things to change and the SSTA could rapidly change between now and the end of November. This was really an assessment of what implications one particular, but none the less very important aspect of circulation could have into the winter months given the situation now. As for the use of analogues, I would caution here. We live in unprecedented times where we face massive polar anomalies and indeed, a time when the north Atlantic has not been so extensively warm. 1977/8 does tend to fit a number of variables quite well, but the SSTA preceeding that winter bore limited resemblence to the current in respect of the warm North Atlantic. I prefer to look at the inferences from various analogues and see how these might fit together best.

Hi Blitzen, as we progress through October and November, we should see the influences of El Nino, and in particular the implication for pressure to fall in the Atlantic. Although we may well be within a ridge scenario with high pressure to our south and east, we are more likely to see storms making their way across the far NW and perhaps a quieter interlude into November with fog and frost as the mid and higher latitudes start to cool down rapidly. GP

What does El Nino mean for the UK Winter ? Probably one of the most frequently asked questions at present. The ultimate answer is that no one factor will influence our weather totally but by looking at the main attributes of this teleconnection, we can at least attempt to put one piece of the winter jigsaw into place. To start, the current status of the El Nino Southern Oscillation (ENSO) is in a positive phase. There are many measures, but my favoured one is the Multivariant ENSO index or MEI: http://www.cdc.noaa.gov/Correlation/mei.data During July and August we recorded MEI values in excess of 0.5 - the monthly threshold of an El Nino. Usually, an El Nino has to span a 3 month period before officially declared although this would appear to have been reached according to the latest NOAA advisory: http://www.noaanews.noaa.gov/stories2006/s2699.htm The current Sea Surface Temperature Anomaly (SSTA) and mid-water profile of the equatorial waters strongly suggest that this 'weak' El Nino will continue into the next few months, a view endorsed by most of the major modelling: http://weather.unisys.com/surface/sst_anom.html http://img444.imageshack.us/img444/4973/wkxzteqanmvb7.gif http://iri.columbia.edu/climate/ENSO/currentinfo/figure3.html http://www.met-office.gov.uk/research/seasonal/elnino/index.html http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/sstaa.gif Note here that most of these latest outputs were made before the large warming recorded towards the end of August, probably making these under-estimates as too the likely strength and duration of +ve MEI conditions. By looking at the composite anomalies for Dec-Jan-Feb under MEI conditions 0.5 to 1.5 to capture the range between weak and moderate strength E Nino's, we have a reasonable size sample. This reanalysis suggests a number of strong likelihoods in terms of pressure patterns and temperatures. The most striking signature of a weak to moderate El Nino are its zonal and vector wind anomalies. Warm equatorial waters lead to a strong thermal gradient to the north and south leading to stronger westerly (N. Hemisphere) winds over the southern 'States. These are accompanied by an increased -ve anomaly or trough in the eastern Pacific and likely jet stream displaced southwards in the Atlantic. These help explain the pressure anomaly patterns with notable troughs in the eastern Pacific, over central and eastern Siberia (likely to pump cold air southwards into Russia) and -ve height anomalies over the central Atlantic with a hint of weak ridging over western Europe. In terms of temperatures, El Nino tends to lead to a moderately mild winter for the UK and NW Europe, probably due to the influence of the mean ridge. However, this analysis masks considerable inter-month variability. Compare the temperature and 500 hPa height profiles for the three months: Decembers tend to be about average, Januarys tend to be significantly below average with a very negative Arctic and North Atlantic Oscillation pattern, whilst Februarys tend to be on the mild side. Now, turning to the possible impacts this winter, I would pick out the following: 1) The west North Pacific is anomalously warm which, if it continues into the next two months, will serve to maintain a strong Pacific High and east Pacific trough enhanced by the colder surface waters there - developing quite an amplified long wave pattern. 2) The colder SSTAs within the tropical Pacific and Atlantic will serve to strengthen the thermal gradient and increase the zonal and vector wind anomalies along the lines shown - strong sub-tropical jet likely to support greater pressure over Greenland and increase the chances of displaced polar jet flow. 3) The overall reanalysis points towards lower pressure in the central Atlantic which coincides with the colder SSTA there right now. The warmer anomalies are essentially to the north of this making it likely that the polar jet flow will be weaker than normal and for low pressure systems to take a progressively lower track. In effect, I see this as a clear signal for the current (-ve) North Atlantic Oscillation to be enhanced by the presence of a weak to moderate El Nino. 4) We are now at the low point of the solar flux . We have also to recognise increasing global temperatures and the potential for an above average December to disrupt the build-up of cold continental air. The use of any comparisons must also reflect the massively polar temperature anomalies. Given these I will follow the SSTA and October / November temperature outturn with great interest. If we observe a more traditional Autumn pattern and the north Atlantic warm anomalies stay as they are now, then I would suggest we could well be looking at an overall winter with some significant and often extreme weather conditions - both mild and cold. GP

