Weather Boy

I may be guilty of a bit of NIMBYism in that it is and always was going to be better in the south. My post of 23 August records Saturday as what I describe as the changeover day in the south, with Scotland following 12-24 hours later. I think now (or last I looked last night anyway), it's looking like Sunday is the changeover day in the south with Scotland following 24-36 hours later, apart from the north of Scotland. On any view, though, I think tomorrow will be a better day than today in the south, although still showery. I agree that the models are struggling. They all get to the same point in the end though, with the consequences you describe. It's all just a bit delayed compared to what they were showing at the start of the week.

Well, it's all very frustrating for those looking for decent BH weather. When the HP takeover was first progged, it had Saturday as what I describe as a 'changeover day' i.e the switch between unsettled and settled weather. Now, it's been put back so that it's Sunday for southern parts only at the very best. Unless the models improve again it looks to be unsettled Saturday throughout (apart from perhaps the far SW) and in much of the country on Sunday too. Monday however should see the vast majority of the country see settled weather, if not very warm. Looking on the bright side, you'd probably settle for the BH itself to be like that. Basically the UKMO flagged up that trend of delay, and the other models joined it, only for UKMO to go yet further and put the change back again! Further ahead seems more promising for some late summer warmth with a stalling low drawing up warm air for a time. However, still plenty of time for that to change and it's not difficult to imagine the models ditching that in favour of more autumnal Atlantic weather. The Meto indicate that, although not until mid-month. Many ensemble members go for a rise in pressure and temperature for the south at least into September.

ECM and GFS singing from the same hymn sheet with some very unsettled weather, initially in the south, then transferring further north (although far from dry further south) with -it looks like- Saturday being the changeover day (at least in the south, the bad weather hanging on for 12-24 hours longer in Scotland) between the very disturbed weather and the settled weather which appears to take hold as far as the eye can see, discarding GFS extreme FI. UKMO, to my eye, has the Low pulling away NE slightly later which, if correct would probably make Saturday a more disappointing day than the other two models. I do however note two things. Firstly, despite its resiliance, the High seems to lack intensity being progged at only c. 1020. Do any of the more experienced members think that this could be an issue? I wouldn't have thought that it would permit any shower activity except perhaps one or two on its northern flank - what do people think? Secondly, there is an unusual feature of a small Azores low in both GFS and ECM which both models treat as irrelevant to the UK, as it just stays there. Could that come into play on later runs?

Only looking at the one run, but there seems to me to be quite a lot of consistency in the models and ensembles for a fair period, meaning that FI is perhaps a little further ahead than usual. All models are showing an unsettled spell starting somewhere around Monday evening to Tuesday morning, depending where you are, and affecting the south more than the north, although it will be unsettled everywhere and even southern Scotland may get some pretty wet weather. Nowhere safe. The spell with heavy showers and longer spells of rain continues for the rest of the week with Saturday/Sunday showing a fairly rapid, but not intense HP build, although not noticeably warm, given what appears to be a NW flow. However, that appears to be in place until true FI. Although that may only be a few days (too far ahead to tell) it would be very surprising if this didn't encompass the BH Monday, which is nice. The other good thing is that this appears to be fine weather more or less nationwide, which would make a change given that most of the summer sunshine and warmth so far has been down south, especially the SE. I doubt that the fine spell is, to use the hackneyed phrase, nailed on for Saturday/Sunday on but the consistency of ensemble members from both GFS and ECM gives reasonable confidence, I think, despite the range. Most gardens getting a decent watering in the meantime.

Is it just my local experience or did (temperature wise at least) the models massively over-do this unsettled spell? For example I logged 21.1 C yesterday. It's similar today. That would have been totally out of the question based on the model output we saw at the end of last week. Even the forecast for yesterday was saying 20C at the very most in Central London. If this premise is right (and I'd be pleased to hear if others agree) what does that tell us for the current output we're seeing? Maybe nothing, or does it mean that the models have been consistently over-doing the Low and the provenance of the airmass impacting on temperatures? Maybe TWS's comments about cold air mixing out have relevance.

Also very cool for practically all of western Europe, in particular Spain perversely cool for the time of year.

