General summer chat

[CryoraptorA303]

5 minutes ago, WYorksWeather said:

To give some context, the modelling states that reaching 40.3C was a 1 in 300-year event in the current climate - that seems absolutely hopelessly optimistic, and the modelling at the regional level on this is hopelessly out of whack with observations of other extreme heatwaves as well (the 2021 PNW heatwave in Canada was estimated at 1 in 1000 years using similar methodology).

Not to mention the other hundreds of events in the last X years that have estimated return periods far beyond what is being observed.

10 minutes ago, WYorksWeather said:

For 38C, I'm not sure if I'd agree that it's 1 in 5, we have a distinct lack of data problem on that one as we've only had three such years. We won't necessarily get another period analogous to 2007-2012, but we can't necessarily rule it out. Even those summers brought forward by 15-20 years wouldn't have a prayer of achieving 38C. I think there is a lot of uncertainty on it. Highly unlikely to be lower than 1 in 10 I would say, and probably not higher than 1 in 3. The period up to 2030 will give us a good idea of which end we're at.

This is a fair point, the dataset is very small and this is a big problem in modelling the overall impact of climate change as it's evolving extremely quickly in the context of planetary science. However its starting to seem like the 37+°C years are becoming analogous to the 34+°C years of old in terms of probability. 1990 can probably be expected to have reached 35°C, 1995 perhaps 33°C, 2003 again 35°C, 2006 maybe 34°C, then the 2007-2012 years fail to reach 30°C or only just scrape it, then 2018 again 33-34°C, 2019 35°C, 2020 reaches high 34°C, then 2022 maybe manages 36°C. All the unmentioned years reach 30-32°C in all likelihood.

22 minutes ago, WYorksWeather said:

I would prefer however to err on the side of accepting some dubious older records, mainly just to avoid any accusations of 'cooking the books' or 'cooling the past', which often gets circulated.

Who really cares what they think; they're wrong anyway. Something like the 1906 heatwave I do tend to take at face value though, simply because the data is not available to settle on another likely figure for that day.

 Metwatch Wellesbourne reached 28.4°C on the 10th. I suppose there was an attempt at celebrating Faversham's 20th birthday 

[LetItSnow!]

 raz.org.rain I'm not so sure 2019-2021 can be described as a string of overall decent summers though

[WYorksWeather]

To bring things back a bit towards more typical summer chat - how about this for a scenario. Summer lasts 13 weeks roughly. Imagine you are allowed to choose your own summer, but with the proviso that it must meet the following criteria (relative to recent averages for your location).

1. One week must be very cool and very unsettled (named storm type stuff, or generally just very wet and cool if not).
2. Three weeks must be predominantly cool and unsettled.
3. Four weeks must be mixed (could include thundery setups).
4. Three weeks must be warm to hot and mostly dry.
5. Two weeks must be very hot and virtually rainless (notable consistent heatwave for the time of year, or a very intense but brief plume).

The key is, you get to choose which weather you get when, but you must fit all of that in.

Just came up with this, but I'm actually going to sleep on it before I come up with my answer I think - it's quite a tricky one!

[LetItSnow!]

 WYorksWeather I think there's already been a thread with this concept.

[WYorksWeather]

 LetItSnow! There was, but for the whole year. I think that made it a bit less interesting, in the sense that you could sort of shunt all the rubbish into parts of the year you don't really care about. It doesn't really force a tough decision in that sense. In other words, if you're a summer fan but hate cold, you could throw all the colder than average stuff into April, May, October and November, which means you don't get any severe cold and snow most likely (an indifferent winter) and then can use your good months for the summer. And for coldies and heat haters, you could shove the warmth into say March, April and October, have a very indifferent summer, and then save up the cold for a cold winter.

Forcing a week-by-week choice in the summer, which is a period that is important to most people (whether because they love heat or hate it), means that you can't entirely duck the issue. You can't just force a 2007/2012 if you hate heat, or a 1976/1995/2018 summer if you love it.

