MattH

The October GloSea update is certainly very interesting, in terms of anomalies not being what should usually be expected. A full review of all the models will be required to determine where the Oct update of the EC sits, in terms of it shifting away from the consistent blocked pattern it had shown in recent months. The December GloSea, in particular, is fascinating as clearly, Scandinavian high anomalies are rare and this pattern would also bring the risk of impacts on the strat as well, while January sees a pattern that is far more -ve NAO than what would otherwise be expected. One key feature I keep looking for in all the seasonal models this year is for the European high to be, essentially, nonexistent. As we all know if we get an inflated and dominant European high that stretches from Iberia into central and eastern Europe through the winter months it often means that upstream the pattern is troughed over the N Atlantic and you've got little or no chance of colder synoptics. Winds are often from the W or SW. As the GloSea update shows, there is clearly not much evidence for a winter that is dominated by a large European high and, to me, that is potentially more of a key feature than actual blocking to the N or NW of the British Isles. Get a trough into Europe and the jet stream will naturally follow, etc. In terms of winter synoptics and shutting off the Atlantic, then the October GloSea update for Dec, Jan and Feb is fascinating... Regards, Matt.

Morning. These kinds of posts here are the ones that just don't help people learn or gain clarity on the outlook and the content here is highly misleading. There are no 'wide confidence levels', whatever that means, and using terminology like 'foolish' when it comes to making forecasting predictions at a time frame that actually requires a forecast, is foolish in itself... That aside back to the forecast and what we see is good clarity on the initial transition to cooler weather mid-week, this has been well documented and forecasted for several days. The process for the south is obviously delayed because of the frontal wave and system from the SW that brings the risk of a sharp thermal boundary and resultant significant rainfall totals on Friday. Therefore, it is a more 'step change' to cooler weather across parts of England and Wales, a more straightforward one elsewhere. The building ridge to the W and NW then ushers in an air mass that couldn't be any more different than what is in place now (850mb temps fall 20 degrees, see below!) and temperatures WILL end up below average, widely, by this weekend with overnight frosts, especially ground frosts and depending on the longevity of the air mass from the N or NW, snow showers are likely across the hills of Scotland as well. The flow is likely to be cut off and we then end up with a building area of high pressure over the UK early next week (cold and crisp) which then looks to become a potential Scandinavia high, it is at that point confidence falls away more significantly. The story for the next 5 to 7 days can be told very well on the 00Z GFS ENS... N England is used in this instance as the example. Regards, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4934845

Morning. These kinds of posts here are the ones that just don't help people learn or gain clarity on the outlook and the content here is highly misleading. There are no 'wide confidence levels', whatever that means, and using terminology like 'foolish' when it comes to making forecasting predictions at a time frame that actually requires a forecast, is foolish in itself... That aside back to the forecast and what we see is good clarity on the initial transition to cooler weather mid-week, this has been well documented and forecasted for several days. The process for the south is obviously delayed because of the frontal wave and system from the SW that brings the risk of a sharp thermal boundary and resultant significant rainfall totals on Friday. Therefore, it is a more 'step change' to cooler weather across parts of England and Wales, a more straightforward one elsewhere. The building ridge to the W and NW then ushers in an air mass that couldn't be any more different than what is in place now (850mb temps fall 20 degrees, see below!) and temperatures WILL end up below average, widely, by this weekend with overnight frosts, especially ground frosts and depending on the longevity of the air mass from the N or NW, snow showers are likely across the hills of Scotland as well. The flow is likely to be cut off and we then end up with a building area of high pressure over the UK early next week (cold and crisp) which then looks to become a potential Scandinavia high, it is at that point confidence falls away more significantly. The story for the next 5 to 7 days can be told very well on the 00Z GFS ENS... N England is used in this instance as the example. Regards, Matt.

Subject to detail changes of course, but just looking at the medium term this afternoon and there definitely is a better model agreement now over Wednesday of next week being the day of change, properly, to a cooler/colder autumnal air mass. The EC highlights this well with the first active and significant cold front of the season with dew points circa +12C to +16C ahead of the front and falling to +4C to +8C behind, with all the additional features that come with a cold front passage. Warm few days ahead, but the change middle of next week potentially will be made even more noticeable by the warmth in the coming days... Cheers, Matt. ECMWF.mp4

The flip in the EC Seasonal for Oct is not helpful in the slightest... Closer inspection also highlights changes to Dec which last few months have been strongly signalled to be a +ve NAO month, this update shifts that to a weakly -ve NAO one, while, clearly, the strong -ve NAO signal through Jan and Feb has been watered down considerably. From a forecaster's perspective, this is exactly what was NOT needed this month, as the 'business end of the year' comes around increasingly quickly. The shift and change in signal, especially losing the +ve height anomalies towards the N Atlantic and Greenland must be linked to some change in starting data, whether this is the dreaded IOD influence it is hard to tell. Obviously, this is just one seasonal model, but after months of consistency to lose that at this point in the year is really not good at all. The IOD is certainly a 'concern', there's enough evidence and papers/journals on it that proves it increases the risk of +ve NAO patterns, as was the case of course through 2019/2020. The behaviour of this event mind is different in terms of SST anomalies there and clearly, it should weaken by the end of the year. The final 'type' of Nino could have some influence, but that's not a big issue, the broader combination of Nino + eQBO is what is of importance. If we have had a neutral or -ve IOD approaching winter then pretty much all the stars may have aligned, but as ever it is very rare to get such a setup. Coming back to the EC Seasonal the key thing will be viewing the monthly data when it is on the Copernicus website next week and also see how the other seasonal models have changed and evolved. If the other models start to shift through Oct and Nov and this blocking signal of recent months is essentially gone by Nov in most or all of the seasonals, then I will certainly be adjusting my winter predictions accordingly but, for now, steady away. Cheers, Matt.

