FINAL MONTH OF THE YEAR - TIME FOR YOUR DECEMBER AND WINTER CET PREDICTIONS

As usual all CET predictions to be sent to me via PM please

Deadline is 2359 on Saturday evening (1 December).

Good luck everyone - especially Darren and Steve

Historic CET summary for December

1971-2000 5.1C (30 years)

1981-2010 4.6C (30 years)

1998-2017 5.0C (last 20 years)

We have not had a cold December since 2010. There have been 4 warm years with 6C or more and three years close to average at 5C. 2015 was of course the record at 9.7C after the second lowest December CET ever of -0.7C in 2010.

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

Direct link to larger version of the chart CHART1

Current model output (at 12z 27 Nov)

GFS (12z) - most ENS members suggesting generally mild conditions  

http://www.wetterzentrale.de/de/show_diagrams.php?geoid=49069&model=gfs&var=2&run=12&lid=ENS&bw=

GEM (12z) - similar to GFS

http://www.wetterzentrale.de/de/show_diagrams.php?model=gem&var=2&geoid=49069&lid=ENS&bw=

Multi Op - the major models all keep it mild in the first week. ECM going colder right at the end but this does not translate to the T2M temps (see below)

http://www.wetterzentrale.de/de/show_diagrams.php?model=multi&var=2&geoid=49069&lid=OP&bw=

The ECM ENS T2m temperatures for De Bilt look very mild

http://cdn.knmi.nl/knmi/map/page/weer/waarschuwingen_verwachtingen/ensemble/detail/ensemble-verwachtingen-detail10.png

Met Office contingency planners outlook 

Not yet available - will update when it appears

Temperature analogues

Looking at years with a similar temperature profile to 2018 since August we have 7 reasonable matches since 1950. We can see from this a very mixed bag as regards December temperatures. So I have tried to narrow it down using some of the standard winter forecast parameters that the legendary Gavin P applies. From this we can see that in fact the best matches are 1953 and 1984. 1953 saw a very mild December and 1984 was close to average. 1983 is also a good match and saw a slightly above average December. So I think this data strongly suggests December will not be a cold month. 

1987 is not a good temperature match for 2018 but does have a number of winter parameters that do match - early SSW (8 December - one of the earliest ever), the QBO is a match as is ENSO. Late summer and Autumn precipitation is also a good match. December 1987 saw a CET of 5.6C so similar to the figures above.

Looking at years with an average October (close to 10.5C) but a warm November (close to 8C) we have a few matches (over and above those mentioned already - 2004, 2002, 1997, 1970. The December CET figures for those years were 5.4C, 5.7C, 5.8C and 4.3C.

So overall a fairly strong signal for a figure between 5.2C and 5.8C. That would suggest (based on the tracker below) a slightly below average second half of the month. A CET maybe of around 7C for the first half and then 4C for the second half (the mean for the second half is 4.75C). 

First look at December temperature tracker

Two words sum it up. Very mild. Perhaps a move back towards average by the end of the second week. But the first third of the month looks like it could be up to 3C above average. If that verifies then the rest of the month would need to be 1.5C below average just to bring the month as a whole back to average. So chances of a below average December look very slim at this point. Would take a major freeze in the second half of the month. Wouldn't rule it out though given the long range model output.

Great work as usual GW. A very difficult month to predict.  

Thanks GW. I'd best get my thinking cap on then ! 

Mine is in for a warmish figure... Maybe....

Well best of luck to those at the high end of the table because this month's signals are wildly conflicting when comparing various models and broad-scale theoretical outcomes.

For example, the GFS 06z gives me an estimate in the high 7s as of 16th, which if there was a very average remainder of the month would yield a final CET in the mid-5s, and if there was a pretty cold one (example 1.5*C below LTA overall), would still bring about a final CET in the low 5s or high 4s.

Yet we have ECM turning markedly colder as soon as 9th and with the pattern looking likely to keep it cold for at least a bit thereafter. 

Coupled with the broad-scale tropical and stratospheric signals favouring something colder for at least a time mid-month, and the range of plausible final CETs is at least 3*C wide in my opinion .

Well best of luck to those at the high end of the table because this month's signals are wildly conflicting when comparing various models and broad-scale theoretical outcomes.

For example, the GFS 06z gives me an estimate in the high 7s as of 16th, which if there was a very average remainder of the month would yield a final CET in the mid-5s, and if there was a pretty cold one (example 1.5*C below LTA overall), would still bring about a final CET in the low 5s or high 4s.

Yet we have ECM turning markedly colder as soon as 9th and with the pattern looking likely to keep it cold for at least a bit thereafter. 

Coupled with the broad-scale tropical and stratospheric signals favouring something colder for at least a time mid-month, and the range of plausible final CETs is at least 3*C wide in my opinion .

Agreed.  Its particularly bamboozling this month.  Good luck to all contenders.

Well best of luck to those at the high end of the table because this month's signals are wildly conflicting when comparing various models and broad-scale theoretical outcomes.

For example, the GFS 06z gives me an estimate in the high 7s as of 16th, which if there was a very average remainder of the month would yield a final CET in the mid-5s, and if there was a pretty cold one (example 1.5*C below LTA overall), would still bring about a final CET in the low 5s or high 4s.