[B87]

 WYorksWeather My attempt:

1-7 Jun: 16c, 15c, 16c, 17c, 19c, 20c, 17c. 20mm on 5 days, 20 sun hours

8-14: 18c, 17c, 20c, 20c, 18c, 19c, 20c. 10mm on 2 days, 40 sun hours

15-21: 21c, 24c, 21c, 22c, 21c, 25c, 23c. 10mm on 1 day. 60 sun hours

22-28: 23c, 24c, 26c, 26c, 27c, 28c, 25c. 5mm on 1 day. 90 sun hours

29 Jun-5 Jul: 21c, 24c, 22c, 23c, 21c, 22c, 19c. 5mm on 1 day. 40 sun hours

6-12: 21c, 22c, 23c, 22c, 21c, 21c, 22c. 15mm on 4 days. 30 sun hours

13-19: 23c, 23c, 22c, 23c, 24c, 25c, 23c. 10mm on 2 days. 60 sun hours

20-26: 25c, 28c, 31c, 32c, 32c, 29c, 30c. 0mm on 0 days. 100 sun hours

27 Jul-2 Aug: 32c, 33c, 34c, 34c, 32c, 31c, 33c. 0mm on 0 days. 80 sun hours

3-9: 31c, 33c, 35c, 36c, 37c, 37c, 33c. 0mm on 0 days. 80 sun hours

10-16: 30c, 32c, 29c, 28c, 30c, 27c, 25c. 5mm on 1 day. 70 sun hours

17-23: 22c, 21c, 19c, 20c, 21c, 22c, 23c. 20mm on 3 days. 10 sun hours

24-31: 23c, 22c, 24c, 25c, 25c, 22c, 22c, 22c. 10mm on 2 days. 40 sun hours

Final stats.

June: av max 21.1c, 45mm on 9 days, 210 sun hours

July: av max 25.6c, 30mm on 7 days, 230 sun hours

August: av max 27.1c, 35mm on 6 days, 280 sun hours

Without realising, I've pretty much created 1995.

 

 

[WYorksWeather]

In answer to my question posed above, and having though about it, here is how I would distribute the summer according to my 'rules'.

June:

1. June starts on a very poor note, with widespread severe gales and heavy rain.
2. Fairly unsettled, but not as bad as the first week.
3. As we approach the longest day, the weather makes a sudden flip to much warmer and drier weather.
4. The last full week turns notably hot, temperatures reaching 30C at my location on at least two days and 34C as the absolute maximum nationally.
5. The June/July transition is marked by a thundery breakdown and largely mixed weather.

July:

1. The first full week of July is predominantly cool and unsettled.
2. The second week is similar, but starts with a very deep low and ends on a more summerlike note.
3. By the third full week, we see a return to something more summerlike, with sunny intervals and showers. Likely feeling warm but a mixed week overall.
4. The final week of July and into the first day or two of August is also mixed, but of a different character as a week of two halves, with a deep low in the first half of the week followed by warmer and drier weather later.

August:

1. The first full week of August again sees a mixed pattern, starting quite warm but turning showery and cool as the week progresses.
2. The second week turns warmer and drier, the first consistently warm and dry weather since late June.
3. The third week is warm overall, but starts very warm to hot and then breaks with intense thunderstorms later on.
4. A historic heat plume hits for the August bank holiday, smashing temperature records with the latest ever 37C on the 25th, and an extraordinarily hot bank holiday weekend overall, which to round out the summer is then capped by yet more thunderstorms as cooler air moves back in.

Overall

This hypothetical year would be like a noticeably improved summer 2023 maybe?

I like the period around the longest day in June to be warm or hot to take full advantage of warm evenings and since the heat is much less humid at that time. Then, if we have another heat spell in mid to late August it'd be like an improved September 2023, which whilst it may have been too hot for some in the south, was merely very warm here and not proper hot weather, as the cloud took too long to burn off on a lot of days. Apologies to those in the south who would prefer not to reach 37C. Plenty of thunder as well in this hypothetical summer, which is always a plus in my book.

Most importantly, whilst the heat would be historic for late August, it's another year where we avoid anything completely ridiculous heat wise - I don't want to see another 40C anytime soon, and a 37C in late August as an absolute max would be a fair bit lower up here than it would be in the south or in East Anglia in most setups.

If I had a choice, I'd probably remove the very unsettled weather at the start of June, and have more weeks in the warm and mostly dry category. I'd probably use those to make July a much better month.  But with the rules as stated one month has to be the poor relation!

 

[LetItSnow!]

 WYorksWeather

June: I'll use the first week of June as mixed. The summer will come in gentle with the Azores generally displaced to our west, starting close by so mostly fine but some showery interludes with rather normal days but some cool nights. Then I'll use the next week as a warm and mostly dry week as the high pressure collapses over the UK. Uppers are close to average so the days gradually become very warm but nights stay cool with days in the low to mid-twenties but some places having single digit minima. Then I'll take the two weeks of mixed conditions to close June as the high pressure gradually relaxes south to allow an Atlantic influence with some wet and windy days interspersed with dry and fine weather and near-normal temperatures. A pulse of warm air in the final week ends June on an unstable, humid note with storms with temperatures in the upper 20s.