The consistency within the seasonal models is most certainly something that remains of significant interest in terms of long-range seasonal forecasts this year, we can often see variability from one month to the next, sometimes losing a signal that many of the seasonal models have one month, for it then to be weaker or gone completely. As you highlight the consistency is quite impressive and not just from individual seasonal models, but across the board and particularly so from the more important seasonal models, like the ECMWF and GloSea and if you put any credit to it, CANSIPs as well, which many do over in the US/Canada. When you throw into the mix the eQBO and Nino combination as well, as I mentioned in a post the other day we have, generally speaking, teleconnection and seasonal models signing from the same hymn sheet which also helps the cause, when there is a clear divide that also reduces confidence markedly, of course. This combination also brings into play the scientific studies done over the years on the risk of a mid-winter SSW as well, clearly, numerous papers highlight a marked increase in the risk of a wintertime SSW with the eQBO and Nino combination, something we've not had for a good few years either. The Oct and Nov updates of the seasonals will be crucial, if we can maintain this signal then it will provide great interest and also a test of the seasonal models as well. It seems to have been a long time since I've seen such cross-model agreement on an overall evolution over a number of months. Granted we can always talk about the so-called "curve balls" that come into play, AGW, H20 content from the Hunga Tunga volcano, the final type (E-based, Modoki etc) and strength of Nino and whether the IOD event will eventually die off by Dec as currently expected. Fascinating outlook and I still stick with my own thoughts that this winter seems to be providing the best footing and foundations for colder winter synoptics than for a good few years... Cheers, Matt.

The period later next week and into the following weekend is an interesting one and, again, some of the model differences are linked to remnant tropical features over the sub-tropics and how these interact to either help amplify ridges or, the opposite, reinforce and develop lows that are then more dominant which move into NW Europe. So those, already suggesting next weekend will be very warm, etc, etc, I urge some caution over that. We continue to be within a resolute -ve AAM regime and the idea of such a pronounced European block, as per the 00Z EC, is, IMO, over-cooked. If we look at the EPS v the GEFS, as an example, we can see that from the US to the Atlantic to Europe the actual anomalies, in terms of 500mb heights are very similar, but is the EPS that is far more 'blown up' in terms of the 500mb +ve anomalies, the key one being the European feature which, therefore, dominates far more significantly than compared with the GEFS. Just sticking with the models for now, using the comparison plot below, with Manchester as a guide, we can see that the ECMWF is by far the most significant in terms of MSLP and also the 850mb temperatures, the other available models at that time frame, drop the 850's considerably as the upper trough moves eastwards and we end up with more of a W or NW'ly flow which is still expected long-term anyway. Without question all this is occurring at a time of year when it should occur, we are in that 'holding pattern' as I always call it at this time of year when it is neither summer nor properly autumn and we can get these significant swings and differences in air masses. Clearly, in a few weeks, the residual warmth drains away and, finally, we drop into 'proper' autumn patterns with little chance of any significant late warmth, etc. So, rounding it all up, there is a lot of legs left in this evolution yet, but from what I've seen and looked at this morning, the EC should most definitely not be taken at face value and I have a feeling the significantly high 850mb temperatures present from the EC now will be watered down. Whether the trough gets in as much as the GEFS (GFS, GEM, lesser extent the UKMO etc.) show also remains to be seen, but my money is firmly on next weekend not being as 'late summer-like' as what the EC is currently showing at all, potentially the opposite, but we shall see. Cheers, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4930180

The period later next week and into the following weekend is an interesting one and, again, some of the model differences are linked to remnant tropical features over the sub-tropics and how these interact to either help amplify ridges or, the opposite, reinforce and develop lows that are then more dominant which move into NW Europe. So those, already suggesting next weekend will be very warm, etc, etc, I urge some caution over that. We continue to be within a resolute -ve AAM regime and the idea of such a pronounced European block, as per the 00Z EC, is, IMO, over-cooked. If we look at the EPS v the GEFS, as an example, we can see that from the US to the Atlantic to Europe the actual anomalies, in terms of 500mb heights are very similar, but is the EPS that is far more 'blown up' in terms of the 500mb +ve anomalies, the key one being the European feature which, therefore, dominates far more significantly than compared with the GEFS. Just sticking with the models for now, using the comparison plot below, with Manchester as a guide, we can see that the ECMWF is by far the most significant in terms of MSLP and also the 850mb temperatures, the other available models at that time frame, drop the 850's considerably as the upper trough moves eastwards and we end up with more of a W or NW'ly flow which is still expected long-term anyway. Without question all this is occurring at a time of year when it should occur, we are in that 'holding pattern' as I always call it at this time of year when it is neither summer nor properly autumn and we can get these significant swings and differences in air masses. Clearly, in a few weeks, the residual warmth drains away and, finally, we drop into 'proper' autumn patterns with little chance of any significant late warmth, etc. So, rounding it all up, there is a lot of legs left in this evolution yet, but from what I've seen and looked at this morning, the EC should most definitely not be taken at face value and I have a feeling the significantly high 850mb temperatures present from the EC now will be watered down. Whether the trough gets in as much as the GEFS (GFS, GEM, lesser extent the UKMO etc.) show also remains to be seen, but my money is firmly on next weekend not being as 'late summer-like' as what the EC is currently showing at all, potentially the opposite, but we shall see. Cheers, Matt.

