[Model Output Discussion October 2012]

Interesting changes in the model output so far today. The GFS and ECM seemed to have swapped places so to speak, with the GFS backing off from its northerly with LP moving in before the coldest air reaches us, whilst the ECM is holding back the LP and showing colder air reaching us.

The GEM has picked up the GFS theme from yesterday by bringing down cold north-easterlies.

There is still quite a lot of consistency in the short- to mid-term amongst the models with the remains of Hurricane Raphael absorbing what is left of our present LP complex. Thereafter, pressure builds to the N and NW.

Looking at the current jet location suggests to me 2 scenarios in the mid- to long-term:

1, In order for the cold air to reach us, there needs to be a more meridional flow over the E of the US and Canada. The existing 500mb high near Greenland would thus be enhanced as warm air heads NE towards Greenland, whilst an extending upper trough develops over the E Atlantic, the UK and W Europe.

2. Alternatively, no major 500mb troughing occurs over N America and the upper trough near us only gets about as far as Scandinavia, and the SW jet pushes back in, as depicted currently by the GFS.

The current upper level configuration still, in my opinion, favours the first scenario. Looking at today's 500mb chart, there are signs of a deepening vortex possibly digging down from the Pacific NW into the W USA which would I think enhance downstream amplification.

At this stage, given the accepted unreliability of the early model runs, and the time frame we are talking about, there is clearly a great deal of uncertainty but the fact that the trend is being shown by more than one model makes me think there is something to it.

I'll see what later runs have to say to see how this forecast trend develops.

[Model Output Discussion October 2012]

Having watched the models dither a lot for a few days, I am really quite surprised today to see the GFS keep a reasonable consistency throughout today's runs, and what a weird outlook it portrays - 528dm thickness values across the whole country!?

I think what has been causing the confusion in the last day or two is the handling of Hurricane Raphael as it transitions into a post-tropical low and the models haven't seemed able to determine where it will go. But now I think there are begining to get a better handle on it, leaving us with its remains as a slow-moving LP out in the Atlantic.

Meanwhile, whilst the GFS is currently decisive in pulling in Arctic air in the medium to long-term, the ECM is somewhat similar but keeps LP much farther north, whilst the other models have HP near or to the east of the UK.

It is worth considering what is happening now. The 500mb is taking on a more decidedly blocked look with an upper high to our N, which has been there a few days, gradually retrogressing towards Greenland and is part of an Omega block in configuration:

As the current active LP systems end up merging over the UK, with the associated upper trough disrupting, it seems reasonable to accept that, as the LP over us weakens, it will merge with the Atlantic LP and draw in warm air for a few days. After that, the GFS development is quite plausible - I have seen this type of transition occur in the past - but of course it is still too far away to put too much trust in it. However, in several days time, if this theme persists, then there is a good chance of some unseasonably cold weather. Personally, I think it will, maybe not quite as drastically as the current GFS maintains, but this type of block occurring now would be most interesting, as would its significance towards what type of flow we can expect in the weeks to come, i.e. the tendency for 500mb patterns to recur. I shall have more to say over the next day or two to see if the hemispheric pattern appears to support the GFS outlook

This has been a year of many extremes, with some notable records broken. Maybe we shall see an "earliest snow" record under threat!

[Model Output Discussion October 2012]

come on that is far too early for it to have any bearing on winter, again see the post from chio about when the Stratosphere thread is usually opened and the comment from GP?

John, I freely admit that my suggestions for longer term weather trends are largely intuitive and so can run counter to what other scientific evidence for these may suggest. As you were a Met Office forecaster of long-standing, I am sure you made use of your "weather instincts" at times when faced with mixed or contradictory model output when making your forecasts. All I do is base what I say on what I see on current surface and upper air charts and what I have seen in the past. Not exactly scientific, I know and I can and do get it wrong! However, we'll see what happens!

[Model Output Discussion October 2012]

Thanks for replying, I always enjoy reading your posts.