SB, not sure at all about those anologs based on a receeding MEI into winter. Even if this happens, the next few months look to be for increasing strength El Nino given the warm sub-surface anomalies which have ballooned up in the last few weeks http://img444.imageshack.us/img444/4973/wkxzteqanmvb7.gif This will ensure at least the core of the winter being influenced by a weak to moderate El Nino if it continues into November. In so far as the EPO, this is really being driven by a continuation of cold anomalies down the eastern Pacific allied to strong positive anomalies to the west very much akin to a -ve phase PDO. The -ve PDO / +ve MEI is an unusual teleconnector - I can find only 3/4 good matches for this during the winter time - although the net effect will I think be increased probability of +ve phase PNA and troughing out east. Could it be the last year that the decreasing solar flux was masked somewhat by the combination of -ve PDO / -ve MEI during the late Autumn and Winter ? This year looks very different in terms of the SSTA: 2005 July - November 2006 July to date http://www.cdc.noaa.gov/map/images/sst/sst.anom.seasonal.gif just look at the differences in the polar anomalies, the eastern Pacific, central Atlantic and Pacific equitorial waters - could not be much more different. GP

In answer to this: http://www.netweather.tv/forum/index.php?s...st&p=781636 What does El Nino mean for the winter ? - I'm working on some reanalysis right now and it certainly makes for some provoking possibilities. I'll post a separate thread if no one has done so by that time. In the interim, I think we need to work on the assumption of a weak becoming moderate El Nino event this winter with a Multivariant El Nino Southern Oscillation Index (MEI) in the range 1 to 1.5. The reanalysis is suggesting: 1) A certainty (and I mean that) for the sub-tropical Pacific and Atlantic jets to be very strong, especially given the SSTA couplets within these regions: 2) Significant inter-month variability in the Arctic Oscillation (AO) and Pacific North America Pattern (PNA) with December panning out as average and quiet, big -ve AO and North Atlantic Oscillation (NAO) January continuing into February but with increasing trends to mild. These are of course are not insulated from other impacts, not least the possibility of a -ve Pacific Decadal Oscillation and warm sea surfaces across the north Atlantic sector currently signalling a -ve NAO. I'm also looking at the potential for quite an amplfied flow pattern care of those cold anomalies in the eastern Pacific which are showing up nicely in current seasonal SSTA maps: http://www.cdc.noaa.gov/map/images/sst/sst.anom.seasonal.gif Much however could change over the next few months, particularly within the Northern Atlantic. GP

depends on your measure... ftp://ftp.ncdc.noaa.gov/pub/data/ersst-v2/pdo.1854.latest.ts 1915, 1932 and 1936.. but the overall nub is that a -ve PDO and MEI > 0.5 are very unusual teleconnectors usually at one with each other - in other words, when the PDO's +ve, the MEI is +ve. It would be interesting to produce the composites for when these were at odds incase this plays out.. GP

