It is better to be late to the party than miss it altogether.  I have been on this site since 2003 and latterly 2006, and I only joined in the CET competition  for 2015 I think. Its been going at least 10 years, I'm sure someone can correct me, and will!

Funnily enough, next week may have a higher CET mean than this week, depending on the ratio of tropical maritime to polar maritime air across the UK. 

GFS has quite a bit more of the latter than ECM for the 2nd half of next week, but despite that, numerous nights widely staying in double digits lead me to anticipate that it would still produce a mean at least on a par with this week's. I've not had the time this evening to process the numbers - might have a go with some of tomorrow's runs.

Thanks to the Professional for his number crunching, makes interesting reading!

as you say Col, the winter months do open up some potential for significant swings keeping it interesting right to the end. 👍

Met Office Hadley             14.0c.        Anomaly       -0.0c Provisional to 19th.

Metcheck                          13.83c       Anomaly       0.11c

Netweather                       14.4c         Anomaly       0.71c

PSJ                                   14.43c       Anomaly       -0.29c.

I think that there was a more informal monthly comp, which evolved into a monthly & yearly comp in 2008 or 2009. 

2009 was the first year I entered and was a little less sophisticated than now, and I think the winner manipulated the fact that you didn't have to PM any forecasts to GW to calculate what they needed to forecast in December after waiting for all other entries to be made, in order to win.

We’ve had a few cracking clear days with low 20 temps but unfortunately the clear sky has meant low temps at night, increasing the diurnal difference and lowering the mean.  Ironically, as mentioned already, with cloudier and poorer weather next week, the daily mean should be higher as the nights are milder. 

Yes. I remember that December well! I think we both lost out that time.....

I started the competition in its current form in 2009. So this is year 11.

I have been taking a bit of a break for the past few weeks to enjoy the summer weather. Also been on holiday for the past 2 weeks. So not been keeping my regular CET tracker up to date. Will get that going again in October.

The CET mean by my calculations for the past 5 days has been 14.9C, 12.4C, 11.3C, 13.3C, 14.1C.

Over the rest of the month the mean should climb very slightly. The daily estimated means based on latest output for the rest of the month are 16.6C, 16.7C, 14.7C, 15.4C, 12.9C, 15.1C, 14.4C. 14.1C, 13.9C, 13.9C.

Based on the Hadley provisional mean of 14.0C to the 19th, the latest output would suggest a finishing CET of 14.25C before adjustments. The downward adjustment tends to be quite large when we have cold nights. So I would not be surprised to see an adjustment of as much as 0.4C.

Hence a final CET just under 14C looks most likely at present. Hence I am quite happy with my prediction of 13.8C. 

Well you might have 

<<< evil laugh >>>

Met Office Hadley          14.1c.       Anomaly      0.1c. Provisional to 20th.

Metcheck                       13.82c      Anomaly      0.14c

Netweather                    14.42c      Anomaly      0.73c

Peasedown St John         14.44c      Anomaly      -0.44c.      

Finally got to look at some numbers too, out of interest.

This current week's mean minimum will likely be somewhere in the mid-single digits, despite the one for Sunday being on the mild side.

The mean maximum could be in the high teens or low 20s. As GW's informative update shows us, this has resulted in CET means near or a tad below average overall - except perhaps for today, which we don't know the final obs for yet. Tomorrow might do enough to mean the CET was very near average for the week as a whole.

Looking at next week and using GFS raw numbers with a slight upward bias adjustment of +0.5*C applied, the mean CET max may only be in the low or mid-17s, a little below par for the time of year. By contrast, however, the mean min looks to be in the mid-high 11s - and that's with the bias adjustment being less than it justifiably could be (I'm a cautious fellow!). Notably mild for late September.

An above-average overall CET mean for the week results. An estimate using the 12z GFS alone gives me 14.5*C to 29th, before a cooler 30th drops it to 14.4*C. Note, though, that my estimates lack the level of precision that GW's do. Even so - I see a finish (after adjustments) just about in the 14s as a possibility. Not something I'd actually bet on though .

  Thanks GW and SC for your informative posts as always.  They are much appreciated and needed to reign in the dreamers!  Me!  

15c?  Doh!  Someone please remind me next year that clear skies mean cold nights!  I did put my guess in very early due to holidays, but I’d have stuck to my original thoughts anyway and by the end of the first week, I thought my guess was looking good!   

You're most welcome Caz 

I think you're being a little hard on yourself here by the way - with a brisk flow from anywhere between southwesterly (tropical maritime air) and southeasterly (drier air but still capable in a strong flow), high pressure has been known to bring warm days without cold nights even very late in the month.

Indeed, there was a time when the models were consistently predicting that sort of setup to dominate the week just gone and even into next week. That's when thoughts of final CETs somewhere in the 15s were circulating.

It took a sudden large uptick in tropical cyclone activity, causing the jet stream to undertake 'narrower' loops (reaching more north and south, but less west and east), to force the ridge to drift a little west of the UK and then slowly back over, leading to an import of fresh air which then stagnated overhead and created near-optimal conditions for the lowest CET minimums achievable at this time of year (except perhaps with a rare Arctic northerly).

So, with a little luck, I think you could easily have been right on the money this month .

You’re too kind SC!    But thank you for your faith and your analysis.

You’re right!  The elements are finely balanced in such a small maritime landmass, which is what makes the British weather so fickle and so interesting!  

Met Office Hadley          14.2c.      Anomaly       0.3c. Provisional to 21st.

Metcheck                       14.03c     Anomaly       0.30c

Netweather                    14.54c     Anomaly       0.85c

Peasedown St John        14.62c     Anomaly       -0.1c.  

Met Office Hadley          14.3c.      Anomaly      0.4c. Provisional to 22nd

Metcheck                       14.9c       Anomaly       0.37c

Netweather                    14.64c     Anomaly       0.95c

Peasedown St John        14.52c      Anomaly       -0.20c.  

Met Office Hadley           14.4c.      Anomaly       0.5c. Provisional to 23rd.

Metcheck                        14.16c     Anomaly      0.44c

Netweather                     14.68c     Anomaly      0.99c

Peasedown St John        14.69c      Anomaly     -0.03c.            

D'you know what Col? It'll be hard to knock you off your spot, even now; and even then, you'll grab it again in October, I bet.

No pressure..

By the calculations worked out by The Professional I will be down to joint leader at 14.10C. If it was just the raw figure that counted I would be fine, loving the nice mild nights at the moment and some more to come but it will be the downgrade that will clobber me this month.

I expect to lose my lead, although it will be close.

Pressure, what pressure :)

Ive a suspicion that the downgrade will be less severe this month if the mild nights continue.  So a finish around 14.2 is not out of the question, which would leave you ahead by a whisker.

Another mild night here last night and forecasts to stay in double figures, although falling slightly to the end of the month.  So daily means here will come in above the current CET, increasing the total slightly. If the CET areas mirror this, Col’s lead is safe! 

Met Office Hadley           14.4c.       Anomaly      0.6c. Provisional to 24th.

Metcheck                        14.20c      Anomaly      0.48c

Netweather                     14.74c      Anomaly      1.05c

PSJ                                14.69c      Anomaly       -0.03c.         

Met Office Hadley          14.7c.        Anomaly       0.7c. Provisional to 25th.

Metcheck                       14.26c       Anomaly       0.54c

Netweather                    14.78c       Anomaly       1.09c

Peasedown St John        14.65c.      Anomaly       -0.07c. 

Come on! Keep going upwards!!

Just to be a pain -

I think that should have said 14.5 not 14.7