WYorksWeather

reef According to most forecasts it's not going to break here all day, but at least it isn't forecast rain I suppose. A useable but uninspiring day, but nevertheless I'll be off the forum in a few minutes because I'm going to go and make use of it .

GFS 6z is one of the best runs I've seen in a long time for prolonged dry weather, albeit probably very mild to warm-ish rather than very warm. Interesting to see first signs that after a weakening in pressure around day 7 or beyond, that there is a further signal for a build in pressure beyond that. High builds in at day 3: Still going at day 5: And day 7: Possible slight weakening at day 10: A slightly more showery interlude at day 12: By day 15, another high builds: And even at day 16, the low to our NW will likely miss or just graze the north of the UK: This signal for a further build in pressure is beginning to be seen on the ensembles, e.g. here on the GFS 00z with the mean having a renewed rise in pressure towards the middle of May: All a very long way off, but encouraging that we have a generally very mild to warm and largely but not entirely dry week to come, and then beyond that we can already see a signal for another high after any breakdown. Those developments a very long way off of course but nice to see a run that doesn't see a full-blown Atlantic breakthrough.

Does show how regional it is - Wednesday and Thursday were the best of this week so far and today I'm stuck under thick, low grey cloud. On the cool side as well - around 11-12C at the moment. At least it is forecast to stay dry I suppose, so still useable. I'll take it in all honesty, my expectations are that low at the moment.

This one is now only 3-4 days away - the improvement starts to kick in around Tuesday. Of course, it'll take more than one nice week to begin to compensate for the recent dross...

MattStoke The state of the comments on any Met Office post on Twitter are simultaneously hilariously stupid and also quite worrying for the state of modern society and scientific education more generally, to be perfectly honest. It's literally the definition of Poe's law - some of the comments are so... unhinged that it's hard to tell whether they're intentionally trolling or actually believe what they're saying.

Final post for tonight most likely - an update to my regular posts on North Atlantic SSTs. Last time you may remember I noted a very rapid warmup due to take place in the North Atlantic - let's see how it is progressing. Here are the SSTs in absolute terms at days 0, 5, 10 and 15: And here are the anomalies: Overall there are a few areas to look at. To our north nothing especially unusual going on, so if we do get chilly northerlies these shouldn't be moderated excessively. However, if we do go into a south-westerly pattern yet again after the high pressure next week, we may well see some absolutely turbo-charged mildness, especially by night. SSTs in the Azores area generally continuing around 1-2C above average. Flat westerlies would be closer to average. Closer to home, there is a very striking warm anomaly around our immediate coasts and towards the near continent as well - this will likely result in a greater propensity for mild nights and less moderation of any warm or hot continental airflows around the middle of the month. In short, not only are we in for a warm start to May, all the ingredients are there for it to continue well beyond that, even if a cloudy and/or wet south-westerly type pattern would limit daytime maxima. Only a significant northerly outbreak as we saw in the second half of April is likely to prevent another notably above average month by mean temperature.

Quick look at UKV for the next few days. We can now see through to Wednesday. It looks like a gradual build in both the extent and level of warmth - from 18C tomorrow up to low 20s by Tuesday and Wednesday. Over the next few days it seems like most areas will have a chance of seeing at least one or two warm days, with the exception of Scotland. Right at the very end, there does appear to be some warmer 850hPa air moving, which under the right surface conditions might raise the temperatures still higher later on next week. For example, the GFS 12z was raising temperatures to 23C next Friday and Saturday. In practice, a first 25C of the year might well be possible given usual underestimation. Summary In short, it looks like we'll see a general improving trend if it's warm and dry you're looking for through the course of the weekend into early next week, and by the middle to end of next week most areas should have seen at least a couple of days of pleasantly warm conditions. Again, nothing notable on the horizon by daily maxima, but consistently very mild to warm is all we need at this time of year for things to end up well above average temperature wise. A very warm first third of May is highly likely. No heatwave on the cards, but certainly a decent spell of weather on offer for many of us. Of course, as is always the way with these things, some areas will probably end up getting it better than others, but that level of precision is probably not worth worrying about beyond the next 2-3 days.