Indeed, how much this arrangement last we will have to wait and see - this is a good arguement for holding onto any winter forecast until as late as possible in my opinion. There was a good discussion on the Eastern US weather forums: http://www.easternuswx.com/bb/index.php?sh...105746&st=0 worth a look regarding possible movement of the anomalies along the lines of the UKMET's statistical predictor suggesting this winter would see a +ve NAO. I'm not totally signed up to this as we have pretty much the entire north Atlantic anomalously warm so it's dicey to use a 50 yr dataset with so few comparables for this. Also, and this may be linked, the last two UKMET statistical forecasts based on 6 month SSTA (Winter 05/6 and Summer 06) have bombed. Other points to note are the continuing signs of a moderate El Nino with the MEI running already at weak El Nino strength, and perhaps more interestingly, the strength of the warm anomaly in the central and western Pacific indicative of a -ve phase PDO emerging (August was -ve PDO) - definately worth keeping an eye on into October and November. GP

ask seek and ye shall find..... http://www.netweather.tv/forum/index.php?s...st&p=771969

One aspect of the current modelling I find quite encouraging is the persistence of height anomalies over Greenland and a strong slow moving or even stationary Icelandic low helping to draw down some of that anomalously cold Arctic Air into the Greenland High. Arctic surface temp anomalies August With the re-emergence of the (SSTA driven) summer pattern into September and the east-Atlantic trough-west European ridge, this will help to maintain the longitudinal pattern of Greenland High - Icelandic Low in turn perpetuating cycles of cold air development over Greenland. The 06Z GFS demonstrates this quite nicely: cold pool building....... http://www.wetterzentrale.de/pics/Rtavn002.html http://www.wetterzentrale.de/pics/Rtavn1202.html http://www.wetterzentrale.de/pics/Rtavn1802.html dispersal..... http://www.wetterzentrale.de/pics/Rtavn2282.html re-building...... http://www.wetterzentrale.de/pics/Rtavn2762.html http://www.wetterzentrale.de/pics/Rtavn3482.html This run has been used to illustrate the theorectical process and is no guarantee of what might happen but it is a trend worth looking for as we head towards October. Notice even at t120 we have -20 850 values. Repeat that cycle several times and a sizeable cold pool could have developed by November. GP

Re: the potential long term pattern shift, February 2005 onwards.... February 2005 marked the beginning of what many members would consider as a significant change to our weather patterns. Some reanalysis which might prove of interest here, particularly in terms of what it might mean as our thoughts turn to winter. 500 hPa geopotential height anomalies Clear evidence of +ve height anomalies (over the period January 2004 to present) existed over much of the mid and high latitudes of the northern hemisphere. This is akin to a cool or negative phase of the Arctic Oscillation. This essentially explains a period of high latitude blocking with notable anomalies across the southern tip of Greenland. http://www.jisao.washington.edu/ao/ 200 hPa zonal wind anomalies Note here the negative (weaker than normal) flow over the normal track of the polar jet across the Atlantic towards the UK and the +ve anomalies towards Greenland supporting the theory of a poleward shift in the jet. But, note also the strong +ve anomalies for the sub-tropical flow across the Atlantic most probably related to weaker stratoshpheric pressure in the Atlantic (and a -ve phase Arctic Oscillation) and possibly sea surface temperature anomalies across the northern Atlantic. 200 hPa meridional wind anomalies Note the strong +ve anomalies indicating greater ridge activity in the mid-Atlantic, certainly confirming a blocked period of weather across the mid-latitudes in western Europe and no doubt key factor in 18 months of low precipitation. Sea surface temperature anomalies (SSTA) and air temperature anomalies Note here the relative warmth of the Pacific and North Atlantics, but also the incredible warmth of the pole. So why does this matter ? Well, it could just be that this reanalysis just paints a very good illustration of what a -ve Arctic Oscillation phase looks like - there have after all been many such instances. This could be put down to an isolated period but consider this, taking the 18 month period from February to August as a rolling mean, we have just experienced 11 out of the last 18 months with a -ve sign Arctic Oscillation (assuming August's return is a -ve). This is marginally greater than the 1950 - 2006 rolling average for the period Feb - August (10.2). However, this is considerably greater than any period experienced during the 1970s, 1980s and the 1990s. In fact the 2000s have a rolling average of 10.2 and this places it on a par with the 1960s in terms of decadal comparisons for the same period (1960s = 10.4 months with -ve sign Arctic Oscillation). There are a number of influences on stratospheric pressure - temperature of the upper layers being the key one. There is however some growing suggestion that mid and upper level tropospheric temperatures also exert an influence 'from below'. This is logical given that a warmed column of air will occupy a larger volume than cooler air and this may be seen to good effect during the mid and late summer period of 2006 where warming of the lower and mid troposphere around the pole lead to positive 500 hPa geopotential heights and a -ve Arctic Oscillation phase: http://www.cpc.ncep.noaa.gov/products/prec...hgt.ao.cdas.gif Now consider if we continue to observe strong warming of the poles way in excess of that around the sub-tropics (with some evidence that the strong sub-tropical jet flow will continue to prevent warming of sea surfaces at mid and low latitudes), there is the potential for warming to predispose the polar region to +ve height anomalies and a greater frequency of -ve Arctic Oscillation phases. Negative Arctic Oscillation anomalies during the winter look like this: http://www.cpc.ncep.noaa.gov/research_pape...DJF.z500.ao.gif …with a strong sub-topical jet and blocking over Greenland in evidence - the ideal synoptics for winter cold for the UK, albeit moderated somewhat by elevated global temperatures. Before we reach for the domesday comparisons, the sample comparison is just 3/5ths of the way through so we cannot draw any meaningful conclusions just yet but statistically this gives some weight to the theory of a long term pattern change delivering more continental type weather for the UK with colder winters and warmer summers. What about this summer ? Why did we observe the second strongest +ve Oscillation phase in the last 56 years during June? Well I think here there was something of a 'bounce' factor going on. By this I mean that the sudden warming of the tropics and mid-latitudes during May (following on the back of a big stratospheric cooling event) coupled with a large amount of cold air at the pole lead to a large differential in stratospheric pressure over the Atlantic leading to strong westerly's which were modified by the underlying meridional flow to sustain more of a southerly wind flow. The real test for this theory is during January. This is a month more typically associated with -ve phase Arctic Oscillation conditions http://www.cpc.ncep.noaa.gov/research_pape...DJF.z500.ao.gif yet we have struggled over the last twenty years or so to achieve this on a consistent basis - potentially the amount of energy in the system is the likely spoiler here and the reanalysis of zonal wind flow is horribly reminiscent of January's past. The next couple of years should help us conclude one way or another whether the warming of our climate will accelerate or whether there will be some surprising and often perverse reactions related to massive distortions in the stratosphere. GP

