May 2024 C.E.T. and EWP forecast contests

[Roger J Smith]

As everyone probably knows, no final CET in range of 14.0 to 15.0 but I took a look at stats to find out what months have at least been in 14.0 to 15.0 range at any point. I excluded first six days as that includes various brief warm spells that did not last very far into the month. So from 7th to 30th (besides 1833) these months have been in range of 14.0 to 15.0: 

 7 _ 15.2 1995, 15.1 1990, 14.9 1804, 14.3 1800, 14.0 1775

 8 _ 14.7 1995, 14.7 1804, 14.6 1990, 14.5 1800, 14.2 1834, 14.1 2008, 14.0 1775&1867

 9 _ 14.7 1800, 14.6 1804, 14.4 2008, 14.3 1834, 14.2 1995, 14.1 1775,1867&1990

10 _ 14.7 2008, 14.3 1804, 14.2 1834, 14.1 1800&1867, 14.0 1833

11 _ 15.1 2008, 14.3 1834, 14.1 1833, 14.0 1804&1867

12 _ 15.2 2008, 14.4 1833, 14.3 1834

13 _ 15.1 2008, 14.4 1833, 14.1 1834

14 _ 14.9 2008, 14.6 1833, 14.1 1834

15 _ (14.9 1833) 14.7 2008 14.1 1834

16 _ (15.2 1833) 14.4 2008, 14.1 1834

17 _ (15.4 1833) 14.2 2008, 14.0 1848

18 _ (15.5 1833) 14.1 1788, 14.0 1848&2008

19 _ (15.4 1833)

20 _ (15.4 1833)

21 _ (15.4 1833)

22 _ (15.4 1833)

23 _ (15.5 1833)

24 _ (15.5 1833)

25 _ (15.6 1833)

26 _ (15.5 1833) 14.0 1848

27 _ (15.4 1833) 

28 _ (15.4 1833) 14.1 1788

29 _ (15.2 1833) 14.0 1848 (ended 13.91) (13.9 1788)

30 _ (15.1 1833) (13.94 1848)

31 _ (15.1 1833) (13.91 1848) (13.76 1788)

__________________________

So there are quite a few dates where only 1833 was above 14.0, and 1788, 1848 were the only other years to get near 14.0 after 18th when 2008 ran out of gas. 1992 was never above its final value of 13.6 and 1947 also (13.5). 1784 was at 13.6 26th-28th and finished 13.55. 2016 peaked on 12th at 13.5 C.

[The PIT]

Sunny Sheffield up to 14.5C +4.7C above average.

[Summer Sun]

13.5 to the 10th

2.3c above the 61 to 90 average

2.7c above the 81 to 10 average

[damianslaw]

Quite likely to be in the 14s at the mid-month stage, quite a feat. The next few days will maintain high CET though after tomorrow, not as high as currently.

I'm not seeing any significant cool weather by the third week, a finish below 13 degrees looking quite slim I say especially given May is a rapidly warming month and the end of it has a habit of being very warm. 

 

[WYorksWeather]

 damianslaw Tonight's UKV also rapidly dropping any chances of a drop. Not even sure that we'll see a drop at all up to Thursday.

Here are maxima from Monday to Thursday:

Just taking a glance at that, you'd expect maxima to average 20C for the CET, at the low end.

Here are minima for the early hours of Tuesday through Thursday:

Again, from this, minima probably also above average for the period, near 10C or so. If you combine with a 20C average maximum, that gives a CET average, possibly even on the slightly conservative side, of 15C.

Of course surface conditions make a massive difference to this even at relatively short range, but I'd now expect that the CET will hold through the first half of next week looking at this, or maybe even rise slightly.

 

[LetItSnow!]

2024 marching into record territory by the looks of it… Well might as well go for a run at 1st or 2nd warmest May in such a warm spring/start to the year. 

[Derecho]

Latest projections from the EC control 12z. A marked change from the last update with the CET holding up a lot more again. The models seem to have done the classic thing of initially going for the low to our west moving south on the operationals, to moving over us bringing cooler air, then swinging back to the old solution again late on.

The CET should rise further next week largely thanks to the high minima but I think Monday could see a further uptick. The CET gradually rises to 14.6C on the 19th through some pretty consistent temperatures.

After that it levels off but that isn't in the reliable anyway. If we get a plume or period of heat in the final week of May I think there is a chance the 1833 record could go...

[Frigid]

 Derecho Honestly I'm not surprised, we've seen exceptional warmth in the last 18 months and this month certainly isn't holding back. In the last year we've had June, September and February come in record breaking status.. that's not to say the other months were cool, October, December and March were also very mild. This year is certainly looking like a record breaking one, unless the summer and autumn is cool which is quite unlikely. Just wondering when a shift to a cooler regime will take place, it has to break at some point. 

[Don]

23 minutes ago, Frigid said:

Just wondering when a shift to a cooler regime will take place, it has to break at some point. 

At some point, but how cool is the question as it would appear climate change has stepped up a gear in recent years?!

[WYorksWeather]

 Derecho Looks like the EC control backs up my early look at the UKV. Key as always will be surface conditions with next week's low I think.

Should have a good chance of staying above 14C to the two-third point (becoming only the second year to be above 14C at that point) and then as you say anything can happen. A benign end with a slow drop into the mid to high 13s, a sharper drop into the low 13s or upper 12s, and frankly sky-is-the-limit if we get one of the insane plumes that seem to just come out of nowhere these days.

There are still ensembles throwing out mid to upper 20s beyond day 10 at the moment. As long as that is showing up it really feels like it'd be crazy to ignore the possibility.