Don I think the key will really be the wind direction. The absolute worst wind direction for the combination of heat and humidity would be a consistent SSW wind direction, coming in from the Mediterranean coastal areas, with heat sometimes turbocharged by more direct southerlies. An ordinary westerly would be just a classic washout, and if we get pure continental flows they'll generally be pretty dry I'd imagine with a higher temperature ceiling but lower humidity. Anyway, we will soon find out. I'm already noting some positive feels-like temperature differentials on weather apps for next week (inaccurate though they are) with e.g. 20C feels like 21C. Not uncomfortable of course at that kind of level, but if we see relatively high humidity with temperatures in the high 20s and low 30s it will feel very uncomfortable. Probably the worst period for that would be mid July to mid August - after that the lengthening nights tend to inhibit very high minima, and before mid July the SSTs are probably not high enough (though this year, with a record warm North Atlantic, we could even see serious heat and humidity combos in June).

Roger J Smith And of course the need to also disentangle the UHI effect under different conditions - you'd probably have to use a different corrective factor by season and of course day vs. night.

BlueSkies_do_I_see I think it'd be very unlikely to get close to record territory limiting maxima to mid-20s. Almost every day would have to be reaching 24-26C to produce a record-challenging July or August under those parameters, with minima around 15C. That is a very high minimum - especially given the recording up to 9am which allows for temperatures falling in the early hours. In fact it has never happened in any month - highest monthly CET minima is 14.0C in July 2006 and August 1997. I do think it might be possible if you extend the parameter to 30C. That way you could formulate a semi-realistic set of daily means. You could have two thirds of the month average something like max 28C min 14C (mean of 21C) and then say ten cooler days with max 23C and min 13C (cloudy, wet and humid, mean of 18C). That would give an overall mean for the month of 20.0C. Obviously exact numbers can be adjusted but that seems like it could be possible. Prolonged CET readings above 15C are very unlikely, hence why you need the higher daytime temperatures so they're not needed. That still means though that somewhere outside the CET region in a favoured spot would probably surpass 30C in practice. I imagine a month similar to that outlined above would have an absolute max around 32C somewhere in the SE, but we wouldn't have any CET days with maxima over 30C. But the entire month not reaching 30C is probably pretty unlikely if it's going to be a record breaker or near-record month.

Worth noting that the GFS ensemble is continuing to extend the overall warmer than average spell. Still room for this to change as we saw in April, but increasingly signs that the first third or even first half of the month will come out notably above average.

The current very odd pattern has actually been relatively favourable locally. Two solidly dry and warm days with some cloud breaks on Wednesday and Thursday, and today though much cooler has still stayed dry apart from a brief rain shower around 2pm, which had been predicted to be much more extensive. Looking forward to next week, which I'm fortunate enough to have booked off work. Weather looks about as nice as you'd reasonably have any right to expect at my location at this time of year. No heatwave but pleasantly very mild to warm every day.

Don It unfortunately does seem quite likely. Unless we get a very notable warm spell to dry out the ground beforehand, and especially if we continue a tendency for our warmer spells to be more south-westerly than southerly to south-easterly, then I could easily imagine multiple spells of high 20s or low 30s with pretty high humidity being possible. Anecdotally I was leaving work one day last June, and I distinctly remember 27C on my weather app, but with a feels-like of 32C. B87 I for one think and hope you're wrong! Not too long until we find out...

LetItSnow! In terms of the 10th specifically, it is of course beyond the range of UKV at the moment, but here is the GFS forecast. These are typically 1-2C under, so 24-25C the likely maximum in reality. I would also note that there's some substantially warmer air, around 12-13C 850hPa only 100 miles or so to the south of the UK. At this range it would take only a tiny adjustment to bring that into southern England, and then you could even have quite widespread 24-25C with that and possibly an odd spot reaching 27C. At this time of year the lapse rates can reach around 1C per 100m or even 1C per 80m, which under the right circumstances can allow a total differential from the 850hPa level to the surface of 15-20C. Again though, that does require the upper end of possibilities. It will be interesting to see UKV's verdict in a couple of days and also see whether we do get any double digit 850s into the UK more consistently, which looks like it would require an adjustment north from the current position, though as I've said not a particularly large one.