Yeah, it's an interesting one and the wait goes on for a more obvious link. There is still evidence for a more coherent MJO passage and associated WWB over the next 7 to 14 days, which may start to tip the balance in favour of a more +ve AAM trend, but this is still not likely to be anything like what happened back in May which contributed to the +ve AAM pattern then. It is also interesting to look at the AAM plot from the last year and, as usual, they tell the story, atmospherically well. We can see the significant propagation of the -ve E'ly AAM anomalies through April and particularly May to the higher latitudes, as the tropics and sub-tropics were dominated by W'ly momentum. Since then we've had nothing and, again tells the story of the summer well. Clearly, the collapse of the AAM in late June/early July was a key event for the summer which was a curveball for us all... As we can see as well since late July the overall AAM trend has been -ve, even though, as you mention, oceanically, we are now in an El Nino state, it's all very troubling for the outlook period. With the IOD peaking through the late year I'm less concerned about this than the other year when it just snowballed everything, while the overall combination of El Nino and an eQBO should bring some results, at a minimum aiding the increased probability of a mid-winter SSW. The one caveat and uncertainty that troubles me is the influence of the high H20 content within the stratosphere from last year's Hunga Tonga volcano. I think there are or now are some papers out on this, produced this summer, but not had time to dig these out. But from what I know the science behind it a much increased H20 content within the stratosphere should/could help to cool the stratosphere more significantly and effectively, thus increasing the chances of a more robust vortex, but, then if that were to come to fruition could lead to a more spectacular vortex demise if an SSW were to occur. As ever, plenty of jigsaw pieces to look at and try and put together, but the pleasing aspect this year, unlike some years which makes an outlook even more difficult, is that, overall, we have both teleconnection and seasonal model support in terms of a general +ve NAO start and then a much-increased risk of -ve NAO winter, in time and, for me, that is still the form horse. Any early cold, potentially short-term driven by the MJO, depending on timing, while the main thrust of colder synoptics likely to follow into the New Year, but, as ever, time will tell. Overall, however, despite all the usual offsets/unknowns that can come with AGW, I believe we will move into a winter that has one of the highest probabilities of bringing colder synoptics for a good number of years, driven, primarily by the eQBO and Nino combination, while the SSW risk should be higher than usual too. Cheers, Matt.

It's an interesting outlook in terms of the Euro high blowing up and creating more of a N and W, S and E split, or perhaps even a NW-SE split. The models continue to play around with the more positively tilted trough, in time, as the European heights build. It is interesting to see something of a shift more towards a cyclonic pattern, with the high being kept more over Europe, this would follow the general upstream pattern and the continued bias on an atmosphere that is more Nina-like than Nino. Clearly, another few weeks and we will start to see an increasing influence from the trop PV as the thermal gradient starts to increase, but for now, my money is a more cyclonic outlook, than an anticyclonic one, but it's a borderline scenario. Snapshot from my LR update yesterday highlights overall thoughts... Cheers, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4926673

It's an interesting outlook in terms of the Euro high blowing up and creating more of a N and W, S and E split, or perhaps even a NW-SE split. The models continue to play around with the more positively tilted trough, in time, as the European heights build. It is interesting to see something of a shift more towards a cyclonic pattern, with the high being kept more over Europe, this would follow the general upstream pattern and the continued bias on an atmosphere that is more Nina-like than Nino. Clearly, another few weeks and we will start to see an increasing influence from the trop PV as the thermal gradient starts to increase, but for now, my money is a more cyclonic outlook, than an anticyclonic one, but it's a borderline scenario. Snapshot from my LR update yesterday highlights overall thoughts... Cheers, Matt.

Ahh the coolness, the freshness!... Extremes of weather are always interesting, as was the longevity of the omega block that helped dominate the significant heat, but what made this more difficult to 'take' was the time of year. While, as an equivalent, early March can still bring late winter weather, early September can still be like late summer, but it just never 'feels' right to me to get that kind of synoptic and heat in September, whether it's the opening week or the last week. Clearly, the longevity of the hot weather was extreme and, without question, that spell last week wouldn't have looked out of place in mid-summer... It was, to an extent nice to enjoy after July and August, but without question, as ever, heat is just harder to deal with than cold, IMO - Far easier to get yourself warmer, than colder and all that, plus like many on this thread I'm just not a fan of that kind of heat, or should I say the humidity, in particular. Heat and sunshine (like June which was stunning!) are absolutely fine, late summer synoptics often bring the dreaded, horrendous humidity as did this past week. Now a case of good riddance, interesting of course, but good riddance....it's now time for the 'best' 6 months of the year! Matt.