July: I'll use up the two hot weeks for the first half of July which will see the thundery trough slowly dissipate and high pressure build. The high pressure is centered in the North Sea and the flow is gently north-easterly with uppers in the 8-12C region. The heatwave is a tame affair with temperatures no higher than 32C and it's not a complete two week heatwave as there are some interruptions like a nearby spoiler low giving cloudier/thundery interludes and some cooler days as the high pressure re-establishes itself more to the west. The second-half of July I'll use up two more mixed weeks. The high pressure backs west enough to allow low pressure to generate over the country and brings a spell of very wet and thundery weather. Once the low clears a generally westerly flow takes hold with low pressure at times and some showery northerlies that prove heat lovers that you don't need warmth for good storms as we see unusually intense storms. Generally though the second-half isn't a washout by any means and high pressure is never far away and begins ridging in again in late July with a return of sunshine and low/mid-twenties temperatures.

August: I'll use my final two settled weeks for the first-half of August with a west-based high pressure system bringing a lot of fair weather days with variable cloud, sunny spells and temperatures in the upper teens/low twenties, some mid-twenties days as well. Nights average pretty cool. The high retrogresses as I use my last cool unsettled week for week three as the high retrogresses with low pressure bringing wet weather. I then save my very cool week for the end of August when we get an unusually potent northerly that sees the Scottish mountains get their first wintry showers and we see ground frost in places with temperatures widely falling into single figures even further south.

I'd imagine June has a C.E.T. around 14.6, July 17.2 and August 14.9.

The warmest temperature of the year would be a modest 32.1C in early July. There would no tropical nights and the warmest night of the year would be a very modest 17C.

Edited March 9 by LetItSnow!

[kold weather]

 CryoraptorA303 Whats most impressive about 76 is just how exceptionally stable that heatwave was for particularly Cs/Midlands.

The fact we've still not had anything even in that heatwaves ballpark in terms of sheer longevity of the hot pattern since then is quite telling of how exceptional the set-up was. In the CET it really does still stand out against even modern heatwaves. The first 10 days of July 76 in the CET is exceptional by any standards, even when compared to the likes of Aug 03 or Aug 20, both of which had exceptional spells of heat.

It feels like alot of the really hot blasts we are getting are being triggered by an Azores low drifiting east of the usual mean and suckering up very hot air from SW Europe. Problem is that pattern is usually too unstable to hold for that sort of time (2-3 weeks as in 76) and usually breaks down into more typical SW/W pattern. 

At some point 76 crown will go for everything, even just by virtue of a warming world causing the synoptics not to need to be quite as extreme anymore. When that will be remains to be seen.

Edited March 9 by kold weather

[B87]

 WYorksWeather Thoughts on my summer?

[Cheshire Freeze]

 cheeky_monkey The sort of July chart I like to see

[CryoraptorA303]

 kold weather Indeed. At the time the 1976 heatwave was estimated to be around a 1-in-300 year occurence. That would mean today the exact same heatwave would be more like a 1-in-80 year event, which is still very uncommon and can be expected around twice per century on average.

July 2006 is probably the last time we got seriously close to challenging 1976's records. Today with 18 more years of warming, it's not implausible that a repeat could defeat 1976's longevity records.

I would bet on the all-time June record going before the longevity aspect is defeated. Temperatures above 34°C in June appeared to have occured around maybe five or six times in the 20th century. These would probably be equivalent to 36+°C today. So far we have seen 34°C or higher just twice in June over this century, which suggets we are simply seeing a lower number of June heatwaves than the background average due to natural factors. We've had some close calls as well: In 2019 we had by far high enough uppers to see well over 35.5°C, but wind direction delivered strong easterlies that heavily nerfed the potential of that heatwave. In 2022 had the heatwave gone just a bit further north we would've seen 36-37°C. And of course, in 2015 we were a single day out of seeing the record defeated with 36.7°C falling on July 1st. So the main player here appears to be very, very bad luck.

Edited March 9 by CryoraptorA303

[SummerShower]

 kold weather I remember reading somewhere that the 1976 heatwave had a weak warm front drifting northeast on the 21st opening the floodgates to very warm air.  The high pressure that was to the east at this time slowly expanded westward and persisted for over 2 weeks.  About 8 to 9 days into this spell there was a shallow low that drifted up from biscay, but didnt get too far north.  This helped to reinforce the hot pattern.  This was a very slow moving setup which kept the heat going for as long as it did.  If i remember rightly there was a 'slight' dip in temperature from 29th june to 1st July to maxes of low 30s in the west, mid to high 20s in the east as more of an easterly set in.  The heatwave could have collapsed at this point but was reinforced from the south.

