Annual CET

[LetItSnow]

A slight addition to the previous message as now a finish in the 14s looks not an impossible task. Assuming a finish of 14.5, if the summer were only 1C above the 1991-2020 average and then the rest of the year "average", it would still produce a finish of between 11.0-11.3C. Given the warmth in the atmosphere a very warm summer can't be ruled out. 10.7-10.9C would be the ballpark if the rest of the year turned out average which is very unlikely. Usually I'm not one for hyperbole but unless a major pattern flip changes, I think we're staring down the barrel at the warmest year on record, an incredible third year in a row at 11C.

In fact, if the rest of the year stays warm and averages around just 1C above normal then we'd possibly be looking at around 11.4-11.7C. I'm not even convinced that's the most unlikely outcome since many months since September have been 1-2C above average even by the 1991-2020 average. Crazy times. Our climate at the moment is about as extreme as the 1690s in terms of anomaly, just the opposite. 

@CryoraptorA303It's a bit grim, innit.

[summer blizzard]

While possible, I'm reminded that we were near record pace in 2020 and backed off. Reversion towards the mean (though possibly still above it) is likely.

[WYorksWeather]

 LetItSnow! Alternatively, if you're a fan of seasonal weather and years being 'deserving' of their records, probably the cruellest outcome would be if summer and September averaged out at bang average 1991-2020 and much wetter than average, and then October through December averaged at 2C above 1991-2020 (and also much wetter than average).

That would mean you'd have the warmest annual CET (possibly by some margin) with a finish well into the 11s, but subjectively from the perspective of seasonality it would be one of the worst years ever. Virtually no winter except a cold and dry spell in January, a milder than average spring but devoid of 'proper' warmth until May (which would probably be the only 'good' month), a poor to mediocre summer, no September heatwave, and from October on ridiculously wet and mild with barely a frost let alone any snow.

If something like this were to happen, it would be simultaneously be both terrible (from a weather experience perspective) and also quite funny (in the sense that I could imagine the reaction if it were announced as the warmest year on record!).

[LetItSnow]

 summer blizzard Trust me, I would much rather this happen than the former.

[TheOgre]

 WYorksWeather Sounds a bit like 2011. That had a cool, drab summer with notable warmth in the spring and autumn. Wasn’t it the hottest or 2nd hottest year on record at the time?

Edited May 17 by TheOgre

[WYorksWeather]

 TheOgre Second warmest at the time. And yes, my hypothetical 2024 would be relatively close to that.

It has now dropped to rank 6 though (almost certainly 7 after this year) which just shows how easy it is to achieve warmth these days.

 

 

[LetItSnow]

 WYorksWeather Same with the once giants of 1949, 1990, 1999, all exceptional at the time and now slipping down the rankings very fast. It's all giving a bit 2002 at the moment which hilariously was about the third warmest year on record at time despite very little fine spells and being very dull. The weather doesn't really change, just the temperature does. Too early to say what will happen for the rest of the year but I would think it would be very unlikely to be below 10.6-10.7C at this time.

 

[WYorksWeather]

 LetItSnow! Yeah it's hard to a finish in mid 10s or lower. Of course to say it can't happen would be foolish, but I would put the odds at about 5%.

[reef]

 LetItSnow! Its a similar story here. Take summer 1995 for example: That summer had a mean of 16.2C here.

In just the last 10 years, 2016, 2017, 2018, 2019, 2021, 2022 and 2023 were all warmer.

All of the last 8 summers were warmer than a "decent" summer like 1996 aswell. Things have changed a lot.

[CryoraptorA303]

 reef August 1995 is still the hottest on record though, and the second-hottest summer month on record behind July 2006. Up to that point the summer really hadn't been that hot, just very dry and sunny. June was actually below average.

I do agree though, in that time the old record holders are being eclipsed quite alarmingly. And while months like August 1995 and July 1983 are still near the top, I'd argue the sort of temperatures experienced in those months don't come close to heatwaves we've experienced in recent years. They were simply very consistently hot to get where they are, and to be fair August 1995's 35.2°C was comparitively far more notable than it is now, the last time such temperatures being reached aside from 1990 being 1976. Now we're reaching those sorts of temps nearly every year.