I like this, definitely in keeping with my own thoughts at this time and really does sum up the current expected thinking looking ahead, not just combining teleconnections, but also the latest seasonal data as well... What we need to see, from the seasonals, is a consistent pattern and evolution over the next 2-3 months. We've started off on a very good/interesting footing for the winter in terms of how the +ve MSLP and 500mb height build over Greenland as the winter progresses. Obviously first appearing last month, but now in the majority of this month's updates as well. For me, seasonal model-wise, the focus still has to be on the likes of GloSea and ECMWF, as compared with some of the other models, but like anything else, more data, more analysis and, usually, a better outcome. Let's see if this signal holds or collapses by the time we get to November. As ever, any sort of signal in the seasonal models that isn't the norm (+ve NAO winter time pattern) has to be taken note of!. I've been on 'edge' with regards to the IOD and I think this is something that needs watching very closely indeed. I think it was 2015 or perhaps 2017 when this went into overdrive and really did dominate the winter patterns upstream but with the usual downstream influences. The likes of solar can always be argued and discussed until we are blue in the face and it isn't anything I take much note of really these days. The key one of significance as well is the eQBO, without question we all know that this can influence the trop and strat PV and a robust and solid eQBO phase through the winter will no doubt open opportunities that wouldn't be there, or not to the same extent/risk, in a strong wQBO winter. When coupled with Nino regimes the end result, as documented in several papers is one that increases the chances of SSW's and colder synoptics as the winter progresses. So coming back to the original post and, again, this sums it up well...slow burner and then let's see how Jan and Feb end up. We are most certainly well overdue a decent Jan and Feb in terms of cold synoptics. Cheers, Matt.

Afternoon. We look to be entering into another period of 'strangeness' in terms of the eastward progression of the -ve VP200 signature, compared with what was originally expected. Far from a scientific word, but it'll do and clearly there was an underestimation of this evolution back in late June and into July which, of course, meant the general pattern remain more La Nina-like (-AAM) than the other way around. Once again, models and analysis of the evolution of this signal are trending the other way. What seemed like a robust signal for a +GLAAM event as September progresses is becoming increasingly watered down, as is, therefore, the signal in NWP for a more anticyclonic pattern. There is still some bias on getting high pressure but of which could be in a locale that leads to a more -ve NAO regime looking ahead. We can see this increasingly cyclonic bias as well from the daily runs of the EC32 for the 18th to 25th of September, a period of September which, a week or two back was more likely to lead to anticyclonic conditions than cyclonic.... If you flick through recent days and runs of the CFSv2 data, as an example, you can see how the high +GLAAM signal a week or two ago has continued to be nibbled away at - https://atlas.niu.edu/forecast/aam/cfsv2_aam_fcst.php Despite the +IOD and Nino progression we are seeing yet another collapse of the MJO that was expected to be far more noteworthy through September than is now likely. The end result, a lower probability of getting high pressure in the right places to bring some further pleasant conditions and with a far more likelihood of a NW European trough looking ahead. I guess it is September now after all and after this last week as well, it really is time for autumn... Cheers, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4921293

Afternoon. We look to be entering into another period of 'strangeness' in terms of the eastward progression of the -ve VP200 signature, compared with what was originally expected. Far from a scientific word, but it'll do and clearly there was an underestimation of this evolution back in late June and into July which, of course, meant the general pattern remain more La Nina-like (-AAM) than the other way around. Once again, models and analysis of the evolution of this signal are trending the other way. What seemed like a robust signal for a +GLAAM event as September progresses is becoming increasingly watered down, as is, therefore, the signal in NWP for a more anticyclonic pattern. There is still some bias on getting high pressure but of which could be in a locale that leads to a more -ve NAO regime looking ahead. We can see this increasingly cyclonic bias as well from the daily runs of the EC32 for the 18th to 25th of September, a period of September which, a week or two back was more likely to lead to anticyclonic conditions than cyclonic.... If you flick through recent days and runs of the CFSv2 data, as an example, you can see how the high +GLAAM signal a week or two ago has continued to be nibbled away at - https://atlas.niu.edu/forecast/aam/cfsv2_aam_fcst.php Despite the +IOD and Nino progression we are seeing yet another collapse of the MJO that was expected to be far more noteworthy through September than is now likely. The end result, a lower probability of getting high pressure in the right places to bring some further pleasant conditions and with a far more likelihood of a NW European trough looking ahead. I guess it is September now after all and after this last week as well, it really is time for autumn... Cheers, Matt.

Morning. Back to some good old-fashioned short-term analysis, but it's worth highlighting a few differences within the models that forecasters have and continue to deal with regard to the remnants of Franklin. In recent days it has been the UKMO model, primarily, that has developed the remnants of Franklin as a simple entity that heads towards Greenland, the southern tip, but that is the least likely evolution. The differences between that solution and the likes of the ECMWF and the GFS have had a massive impact on the weather for the weekend. If we jump back to the 12Z UKMO from yesterday you'll see what I mean... What this does is alter the downstream pattern over NW Europe to the point we move over the weekend in a far more troughed regime, perhaps thundery too, especially across the south. The key reason is that there isn't as much WAA to help build the ridge, as is now expected. This has been a battle to figure out over the last 48 hours, but in this instance, it looks like the UKMO model has got this one wrong. If we look at the other solution, the most likely solution, that is the remnants of Franklin are left behind, at least, for a time, this is then better for the UK this weekend as eventually the remnants are picked up, but create an atmospheric pattern that is far more conducive to building heights through WAA, the 00z ECMWF highlights this perfectly... The low towards Greenland on the ECMWF (and other models) is not Franklin, Franklin is left floating around over open waters, but this difference is what stops the upper trough dominating (like the UKMO) solution and instead creates a far better pattern for height rises, which is now the preferred outcome. Clearly, September and, to an extent, October is 'silly season' with remnant features and this last 48 hours or so is a textbook example of how these remnant features can have massive impacts on the downstream weather for the British Isles and how even at short-lead-times, the forecast can change or hang in the balance until a better understanding and representation of these features is visible. Thankfully, in this instance, the UKMO model has been incorrect and Franklin won't end up over Greenland, and we, as a result, end up with a very pleasant weekend ahead... Cheers, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4913129

