September 2023 C.E.T. and EWP forecast contests

[Methuselah]

29 minutes ago, Don said:

Well, until we get a cold winter following a very warm September, this will continue to be debated!  However, nothing wrong with that of course.

Like I said, an intriguing winter season coming up and not only because of the warm September.  No thinking lightly from me!

That's true enough. But, as there are so few 'very' warm Septembers for an equally unlikely cold winter to follow, it's hardly surprising that the two seldom coincide. 

Reaches for lucky pants! 

Edited September 24, 2023 by Methuselah

[Roger J Smith]

Another day with no Hadley CET update showing yet, would estimate that yesterday's mean was around 13 C and the running CET is therefore around 17.6. 

 

[damianslaw]

Still touch and go whether we beat the record for September and also June.. I suspect we will just come under but it will be a close call.

 

[snowray]

1 hour ago, damianslaw said:

Still touch and go whether we beat the record for September and also June.. I suspect we will just come under but it will be a close call.

 

Yes I think it will be close, does not look that cold for the rest of the month so we should not see many more 0.2c drops, more likely some 0.1c days and/or no change maybe.

[Derecho]

20 hours ago, Don said:

Well, until we get a cold winter following a very warm September, this will continue to be debated!  However, nothing wrong with that of course.

Like I said, an intriguing winter season coming up and not only because of the warm September.  No thinking lightly from me!

Well looking at the CET record you get the following warm CETs followed by a colder then average winter:

1780, 1750, 1779, 1678, 1808, 1933, 1784, 1741, 1846, 1777, 1796, 1880, 1890, 1985

You can't judge what a very warm September could do from such a small sample size but I don't believe there is any physical mechanisms anyway. 

The warm September mild winter theory was one that used to annoy me in the old netweather days lol.

Back to the CET for this month. I think there is a chance it could finish on 17.0C, especially if that warmth from the SW speeds up a bit over the weekend and makes it for the 30th. At the moment I'm predicting a CET of 16.9C which makes it the joint record holder with 2006.

[The PIT]

Sunny Sheffield down to 17.1C +2.4C above normal. Rainfall up to 67.9mm 103.2% of the monthly average.

[Don]

2 hours ago, Derecho said:The warm September mild winter theory was one that used to annoy me in the old netweather days lol.

All the more reason to hope for a cold winter this year then!

[Addicks Fan 1981]

2 hours ago, Derecho said:

Well looking at the CET record you get the following warm CETs followed by a colder then average winter:

1780, 1750, 1779, 1678, 1808, 1933, 1784, 1741, 1846, 1777, 1796, 1880, 1890, 1985

You can't judge what a very warm September could do from such a small sample size but I don't believe there is any physical mechanisms anyway. 

The warm September mild winter theory was one that used to annoy me in the old netweather days lol.

Back to the CET for this month. I think there is a chance it could finish on 17.0C, especially if that warmth from the SW speeds up a bit over the weekend and makes it for the 30th. At the moment I'm predicting a CET of 16.9C which makes it the joint record holder with 2006.

Would be a fluke if June and September were joint warmest months of the year, but with climate change now anything is possible.   

[Summer Sun]

17.4c to the 24th

3.9c above the 61 to 90 average
3.1c above the 81 to 10 average

[Roger J Smith]

Well the CET tracker is back, and my estimates were okay, to second decimal the 17.4 value is close to limit of 17.44 so it just crept down from about 17.55 to 17.44 to preserve estimates of 17.8 and 17.6 for two days we had no reports. Now only 0.3 above previous highest running mean, table now back on page 12 shows that 1865 handed the baton to 2006 on 23rd. Record values are 17.1 24th to 26th, 17.0 on 27th to 29th, and 16.9 on 30th. (it used to be 16.9, 16.8 last two days before v2.0.1.0 bumped them up, no changes were made to daily values, just the protocol for calculating mean changed).  If you want to get very technical 2023 will be warmer than 2006 and will appear in first place in tables if it manages an average above 16.85 (2006). But we will tend to think of it as a tie at 16.9 rounded from any values. 

With the second decimal cushion, today's likely warm average around 16 could hold the running mean at 17.4 in tomorrow's report but it could be 17.3 also. From an estimate of 17.35 after 25 days, I would say the run out to end of month will be a near record pace of 17.2 (26), 17.1 (27), 17.0 (28), 16.9 (29) and close to 16.85 for an absolute tie of 2006, could go either way. Will continue to track second decimals (in the past, they have not been exactly as calculated from daily means, indicating the calculation is from a consideration of mean daily maximum and minimum. 

EWP a bit under 80 mm now and should finish near 90. 

As noted earlier in thread, good CET forecasts are all too dry and good EWP forecasts are all too cool. The best combined will certainly be Summer Shower with 4th EWP (85 mm, second entry) and 19th CET (15.8 C, second entry). Roger J Smith is likely second in best combined at ranks 23 and 6* (58.4, 16.2 C) and 3rd would be snowray (15, 15 for 15.9, 62.0); DR(S)NO will take next spot with ranks 20, 12 (60, 16.0). It is unusual for all "best combined" to fail to produce combined ranks adding up to 12 or less, but it does occasionally work out like that. 