Thank you Frosty, much appreciated!

[Model Output Discussion October 2012]

Should we be looking towards NE Europe for the first wintry blast then OldMetMan?

My guess is that the first sortie will more likely be from the N, as I said, so much depends on this northern block developing. Bit too early to expect any real cold yet, which is why I am following the thickness charts closely to watch for any cold pooling in the area you mention, plus the Arctic region in general. Like I said in another post, the cooling seems to be happening quite quickly.

Give it a few more days and see if the longer term trends are coming into line in the model output with regard to blocking or not.

[Model Output Discussion October 2012]

That's a perfect undercutting low if ever I saw one. Can't say I really pay much attention to the GEM model, I always thought it was one of the cannon fodder models?

12z GFS keeps high pressure over Greenland for the entire run but also traps low pressure over us for the foreseeable

Hi Daniel, I don't look at the GEM that often also, but I have noticed it prove correct on long terms trends on a number of occasions, usually at odds with what all the other models are saying.

[Model Output Discussion October 2012]

Just as a quick addendum, here is a fascinating view from the latest GEM model output, a model I tend to trust the most when it comes to longer term trends. It shows very clearly the type of northern blocking we've been talking about that brings really cold conditions in winter - bit too early for that now I think but it'll be most interesting to see if that is how it turns out and what subsequently follows.

.

[Model Output Discussion October 2012]

omm - not sure how old you are but how often do you recall the polar pattern in the last third of october reflecting that currently shown on the models ?

Hi Bluearmy, not that old but I joined the Met Office in 1969 which should give you some idea!

I cannot offhand recall this pattern before in October. However, in the really cold winters I can remember, there have been some early clues, especially late 1962 which I seem to recall there being some unusually cold weather late autumn, which in turn had been preceded by a cool, unsettled summer such as we have just had.

I think in the current situation, that it may only suggest, as I said, possible signs of an early cold spell, which in itself, doesn't to me indicate that the following winter will necessarily be cold.

However, as I explained in my post, this has been such a lack of persistent HP near us for so long now, plus the endless run of LPs, I am inclined to think this will balance out soon. That, together with the trend towards a much more amplified upper flow shown currently by the models, makes me think that blocking is imminent. This year has shown some remarkable spells of persistent upper level patterns, notably the upper low that was over or to the west of the country for ages. If this trend continues, then I would expect the opposite to occur in the coming months, with a blocking upper high close by. Exactly where this settles will clearly be crucial as to what type of persistent weather we get, but an upper high to our north now is very interesting as, if it does repeat, then cold conditions could be persistent over us and W Europe.

After so many years looking at charts, I get gut feelings about what I see - hardly scientific I know - but at the moment, as I see it, the clues are there for a taste of winter. As we all know, there are never any guarantees. Look what happened after December 2010.

For now, though, the next few weeks might provide further evidence of the winter to come. In particular, I shall be watching the rate at which the polar regions cool, not just to our north and west, but also what's happening in N Russia and Scandinavia.

All in all, I am really looking forward to this winter as I sense we will have plenty to talk about here!!

[Model Output Discussion October 2012]

I just wanted to add a few thoughts on the upcoming winter as I am seeing some intriguing signs.

At present, there is nothing much in the model output to suggest the current unsettled spell will stop any time soon. Indeed, with a powerful looking jet heading out across the Atlantic in a few days, it could become quite stormy at times.

What has caught my eye in recent days is the HP developing over the Norwiegan Sea and pushing towards Greenland and, as legritter points out, in spite of the much-hyped loss of sea ice from the Arctic and from Greenland this summer, there seems to be a quite rapid cooling occuring with some 498dm thickness values appearing over Greenland at times this week - quite unusual for this early in the season. The Canadian cold pool is also getting quite pronounced already - another innteresting sign.

Overall, the models are showing a much more meridional flow in the short- to medium term, so, as others have suggested, there seems potential for an early taste of winter within the next few weeks, if the block to the north of us persists. That, together with some late season tropical storm activity currently going on, and the push of very warm air over the W Atlantic that is likely to accompany it, could certainly favour a cold pool over the UK and near continent quite soon.

