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Offline Global Warming  
#1 Posted : 27 December 2012 22:43:08(UTC)
Global Warming

Rank: Advanced Member

Joined: 07/10/2006(UTC)
Posts: 6,258

We reach a new year and so time for a brand new annual CET competition in addition to the normal monthly competition. I will start with a reminder of how the competition works and also set out some new rules to accommodate those who miss a month or two during the year. This should enable as many people as possible to remain in the competition throughout the whole year.


How do the competitions work?

Each month a new thread is opened a few days in advance of the start of a new month. Your challenge is to predict the mean Central England Temperature (CET) for the following month. The CET is the longest running temperature series and goes back to the mid 1600's. Each month I post some statistics about the CET for that month in recent years as well as a summary of some of the latest model output and long range forecasts to provide some context to assist you in making your prediction.


Predictions can be made either to one or two decimals (the actual data is published to two decimals). The closest person or persons to the final figure at the end of the month are declared the winner. There are no prizes. This competition is just a bit of fun and the chance to amaze your fellow posters with your skill and foresight in predicting the weather (or you can just make a random guess!).


We use the Hadley data for the purposes of this competition which is maintained by the Met Office. Provisional figures are published daily with a final adjusted number usually issued on the first day of the following month. Other CET series are available (such as that maintained by Philip Eden) but are not always updated daily which is the main reason why we use Hadley.


In addition to the monthly competition there is an annual competition which runs throughout the year (this is different to the one off up-front annual CET prediction competition which is in a separate thread). The annual competition keeps a running total of the cumulative prediction errors from each month for each person. Absolute differences are used so it makes no difference if you overpredict or underpredict the CET in any given month. At the end of the year the person with the lowest cumulative prediction error after totalling each of the 12 months is declared the winner for the year. This is always a hard fought contest and requires a consistency of good predictions in order to win.


Summary of important rules


- Predictions must be made by 23:59 of the final day of the month in order to avoid penalties


- All predictions should be made in the CET thread for the relevant month where possible (except for the final two months of the year - see below). As the thread is usually only opened 4 days before the end of the month, if you expect to be away or unable to post for any reason you can send me your prediction earlier by way of private message and I will post it in the thread when it is opened.


- Predictions for November and December are to be made by private message to me. This is to avoid tactical predicting at the end of year rather than predictions based on expectations of the weather. The purpose of the competition is to predict what you think the temperature will be not to protect your position in the league table.


- Once you have posted your prediction you are only permitted to change it once. Any subsequent amendments will be ignored. No amendments are allowed after 23:59 on the last day of the month


- You may make a prediction to either one or two decimals. You can predict the same figure as someone else.


- Late entries will be accepted up to 23:59 on the 2nd of the month. Late entries are subject to a penalty for the purposes of the annual competition. For 2013 the penalties will be 0.2C for each day the entry is late (i.e. an entry made on the 2nd of the month will incur a penalty of 0.4C).


- Where two members have the same cumulative prediction error for the year at the end of any month, the order of ranking in the competition table will be determined by which person has had the closest prediction to the actual CET in any month. If there is a still a tie I then look to the second closest prediction for each person and so on until the tie is broken. If the tie cannot be broken (very unlikely by December but can happen in the first couple of months of the year) then each person impacted is awarded the same position in the table.


New rule for 2013


In previous years anyone who did not make a prediction in every month of the year became ineligible for the annual competition. There have been a number of requests for this to be changed as there are sometimes unforeseeable reasons that prevent people making a prediction in time. I have devised a new rule to accommodate this request which hopefully does not give those missing predictions any sort of unfair advantage. The new rule will work as set out below.


If a person in the annual CET competition does not make a prediction in any one month (including January) their prediction error for that month will be calculated as follows:


- the upper quartile (75th percentile) of the prediction errors of all the people in the annual competition who did make a prediction for that month will be calculated;


- the normal penalty for a late prediction on the 2nd of the month (i.e. 0.4C) will be added to the figure above


The result of the above calculation will be used as the CET prediction error for any person who misses a prediction in a particular month subject to one further point:


- If, for any person, their average monthly prediction error for all the previous months in the year to date is higher than the 75th percentile of errors (for those that did make a prediction) in the month the person in question made no prediction, then the average prediction error will be substitued instead of the 75th percentile figure. The 0.4C penalty will still be added on top.


This override is only likely to apply to those people towards the foot of the table. Let me give you an illustration from the 2012 numbers. Lets say vince had failed to make a CET prediction in November. The 75th percentile of errors for those that did make a prediction was 1.30C. The average prediction error for vince in the months January to October was 1.86C. So in this situation vince would be given a prediction error of 1.86C+0.4C=2.26C for November if he had failed to make a prediction. In fact he did make a prediction and had an error of 1.45C.


The above may sound a little complicated but it is actually quite simple to apply as I can easily calculate the upper quartile figure in my spreadsheet. I didn't think it would be fair to just give anyone who missed a prediction the same error as the worst prediction that month. Equally going with the median error is not really fair to everyone else in my view. Hence why I have gone for the upper quartile figure.