Morning. Back to some good old-fashioned short-term analysis, but it's worth highlighting a few differences within the models that forecasters have and continue to deal with regard to the remnants of Franklin. In recent days it has been the UKMO model, primarily, that has developed the remnants of Franklin as a simple entity that heads towards Greenland, the southern tip, but that is the least likely evolution. The differences between that solution and the likes of the ECMWF and the GFS have had a massive impact on the weather for the weekend. If we jump back to the 12Z UKMO from yesterday you'll see what I mean... What this does is alter the downstream pattern over NW Europe to the point we move over the weekend in a far more troughed regime, perhaps thundery too, especially across the south. The key reason is that there isn't as much WAA to help build the ridge, as is now expected. This has been a battle to figure out over the last 48 hours, but in this instance, it looks like the UKMO model has got this one wrong. If we look at the other solution, the most likely solution, that is the remnants of Franklin are left behind, at least, for a time, this is then better for the UK this weekend as eventually the remnants are picked up, but create an atmospheric pattern that is far more conducive to building heights through WAA, the 00z ECMWF highlights this perfectly... The low towards Greenland on the ECMWF (and other models) is not Franklin, Franklin is left floating around over open waters, but this difference is what stops the upper trough dominating (like the UKMO) solution and instead creates a far better pattern for height rises, which is now the preferred outcome. Clearly, September and, to an extent, October is 'silly season' with remnant features and this last 48 hours or so is a textbook example of how these remnant features can have massive impacts on the downstream weather for the British Isles and how even at short-lead-times, the forecast can change or hang in the balance until a better understanding and representation of these features is visible. Thankfully, in this instance, the UKMO model has been incorrect and Franklin won't end up over Greenland, and we, as a result, end up with a very pleasant weekend ahead... Cheers, Matt.

Afternoon... Short-term and, a case of 'as you were', the connections between upstream Pacific activity and downstream influences are highly obvious even in general 500mb height anomaly charts, with a high wave number pattern dominating through the short-term. You guessed it, where the ridge and trough end up near the British Isles, as has been the case since early July; N Atlantic and then over the British Isles. However, all eyes are once again firmly on the upstream developments, long-term, looking ahead towards and beyond mid-September. While there were clearly uncertainties and divergences earlier in the summer with regard to the influence the AAM would have on the pattern, this upcoming development looks far more robust. Therefore, and "unfortunately", I would put money on September producing synoptic patterns that all the summer fans would have wanted 4 to 8 weeks prior - I fully expect this September to do what numerous others have done and produce better conditions for fine weather than much of the summer, is this becoming a new norm one may ask as a long-term trend, another topic of discussion perhaps(?) The upcoming pattern changes further into September are linked to the expected eastward movement of a significant -ve VP200 anomaly, associated WWB and subsequent rise in AAM, this, as per all the usual mechanics, will alter the upstream and downstream pattern. One caveat to add is the Atlantic hurricane season, a muted period ahead, but as we all know remnant features can be a troublesome aspect. However, that aside it remains interesting that not only did the monthly continue to correct itself with the current AAM state, but the rise looking ahead looks noteworthy. The useful CFSv2 plot as well showing what may happen to the GWO, but not to be taken too literally, of course. It is also worth running through previous runs of this model to gain better clarity on the direction of travel rather than just taking one graphic as a snapshot - The link is here - AAM Forecast Archive ATLAS.NIU.EDU So, at this juncture there isn't much more to add, yes summer (meteorologically speaking) will now no doubt come and go and that will be that and September will soon be here. As can often happen in March as well, winter synoptics appear when many wanted them weeks back and I would put money on the opposite occurring this time, through September, with anticyclonic patterns pulling through. Clearly, this can still bring some very pleasant conditions indeed, welcomed by many though clearly not likely to bring the more significant or noteworthy temperatures and conditions that can occur in July and August. All eyes on the Pacific in approx a week's time and then a close eye on FT and MT tendencies within the opening 7 to 10 days of September and then potential changes towards mid-month, as a rough guide. Cheers, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4910007