I've said it before, but this has been a peculiar year in many ways, with many extremes. I think it reasonable to expect there to be some longer spells of drier conditions than we have had for some months in the months to come, as there has been such a lack of prolonged HP anywhere near us for a while.

I shall watch the block to the N with great interest in the next week or two - might be a sign of things to come!

[Model Output Discussion 26/08/2012]

I've been watching the model output all week regarding the threatened intense LP for this weekend and I have to say that I do not recall any such development happening before.

Hurricane Nadine has been an enigma since it formed and i know that the National Hurricane Centre in Miami have really been struggling with it's behaviour and forecast all week. In particular, the track has been shown to vary greatly from model to model and run to run and at times, they have not even been sure what sort of beast Nadine is - is it still a tropical storm, a post-tropical depression?

Since Nadine arrived near the Azores, the models have, and continue to have a bewildering variety of solutions as to what to do with Nadine. What I find so intriguing is that, while ex-tropical storms do arrive on our shores from time to time, I cannot remember seeing a LP that has been apparently generated by such a storm. Even more puzzling is the way the models have been maintaining Nadine, even intensifying it in the days to come.

As far as the threatened storm here is concerned, yes there is certainly a large amount of very warm, moist air travelling NE towards the UK that apparently originates with Nadine, and that, together with the presence of the jet, could indeed be a situation to allow a rapidly deepening LP to form. The upper low to the W and NW is sharpening as the surface LP sinks SE. But in recent runs the models have had difficulty in deciding which LP will be dominant. The last 2 runs of the GFS have backed off quite considerably on the new LP's intensity but the ECM has gone quite mad and is showing a very intense system developing.

Meanwhile, the UK Met is sticking to it's guns, as it has for several days now, of developing the LP quite rapidly.

I find it unusual that there is so much model divergence so close to the time. I think it will be most informative in this situation to watch the satellite images very closely over the next 24 hours as LPs such as these have distinct signatures.Interesting few days ahead!

[Model Output Discussion 26/08/2012]

I've been sitting back for a while to see how things would start to shape up now we are officially out of summer and, as I mentioned some weeks ago, the long overdue HP has finally arrived on our doorstep. The Atlantic hurricane season is currently working in our favour with the remains of Hurricane Kirk pushing very warm air over and to the W of the UK.

At long last the 500mb flow has shifted enough to replace the persistent upper low that has been over the US and Canadian NE and the one to our W with upper low emphasis now to our immediate NW and a cut-off upper low over southern Europe.

The models are showing consistency in maintaining HP for a while with rebuilds occuring behind cold fronts.

I am most interested in the handling of Tropical Storm Leslie, notably by the GFS, as it seems set, as others have mentioned, to become a very intense extra-tropical LP. The big question is where will it track. The latest GFS shows it on a much more southerly path but earlier runs have taken it to the NE. In any event, it is likely to disrupt the upper pattern, at least for a while, to break down the HP here.

The tropical storms this year have shown a marked tendency to recurve well to the E of the US, with the notable exception of Hurricane Isaac, so there is a distinct possibility of further storms getting picked up by the Atlantic jet as the month progresses.

Meanwhile, let's enjoy a bit of late summer and keep an eye on TS Leslie!

[Model Output Discussion 22/07/12 Onwards.]

It seems to be the "3 fine days and then a thunderstorm" situation we're in at the moment.

The current HP strengthening over and to the E of the UK at the moment is a little more developed than was shown by the models earlier in the week, but the theme of keeping it transitory remains, with some consistency, across the models today. Thereafter, a new significant LP development looks likely to our W sweeping the remnants of the current LP to our SW, NE across us, accompanied by what I think is a strong possibility of thunderstorms.