If recent set ups are taken into account, a warm front moved east on 16th June 2017 which allowed that 5 day heatwave of 32+ under high pressure.  This would account for intensity.  To prolong it you'd then need something like a june/july 2018 scenario, where the high pressure was persistent, and buoyed up by a biscay low around the 30 June/1st July, which didnt push too far north.

So, something like a June 2017/June and July 2018 combination of synoptics could at least equal, if not beat 1976 I feel.

[kold weather]

 CryoraptorA303 In fact that June 2019 flow was one of the hottest ever recorded (I think 25.8c was recorded in the SW at 850hpa, 24-25c was recorded in Kent on the 29th), it was roughly a similar intensity as the Jul 22 heatwave, though more limited in terms of how far north the most intense heat got and obviously severely nerfed due to the undercut easterly (so much so places ended up under a modest inversion close to the east coast such was the uppers)

I remember a pro met on another forum calculated that under perfect conditions that flow was capable of a 40-42c, the uppers were a hair lower but thickness a hair higher than in the Jul 22 heatwave. I had serious doubts at the time but seeing how the July 2022 heatwave evolved that 2019 flow probably would have been capable were it not for that undercut. It'd have basically been of a similar calibre to that extreme NW Canada heatwave had it come off, but I suppose those are real rare beasts for a good reason.

I've no doubts that the June record will go within the next 5-10 years.

 

Edited March 9 by kold weather

[WYorksWeather]

 B87 Some interesting similarities and also differences with my own. We both had early June and early July as the dross periods. Difference was the distribution of the warmer weather - you went for a traditional late July to mid August heatwave, with a more typical autumnal end to the summer, whereas I traded a worse late July for a better late June, and so July ended up particularly poor. Of course actual temperatures at my location are lower than yours - hence I tend to quote the national max and assume 2-3C lower up here.

 

[CryoraptorA303]

13 hours ago, kold weather said:

24-25c was recorded in Kent on the 29th

Are you seriously telling me Kent missed out on setting the June record? That must be a once in a lifetime chance considering how strong the easterly tends to be in early summer. Saying that, Gravesend did achieve the 2011 annual maximum during that June heat spike (the same one that broke records in France and so is another misses opportunity to defeat the 1976 record this century), and East Malling holds the daily record for June 30th, set during the 1957 heatwave, so it can happen if the North Sea is warmed above seasonal averages enough. There seems to be an M-shaped curve for Kent maxima - it starts seeing higher and higher placements in the national table until peaking in late May, and then sharply declines in June before rising again from mid-July until seeing its highest national performance in low autumn.

[CryoraptorA303]

16 hours ago, SummerShower said:

So, something like a June 2017/June and July 2018 combination of synoptics could at least equal, if not beat 1976 I feel.

That's an interesting proposition actually.

The 2018 heatwave would've likely achieved even higher temperatures if it happened in 2017 instead. Autumn 2016 had been notably dry, spring had been one of the warmest overall and there had been no significantly wetter than average months since June 2016. June 2018 but with the 2017 heatwave inserted would probably outright break the 35.5°C record with how intensely dry it was and now it was working with soil that was already dry by this point instead of having to do all the work after a very wet low spring. The final heatwave in July would then likely see 36-37°C and it'd be the first 20°C CET month.

Bonus points if you then want to shove the July 2019 heatwave in, that probably would've seen temps exceeding 40°C after this insanely dry and hot period. You could have it at the same time but that would likely displace the final 2018 heatwave so I'd move it to early August instead. First having a 36-37°C heatwave (for consecutive days as well) and then having another 40°C heat spike immediately after would be carnage.

[kold weather]

 CryoraptorA303 It probably was of the scale of the NW Canada heat anomaly at 850hpa considering we aren't even quite at peak summer in late June.

Here was the 25c in the far SW (25.8c at Cambourne I think?) Kent got to about 24-25c briefly on the Saturday but by then it was moving out, akin to the Jul 22 shot.