* rank 6 for 16.2 could improve if CET ends at 16.7 or lower but it likely will not. Only forecasts 16.7 to 17.2 are not yet certain as to eventual ranks, I believe. I won't be jogging CET ranks for current contest because late entries will be offset by extra accuracy points, so I will just leave them as is for calculating best combined.

The average gain of CET rank by the ten who upgraded forecasts looks to be about ten to fifteen spots which is usually worth about two gained in the annual contest. The one or two changed EWP forecasts generally went the wrong way (down instead of up) but no serious harm done. 

Edited September 25, 2023 by Roger J Smith

[damianslaw]

Will be interesting to note how June and Sept 2023 will be remembered in years to come. June was very good here, but the latter part not great, and overall I won't be classing it a classic summer month.

First 10 days Sept, excellent, the rest of the month a washout. Will not be remembered at all as a good month regardless of the warmth. 

Edited September 25, 2023 by damianslaw

[Man With Beard]

10 hours ago, damianslaw said:

Will be interesting to note how June and Sept 2023 will be remembered in years to come. June was very good here, but the latter part not great, and overall I won't be classing it a classic summer month.

First 10 days Sept, excellent, the rest of the month a washout. Will not be remembered at all as a good month regardless of the warmth. 

I suspect September will be remembered, as it was clearly the best September heatwave in recorded history by some margin. However, I'm not so sure about June - it was consistently very warm in the CET zone, but it wasn't always warm in some spots like the east coast, and it didn't have the qualities of a classic heatwave, which I would call a long period of consecutive days above 30C with the peak around 34C or more - all of the heatwaves considered historic qualify with this criteria (e.g. 1976, 1995, 2003, 2006, 2018). 1983 was similar - consistently hot, but no signature heatwave in its own right.

[Weather-history]

13 minutes ago, Man With Beard said:

I suspect September will be remembered, as it was clearly the best September heatwave in recorded history by some margin. However, I'm not so sure about June - it was consistently very warm in the CET zone, but it wasn't always warm in some spots like the east coast, and it didn't have the qualities of a classic heatwave, which I would call a long period of consecutive days above 30C with the peak around 34C or more - all of the heatwaves considered historic qualify with this criteria (e.g. 1976, 1995, 2003, 2006, 2018). 1983 was similar - consistently hot, but no signature heatwave in its own right.

I think the summer maybe remembered for one of those that go belly-up after June. 

[Scorcher]

14 hours ago, damianslaw said:

Will be interesting to note how June and Sept 2023 will be remembered in years to come. June was very good here, but the latter part not great, and overall I won't be classing it a classic summer month.

First 10 days Sept, excellent, the rest of the month a washout. Will not be remembered at all as a good month regardless of the warmth. 

Not sure how June doesn't come into the 'classic' category given it was the warmest in our lifetimes...it was also particularly notable in your part of the country.

245 hours of sun here along with it being record-breakingly warm- I don't know what more it has to do to be a classic.

Even the all time great months had cooler spells at some point. 1976 is a case in point- pretty unremarkable until the last 10 days of the month. Is that not a classic either?

[Summer Sun]

17.4c to the 25th

3.8c above the 61 to 90 average
3.2c above the 81 to 10 average

[The PIT]

Sunny Sheffield down to 17C +2.4C above average. Rainfall unchanged.

[Earthshine]

I think we are in for a good chance to beat the all-time maximum CET record for September.  22.1C up to the 25th September compared to versus 20.9C for 1895 and 2006.

[Roger J Smith]

Only a slight drop in CET in two decimals, estimate we are now at 17.41 as yesterday's mean was 16.6. Looking a little more likely to land on 17.0 rather than 16.9 now. Also EWP could fall a bit short of 90 mm and end up closer to 85 mm, heavy rains are skirting most of the grid tomorrow and later in week, parts of south, southeast stay dry. Only a few contest ranks are affected in either case. 90% of points and ranks are pretty well a foregone conclusion now. 

As to outcome of mean maximum, 22.1 after 25 days from a total of 551.7 degree days, so it's close to 22.07, if average is 18 to end of month, total is 641.7 and average would be 21.39, even for 16 it ends up at 631.7 and 21.06, a tie only needs about 15.6 for an average. Guidance says 17-18 and average 21.2. 

[Frigid]

It will be both hilarious and interesting if September matches June's CET of 17.0. Plus they'll beat the previous place holder by 0.1C.

[Don]

4 hours ago, Frigid said:

It will be both hilarious and interesting if September matches June's CET of 17.0. Plus they'll beat the previous place holder by 0.1C.

Well, I can think of funnier things to be honest!