Over N America, there are some shifts in the 500mb flow that are interesting. The persistent upper high is retrogressing to the W and there is now a stronger, more southerly positioned and growing amplitude upper low over Canada, extending down the US east coast. Downstream it seems to be setting itself up for a Rex block, but not one in our favour, with the upper high well north of us and the upper low close by. At the surface, with hot air on the near continent, there is considerable potential for thundery downpours with any frontal or trough activity.

I've mentioned from time to time the influence of the tropical Atlantic on the patterns here and interestingly the GFS, a long way ahead admittedly, is showing a low, clearly of tropical origin that is forecast to become quite a vigorous extra-tropical LP heading our way. There is currently much potential tropical storm activity developing and it looks as if the upper flow over the Caribbean is changing and likely to turn any storms poleward rather than due W as has just happened with hurricane Ernesto, which, at this stage at least, would only enhance the LP dominated weather here..

So, all things considered and given the consistency across the models, unsettled seems to be the key word. The quite intense HP forecast to extend from Scandinavia across to Greenland I find intriguing for this time of year - not that it helps us any! I stick by my opinion that late August and September will see things settling down - ex-tropical storms notwithstanding!

[Model Output Discussion 22/07/12 Onwards.]

With the prospect of a rather feeble looking HP to come later in the week, we seem to be heading for a fairly brief summer-like spell.

As others have pointed out, this HP has been consistently forecast by the models to be quite transitory and, given the very persistent 500mb pattern, this seems reasonable. There is still a major upper low over NE Canada as well as another off to the NW of Canada over the NE Pacific so the recurrent pattern of a major upper low either to the W or over the UK looks set for the foreseeable future.

It seems likely to get quite hot for a time as the 564 red thickness line pushes NW over the S of the country later this week , but there may well be some persistent cloud associated with the decaying front over England, at least at first. Beyond that, a thundery trough could well move NE as the models suggest as the remnants of the LP to the SW now, gets swept NE as a new LP develops to our W.

I am really quite amazed at the persistence of this upper pattern and it is hard to see at this stage how it will break down, other than temporarily as it seems likely to do shortly. The Atlantic tropical storm season is hotting up but at present at least, most of the action is being kept south by a strong sub-tropical ridge so it's unlikely to affect things here.

I think as we head towards September and the autumnal cooling starts over the Canadian arctic, we could see the upper low there expand and sink SE and for this finally to shift the jet to a more NE trajectory so late August onwards could see some proper Azores HP offshoots heading in our direction.

This has been the most peculiar year weather-wise that I can remember, and that goes back 45 years, so I am going to be fascinated to see how late summer and early autumn turns out - a lot of dry weather I suspect.

[Model Output Discussion 22/07/12 Onwards.]

Some early thoughts on today's model output.

There is much agreement in there being LP domination for the short- to mid-term, with the unusually deep low wandering slowly across the UK for some days to come slowly filling. I am still intrigued by the forecast warm sector trough the UK Met is showing, suggestive of the possibility of a thunderstorm line forming. At the moment, there is not much sign of instability over France and Spain and the 500mb upper trough is not that sharp, but I notice from the IR satellite this morning that the cold front on this developing LP seems quite active with extensive cold cloud tops suggesting it is quite an active feature in itself, which is somewhat unusual. I think much depends on how quickly this front moves through and how hot it gets over France tomorrow ahead of it but I think the risk remains. I suspect any such storm line would form very quickly if it is going to, so the satellite images need watching overnight and into tomorrow.

Beyond that, there is not much in the way of clarity from the models as to where we might go after the LP fills. I notice the GEM is being quite decisive and brings yet another LP towards us in the mid-term to long-term and this looks plausible given the current 500mb configuration. We seem to be stuck in a quite stable wave pattern at that level, with quite a deep vortex over NE Canada and one off the US/Canada west coast, whilst there is still a 500mb high covering much of the USA. I can't see all this changing any time soon.

I believe we need to keep an eye on the US to see if the upper high starts to erode and if the Canadian vortex starts to move further S or SE which may finally shift the pattern E bringing us closer to the downstream Atlantic ridge. Again, as I keep saying, any tropical storms could heavily influence such a process.