Yet we have ECM turning markedly colder as soon as 9th and with the pattern looking likely to keep it cold for at least a bit thereafter. 

Coupled with the broad-scale tropical and stratospheric signals favouring something colder for at least a time mid-month, and the range of plausible final CETs is at least 3*C wide in my opinion .

I went higher than average, but purely for reverse-psychology reasons.

 

 

I went higher than average, but purely for reverse-psychology reasons.

  I chickened out and went average!  

I went with 7.3C, the same as I did in November. I feel it will be a very mild month. There has been a major pattern change to zonality and I don't think that will be shifted for a while.

You could Knock me down for 6 with mine,

Here goes December with some high figures.  Not what we require.

Met Office Hadley          8.5c      Anomaly     3.7c Provisional to 1st.

Metcheck                       9.66c     Anomaly     4.66c

Netweather                    9.71c     Anomaly     4.62c

Bordon                          11.2c     Anomaly      1.9c

Canvey Island                11.6c     Anomaly      4.1c

Cheadle Hulme               9.5c       Anomaly      2.58c

Clevedon Weather           11.3c     Anomaly      3.18c

Darwen                          9.7c       Anomaly      2.74c

Hexam                            6.1c      Anomaly      0.34c

Mount Sorrel                   10.4c     Anomaly      3.86 

Forest Town Mansfield      9.4c       Anomaly      2.8c

Peasedown St John 9.5c    Anomaly   3.38c

Treviskey Redruth            12.1c      Anomaly      3.14c

Mean Of My 10 Watched Stations   10.8c  Anomaly  2.81c.               

Here goes December with some high figures.  Not what we require.

Met Office Hadley          8.5c      Anomaly     3.7c Provisional to 1st.

...  

Looks like normal winter service has been resumed once again, as far as the CET is concerned (which usually means above average anomalies).

 

I went with 7.3C, the same as I did in November. I feel it will be a very mild month. There has been a major pattern change to zonality and I don't think that will be shifted for a while.

I decided that at top-10 finish isn't worth much so went with an adventurous estimate .

For what it's worth, the GFS 12z with it's not-bad easterly interlude and then a cold ridge for a few days manages to crash my rough CET estimate from 8.0*C as of 9th to 5.3*C as of 17th with a slight further drop to 5.2*C the following day.

If the rest of the month was then bang-on average, we'd go on to finish in the mid-4s by my reckoning.

So that gives an idea as to how important it is how much of a mid-month cold spell actually takes place. Obviously what happens afterwards will also matter a lot, especially if you're somewhere near my 'prediction'  - as to what that is, well you'll soon see when GW posts his usual graphics .

I decided that at top-10 finish isn't worth much so went with an adventurous estimate .

For what it's worth, the GFS 12z with it's not-bad easterly interlude and then a cold ridge for a few days manages to crash my rough CET estimate from 8.0*C as of 9th to 5.3*C as of 17th with a slight further drop to 5.2*C the following day.

If the rest of the month was then bang-on average, we'd go on to finish in the mid-4s by my reckoning.

So that gives an idea as to how important it is how much of a mid-month cold spell actually takes place. Obviously what happens afterwards will also matter a lot, especially if you're somewhere near my 'prediction'  - as to what that is, well you'll soon see when GW posts his usual graphics .

So many permutations this month, its been challenging.  Meanwhile, I'm most interested in how the top 2 or so have guessed.  I didn't bother going for glory, I kept my thoughts grounded and close to average.  I may regret my decision, time will tell.

 So many permutations this month, its been challenging.  Meanwhile, I'm most interested in how the top 2 or so have guessed.  I didn't bother going for glory, I kept my thoughts grounded and close to average.  I may regret my decision, time will tell.

Nail biting stuff Phil ! 

I've remained focused on my own game again this month rather than get distracted by wondering what Darren has predicted. I did that in 2014 when 2nd in the competition going into December with Darren leading. The gamble didn't pay off, I crashed and burned and finished 5th. As a result I've not gambled this time. 

Darren could well be crowned champion tomorrow if his prediction is within 0.14 of mine.

Soon find out.  

 

Nail biting stuff Phil ! 

I've remained focused on my own game again this month rather than get distracted by wondering what Darren has predicted. As a result I've not gambled. 

Darren could well be crowned champion tomorrow if his prediction is within 0.14 of mine.

Soon find out.  

All I'll say is that I waited until last night's 18Z came out before sending in my guess. 

 All I'll say is that I waited until last night's 18Z came out before sending in my guess. 

Did you ? I hadn't noticed that .

Oooh, you two are keeping us guessing!  You little monkeys!  

Good luck to you both and may the best CETer win!  It’s been a really tough but most exciting year, that’s for sure!  

High figures, No decent fall until the 9th December,

Met Office Hadley       9.6c       Anomaly    4.6c   Provisional to 2nd.

Metcheck                    10.38c    Anomaly   5.39c

Netweather                 11.04c    Anomaly    5.95c

Canvey Island              11.9c     Anomaly    4.4c

Hexam                         7.1c      Anomaly     1.34c

Forest Town Mansfield 9.7c  Anomaly   3.1c

Peasedown St John 10.6c   Anomaly   4.48c

Treviskey Redruth  12.1c  Anomaly  3.14c.

Mean of my 10 =10.52c Anomaly 3.25c.