[Roger J Smith]

Before 2023 top 28 September outcomes in terms of temperature differential from warmest month 

Closest 28 to year's warmest month (in one case, 1890, warmest), regardless of rank during year (ranges 1st to 4th)

 

Rank ___ Year ____ Sep relative to (other) warmest month(s)

_ 01 ____ 1890 ____ +0.1 July ___ Sep 1st (14.6 vs 14.5)

_ 02t____ 1729 ____ -0.2 July ___ Sep 2nd (16.6 vs 16.8)

_ 02t____ 1961 ____ -0.2 Aug ___ Sep 2nd tied July (15.2, 15.2 vs 15.4)

_ 04 ____ 1865 ____ -0.3 July ___ Sep 2nd (16.3 vs 16.6)

_ 05t____ 1784 ____ -0.4 July ___ Sep 2nd (14.8 vs 15.2)

_ 05t____ 1895 ____ -0.4 Aug ___ Sep 2nd (15.4 vs 15.8)

_ 05t____ 2011 ____ -0.4 Aug ___ Sep 3rd, July 2nd (15.1, 15.3, vs 15.5)

_ 08 ____ 1795 ____ -0.6 Aug ___ Sep 2nd (16.0 vs 16.6)

_ 09t____ 1907 ____ -0.7 Aug ___ Sep 3rd, July 2nd (13.6, 14.1 vs 14.3)

_ 09t____ 1929 ____ -0.7 July ___ Sep 3rd, Aug 2nd (15.3, 15.4 vs 16.0)

_ 11 ____ 1958 ____ -0.8 July ___ Sep 3rd, Aug 2nd (15.1, 15.8 vs 15.9)

_ 12t____ 1843 ____ -0.9 Aug ___ Sep 3rd, July 2nd (14.8, 15.3, vs 14.4)

_ 12t____ 1891 ____ -0.9 July ___ Sep 3rd, June 2nd (14.2, 14.7, vs 15.1)

_ 12t____ 1978 ____ -0.9 Aug ___ Sep 3rd, July 2nd (14.1, 14.7 vs 15.0)

_ 15t____ 1730 ____ -1.0 Aug ___ Sep t2nd with July (15.3, 15.3 vs 16.3)

_ 15t____ 1854 ____ -1.0 July ___ Sep 3rd, Aug 2nd (14.4, 15.2 vs 15.4)

_ 15t____ 2016 ____ -1.0 Aug ___ Sep 3rd, July 2nd (16.1, 17.0, vs 17.1)

_ 18t____ 1812 ____ -1.1 Aug ___ Sep 3rd, July 2nd (13.2, 14.2, vs 14.3)

_ 18t____ 1913 ____ -1.1 Aug ___ Sep 4th, June 3rd, July 2nd (14.1, 14.3, 14.6, vs 15.2)

_ 20t____ 1760 ____ -1.2 Aug ___ Sep 3rd, July 2nd (15.7, 15.8, vs 16.9)

_ 20t____ 1841 ____ -1.2 Aug ___ Sep 3rd, July 2nd (13.4, 13.8, vs 14.6)

_ 20t____ 1875 ____ -1.2 Aug ___ Sep 2nd (14.9 vs 16.1)

_ 20t____ 1998 ____ -1.2 Aug ___ Sep 3rd (14.8, 15.4 vs 16.0)

_ 24t____ 1777 ____ -1.3 July ___ Sep 3rd, Aug 2nd (14.6, 15.3, vs 15.9)

_ 24t____ 1796 ____ -1.3 Aug ___ Sep 3rd, July 2nd (14.6, 14.7 vs 15.9)

_ 24t____ 1810 ____ -1.3 July ___ Sep 4th, June, Aug t2nd (13.9, 14.6, 14.6, 15.2)

_ 24t____ 1898 ____ -1.3 Aug ___ Sep 3rd, July 2nd (15.2, 15.3, vs 16.5)

_ 24t____ 1980 ____ -1.3 Aug ___ Sep t2nd July (14.6, 14.6 vs 15.9)

 

[Weather-history]

July being only the 4th warmest of the year for the CET is truely exceptional

The climatic odds of this happening must be very small. The CET goes back to 1659.

If it has happened in the UK in the last 364 years, then it has occurred at a local level. 

[richie3846]

30 minutes ago, Weather-history said:

July being only the 4th warmest of the year for the CET is truely exceptional

The climatic odds of this happening must be very small. The CET goes back to 1659.

If it has happened in the UK in the last 364 years, then it has occurred at a local level. 

What I find particularly interesting about this fact, is that the setup was nothing special really. Yes we had a settled June, but that's not unusual and has happened before. We've had mediocre July and August, and indeed temperatures this time round were not below average by very much. Early September was the only spell that could truly be classified as exceptional or unusual.

So for July to come in 4th seems to boil down to the particular sequence of weather patterns, and timings. A fluke, I guess. 

[Roger J Smith]

It has to beat October yet.  could be fifth. 

[Scorcher]

5 hours ago, Weather-history said:

July being only the 4th warmest of the year for the CET is truely exceptional

The climatic odds of this happening must be very small. The CET goes back to 1659.

If it has happened in the UK in the last 364 years, then it has occurred at a local level. 

Yes and what it makes it more remarkable is that July wasn't that cool at all.