One final important point. No one person may miss more than two predictions during a calendar year. If a third prediction is missed that person will be eliminated from the competition (otherwise it would mean 25% or more of the annual error being calculated on non-existent predictions which would reduce the credibility of the competition too much).


Lets see how this works out in 2013. Hopefully it strikes a reasonable balance but it can be changed again next year if necessary. I will not make any changes to the rules during the year. 


January historic data summary

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


12 of the last 20 January's have seen a CET more than 0.5C above the 1971-2000 mean. Only 3 were more than 0.5C below average including 2009 and 2010.


Long run averages:
1971-2000: 4.2C
1981-2010: 4.4C
1988-2012: 4.8C


In 2012 the January CET was 5.45C. in 2010 it was just 1.39C. In 2007 we saw a CET of 7.0C which was the warmest since 1921.


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

 

´╗┐Here are some details of what the models and forecasters generally are saying at the moment

GEFS
http://www.wetterzentrale.de/pics/MT8_London_ens.png
http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

The first 10 days of the month look to be well above average but this is not necessarily reflective of what will happen in the rest of the month. This time last month the GEFS showed below average figures for the whole of the first 12 days of December and this did indeed turn out to be correct although since then it has been very mild.

ECM ensembles (De Bilt)
http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html
Very mild throughout.


Weatheronline
http://www.weatheronline.co.uk/cgi-app/reports?MENU=Month-ahead
No recent updates. But their forecast looks quite accurate for the start of January - i.e. mild. Possibly turning cooler mid month.


Netweather
http://www.netweather.tv/index.cgi?action=winter-forecast-2012;sess=

Prolonged cold spells


Met office
http://www.metoffice.gov.uk/media/pdf/c/2/A3-plots-temp-JFM.pdf
Slightly cooler than average most likely scenario but high degree of uncertainty.

http://www.metoffice.gov.uk/public/weather/forecast/

Average or above average but possibly turning cooler late in the month

Pattern matching (just for fun)

I looked briefly at years since 1900 with mean Oct / Nov temperatures of 8C to 8.6C (2012 8.26C) and a December CET between 4.3C and 5.3C.


There are only 8 matches so this year's pattern is quite unusual.


3 years had a January CET within +-0.5C of the 1971-2000 mean. One year was very mild (1930 at 6.3C). 3 years had a CET between 2.5C and 3.4C. Finally there was one very cold year (1958 at 1.6C).


So not much to go on there but overall a slight bias towards cooler than average conditions (very similar to the Met Office contingency planners summary).


Low confidence though and given the very mild first 10 days expected from the latest model guidance I would be surprised if the CET finished more than 0.5C below average. More likely to be above average I would think.

SHOW EXTERNAL IMAGES

Edited by moderator 01 January 2013 15:44:06(UTC)  | Reason: Not specified

Chineham, Basingstoke, Hampshire, 86m asl

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Offline Snow Hoper  
#2 Posted : 27 December 2012 22:47:30(UTC)
Snow Hoper

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United Kingdom
Location: Thorndon, Suffolk

No knee jerks from me. I have my own theory for the winter so start with 6.1C

By the time you realise your parents were right, your kids already think that you're wrong!
Home : Thorndon, Suffolk.
Work: Around Bury St Edmunds.
Offline Stormchaser  
#3 Posted : 27 December 2012 23:32:12(UTC)
Stormchaser

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Location: West Hants

With a strat. warming forecast by both GFS and ECM, there is a real wild card in the mix for this month.


I'm going to take a deep breath and predict 2.7°C, with a slightly above average first week to ten days followed by the rest of the month averaging on the cold side though not exceptionally so (so a CET somewhere near 1.5°C although I can see how it could end up a good deal colder if we struck lucky!).


This is a low confidence prediction due to both the SSW and the fact that the anticyclonic conditions modelled for the first 4-7 days of the month could bring a wide range of conditions depending on how much cloud cover and moisture is associated with it - CET returns from near zero (major inversion under dead calm conditions, with fog lingering all day) to double figures are theoretically possible.


- just so you know, all I've done is looked at the current model output and the strat. forecasts and then smothered it with a generous helping of "I don't really know but hopefully this will happen..."

If you have any problems or queries relating to TWO you can Email twomoderationteam@gmail.com :)
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Offline moomin75  
#4 Posted : 27 December 2012 23:43:47(UTC)
moomin75

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Joined: 24/05/2006(UTC)
Posts: 5,198

Exceptionally mild first week or so, followed by something considerably colder, will, I believe, keep the CET just below the average.


I will therefore go for 3.8 degrees please. Obviously very much against my winter LRF, which has been a disaster for the first month...but we can but hope!