Afternoon... Short-term and, a case of 'as you were', the connections between upstream Pacific activity and downstream influences are highly obvious even in general 500mb height anomaly charts, with a high wave number pattern dominating through the short-term. You guessed it, where the ridge and trough end up near the British Isles, as has been the case since early July; N Atlantic and then over the British Isles. However, all eyes are once again firmly on the upstream developments, long-term, looking ahead towards and beyond mid-September. While there were clearly uncertainties and divergences earlier in the summer with regard to the influence the AAM would have on the pattern, this upcoming development looks far more robust. Therefore, and "unfortunately", I would put money on September producing synoptic patterns that all the summer fans would have wanted 4 to 8 weeks prior - I fully expect this September to do what numerous others have done and produce better conditions for fine weather than much of the summer, is this becoming a new norm one may ask as a long-term trend, another topic of discussion perhaps(?) The upcoming pattern changes further into September are linked to the expected eastward movement of a significant -ve VP200 anomaly, associated WWB and subsequent rise in AAM, this, as per all the usual mechanics, will alter the upstream and downstream pattern. One caveat to add is the Atlantic hurricane season, a muted period ahead, but as we all know remnant features can be a troublesome aspect. However, that aside it remains interesting that not only did the monthly continue to correct itself with the current AAM state, but the rise looking ahead looks noteworthy. The useful CFSv2 plot as well showing what may happen to the GWO, but not to be taken too literally, of course. It is also worth running through previous runs of this model to gain better clarity on the direction of travel rather than just taking one graphic as a snapshot - The link is here - AAM Forecast Archive ATLAS.NIU.EDU So, at this juncture there isn't much more to add, yes summer (meteorologically speaking) will now no doubt come and go and that will be that and September will soon be here. As can often happen in March as well, winter synoptics appear when many wanted them weeks back and I would put money on the opposite occurring this time, through September, with anticyclonic patterns pulling through. Clearly, this can still bring some very pleasant conditions indeed, welcomed by many though clearly not likely to bring the more significant or noteworthy temperatures and conditions that can occur in July and August. All eyes on the Pacific in approx a week's time and then a close eye on FT and MT tendencies within the opening 7 to 10 days of September and then potential changes towards mid-month, as a rough guide. Cheers, Matt.

Morning. Just a quick addition to recent posts, but with the overall trend in AAM yet again on a downward path, it is, perhaps, no surprise that any sort of build of heights over W Europe continues to be blown away looking ahead and we end up with a more cyclonic pattern soon returning. We can see from the GWO plot that we are heading back towards phase 8 and, no doubt dropping down into phase 1, all indicators of a falling AAM regime. The tendency plot highlights this well, with a pronounced change in recent days. The actual AAM profile is quite interesting with a 4-way split in terms of the expected +ve W'ly anomalies through the tropics (linked to the recent WWB/MJO activity), weak E'ly anomalies circa 40N, W'lies again near 50N and a very weak E'ly anom at circa 60N and above. Once again the story of the summer can be well told by the GSDM pattern and evolution since late May onwards. In terms of model data looking ahead, we can see the downward trend in the expected AAM pattern through the rest of Aug on the below... Obviously, there is some evidence for another rise into September, but it's probably not even worth bothering about that too much at the moment, but what are you betting we end up with summer synoptics, through some part of September, that many wanted in the previous 6 to 8 weeks. Equally, after the way July and, most likely, August will pan out, a fine week or two of September weather wouldn't go a miss! As I mentioned a week or two back even I have been surprised by how 'locked in' the cyclonic pattern has been since early July, even though the initial trend towards a more cyclonic period into July was most certainly expected, once the huge WWB event through May and into June eased away, etc. I think it was Tamara who highlighted well also how the unknowns, linked to AGW and all the mesoscale and macro-scale extremes around the planet may well be providing and producing 'curve balls' that cannot be foreseen and can tip the balance away from what is usually/most likely expected. In terms of the rest of August then I think the best one can hope for is a repeat of the pattern that plays out this week, with a transient S or SW'ly bringing some warmth and humidity. Otherwise, IMO, the writing is on the wall now for the rest of meteorological summer and I can't see much evidence if anything, that will mean a solid week or more of anticyclonic, late summer weather will arrive before the end of Aug, and this summer will end up going down as yet another one of those where the best of the weather of the year was through May and June and then the 'wheels came off' again as has happened a handful of times now over the last 10 to 20 years. Regards, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4901306

Morning. Just a quick addition to recent posts, but with the overall trend in AAM yet again on a downward path, it is, perhaps, no surprise that any sort of build of heights over W Europe continues to be blown away looking ahead and we end up with a more cyclonic pattern soon returning. We can see from the GWO plot that we are heading back towards phase 8 and, no doubt dropping down into phase 1, all indicators of a falling AAM regime. The tendency plot highlights this well, with a pronounced change in recent days. The actual AAM profile is quite interesting with a 4-way split in terms of the expected +ve W'ly anomalies through the tropics (linked to the recent WWB/MJO activity), weak E'ly anomalies circa 40N, W'lies again near 50N and a very weak E'ly anom at circa 60N and above. Once again the story of the summer can be well told by the GSDM pattern and evolution since late May onwards. In terms of model data looking ahead, we can see the downward trend in the expected AAM pattern through the rest of Aug on the below... Obviously, there is some evidence for another rise into September, but it's probably not even worth bothering about that too much at the moment, but what are you betting we end up with summer synoptics, through some part of September, that many wanted in the previous 6 to 8 weeks. Equally, after the way July and, most likely, August will pan out, a fine week or two of September weather wouldn't go a miss! As I mentioned a week or two back even I have been surprised by how 'locked in' the cyclonic pattern has been since early July, even though the initial trend towards a more cyclonic period into July was most certainly expected, once the huge WWB event through May and into June eased away, etc. I think it was Tamara who highlighted well also how the unknowns, linked to AGW and all the mesoscale and macro-scale extremes around the planet may well be providing and producing 'curve balls' that cannot be foreseen and can tip the balance away from what is usually/most likely expected. In terms of the rest of August then I think the best one can hope for is a repeat of the pattern that plays out this week, with a transient S or SW'ly bringing some warmth and humidity. Otherwise, IMO, the writing is on the wall now for the rest of meteorological summer and I can't see much evidence if anything, that will mean a solid week or more of anticyclonic, late summer weather will arrive before the end of Aug, and this summer will end up going down as yet another one of those where the best of the weather of the year was through May and June and then the 'wheels came off' again as has happened a handful of times now over the last 10 to 20 years. Regards, Matt.