 

The thicknesses I believe were the highest ever recorded (though I'm not sure if that has now been beaten by July 22, it'd be close either way) but the far south had about 60hrs under 20c at 850hpa. The peak intensity was maybe a shade under Jul 22, but longer holding and more than comparable when you put the two against each other.,

Using the usual Skew-T average profile it was worked out such a flow was theoretically capable of a 41-42, maybe a rounded up 43c given thickness, 850hpa temperatures and peak solar warming. Of course we probably would not have gotten that theoretical temperature but I'm sure it would have utterly smashed the previous record for June given how high the Jul 22 thrust went. Its interesting that just a month later we did get a properly oriented blast for the record, albeit more limited in some respects at higher levels.

[CryoraptorA303]

 kold weather Bloody hell, that really is an exceptional plume, especially for June. What a massive miscarriage of justice that it got so incredibly nerfed by the easterly.

I don't know if the 42°C figure could have ever been achieved in reality as that probably assumes impossibly ideal conditions for late June, but without the strong easterly it would've easily been 38-39°C, possibly 40°C. Considering the easterly breeze I would guess Crawley, Wisley or a London station would get the final record. Maybe Frittenden could do it if the angle of the easterly means it is completely sheltered and it has perfectly ideal sunshine with zero cloud throughout the day at all. Overall I'd prefer a more western station like Benson or Pershore to get the June record, but the weather doesn't care about my feelings.

What'd also be interesting is how this affects the July heatwave. It's possible that a proper severe heatwave in June where we actually do see three or four consecutive days above 35°C and a ceiling of 38-40°C would have dried out all of that rain from the May-June border, and then as July up until the heatwave was quite dry, if humid, in the southern half of England where it mattered, the now much drier ground would lead to the July heatwave achieving far higher temperatures, perhaps 40-41°C, more in line with the rest of western Europe during that heatwave. I'm not sure how exactly high the uppers went in July 2019, but they must have been well over 20°C as anything below that would not achieve 38.7°C with such wet soil.

2019 was a very unusual year, it was both very warm and also wet. We ended up right on the border of the jet stream storm track and the extreme heat further south in Europe, so most of the time it was very humid in the south. I remember how as soon as the Sun came out around mid-June after the monsoon, 24°C already felt more like 32°C with the insanely high humidity. July was even worse with it often reaching 25-27°C in the southeast by day but also with quite a bit of cloud and disgusting humidity. Part of the reason I barely slept all summer was because of the humidity. The bank holiday heatwave was the worst though (aside from the July heatwave), after the heat passed and thunderstorms moved in the humidity rose to extreme levels. That day must've been the highest humidex I've ever experienced. Temps were in the mid-20s or so but it was absolutely oppressive, the RH must've been nearing 100%. The September 2023 heatwave was bad with ~70% humidity at 30°C on some days but that didn't feel as comparitively oppressive as that day. 2019 is probably my most hated summer.

I have also realised through the course of this post how many words rhyme with June

[Greyhound81]

 CryoraptorA303 Would 30°C feel warmer in May than it would in September?  High temperatures in the Spring usually seem warmer that high temperatures in the Autumn.

 

Even though 2018 was a very good summer it did not seem all that oppresive compared to the really hot days in 2019 and 2022.

 

Edited March 12 by Greyhound81

[CryoraptorA303]

 Greyhound81 The Sun is stronger in May than in September, but September is often far more humid, simply because the air has had more time for water to evaporate over the summer. The September 2023 heatwave transplanted into May would have the Sun feeling considerably more intense, I remember May last year despite the lack of extremes felt very warm in the Sun when no wind was blowing just from the very high sunshine hours, but good luck getting 70% RH at 29-30°C in May. Unlike with the May sunshine, there is no way of escaping high humidity, so I think I'd prefer to see such temperatures in May or a normal-humidity June (I say that because June 2023 was unusually humid for the time of year which made the heat feel far more disgusting than you'd expect) than in September. Not to mention, as the humidity is far lower and the easterly breeze is stronger in May, it doesn't stay anywhere near as warm at night as it does in September, even with the shorter nights in mind.

Edited March 12 by CryoraptorA303

[*Stormforce~beka*]

Are we nearly there yet? ...

[raz.org.rain]

I'm not sure if anyone else noticed this, but a 20°c hPa was suggested by an outlier the other day. Very unlikely to happen, but the fact that it's considered a remote possibility is unusual.

 

 

 

[Addicks Fan 1981]

I think the strongest analogues to summer of this year are 1973 as I've said before, 1995 and 2016.   

[John S2]

Could you enlighten us why 1973 is considered an anologue? It had a lovely dry and anticyclonic start to the year. 

E&W rainfall for 1973: Jan - 46mm, Feb - 45mm, Mar - 23mm