December 2021 C.E.T. and EWP forecast contests -- start of the new contest year for 2021-2022

[Roger J Smith]

On behalf of J10 and myself, welcome to another new competition year with the winter season of 2021-22 fast approaching. The contests will include the CET forecast and the (still optional) EWP forecast, with some guidance provided in two sections below ... 

 

CET averages and extremes for December

--- all CET values 1981 to 2020 are in the table --- they are in highlighted type to make them easier to find

--- --- --- bold type for warmest, italic for middle and underlined for the coldest thirds of these 40 most recent years. 

--- --- --- due to ties for 4.8 C there are 15 in total among the middle third and 12 for the coldest, 13 for the mildest. 

 

13.1 ... warmest daily mean, 19th 2015

12.9 ... previous warmest daily mean, 12th 1994

 9.7 ... warmest December 2015
 8.1 ... tied second warmest Decembers 1934 and 1974
 7.7 ... fourth warmest December 1852

 7.6 ... fifth warmest December 1733

 7.5 ... 1988

 6.9 ... 2018

 6.5 ... 2006

 6.4 ... 1994

 6.3 ... 1985, 2013

 6.2 ... 1986

 6.0 ... 2011, 2016

 5.9 ... has never happened in 362 tries

 5.8 ... 1997, 2000, 2019

 5.7 ... 2002

 5.6 ... 1983, 1987

 5.5 ... 1993, 1998

 5.4 ... 2004

 5.2 ... 1984, 2014

 5.1 ... average for 1971-2000* and 2001-20

 5.0 ... average for 1991-2020 and 1999, 2020

 4.9 ... 1989, 2007

 4.8 ... 2003, 2012, 2017

 4.7 ... average for 1961-90 and 1991

 4.6 ... average for 1981-2010, also 1901-2000

 4.4 ... 1982, 2005

 4.3 ... 1990

 4.1 ... average for 1659-2020 (all 362 years)

 4.0 ... average for 1801-1900

 3.9 ... average for 1701-1800

 3.6 ... 1992, 2001

 3.5 ... 2008

 3.4 ... average for 1659-1700

 3.1 ... 2009

 2.9 ... 1996

 2.3 ... 1995

 0.3 ... 1981

--0.4 ... tied fourth coldest 1788 and 1796
--0.5 ... third coldest 1676
--0.7 ... second coldest 2010
--0.8 ... coldest December 1890

-10.8 ... lowest daily mean 25th 1796

_______________________________________________

Enter your forecast before midnight on Tuesday 30 November, or with the increasing late penalties for entries 1-3 Dec.

*1971-2000 is in fact the highest 30-year average for December in the CET series, and the only one that rounds to 5.1, from 5.06. With the exception of June, this is the furthest back one has to go to find the maximum value. For most months it is one of the past five (1987-2016, 1988-2017, 1989-2018, 1990-2019 or 1991-2020). For June, however, it was 1822-51 (14.72) followed closely by an earlier peak, 14.70 for 1772-1801. We are closing in on that one with 14.69 the average for 1991-2020. 

As you might expect, the Maunder period produced cold Decembers, the mean was as low as 3.2 (1665 to 1694). It then rose as high as 4.29 by 1709-38. There was a colder period than any in the Maunder; the lowest 30-year average was 3.09 from 1783 to 1812; rounded off 1784 to 1813 was equal.

The running mean climbed as high as 4.61 for 1823-52 before falling back to 3.48 for 1867-96. Decembers in the first third of the 20th century were generally a bit milder than the mid-century period, means as high as 4.73 were reached in 1893-1922 and 1907-36. The lowest since those peaks was 4.33 for 1923-52. The last time that the running mean was 4.5 was 1957 to 1986. The table above tracks the changes since then, but worth noting that the cold December of 2010 dropped the running mean from 4.84 to 4.63 but it then went back up to 4.82 for 1982 to 2011 as that period dropped the cold December of 1981 (mean 0.3). 1981-2010 was the only 30-year mean at 4.6 after 1960-89. 

_______ _ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _ ________

 

Optional EWP (Precip) Contest -- details

The EWP contest now enters its fifth year. It remains entirely optional, in the first four years more than two-thirds of the regular temperature forecasters entered this second contest. (there were no precip-only forecasters). 

The contest asks you to predict an amount in mm (not a percentage) for this statistic. Any forecasts entered as percentages are converted using 1991-2020 averages.

After using the 1910-2017 "NCIC" precip values for the first contest, and scoring Hadley as an alternative, I went with the somewhat later appearing Hadley values for the second contest year, to reduce the complexity of scoring and reporting. You will have to be patient as Hadley posts their numbers around the 5th of each month. Preliminary numbers are available on the 2nd of each month and they rarely change much when given a decimal. Then the practice is to tweak the numbers through the following several months, which led me to start an "ultimate scoring" alternative table that adjusts the contest scores by these later amended values. However, the first reported values are what we use for the official contest results. In any case, most people stay within one rank or at the most two ranks of where they were in the immediate scoring. There was no appreciable differences in the ultimate scoring so I dropped that after 2019.

For December, here are the averages and extremes for your guidance. Data (from the Hadley EWP tables) go back to 1766.

The last twelve December EWP amounts appear in the table below. Both 2010 and 2012 qualified as min and max values for the period 1981-2020.

... the average of these past twelve Decembers is 111.7 mm. It can be seen from the 30-year normals and that last figure, that a general increasing trend is underway for Dec EWP.

