A somewhat disappointing end to the summer notwithstanding a great bank holiday weekend for many of us. We move into Autumn. Will the generally warm theme of 2017 continue? Many of the long range models seem to think so.

Please post your CET predictions for September in this thread. Entries can be made until 23:59 on the 3rd (Sunday evening) without penalty.

Historic summary for September

1971-2000 13.7C

1981-2010 14.0C

1997-2016 14.5C

2016 was exceptionally warm at 16.0C although below the record 16.8C reached in 2006. Since 1994 we have only had two rather cool Septembers in 2012 (13.0C) and 2015 (12.7C).

Here is a chart of the September CET for all years since 1961:

Current model output

850's showing something of an upward spike in the first week of September based on the op runs followed by something a bit cooler. But the ENS show a different story - massive scatter. So difficult to say what we might see in the first half of September.

http://www.wetterzentrale.de/de/show_diagrams.php?model=multi&var=2&geoid=1140&lid=OP&bw=

http://www.wetterzentrale.de/de/show_diagrams.php?geoid=1140&model=multi&var=5&run=0&lid=OP&bw=

http://www.wetterzentrale.de/de/show_diagrams.php?geoid=1140&model=gfs&var=2&run=0&lid=ENS&bw=

http://www.wetterzentrale.de/de/show_diagrams.php?geoid=1140&model=gfs&var=5&run=0&lid=ENS&bw=

Met Office contingency planners outlook

http://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-temp-son-v1.pdf

Suggests a warmer than average September and a significantly warmer than average Autumn.

Pattern Matching - JFF

Looking back at last month I hinted there was no strong signal for August with temperatures likely to be close to or slightly above average. This is broadly what we have seen with the August CET likely to be close to the 1971-2000 mean but slightly below the 1981-2010 mean.

For the summer as a whole there are very few years where the temperature profile is similar to that of 2017. The only close match is 2005. This year saw a very warm September and October followed by much cooler conditions in November and December. That seems to fit quite nicely with what some long term forecasts are suggesting. 2006 also saw a very warm June and average August but of course July was way warmer than this year. That year also saw very warm conditions in September and October.

To find another decent match you have to go back to 1837. This year saw a cool September and an average October. 1834 is also a reasonable match and saw average conditions in September and October. 1772 is also a match with a slightly cool September and a mild October. Finally we have 1707 which saw an average September and a cool October.

So the recent matches suggest maybe a warm September whereas the older years suggest fairly average conditions are likely. Not really sufficient data points this month to draw any meaningful conclusions.

15·0c for please......Thank you for posting the September CET....

14.5°c please.

15.1 please GW

14.7c for me plz

14.0 please

14.9 C please GW.

I'll go for

15.0C

Now the English schools are due back after their summer hols, I think the weather will improve.

So I'm going for 15c please 

13.9c thankyou

13.5c thanks

Another tough one as conflicting signals at the moment some warm some very Autumnal. 

Going warm 15.85c 

cheers GW great effort as always

15.1C for me please