Meanwhile, coolish, showery conditions with more organised convection along any troughs that form seem to be on the cards for some time yet, plus once again the threat of slow-moving deluges as the LP fills.

[Model Output Discussion 22/07/12 Onwards.]

Quite a day for strong convection - don't recall seeing such widespread lightning plots for a long time, plus some very intense radar echoes.

The models are sticking to their guns with a vigorous LP forming to the W mid-week and then sticking around within the reliable forecasting timeframe. What I find interesting today is that the UKMet have analysed a trough line in the warm sector of this developing LP by Wednesday, which brings the risk of a storm line as the hot, unstable air over France gets involved.

Beyond that, I still think similar situations will arise with hot air getting involved with frontal activity once the main frontal zone for this developing LP has passed. It's also interesting to note the presence of a strong gradient on the S side of this LP which the models have been showing for a couple of days.

Another significant feature I noticed on the last GFS analysis is the presence of 564dm thickness ( the "red" line) just SE of Greenland which I think is pretty remarkable, even at this time of year. Hence the unusually low thickness values over us today. I tend to watch the thickness charts more than the 500mb, especially the "red" line and what sort of latitude it's at, as well as the thermal gradient, as it is a good indicator of temperature ranges and LP development.

The models are still a bit all over the place as far as the longer term is concerned. There have been hints of a return to HP from the GFS as well as the GEM model. Still, thunderstorm lovers should have plenty to watch in the coming days!

[Model Output Discussion 22/07/12 Onwards.]

In spite of a reasonable consensus among the models on a LP dominated week, I think it has some potential for some interesting weather and some warmer days later in the week.

The GFS in particular is suggesting the possibility of rising thickness values over France as the week goes on brings with it the possibility of thundery activity as the frontal zone waves associated with the LP pull in hot air from the continent. With last weeks storms, we came within a whisker of some very violent storm cells just out in the Channel so maybe things will be further N this time.

The GEM is interesting as it shows a progressive slackening of the pressure pattern across the E Atlantic and much of Europe - this model seems quite good at anticipating trends - so this suggests the temperature may slowly start to rise again - perhaps with slow moving showers and thunderstorms. Early August in my experience seems to be the time when the Atlantic is at its quietest - notwithstanding any ex-tropical storms that might come our way.

Speaking of which, after an unusually early and busy start, the Atlantic hurricane season has gone very quiet for some weeks now. What happens in the coming days on that score could significantly affect our weather if storms begin to form and track up the US east coast as they did early in the season, by pushing a lot of warm air NE and helping to strengthen the Atlantic flow.

I suspect none of this will happen for a while though but I still believe September will bring more reliable HP and dry weather.

[Model Output Discussion 22/07/12 Onwards.]

There is quite a consistency in the model output today for the continuation of the upper low near or over the UK within the reliable timeframe so the likelihood of a return to anything summery such as we have had this week seems remote. The risk of thunderstorms in the next 24 hours seems to be decreasing steadily, even though a trough is still approaching us from the SW, there seems little weather on it, as there does on the cold front associated with the low moving down towards us. I guess there is still a chance for some heat storms in the SE tomorrow but the hot air seems to be getting replaced quite steadily as winds turn more towards the W and NW so the window for this to happen looks small.

I apologise to the Met O for my comments earlier in the week regarding the likely weather for the Olympic Opening Ceremony - clearly they saw the situation as marginal at best and not worthy of any sort of warning so it's time for me to eat humble pie!

However, with LP likely to dominate for some days, we again run into a situation where local high rainfall totals are possible, especially as thickness values are forecast to fall quite a lot so plenty of scope for intense convection.

As I see it at this stage, even at such a long way out, the GFS could well be onto something building pressure NE to Scandinavia, but it will take its time for sure. The upper low may finally sink away to the SE during August, allowing us the benefit of a more long-lasting upper ridge, but I still have a feeling we may have to wait until September to see any persistent dry weather.