Witney, Oxfordshire
100m ASL
Offline Zubzero  
#5 Posted : 27 December 2012 23:46:08(UTC)
Zubzero

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Location: Cambourne

1.4 C The zonal train is going to derail soon, and Winter will return 

Edited by user 27 December 2012 23:49:57(UTC)  | Reason: Not specified

Offline Hungry Tiger  
#6 Posted : 27 December 2012 23:59:27(UTC)
Hungry Tiger

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Joined: 11/04/2006(UTC)
Posts: 25,072
Location: South Cambridgeshire

I'll wait a day or two before staking my claim - but this winter has alread been totally different from what I thoght it would be.


 

Gavin S.
TWO Moderator.
Contact the TWO team - twomoderationteam@gmail.com
South Cambridgeshire. 93 metres or 302.25 feet asl.
Offline Dougie  
#7 Posted : 28 December 2012 02:34:53(UTC)
Dougie

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Location: Sidcup, Kent.

I am glad to see you are still firmly commited to this competition Simon. I know it takes up quite a bit of your time so thanks for that.


The battle of heart and mind for January, is a bit like the battle of the Atlantic versus the rest of the weather solutions, but overall I am going for a slightly below average of 3.9°c.


The changes you have introduced seem fair to me, and should help to keep the competition keen, so for all those taking part, good luck.

Ha'way the lads
Offline Chidog  
#8 Posted : 28 December 2012 04:30:06(UTC)
Chidog

Rank: Advanced Member

Joined: 28/12/2012(UTC)
Posts: 149
Location: Coulsdon

Newbie here, attempting some wild guesses. I am going to go for 4.8 for January! Starting warmer but then chilling out slightly to end. GL all 

Offline Global Warming  
#9 Posted : 28 December 2012 07:35:08(UTC)
Global Warming

Rank: Advanced Member

Joined: 07/10/2006(UTC)
Posts: 6,258

Originally Posted by: Chidog Go to Quoted Post


Newbie here, attempting some wild guesses. I am going to go for 4.8 for January! Starting warmer but then chilling out slightly to end. GL all 



Welcome to TWO. Always good to have some new names joining in at the start of the year.

Chineham, Basingstoke, Hampshire, 86m asl
beaufort  
#10 Posted : 28 December 2012 08:11:03(UTC)
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Posts: 6,714

4.2C please.

Offline Hungry Tiger  
#11 Posted : 28 December 2012 09:31:23(UTC)
Hungry Tiger

Rank: Advanced Member

Joined: 11/04/2006(UTC)
Posts: 25,072
Location: South Cambridgeshire

I won't bother waiting any longer especially after having just looked at another run of charts.


It's almost TU to any cold weather unless there is a very dramatic change.


I'll go for a mild one, but not very very mild.


6C

Gavin S.
TWO Moderator.
Contact the TWO team - twomoderationteam@gmail.com
South Cambridgeshire. 93 metres or 302.25 feet asl.
Johnny25  
#12 Posted : 28 December 2012 10:06:04(UTC)
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4.85C for me.
Offline scillydave  
#13 Posted : 28 December 2012 10:39:17(UTC)
scillydave

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Location: Birdlip, Gloucestershire 292m asl

5.4 for me please

Birdlip, highest village in the Cotswolds and snow heaven in winter.
Offline ARTzeman  
#14 Posted : 28 December 2012 10:50:50(UTC)
ARTzeman

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Location: Peasedown St John. N.E. Sommerset

4.7c. Is Mine...



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Others just get wet.
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Online Saint Snow  
#15 Posted : 28 December 2012 11:58:10(UTC)
Saint Snow

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4.6c

"Conservatism consists of exactly one proposition, to wit: There must be in-groups whom the law protects but does not bind, alongside out-groups whom the law binds but does not protect."

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Offline Surrey John  
#16 Posted : 28 December 2012 12:23:13(UTC)
Surrey John

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Location: Kingston upon Thames

A new year and I haven't a clue about second half of January, ideally I would wait couple more days, but I will probably forget to submit if I do

I'm going to try 4.2c please

Kingston upon Thames

15m ASL
DTHFCJ  
#17 Posted : 28 December 2012 12:32:36(UTC)
Guest

Rank: Guest

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Posts: 6,714

5.5C for me please....Happy New Year to come for all

Offline Tractor Boy  
#18 Posted : 28 December 2012 12:43:02(UTC)
Tractor Boy

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Joined: 05/07/2006(UTC)
Posts: 274

3.8C for me please.


I am thinking a return of high pressure (its got to come back to us at some point) with some foggy inversions. Drier than average. 

Dave
Cropton, North York Moors
Offline warrenb  
#19 Posted : 28 December 2012 13:08:26(UTC)
warrenb

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Location: Tonbridge, Kent

4.8C for me please. More of the same I feel.
JupiterPluvius  
#20 Posted : 28 December 2012 13:15:30(UTC)
Guest

Rank: Guest

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My first ever attempt at this, so here goes nothing.


I'm going for a very average 4.95c


A month of mild, damp, driech conditions and occasionally very very stormy


 


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