The upper level anomalies might suggest an ESE type flow, but I think with a shallow trough out to the SW and jet flow strong to the south in particular, the lower levels would largely be SSW'ly overall. The current SSTA show a couple of hundred miles draw of air 0.5 - 1 C above to the SW whilst a mean trough there could only result in abvove average conditions I think.

September - a tricky call with noted significant recent trending for much above average returns but more recent August form offering a more average outlook. Statistically, a month for neutral Arctic Oscillation (AO) conditions to likely prevail with 59% of all Septembers since 1950 falling within the neutral bandings (+0.5 > -0.5), and a slight preference for -ve conditions if not with 19% of these recorded. Recently, the AO has shown a neutral to -ve tendency with notable height anomalies since the end of August: http://www.cpc.ncep.noaa.gov/products/prec...hgt.ao.cdas.gif I suspect that with the cooling of the Pole we shall see this reverse, but for the first week to ten days I suspect this pattern to continue. The composite anomalies for the September AO look like this: http://www.cpc.ncep.noaa.gov/research_pape...ASO.z500.ao.gif The North Atlantic Oscillation (NAO) is strongly lead by the AO during this month: http://www.cdc.noaa.gov/Correlation/Table/corr.table.sep whilst the oceanic sea surface temperature anomaly (SSTA) signal for the NAO remains negative with strong anomalies in the northern sector and less warm anomalies over the sub-tropical region. This leaves the door open for a SSTA-driven month which is now being influenced on a broader hemispheric scale by a weak El Nino: Note also the arrangement of the North Pacific anomalies likely to induce an amplified flow pattern which will vary the Pacific North America (PNA) +ve and -ve as the waves are propogated eastwards resulting in ridge - trough sceanarios on the Eastern Seaboard of the USA. Conditions in the Atlantic remain much the same as they did in the early Summer with a notable warm SSTA to the west and cooler SSTA to the east and south favouring a western ridge-eastern trough scenario in the jet with low pressure to our SW. There are not many Septembers to allow a robust composite anomaly analysis, but for what it's worth, a weak El Nino (and for that matter neutral conditions) favour a strongly meridional pattern with the jetstream and Azores high pushed SW into Atlantic, but with a ridge solution over Scandinavia. This leaves the UK in a warm SW'ly airstream. This solution fits quite well the likely SSTA drivers so I'll give the greatest probability to a neutral or even weakly -ve AO and NAO to prevail within the context of ridge-trough in the jestream over the Atlantic leading to an increasing ridge developing mid to late September over Scandinavia and shallow trough to our SW which will no doubt draw some warmth from ex-tropical depressions. This will be tempered somewhat by the continued low latitude ITCZ and -ve phases of the AO. The sea temperatures to our SW remain much above normal, so given this and the prospect of some late September warmth, I'll go for a CET return of 1.2 above. 14.9 C for me thanks. GP

