The warm weather has returned during September with another month more than 1C above the 1971-2000 mean. A record CET year therefore is very much back on track. October looks like starting on a warm note as well. The models have for some time now wanted to break down the warm settled weather from about T240. But every day this breakdown gets pushed out further. So it is very difficult to assess at the moment when the breakdown / pattern change will occur. It could be just a week away or it could be much longer. Even if it does turn more unsettled it may still remain fairly mild. October can be a very difficult month to predict as it is often the time that the Atlantic storms start to roll in, as we saw last year, when the temperature gradients between the Poles and the Tropics start to crank up. But if we keep high pressure and blocking in place for much of the month then we will see very different weather conditions. Even high pressure causes problems at this time of year. Will it be cool and rather cloudy with a fog and frost risk or will the position of the high draw in warm air from the south?

Please post your October CET predictions in this thread. The deadline for entries without incurring any penalty is 23:59 on Tuesday evening (30th). However, entries will be accepted up to 23:59 on 2 October.

October historic data summary

Here is the usual rundown of historic data for previous years.

There have been six very warm Octobers since 1995 with a CET of 12.5C or more - 1995, 2001, 2005, 2006, 2011 and 2013. There have been a small number of cold Octobers below 10C in the same period being 2003, 2008 and 2012.  

Have we ever had an October warmer than May when the May CET was more than 12C? Well yes we only have to go back to 2011 when the May CET was 12.2C and October was 12.6C. 2006 and 2001 also saw a similar pattern. Maybe something similar again this year?

Long run averages:
1971-2000: 10.4C
1981-2010: 10.7C
1989-2013: 10.9C
1994-2013: 11.4C

Here is a chart of the October CET since 1961 with a 10 year moving average.

The 10 year moving average has now hit 11.4C which is the highest ever for October. This is a full 0.5C above the 15 year moving average of 10.9C.

Here are some details of what the models and forecasters generally are saying at the moment.

GEFS (850 and 2m temps)
http://www.wetterzentrale.de/pics/MT8_London_ens.png
http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png
http://www.wetterzentrale.de/pics/MT2_Manchester_ens.png
http://www.wetterzentrale.de/pics/MT2_London_ens.png
The op run is above average throughout but something of a split in the ensembles from 4 Oct with a few runs turning much cooler.

ECM(De Bilt) maximum and minimum temps
http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php
http://www.knmi.nl/exp/pluim/kansverwachtingen_staafdiagram.php?run=00&type=tx
http://www.knmi.nl/exp/pluim/kansverwachtingen_staafdiagram.php?run=00&type=tn
Also looks fairly warm initially but the 2m temperatures turn cooler from the 5th on the op run and the mean but with a lot of scatter. Plenty of runs keep it very mild.

Met office
http://www.metoffice.gov.uk/public/weather/forecast
Generally warm days but rather cool nights. In the second half of the month temperatures may trend back towards average overall.

Pattern matching (just for fun)
If we look at years where both the August and September CET have been close to 15C there are not too many matches. The best matches since 1900 are 1929, 1934, 1961, 1985 and 2011. The October CET was above average in all those years except 1929 when it was 9.6C. 2011 of course was very warm with 12.6C.

If we look at years with a September CET of 14.5C or more and rainfall on the EWP of less than 50mm then we have 1929, 1941, 1947, 1959, 1985 and 1989. Again all years saw a CET of at least 10.4C except 1929.

Finally considering years with a very warm CET overall (>11.3C as at the end of September) we have 14 matches since 1900. Only 1 of these 14 years had an October CET less than 10C. No fewer than 8 years saw an October CET more than 11.5C.

Bringing this all together there does seem to be a fairly strong signal for a warm October.

In my view the best overall match with 2014 is possibly 1989. That year did of course see a very warm winter so I personally would not rule out a repeat of last winter. Many people have been talking about similarities with 1985. Certainly August and September have been very similar but otherwise 1985 was quite different.

Looking further back in the archives one year that has a number of similarities to 2014 is 1846 (which holds the record currently for the warmest Jan-Sep period in the CET history). That year saw a cool October followed by an average November and then a very cold winter with December being especially cold at 0.5C. But equally one could point to plenty of differences between 1846 and 2014.

So as ever this is JFF and anything is possible. But on balance I favour a warm or very warm October with only about a 15% chance of a colder than average October.  

Latest forecast October CET tracker

Turning cooler from the 5th on the latest output but still staying slightly above average. Even with this cool down we are still 1.2C above the 1971-2000 mean by the 11th.

Prediction via PM from roger63

October CET 11.5 C.

Thanks

roger63

I'll have a punt at 10.4c 

I reckon the models are going to swing cool and unsettled for the last half of the month, sufficiently so to overcome the warm start.

Well that and I wanted to to go cool, all these above average guesses are getting tedious

No doubt another month being high until end of the last TWO weeks.. ..Not referring to my socks either....

11.5c please gw

11.9c for me, thanks

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Gary

I'll have a punt with 12.0C please

:)

11.7C for me please

Not as warm as first appearing. 10.9C please.

12.03c for me please.

Very hard month to predict but I'll go for 10.49c please.

I'll go for 11.25C.

Punting at 11.3C please. 

The models have really shifted since I opened up this thread just two days ago. A change to much cooler and very unsettled conditions was always on the cards from the 5th but this has now firmed up and been accentuated in the latest output. So much so that by the 13th the CET may now only be 0.3C above the 1971-2000 mean (entirely due to the first few days) and actually slightly below the 1981-2010 mean.

These sudden shifts from benign and warm late summer to full on Autumn are not unusual. For example this year is taking a very similar path to 2004. In that year September saw a CET of 14.9C which is basically the same as we have had this year. The last day of September closed on a CET of 15.3C. It was also a fairly dry month, although not as dry as this year, with 50mm on the EWP which is well below the mean of 78mm.

October 2004 opened up with a CET of 11.1C and remained at around 11-12C for the first few days. Then between the 7th and the 21st the CET was frequently in single figures with a few days nudging above 10C. It was also wet. The 3rd saw over 22mm on the EWP although much of the first 12 days saw relatively small amounts of rain. But from the 13th onward it was very wet. In broad terms I sense something similar shaping up for 2014.

Very difficult this month but I'll go for 11.2C. Unsettled for much of the month and cool at times. Maximums likely to be depressed but minimums probably holding up well due to regular wind and rain. Hence why I am going for something over 11C rather than in the 10's.