To answer the original question, I don't think 2024 will see the hottest day on record, but to be honest that's always the safer bet. To give a view of where I see the probability more broadly, I think it's 50-50 whether the Coningsby record will survive until 2030 and overwhelmingly likely that it won't survive until 2040. I do echo @raz.org.rain's comment I think - I wonder whether this summer might be consistently warm to hot (likely humid with very mild sea surface temperatures) rather than having ridiculous heat spikes. In other words we could see monthly CET / UK records challenged or broken and have a very warm summer overall, but with an absolute max around 35-36C, which is no longer that exceptional.

B87 I don't see why that's a safe bet at all other than through pure cynicism. Obviously any predictions are pretty much guesswork but to not get a single month above 200 hours of sunshine between May and September is a pretty rare occurrence for your location, surely?

Worth having a look at UKV for the next few days in terms of temperatures - I often find it to be much closer to the mark than the GFS once it does come into range (though admittedly it still gets things wrong from time to time). Tomorrow looks like a poor day for temperature almost everywhere except western parts of Scotland. A particularly poor day for Wales, some central/southern counties of England and also East Anglia well below average. A very odd pattern with temperatures generally increasing the further north and west you are, this is courtesy of a very odd 850hPa temperature distribution with the warmest air over northern England and Scotland, and surface temperatures highest in NW Scotland due to the shelter from easterly breezes. Absolute max projected at 22C for NW Scotland - very impressive for the time of year at that location. Overnight lows average to well above average away from the SW and south-central areas. Saturday sees a bit of a change - still a warm day for NW Scotland and not quite as chilly with close to average temperatures across an irregular triangle roughly from Cardiff to Norwich to York. Wales and NW England getting the worst of the temperatures. Max of 20C for NW Scotland. Minima again average to slightly above average, well above average for NW Scotland. Moving onto Sunday we see a slightly more 'normal' pattern with the warmest temperatures across central, eastern and southern England, caused by mixing out of the warm air plume over Scotland. Max predicted at 18C, but on that I do wonder if it might climb closer to 20C in a few places in reality if there are sufficient cloud breaks. Minima above average away from eastern coastal areas. Similar pattern into Monday but with a slightly more favourable outcome for the south-west with cooler air moving into the London area and along the south-east and south central coasts. Slightly cooler minima but still average to above average. Finally on Tuesday we get much more of a 'west is best' kind of day. Summary In short some decent weather on offer once we get tomorrow and Saturday out of the way (unless you live in NW Scotland, in which case enjoy tomorrow and Saturday!). Sunday and Monday look to be the best days further east, Monday and Tuesday better further west. In terms of the temperatures I'm a little dubious about the idea that with 850s into the 5-6C range at this time of year that we won't see one or two spots climb into the low 20s on Sunday and Monday - it is often the case that as a spell of high pressure gets going the ground dries out and temperatures climb a little higher. Longer term Looking at the ensembles we do see a trend for 850s to rise a little further into next week - this might allow temperatures to reach the low 20s more widely, with maybe an outside chance of 25C at the upper end of possibilities for one or two spots if conditions allow. However, the main expectation for the next week to 10 days seems to be consistently above average temperatures for most areas, but without any particularly impressive absolute maxima. No sign of a heatwave, but at this time of year you don't need a heatwave to still come in well above average.

All looking generally solid again after the wobble yesterday - all models have a decently strong high at day 7. GFS, ECM, GEM, UKMO in that order: ECM probably the pick of the bunch for warm and dry, but all looking reasonably dry and quite warm, though GEM probably showery in the north. To bring it onto a different topic - I've noticed quite a few people wondering why temperatures aren't running very high at the surface based on the 850hPa temperatures. I think part of this is orientation of the high and the still damp ground, but I've not noticed anyone yet mention model bias. In this instance, it is an important factor. Using the GFS as an example, in most situations it under-predicts, but where the ground is excessively dry, it over-predicts temperatures. In most instances, the UK is subject to underestimation of temperatures, with the only recent exception that comes to mind being the July 2022 record-breaker, which some models overdid because of the excessively dry ground - a few runs even shortly beforehand had 41-42C. But outside of that, let's just take today, for instance. Here is the high-res UKV model output for this afternoon from the morning 03z run: You can see that none of these charts feature a max above 20C. And yet, the Met Office had a provisional maximum of 22.1C at Santon Downham, partly due to just a few cloud breaks at the right time. Other models are typically worse for this than the UKV, which is normally only out by a degree or so. ECM can even be 3C or 4C too low sometimes. Another pattern is that temperatures tend to be revised up closer to an event or even on the day. The afternoon UKV, actually issued retrospectively, did do better, with a raw max of 21C, which is close enough. Another pattern is that temperatures get revised up typically closer to an event. This was something I noticed in the run up to the September 2023 heatwave in particular - a lot of model output initially was translating 15-20C 850hPa air with cloudy early mornings and clear afternoons into temperatures only around the 26-29C range. As we got closer to the event, those figures got revised up, and we ended up reaching 33C on the hottest day and recording seven consecutive over 30C. Again, the current warm spell is not in the same category, but if we happen to record one or two days in the mid-20s when we're only 'supposed' to record low 20s, it really wouldn't surprise me very much.