I'd also argue months like August 1995 are only still at the top nationally because they are among the last ones to include Scotland and NI. Along the east coast, August 1995 and July 1983 are nowhere near the hottest on record anymore, they have been absolutely rubbished here. August 2022 is the hottest on record in this region, even above 2003, and July 2018 is the hottest in its category. Across a lot of England July 2018 beat even 2006 but further north wasn't included so it ends below older giants nationally but way above them on the more local scale. I would suggest this is down to later events being overall less notable in terms of anomaly than the old giants, but are being greatly amplified by climate change to produce much higher temperatures than would have been seen 30+ years ago. Once an event comparable in anomaly to something like August 1995 does respawn, it's going to absolutely tear the existing records to pieces, think the kinds of anomaly April 2011 or December 2015 have but in July or August.

[LetItSnow]

1 hour ago, CryoraptorA303 said:

Up to that point the summer really hadn't been that hot, just very dry and sunny. June was actually below average.

That’s not true of the summer of 1995 at all. The first half of June was very cool (though less so in the west) but then became hot basically from around the solstice onward. So much so that the month was very slightly warmer than average. July 1995 was a very hot month with often warm to hot temperatures between the mid 20s and low 30s. It has a CET in the 18s. Unless I misunderstand your comment?

[CryoraptorA303]

 LetItSnow! 

June was cool but exceptionally dry.

July however was very warm, even warmer than July 2022. My bad, I was under the impression July hadn't been exceptionally warm either. Only three Julys since then have been warmer and 2021 matched it. Overall it's still the joint-fifth hottest on record (weird to think that July 2021 is fifth-warmest).

Looking at Heathrow, it doesn't really look like a month that at the time would have been the second-warmest on record. I suspect the nighttime minima were helping its case.

[LetItSnow]

 CryoraptorA303 The CET must not reflect cooler eastern regions. Admittedly the first half of June was very poor there. 

[CryoraptorA303]

 LetItSnow! It looks like western Scotland was the warmest area of the UK that June if anything, being the only place that seems to have reached 20°C almost every day. Given the current situation, it makes you wonder whether we're heading for a repeat

[summer blizzard]

 CryoraptorA303 I think the key thing they separates the likes of 03, 06, 95 or even 18 is that it's widespread as well as consistent.

Note July 22 for example. While it's CET is comparable to July 13 or 95 for example, in Yorkshire and Lancashire it was an incredibly mediocre month that bar 2 days was no more notable than say July 10 so it wasn't nationally notable. 

[summer blizzard]

Rolling CET for Oct-Sep falls to 11.05C.

Also seen a 4 month average below the 1991-2020 average for the first time in a few years (modelling may allow for a 5 month period) since possibly 2015.

Edited October 4 by summer blizzard

[Relativistic]

 summer blizzard Not Jan-May 2021?

[Don]

 summer blizzard At 17C, wasn't August above the 1991-2020 average?

[LetItSnow]

 Don He means the average of the four months. Even with August +0.5C above average the period from June to September averages -0.2C below average.

[summer blizzard]

 Don Yes but as Let it snow said, the overall period is below average (don't even think August wiped out June).

[summer blizzard]

 Relativistic Ah yes, you are correct. 

[Don]

 summer blizzard yes, I’ve acknowledged that. 

[Cloud2]

12 month rolling CET now down to 10.96C, I believe that's the first time its been below 11C since November 2023.

[WYorksWeather]

 Cloud2 Yep, a cooler few months with some nearer average values has dropped it quite a bit. Last November was mild at 7.4C, but given the very mild start it's possible we could beat that this time. If we were to record a CET in the 8s, that would be enough to take the rolling CET back into the 11s.

Overall on the October CET thread, I calculated that somewhere in the low to mid 7s would be required for the Nov / Dec combined average, in order for the annual CET to finish at 11C. Now that October has finished, I calculate the requirement as 7.2C.

Edited November 2 by WYorksWeather

[summer blizzard]

Seems a reasonable chance now that we will see the CET end the year below 11C.