Morning. One has to acknowledge the 'painful' progression that this summer has taken, since late June all linked to the fall in AAM, as well advertised and discussed for some time. A few weeks ago I provided a screenshot of a piece of work on the long-range outlook with the phrase "locked in for some time" within it; even I have been surprised and incorrect about how long this cyclonic pattern has persisted. While I still don't think this summer can be compared with the likes of 2012, 2007 et al, as yet, the broader evolution (yet again!) of the best weather arriving earlier in the summer, or late spring, and then the proverbial 'wheels coming off scenario', is playing out again this summer. We have seen this a handful of times say in the last 10 to 15 years. Is this perhaps becoming a more common occurrence due to global warming and all the unusual unknowns in play?, possible, but hard to tell - It is clear, however, that we are certainly in a period of heightened uncertainty and questions, more generally, than say 10, 20, 30 years ago, due to the way global warming is influencing the climate at an ever rapid rate. AGW aside and the AAM and the Pacific developments have and are now evolving as long predicted, we can see that in both model and observed data... However, there is still little evidence of the AAM patterns and anomalies that were present in May and June. Clearly, this current rise in AAM is not as significant as back in May, equally, the AAM is also rising from an unexpectedly low point too. There are some 'messy' solutions now within NWP showing up in the long-term, but still, no clear-cut signal for the Atlantic trough and downstream ridge pattern before the opening week of August has passed, so that's another week gone. While I can be far from certain, when working over the weekend I was looking at the QBO and wondering whether the influence of this, as some have picked up on in here, could well be a player this summer, more so than was envisaged and/or expected. As is the case during the winter, in a changing QBO phase the lower levels of the stratosphere can be 'washed out', not a particularly scientific phrase, but it does highlight the situation well. Last summer, it was generally the opposite. We are now well within a strong East Descending phase, the E'ly winds are now down to 30hPa (all very interesting for the winter!), beneath this and the W'lies are still in play - Is there some scope to suggest that this transitional phase of the QBO has arrived at the wrong time, to aid in juicing up the W'lies and the PFJ as the summer has ticked by? - I suggest it could well be. Since May and June, the QBO has continued to become more E'ly in the upper levels, flushing down the more W'ly anomalies, has this reinforced a more active jet stream pattern, especially when coupled with a complete breakdown in the +ve AAM pattern that dominated the late spring and early summer. It's a piece of the jigsaw puzzle that is open for discussion, but while there has been an underestimation of how far AAM has fallen and, how, Tamara mentioned a few days ago, the atmospheric pattern, in particular, has resembled a more Nina regime, I feel there may well be more at play than just the GSDM/AAM this summer now. I still think this rise in AAM will help to at least alleviate the pattern that has dominated the last 4-5 weeks, but will it bring us a solid 2-week spell of 'high summer' weather through August, I'm beginning to think not, especially seeing that it is likely that AAM will take something of a fall again through the second half of August. The additional complication through August as well will be remnant tropical features, as we all know sometimes these can help to bring some summer weather, but also reinforce a more cyclonic pattern too, that, however, is all for the short-term. For now, a case of 'more of the same' as the summer increasingly quickly rattles on... Cheers, Matt. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4895291

Morning. One has to acknowledge the 'painful' progression that this summer has taken, since late June all linked to the fall in AAM, as well advertised and discussed for some time. A few weeks ago I provided a screenshot of a piece of work on the long-range outlook with the phrase "locked in for some time" within it; even I have been surprised and incorrect about how long this cyclonic pattern has persisted. While I still don't think this summer can be compared with the likes of 2012, 2007 et al, as yet, the broader evolution (yet again!) of the best weather arriving earlier in the summer, or late spring, and then the proverbial 'wheels coming off scenario', is playing out again this summer. We have seen this a handful of times say in the last 10 to 15 years. Is this perhaps becoming a more common occurrence due to global warming and all the unusual unknowns in play?, possible, but hard to tell - It is clear, however, that we are certainly in a period of heightened uncertainty and questions, more generally, than say 10, 20, 30 years ago, due to the way global warming is influencing the climate at an ever rapid rate. AGW aside and the AAM and the Pacific developments have and are now evolving as long predicted, we can see that in both model and observed data... However, there is still little evidence of the AAM patterns and anomalies that were present in May and June. Clearly, this current rise in AAM is not as significant as back in May, equally, the AAM is also rising from an unexpectedly low point too. There are some 'messy' solutions now within NWP showing up in the long-term, but still, no clear-cut signal for the Atlantic trough and downstream ridge pattern before the opening week of August has passed, so that's another week gone. While I can be far from certain, when working over the weekend I was looking at the QBO and wondering whether the influence of this, as some have picked up on in here, could well be a player this summer, more so than was envisaged and/or expected. As is the case during the winter, in a changing QBO phase the lower levels of the stratosphere can be 'washed out', not a particularly scientific phrase, but it does highlight the situation well. Last summer, it was generally the opposite. We are now well within a strong East Descending phase, the E'ly winds are now down to 30hPa (all very interesting for the winter!), beneath this and the W'lies are still in play - Is there some scope to suggest that this transitional phase of the QBO has arrived at the wrong time, to aid in juicing up the W'lies and the PFJ as the summer has ticked by? - I suggest it could well be. Since May and June, the QBO has continued to become more E'ly in the upper levels, flushing down the more W'ly anomalies, has this reinforced a more active jet stream pattern, especially when coupled with a complete breakdown in the +ve AAM pattern that dominated the late spring and early summer. It's a piece of the jigsaw puzzle that is open for discussion, but while there has been an underestimation of how far AAM has fallen and, how, Tamara mentioned a few days ago, the atmospheric pattern, in particular, has resembled a more Nina regime, I feel there may well be more at play than just the GSDM/AAM this summer now. I still think this rise in AAM will help to at least alleviate the pattern that has dominated the last 4-5 weeks, but will it bring us a solid 2-week spell of 'high summer' weather through August, I'm beginning to think not, especially seeing that it is likely that AAM will take something of a fall again through the second half of August. The additional complication through August as well will be remnant tropical features, as we all know sometimes these can help to bring some summer weather, but also reinforce a more cyclonic pattern too, that, however, is all for the short-term. For now, a case of 'more of the same' as the summer increasingly quickly rattles on... Cheers, Matt.