EDIT: SORRY MY LINKS DON'T WORK: INSTEAD I'VE POSTED THE CHARTS Looking at the 0z, I prefer (by which I mean, I would like to see, not think is more likely) the ECM which sees good ridging and the prospect of a decent settled spell around next weekend, which is borderline FI. The GFS meanwhile, is rather a frustrating run in that it starts to go the same way as the ECM but never seems to quite complete the job. See here on Thursday, actually ahead of the ECM evolution: ..you would expect to see some nice ridging in to complete the evolution, but then into early FI you end up with: http://www.netweathe...ction=nwdc;sess= the same pesky low comes back to haunt us with a chart that is only a little better than what we are promised for the coming couple of days. I'd like to say that it was unconvincing, but I said that about the current set up which came to pass (although I do think that the charts and indeed the weather are nowhere near as bad as the models would have had us believe at least in my location). Then deeper FI gives us a low pressure train to the north of Scotland suggesting the same old SE/NW split, although the SE being far from perfect. Looking at the ensembles, I agree that there's virtual across the board agreement on a pressure rise from the middle of the week onwards, but that's hardly surprising as it would be extraordinary to see such sustained low pressure from now into FI at this time of year - even a train of lows would give us higher pressure than now-. However it's worth noting that no member gives us particularly high pressure (or indeed temperatures) with even the most optimistic member having pressure well south of 1030 for the whole of the run. So it looks to me that whilst more benign weather is very likely after mid/end-week, hot and/or very sunny weather seems a bit of a distant dream, although the SW seems better placed to take what's on offer for the foreseeable.

And what's that over Greenland? Can it be low pressure?

That's consistent with the Netweather forecast. Someone made a comment that warm sunny Augusts rarely seem to follow unsettled Junes/Julys. I certainly can't recall one, well, probably ever really. Mr. Data? That doesn't mean it won't happen though - the exception that proves the rule!

Looking at the 00z this morning, I can't really get my head round the ECM. It has the low for next weekend rushing towards us at an extraordinary pace, and then stalling over Scotland and/or the North Sea. I can't recall ever seeing an evolution like that before where a very fast moving system suddenly just stops in its tracks and I think it somewhat likely that this will be changed. Whether it will change to match the GFS or changed so to be more progressive, who can say? I'd also comment that by that point (Monday) we are borderline FI so it would be surprising to see no changes in either model. As it is, we know one of them are going to change at some point because they contradict each other. I can't quite see how the UKMO is allegedly supporting the ECM? To my reading it doesn't quite go far enough with the end of the run leaving the viewer unclear as to whether it is going to go for the ECM or the GFS, or somewhere in between. Finally, that is an unusually deep low for the time of year (on the ECM) and I'd therefore be inclined to think that the less extreme version is generally more likely seeing as, by definition, the extreme versions are rarer. For these reasons, not sure why some are of the view that the GFS will fall into line with the ECM - and perhaps those more knowledgeable than me could justify this view?

If that's right, then they agree with me, for reasons in my original post. The ensembles are generally supporitve though. Surely ECM plus GFS plus ensembles are collectively quite a bit of support? Also the teleconnections weren't too great over the winter, IIRC. How can we look at the teleconnections please?

Not sure I agree. The 06z looks remarkably similar to the 0z that I commented on a few posts above. In the longer term (i,e from c. Sunday -depending on where you are) onwards it looks rather settled, if not especially warm to a significant, but rather surprising degree. Someone commented that next week looks like a re-run of this week, which looks a reasonable comment, except with a later unsettled spell and potentially a longer settled spell thereafter.

The current GFS 0z run looks quite good if we look beyond the coming unsettled spell to, say Sunday/Monday which should be withing the reliable. It looks as if we have HP dominating nationwide until deep FI However, I am concerned that it does something quite unlikely. If you see the chart for Tuesday http://www.netweather.tv/index.cgi?action=nwdc;sess= HP covers the UK, but out in the Atlantic is a Low that you would expect to steamroller into Scotland, but instead it goes far north leaving the vast majority of us still with HP: http://www.netweather.tv/index.cgi?action=nwdc;sess= before a slow breakdown in deep FI. For me, the ECM is a little more convincing in the earlier time frame, with the LP moving to Scandavia a little faster. However, it too has the same LP to the West of Scotland on Tuesday http://www.netweather.tv/index.cgi?action=ecm;sess= and it does something even weider which is having the LP just fill and disappear virtually overnight. Taking the big two together at face value on just this run, you might think that we were in for a fairly long settled spell, but I find the runs by that late stage (which is borderline FI) somewhat unlikely. The GFS ensembles also seem to back a more sustained higher level of pressure, and also reasonably high temperatures with few cold or LP members.