Just as a PS, I notice some sharp radar echoes are currently showing up in the Channel with one or two lightning plots but the mid- to upper level flow is veering more to the W, so it's touch and go as to whether they will get to our shores!

[Model Output Discussion 22/07/12 Onwards.]

Quite a variation today in model output, but the thing that caught my eye in particular is how the UKMet FAX has slowed the SE progress of the cold front for Thursday/Friday, thus the heat will linger a bit longer over Kent/Essex. If that happens, it would also allow more opportunity for either heat storms or convergence lines of storms to form ahead of the front.

Looking at the developing upper flow over and to the W of the UK, the sharpening upper trough seems to be developing quickly as is the upstream upper low near Newfoundland, as can be seen clearly in this WV satellite loop:

http://www.ssd.noaa....l/flash-wv.html

Note also a large area of moisture moving out of Spain, associated with a significant thunderstorm outbreak, so I would not be surprised to see medium-level storms S and SW of the upper trough forming by tomorrow and tracking our way.

The broader and longer term view does show, as I said, some variation but there is a reasonable consensus for the short- to mid-term with an upper low very close to the UK. The GEM goes a bit weird with the main LP sitting to the SW and deepening but overall it seems mostly a mobile longer term, although pressure may remain high-ish over the south.

[Model Output Discussion 22/07/12 Onwards.]

Interesting Met O FAX for 96hrs:

The 120hrs shows the cold front sweeping through quickly as mobility restarts from the Atlantic, so as I see it, there is still a good chance of significant storms ahead of the front, although based on this chart, and the GFS which is comparable, I will admit the thundery activity from France would seem less likely on Friday, although overnight storms originating there may head N/NE overnight Thursday/Friday

However, there is still a certain amount of ambiguity in the short term with all the models as to how amplified the upper flow becomes in the next 2-3 days, especially upstream - if there's a deeper trough near the US coast, I think it would favour sharper troughing to our west with the developing LP to the NW digging further S, the cold front slowing down in its SE motion and thus more hot, thundery air from France becoming involved in the circulation than otherwise would.

I shall watch developments with interest!

[Model Output Discussion 22/07/12 Onwards.]

Spot on. I spoke of this last week....big concern IMO for start of olympics. The air masses could bring fireworks......

Summer begins according to MetO................ok

BFTP

Thanks BFTP, guess we're in the minority at the moment. I'm looking forward to the Met O FAX later on, might clarify things a bit.

OMM

[Model Output Discussion 22/07/12 Onwards.]

Out of interest, I have included the GEM output for Friday. This model doesn't get that much attention but, in my view, it has proved accurate in the past in some tricky forecasting situations and I tend to look at it more closely than the GFS for the 5 day period when in such a situation.

It is basically showing a thundery LP getting pulled NE across England in association with the developing LP to our NW. Note the amplitude of the 500mb trough to the west, much sharper than shown elsewhere and thus more likely to bring any thundery activity to our shores.

We'll see!

[Model Output Discussion 22/07/12 Onwards.]

come on as an ex metman do you seriously think that is even a remote possibility?

Hi John I am not suggesting that the data has somehow been tweaked, merely that the threat shown by the models at this point should merit at least, as I said, a vague yellow advance warning. Goodness knows, the Met has been issuing warnings left, right and centre throughout the summer, with some considerable success I should say, but they have erred on the side of caution consistently, even 5 days out, so why stop now?

It has been widely reported in the press for some time that the Met has been "requested" to put a positive spin on forecasts at various times for various reasons, such as "public morale". But it is the timing of all this that makes me suspicious, i.e. had it not been the Opening Ceremony, I am sure a warning would have appeared by now.

I agree with what you say regarding the variability of the model output and the difficulties of forecasting with this kind of set up. It will be what it will regardless, yes, but let's see how the forecasts develop in the next couple of days.

[Model Output Discussion 22/07/12 Onwards.]