In terms of probability I'd put a 14s finish at maybe 50% going off the latest output and given the lack of any real cold signal. 13s and below gets 40%. 15s and above gets 10%. The 10% I think is a reasonable educated guess based on the number of ensemble members at the moment that go very warm / hot in the final week to ten days, which is what we'd need for that sort of finish.

[WYorksWeather]

 Don I think we still don't have enough of a sample size yet to know how rare below average 1961-1990 months are now. Up until recently I was thinking 10%, about one per year. If we don't get one by the end of this year though, I might have to reassess. Possibly you'd have to start saying 5%.

It's definitely going to happen at some point - the middle of January and second half of April this year prove we can still get significantly below average spells of weather - we just need one to be sufficiently prolonged to enable a below average month and to not be counteracted by a strongly above average spell at another point in the month. Very difficult to predict when it might happen, though.

It's just that the odds indicate that it pretty much must happen at some stage, since I can't really believe that we've moved so far in the last two years that e.g. a December 2022 repeat will never happen again. Even if you added a bit on to the anomaly it'd still be below average if the same synoptic had repeated last winter.

As always, more data needed. If we go another full year or two with no below average months on 1961-1990 I'll have to revisit this question.

[Don]

39 minutes ago, WYorksWeather said:

It's just that the odds indicate that it pretty much must happen at some stage, since I can't really believe that we've moved so far in the last two years that e.g. a December 2022 repeat will never happen again. Even if you added a bit on to the anomaly it'd still be below average if the same synoptic had repeated last winter.

I'm 100% sure we will have a month with a CET below the 1961-90 average, but the question is how rare will they be now?  December 2022 was fairly significantly (not exceptionally) below the 61-90 average but would have been notably cold had it not turned much milder in the run up to Christmas lasting through to New Year.  However, what has changed since then is the record breaking warm north Atlantic SST's, which most likely prevented us from having a month below the 61-90 average in 2023?  All the time the SST's are at the level they are now, any milder spell is likely to counteract any cold periods during a monthly period. 

Edited May 12 by Don

[BlueSkies_do_I_see]

I'm surprised by those latest projected values from Derecho. A late May plume would be pushing us into high 14s range, though to challenge 1833 would require a prolonged plume like we experienced in early Sept 2023.

[Scorcher]

 BlueSkies_do_I_see It's not that surprising really when you consider these past few days and next week are not a lot different to what you'd expect in a UK summer month.

Minima have been in the 10-13C range and will probably continue at those sorts of levels into next week. Minima of 10C (which may be conservative for next week) and maxima of 20C would keep the CET edging upwards.

We wouldn't need an extreme plume to take us past 1833 IMO. Another spell like this one could do it. A cooler spell could scupper any chances though.

[WYorksWeather]

 Don I guess the SSTs probably prevented July 2023 from being below average, for example.

 Scorcher Especially when you consider that another spell like this one in two weeks time would by definition be hotter. So rather than temperatures maxing in the 24-26C range most days you'd have maybe 26-28C.

[The PIT]

Sunny Sheffield up to 14.7C +4.7C above average. Rainfall unchanged.

[LetItSnow!]

 WYorksWeather That was definitely the case for July 2023. If that pattern had occurred just a couple years earlier it would have been cooler I think. If that pattern had occurred in 2015 in the peak of the cold blob era then it would have been quite chilly. 

[Earthshine]

Next week not looking as bad as previously feared.  A grotty day tomorrow but temperatures recovering to 18-20°C for the rest of the week.  A touch above average for May!

[WYorksWeather]

 Earthshine And your location has close to the worst of it. Even with a slight overnight downgrade the UKV this morning shows absolute UK maxes of 23C tomorrow, 20C Tuesday, 22C Wednesday and 21C Thursday.

All in all as you say not a horrendous first few days to come, just less good than this week.

[WYorksWeather]

 Derecho Was going to ask actually - what's your methodology for compiling these (i.e. which site do you use for the raw data and to obtain values for the CET stations - the maths isn't an issue)?

Just asking because I'd be interested in trying to do something similar for some of the more extreme ensembles that are popping up - in other words to try and see if some of the hotter ensemble outliers would be enough at this stage.

At the moment my feeling is that only the very hottest ensemble members are likely to do it, but it would be good to check my working.

[Summer Sun]

13.7 to the 11th

2.6c above the 61 to 90 average

2.9c above the 81 to 10 average

[Derecho]

1 hour ago, WYorksWeather said:

Was going to ask actually - what's your methodology for compiling these (i.e. which site do you use for the raw data and to obtain values for the CET stations - the maths isn't an issue)?

I go onto the WZ website and the ECM ensemble diagrams. Then I select 2m temperature for Luton, Pershore and Preston. I then take the morning min and daytime max to calculate the daily CET values.

Given the EC regularly underestimates max temperatures, I add +1C to the Preston and Luton maxes and +1.5C to the Pershore max (EC seems to particularly underestimate maxes here).

Don't know if those model bias adjustments are at the right level though it's working ok - I think with a little bit of error each day...

You can pick any of the 50 ensemble members on there up to T360. They take a bit of time to update though and the OP only goes out to T240... 

[WYorksWeather]

 Derecho Thanks - I've tried using Meteociel for the temperature tables and they're not as good - will have a go with Wetterzentrale later.

I'll probably pick something eye-catching off the 12z runs and see what I can come up with.

[Derecho]

 Scorcher With the way the EC ends on this morning's run we'd be in with a shot for sure.

[Roger J Smith]

Assuming today's warm readings will leave CET near 14 C, the current GFS run looks to be a flat-line run of values within 1 C of that value so difficult to see how it gets very far away from 14.0 to nearly end of month, if guidance is accurate. 

EWP has been stuck on 20 mm for a while, looks likely to reach 65 mm near end of month.