Morning. Another week and another cyclonic one at that, the emphasis, as a few have mentioned in recent posts, is for a more cyclonic push just in time for another 'summer weekend' as well, with low pressure returning more significantly by Fri and into the forthcoming weekend as well. That aside and the medium and long-term processes to, eventually, change the pattern are underway and a close watch is now required on rather than having the primary trough over the UK to see it pull back westwards. At a minimum even if the weather remains more cyclonic, with the trough just to the W, a trend towards a greater risk of S or SW'ly flows, than compared with W or NW'lies should develop. We can see on the OLR plot and the latest AAM data that upstream Pacific changes are now starting to take place as long predicted, but clearly incorrectly in terms of timing. You do have to admit though that the outlook for the rest of July is looking increasingly poor and the key area where any predictions have gone array for July are, again, linked to timing rather than the overall expected changes. So, therefore, one has to hold your hands up and say that any upstream changes now don't look like saving July, or not in any significant way. There may still be a change for the upper troughed pattern to pull back westwards within the next 10 to 14 days, with a late July 'warm up', but that may still coincide with a more cyclonic pattern. Until that happens as well then temperatures are really going to struggle in what is, on average, the warmest part of the year/summer. However, as discussed a handful of times the upstream Pacific changes are on the way so a close eye on late July onwards is now certainly required, but even I have been surprised by how 'locked in' the cyclonic pattern this July has become and looks set to continue as well, the reasons for that are open to discussion I guess. All that aside and yes, after the superb May and June, July 'feels' even worse and clearly a 'polar opposite' regime to what was in place during May and June. However, this is the British Isles after all and even in the best of summers, do we get three months of sunny, warm weather? - the answer is obviously, no, we don't. After the current spell clears through though we still have the whole of Aug left and a few decent weeks of summer weather in Aug, when coupled with what we got in May and June would still, IMO, make this a reasonable summer overall. The upcoming rise in AAM certainly brings significant hope for Aug and could well be a key story for how the rest of the summer plays out... Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4890522

Morning. Another week and another cyclonic one at that, the emphasis, as a few have mentioned in recent posts, is for a more cyclonic push just in time for another 'summer weekend' as well, with low pressure returning more significantly by Fri and into the forthcoming weekend as well. That aside and the medium and long-term processes to, eventually, change the pattern are underway and a close watch is now required on rather than having the primary trough over the UK to see it pull back westwards. At a minimum even if the weather remains more cyclonic, with the trough just to the W, a trend towards a greater risk of S or SW'ly flows, than compared with W or NW'lies should develop. We can see on the OLR plot and the latest AAM data that upstream Pacific changes are now starting to take place as long predicted, but clearly incorrectly in terms of timing. You do have to admit though that the outlook for the rest of July is looking increasingly poor and the key area where any predictions have gone array for July are, again, linked to timing rather than the overall expected changes. So, therefore, one has to hold your hands up and say that any upstream changes now don't look like saving July, or not in any significant way. There may still be a change for the upper troughed pattern to pull back westwards within the next 10 to 14 days, with a late July 'warm up', but that may still coincide with a more cyclonic pattern. Until that happens as well then temperatures are really going to struggle in what is, on average, the warmest part of the year/summer. However, as discussed a handful of times the upstream Pacific changes are on the way so a close eye on late July onwards is now certainly required, but even I have been surprised by how 'locked in' the cyclonic pattern this July has become and looks set to continue as well, the reasons for that are open to discussion I guess. All that aside and yes, after the superb May and June, July 'feels' even worse and clearly a 'polar opposite' regime to what was in place during May and June. However, this is the British Isles after all and even in the best of summers, do we get three months of sunny, warm weather? - the answer is obviously, no, we don't. After the current spell clears through though we still have the whole of Aug left and a few decent weeks of summer weather in Aug, when coupled with what we got in May and June would still, IMO, make this a reasonable summer overall. The upcoming rise in AAM certainly brings significant hope for Aug and could well be a key story for how the rest of the summer plays out...