Nick, I was thinking more along the lines of a convergence zone forming ahead of the frontal zone, somewhat similar to the situation we saw in late June when that line of severe storms formed, rather than heat storms, although that would be a distinct possibility given the increasing heat, humidity and falling pressure.

I agree with you regarding the return of the limpet upper low, there seems no real end in sight for its re-occurence to finally end.

I think a lot depends on how quickly the upper trough/low develops and the surface LP deepens, which in turn will be influenced by what happens upstream, specifically whether the meridionality is marked enough.

I also think it is worth noting that the GFS in the last few days has been showing a significant LP actually tracking N and then NE right across England but it has backed off that idea today. Interesting situation.

[Model Output Discussion 22/07/12 Onwards.]

Looking at the GEFS ensembles they have toned down the precip amounts for London for Friday, quite a few do have that miracle dry gap. It really is touch and go, the timing of the front moving se is still open for revision and those thunderstorms over France do get quite close to the se.

I find it increasingly curious the way the models are trending at the moment, especially with regard to Friday and these mysterious dry gaps. Given that these "plume" events are notoriously difficult to predict, at the risk of sounding like a conspiracy theorist, I can't help but wonder if the Met O is being leaned on to minimise the potential threat the models are showing.

As I see it now, the models are showing the distinct possibility of a significant thundery event. Increasing heat over the UK and France with falling pressure, plus a slow-moving cold front moving SE, followed by a developing LP and accompanying sharpening trough to the NW and W is, in my experience a receipe for severe storms.

As you rightly point out, Nick, the location of any such trough line is very difficult to determine this far out. Yet, not even a hint of any warning from the Met even though it's within the range of its advance warning system, so I would have thought a vague yellow warning would be appropriate at this stage.

Yesterday's 120 hrs UKMet FAX shows the threat very clearly:

With this arrangement, the LP to the NW usually sinks SE as the developing LP over France heads NW and the area of major thundery activity forms ahead of the greatest air mass contrast. It is somewhat complicated by the presence of 2 cold fronts in this case but the most likely area for thie storm line if this chart were actualised would be the Midlands and E Anglia.

However, areas of thunderstorms also form within the developing LP over France, travelling N and then NE across the SE of England ahead of the upper trough. The trough line shown over France on the above chart suggests this, although the actual situation would no doubt be more complicated.

I think this developing synoptic pattern needs careful watching.

[Model Output Discussion 30/06/2012]

Well, it seems the long-awaited HP looks finally to be on the way. Interesting the media hype about it - can't help but wonder what pressure is being put on the Met to "optimise" the forecast as we head for the Olympics. I've had a feeling for ages that it would turn hot when that started.

I like what you say above Nick about the opening ceremony, just what I have been thinking! As far as the models go, there is a reasonable consensus for this HP to build over us, but the GFS is making the whole affair rather transient, and I have also noted the point you made Nick about the Iberian LP.

Now that the pattern has finally shifted over the US and the greater upper heights have shifted W into the Pacific, I think it logical to expect a retrogression in the downstream flow, plus the much-discussed repositioning of the jet. As I see it, the prolonged upper high over the US caused a strong baroclinic zone and associated jet over Canada that just kept barrelling out across the Atlantic bringing the seemingly endless string of LPs over us, and the last time I posted, I thought that this situation would finally break down come mid-July - well a bit late I suppose.

There are still some inconsistencies though in the model output, notably the aforementioned possibility of a hot and thundery LP developing over France and Spain, but overall, none of the models suggest that the Atlantic flow will weaken enough to allow prolonged HP to sit right over us - more likely mobility still but with higher pressure so transient HP affecting England and Wales mostly, weak cold fronts and then renewed HP building - BUT with the distinct possibility of a sharper upper trough developing at some point between ridges bringing heat and storms temporarily.

I have a feeling that for more intense and longer lasting HP to get established over the UK, we might have to wait until September - I suspect a dry autumn awaits us.