a winter of strong jet flow running from the SW USA across the Atlantic to the UK: and a complete lack of blocking to the north. Could happen again, but I think the established meridional pattern would make weaker jet flow a more probable outcome.

No. As a transitional phase, Autumn is a difficult call and a period best watched in terms of the winter forecast, not least the SSTA.

Indeed, a stunner which reflects the recent trend as we enter the crucial period when residual SSTAs are most likely to inlfuence the long term winter patterns... Highlights for me: 1) largely inactive Pacific with cold anomalies in the eastern N-Pac likely to induce a neutral East Pacific Oscillation (EPO); 2) generally -ve North Atlantic Oscillation signal arising from the stonking warm anomaly mid-Atlantic; 3) continued cold anomalies in the Azores - likely to drive the sub-topical and polar jets southwards and displace the high pressure core NW towards the central north Atlantic warm anomaly zone - resulting in mid-Atoantic mean ridge. If, repeat if, the current trend for -ve Arctic Oscillation continues into December, this would auger extremely well for western Europe to be staring down the barrel of a cold Winter. On the other hand, should polar region cool or another stratospheric cooling event take place, a +ve AO will likley trend the Scandinavian ridge and southerlies rather than northerlies result. Continued strong anomalies to the meridional wind pattern looks very probable in either scenario though. GP

We'll have to wait until August's data is in before commenting definitively, however the -ve AO and NAO are certainly delivering the conditions I had envisaged (wrongly) throughout the Summer. Whether this was as a result of the second strongest +ve AO recorded in the last half century during June into July or the result of an underlying predisposition for west European ridge (I suspect a combination of the two) we will have to wait until late September for the verdict. GP

July data: 200 hPa meridional flow pattern ...amplified across the hemisphere and intitiated over the Pacific - the main reason why in my book the UKMET's Summer Outlook was wrong (allied to strongly +ve AO for June). The +ve anomalies indicate the leading edges of ridges. 200hPa zonal flow pattern ... +ve anomalies in the NW Atlantic showing displaced jet flow and lack of it towards our locale. Also shown quite nicely is the weak westerly phase of the QBO in the western / central Pacific. 500 hPa height anomalies ..... says it all.... no Azores, all +ve anomalies over Germany / Scandinavia. mslp .... once again, no real comment necessary... surface temps ....confirmation of the record heat. So we add June to July and the story of the Summer verfies with Steve Murr's LRF so far. One thing I have been surprised at is the ease of removal of the ridge during the early days of August - this has been strong enough to over-ride the feedback loops. In my mind the shifting profile of the Arctic airmass has been the cause here, so August's data should provide some real insight into the Summer pattern. Or could it be that Winter is already making its presence felt ? GP

I very much agree with these sentiments. As things stand, several factors look favourably placed: 1) the warm north Atlantic and cooler central Atlantic bipole - the residual SSTA built up over several months now will not change for the current Winter so a -ve NAO will be a stronger prospect allowing for the leading of the Artic Oscillation. 2) Solar minima. 3) Weaker Pacific Jet and much more amplified jet pattern across the hemisphere. Taking these into account, I would suggest at this early stage, the probabilities of a large pool of cold air developing to our east are reasonable, and crucially with no Pacific Jet to blast it away, we might stand a better chance of landing the easterly this time round. GP