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

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.

[Model Output Discussion - Mid Summer Onwards]

PanguWeather has a brief wedge of warmth for start of October

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

How are we looking for beating the old maximum CET record of 20.9C for September?  Starting to plummet a bit now but still 22.8C.  Could be in for a good chance!

[October 2023 C.E.T. and EWP contests]

14C and 110mm please Roger

[If you could travel back in time to relive a memorable weather event]

Back to July 2022 and the run up to the 40°C.  Most extraordinary temperature ever seen in the UK and what many people here thought was impossible until recently.

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

1 hour ago, Derecho said:

The models this morning are again hinting at warmth from 24th-30th Sept. The GFS 00z OP however is quite anticyclonic and the CET returns aren't that high  (around the 14s for that week). It finishes up at 16.7C, just short of the record.

We are getting to that stage now where high pressure can lead to some cool nights even with warm uppers overhead, so getting a southerly flow and the high further east will be crucial.

The EC control is warmer, producing the following returns (running mean with dailies in brackets):

17th: 18.8 (17.5) - Yesterdays CET hasn't come in yet.
18th: 18.6 (14.9)
19th: 18.5 (16.9)
20th: 18.3 (15.1)
21st:  18.1 (12.8)
22nd: 17.7 (10.6)
23rd:  17.5 (13.6)
24th:  17.5 (17.1)
25th:  17.4 (15.3)
26th:  17.3 (14.2)
27th:  17.3 (16.5)
28th:  17.3 (16.6)
29th:  17.3 (18.0)
30th:  17.2 (15.0)
 

So the EC control sees the record go with a warm final week, the CET finishing at 17.2C. The warmest GFS ens member finishes at 17.3C and the warmest EC 17.6C (P30).

Plenty of cooler ens in there so still no guaranteed record. 

A 17.2C CET September would be just remarkable.  A roughly 3.7C anomaly over the 1961-1990 mean.  

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

23 minutes ago, Scorcher said:

You certainly won't be far off with that guess. I'd say something around the 17C mark is favourite at the moment.

Absolutely incredible to have two 17C+ CET months with neither being July or August.  That would be just just bizarre.

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

Feeling better about my last-minute 17.2C guess this morning.  When was the last time the highest guess was too low?  Was it December 2015?

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

12 of the first 14 days of September have all recorded a maximum CET >20°C, impressive!

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

41 minutes ago, Roger J Smith said:

At 20.4 after 11 days, this value would still beat 2006 and 16.9:

average 12-30 of 15.0 will give outcome of 17.0

Would require an average of 15.4 to get to max forecast of 17.2. 

I took a look at 06z GFS and would estimate average of 15.5 to 16.0, 16.0 would produce outcome of 17.6 (GFS runs to 28 Sep today but looks set into similar values near end) ... time for all this to change.

EWP currently at about 10 mm, grid average 50-60 to 28 Sep, so 60-70 mm predicted by GFS. 

That's an extraordinary statistic Roger.  At 17.6C September 2023 would be warmer than all but 20 Augusts...

[Model Output Discussion - Mid Summer Onwards]

If GFS Op 06z run is to be believed we would absolutely smash the all-time warmest September mean temperature to pieces.

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

3 minutes ago, Methuselah said:

Even more so given the 1961-90 mean? But 1976 is still the deniers' first port of call when denying the obvious reality of AGW. Just how hot were the first ten days of July 1976? 

First 9 days of July 1976 had a pretty bonkers mean CET of 22.7°C by my calculations, around 6.8°C above normal.  First 9 days of September 2023 are 6.7°C so this is the July 1976 of Septembers, at least in terms of the first third.  Mean max was about 30.3°C up to the 9th so July 1976 was actually more anomalous than this month up to the 9th.

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

2 minutes ago, Stationary Front said:

Have there been many first 10 days of July warmer than this September? 

I think 1976 was more anomalous, particularly for maximum CET.

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

The rolling mean CET up to the 9th for July 2018 and September 2023:

July 2018: 20.1°C

September 2023: 20.3°C

The mean maximum CET is an absolutely ludicrous 26.5°C, 9.0°C above the 1961-1990 mean.  Absolutely INSANE!  This has got to be by far the hottest start of any September.

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

Saw a stat on Twitter that the first week of September, in terms of maximum CET, was the 8th hottest of ANY month on record.  That is absolutely nuts for September, almost 3 months after peak solar insolation. 

 

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

23 minutes ago, Summer Sun said:

18.7c to the 6th

5.5c above the 61 to 90 average
3.6c above the 81 to 10 average

Actually 19.1°C now!

[Summer 2023 chat]

48 minutes ago, In Absence of True Seasons said:

Looks beautiful, much more pleasant than the weird off-white haze that's in London at the moment. The sky is actually blue there! As it should be.

Sarah dust?

*Saharan dust for god's sake

[Summer 2023 chat]

Currently in Amsterdam for the first time for my first presentation at an international conference on atmospheric remote sensing. What an absolutely perfect week for it, gin blue skies and 28°C.  Absolutely divine.

[Model Output Discussion - Mid Summer Onwards]

Drop in temperatures after this weekend has been watered down on latest GFS and there is a support for a warm up next week too.

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

Feeling better about my last minute 17.2°C guess now

[Summer 2023 chat]

Not impressed.  Take 3 weeks off in June to go to France, missed the hottest June on record.  Back home for two months and welcomed by crud.  Now I'm in Amsterdam next week sat in a conference room all day and, of course, the heat returns.  I'm cursed!

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

Could rolling CET reach as high as 20°C sometime next week?  Would be a first!

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

19.4°C to the 10th would be absolutely insane.  Could we see two 17°C+ CET months this year?

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

CET after the first week will surely rocket into the 18s

[Model Output Discussion - Mid Summer Onwards]

9 hours ago, Metwatch said:

Interesting! Howcome?

I would imagine it perhaps results in a very strong refractive index gradient.  My PhD research is currently exploring how to exploit the refraction of aircraft radio signals to retrieve humidity data for use in NWP models.  We could see some interesting refractive effects next week.