I read this thread so that I can get a better interpretation of the models from people who know more than me, but sometimes I despair.......writing off July on the back of a couple of runs: I ask you! Yesterday, the GFS had a marvellous summer coming up after a showery blip mid-week. The ECM didn't see it as a blip but a breakdown to something more unsettled for the foreseeable. Now, the GFS looks as if it wants to confine the better weather for the end of next week to the SE quarter, with the ECM agreeing - and even here unsettled weather cannot be ruled out. So, in the case of the GFS that's a pretty strong turnaround in 24 hours for a prediction that should be towards the end of the time period. Who knows if it will be sticking to the same story tomorrow or Monday? The point I am making is that to write off a period of weeks on the strength of one day's runs is ridiculous. I also note that people are ignoring the fact that we have a number of days of extremely pleasant weather progged with next weekend's weather on the edge or reliability. But the doom merchants want to look at the possible breakdown and beyond and from there proceed to write off the next 4 weeks! All we know is fine weather until around Wednesday - rather unsettled after that but for a period of time that is unknown, but with a greater likelihood of more settled weather in the SE than elsewhere.

Regarding the possibility of a return of the heat, Rob McElwee makes some interesting comments in his long-range forecast for the BBC. http://news.bbc.co.uk/weather/forecast/10209 In particular: "It isn't possible to forecast a heatwave more than seven days in advance. But the pressure pattern conducive to summer heatwaves is forecastable much further in advance. Bearing that in mind, over the next four weeks we see such a pressure pattern more than once, so it's fair to say that another heatwave is possible." I'm obviously not qualified to contradict Sir Rob, but it seems to me that I can see the logic in what he says. The models have a general rule of thumb of not being particularly accurate beyond trends of c. 7 days. Only in that time frame would it be possible to predict air masses' situation so accurately, that you could say with any confidence that there was going to be a heatwave. After all, a relatively small shift could scupper it quite easily, so hard to see how you could predict beyond 7 days. On the other hand, it may well be possible to virtually rule out a heatwave much further ahead, if the trends and synoptics don't support that as a possibility. I say 'virtually' because of course the models could simply be completely wrong at that range. It sounds that both what Rob and GP are saying is that the trends indicate that further heat is possible, but of course that is only one of a range of possibles. We know that there won't be a heatwave in the coming 7 days. Beyond that, it's possible and could well happen, but it's too early to say.

Would you be kind enough to explain the significance of that....? Many thanks.

Yes, it seems crazily deep to me, given the time of year and its proximity to the High. Does it ever get as windy as that at this time of year? Guess we'll find out.

Sorry if you're feeling badgered MB, but how is it that in your forecast you say that you are 100% confident, yet in your posts you say that the methodology is not proven and you clearly allow for the possibility of failure?

I understand that warming of stratosphere doesn't equate to cold here in the UK (but it seems to be a good sign of that being likely). Maybe this is dealt with elsewhere in the thread (I haven't read it all) but can anyone explain for me please: 1. Why warming of the stratosphere tends to point to cold in the UK (in winter at least) and 2. What causes the stratosphere to warm or cool at this time of year when the sun is very weak. Much obliged for the assistance and sorry if it involves going over old ground.

Hi, yes I had noticed you from Royston - in fact I have a feeling there is someone else also. Raining here, but the temp is falling and it's not unusual for it to be rain-snow-rain and comments from west of us (MK) back this up, so we may well get some snow still, although I suspect that it will be too brief to be very exciting - maybe a couple of hours. Current temp 1.2. As I said before surface temps very far from telling the whole story, but that's easily cold enough for snow.

Hmmm, the Met seem extremely confident in putting out severe weather warnings etc but we all know that snow is very difficult to forecast. There's only a certain amount that you can gain from monitoring surface temps, but it is 1.6C here and falling gradually so overnight snow is not that difficult to imagine. People make comments about the Met being very media focus and warning if there is a chance of snow (even if they don't think there will be snow) but in my experience they tend to say "risk of" if they think that it probably won't be snow but want to cover themselves. Therefore, I think that they are making a sincere prediction and they have been excellent during the cold spell generally. On the other hand I can see the argument that they do seem to be overdoing it. Perhaps the reality is a couple of hours of snow with no or very limited disruption i.e somewhere between the two extremes!