damianslaw It's based on the 90th of maximum temperatures at the hottest part of the year (July), for 1991-2020, with a minimum set at 25C for the qualifying threshold. The definitions are redone every 10 years - I expect the 2001-2030 definition will see a number of areas increase. Probably a first 29C for parts of London and the SE, and many other areas being raised accordingly. I expect West Yorkshire must have been pretty close to reaching the 26C definition last time it updated, so I think we will do next time.

Addicks Fan 1981 Yep, I was going to come back later to comment. The mean sometimes gives a misleading view through averaging various scenarios in the model view format, so I prefer the numerical ones. For the GFS at least you're right that the GFS outcome is on the bottom end of the ensemble for MSLP, but it's not a ludicrous outlier. It should be noted that MSLP is only above 1020mb on the mean from the 8th-11th. ECM ensemble / clusters to follow later, which I guess will give more insight.

And GFS tonight throws the high pressure for next week out the window, after the wobble from the ECM this morning. GEM still good tonight, but I have a sinking feeling about where this is going again - we've only been here about 27,461 times since last June. You'd practically put money on the worst possible option verifying as far as any sort of prolonged dry spell for the UK. The wait has to end at some point though...

And proving that caution where we don't have cross-model agreement is a good idea - the GFS is now having a wobble. Days 8, 9 and 10 on the 12z vs. the exact same timestamp from the 00z: 12z: 00z: Absolutely massive downgrade. In contrast, GEM is still strong with the high at days 8, 9 and 10: So out of the big three only ECM to wait for - still looks like we're not going to have cross-model agreement tonight. I think the wait goes on until we get agreement on the broad pattern for next week. Of course also ensembles to check out later - not worth considering only the OP runs - in particular we need to see whether the GFS was rogue or whether there is ensemble backing for a downgrade.

summer blizzard It may be correlation rather than causation (I wrote my post carefully to avoid any implication of direct causation). Here is a paper with some more details if you're interested (which I posted on the model thread a couple of weeks ago). But to summarise, if the polar vortex is stronger than usual in May, this tends to correlate to a later final warming in the lower stratosphere, and this then propagates down to possibly increase the chance of +NAO in at least early summer. Skilful predictions of the Summer North Atlantic Oscillation WWW.NATURE.COM The Summer North Atlantic Oscillation responds sensitively to an anomalous strength of the stratospheric polar vortex in spring, which can be exploited for seasonal predictions, according to large-ensemble... Again though, causation with this stuff is difficult, so I will continue to refer to it as a correlation.

Addicks Fan 1981 The other thing in our favour is the stronger than average polar vortex, which I mentioned on the model thread a few weeks ago. Generally if the May polar vortex is stronger than average it correlates moderately with a warmer and drier summer via a positive NAO.

Topclassweatherforecaster Depends on what we mean by heatwave. If we mean the 'official' heatwave definition, then we need three consecutive days to surpass the following daily maximum temperature threshold depending on where you live: There have been occasions that have met this criteria as early as late April or early May in the past, but usually heat in the UK is 'backloaded' towards the middle or end of summer. In short, there is more likelihood of a heatwave in September than in May, and in August than June. Any prediction beyond the 10 day timeframe is fraught with difficulty so anything anyone says here including me will be nothing more than a guess, but given various background factors pointing to a warmer than average summer I think this one might go against the general rule. Therefore, I'll take a wild stab in the dark and say that we'll see an early heatwave in either late May or early June. If you mean the more general sense of a heatwave as in a spell of warmer than average weather - well then next week may well produce it - moderately warm, temperatures quite widely into the low 20s being the most likely scenario.