 

Max on record ____193.9 mm (1876)

Max since 1981 ___ 175.2 mm (2012)

____2020 _______ 159.2 mm

____2015 _______ 145.9 mm

____2013 _______ 134.2 mm

____2019 _______ 121.4 mm

____2018 _______ 116.0 mm

____2011 _______ 113.6 mm

____2017 _______ 113.4 mm

____2009 _______ 109.1 mm

_ mean 2009-20 __ 111.7 mm

Mean 1991-2020 __103.6 mm

Mean 1981-2010 __ 97.4 mm

Mean 1766-2020 __ 88.9 mm (all 255 years of data)

____2014 ________ 77.3 mm

____2016 ________ 41.3 mm

Min since 1981 ____34.1 mm (2010)

Min on record _____ 8.9 mm (1788)

____________________________________________________

Note, the highest 30-year mean of December EWP was 106.6 mm (1896-1925). The lowest was 67.5 for 1864-1893. 

Since the peak value the lowest was 84.8 mm (1925-54). It has been gradually increasing since then and is now within 3 mm of the earlier peak. 

 

Your forecast should be in mm with one decimal allowed. If you enter a percentage, that will be applied to 1991-2020 mean of 103.6 mm to derive your contest entry. Any number that appears without a % sign or mm, will be taken as that number of mm, with .0 added. It will be up to you to clarify your contest entry.

Deadlines are the same as the temperature contest. EWP late penalties are 0.3 points per day (scoring runs from zero to 10.0 points each month).

______________________________________________________

Note that in both contests, there is a scoring deduction applied to forecasts of similar rank submitted later. 

We encourage you to enter each month as the contest year results depend on entering at least ten of the twelve contests. There are seasonal sub-contests which is why we start the contest year in December rather than January. Once you have missed three contests, you are no longer scored in the main CET scoring table, and while the EWP does not divide into two tables, effectively by scoring no points for three contests you are probably not going to finish among the top 20-25 totals. 

Good luck !!

 

[Bobd29]

4 hours ago, Roger J Smith said:

On behalf of J10 and myself, welcome to another new competition year with the winter season of 2021-22 fast approaching. The contests will include the CET forecast and the (still optional) EWP forecast, with some guidance provided in two sections below ... 

 

CET averages and extremes for December

--- all CET values 1981 to 2020 are in the table --- they are in highlighted type to make them easier to find

--- --- --- bold type for warmest, italic for middle and underlined for the coldest thirds of these 40 most recent years. 

--- --- --- due to ties for 4.8 C there are 15 in total among the middle third and 12 for the coldest, 13 for the mildest. 

 

13.1 ... warmest daily mean, 19th 2015

12.9 ... previous warmest daily mean, 12th 1994

 9.7 ... warmest December 2015
 8.1 ... tied second warmest Decembers 1934 and 1974
 7.7 ... fourth warmest December 1852

 7.6 ... fifth warmest December 1733

 7.5 ... 1988

 6.9 ... 2018

 6.5 ... 2006

 6.4 ... 1994

 6.3 ... 1985, 2013

 6.2 ... 1986

 6.0 ... 2011, 2016

 5.9 ... has never happened in 362 tries

 5.8 ... 1997, 2000, 2019

 5.7 ... 2002

 5.6 ... 1983, 1987

 5.5 ... 1993, 1998

 5.4 ... 2004

 5.2 ... 1984, 2014

 5.1 ... average for 1971-2000* and 2001-20

 5.0 ... average for 1991-2020 and 1999, 2020

 4.9 ... 1989, 2007

 4.8 ... 2003, 2012, 2017

 4.7 ... average for 1961-90 and 1991

 4.6 ... average for 1981-2010, also 1901-2000

 4.4 ... 1982, 2005

 4.3 ... 1990

 4.1 ... average for 1659-2020 (all 362 years)

 4.0 ... average for 1801-1900

 3.9 ... average for 1701-1800

 3.6 ... 1992, 2001

 3.5 ... 2008

 3.4 ... average for 1659-1700

 3.1 ... 2009

 2.9 ... 1996

 2.3 ... 1995

 0.3 ... 1981

--0.4 ... tied fourth coldest 1788 and 1796
--0.5 ... third coldest 1676
--0.7 ... second coldest 2010
--0.8 ... coldest December 1890

-10.8 ... lowest daily mean 25th 1796

_______________________________________________

Enter your forecast before midnight on Tuesday 30 November, or with the increasing late penalties for entries 1-3 Dec.

*1971-2000 is in fact the highest 30-year average for December in the CET series, and the only one that rounds to 5.1, from 5.06. With the exception of June, this is the furthest back one has to go to find the maximum value. For most months it is one of the past five (1987-2016, 1988-2017, 1989-2018, 1990-2019 or 1991-2020). For June, however, it was 1822-51 (14.72) followed closely by an earlier peak, 14.70 for 1772-1801. We are closing in on that one with 14.69 the average for 1991-2020. 

As you might expect, the Maunder period produced cold Decembers, the mean was as low as 3.2 (1665 to 1694). It then rose as high as 4.29 by 1709-38. There was a colder period than any in the Maunder; the lowest 30-year average was 3.09 from 1783 to 1812; rounded off 1784 to 1813 was equal.

The running mean climbed as high as 4.61 for 1823-52 before falling back to 3.48 for 1867-96. Decembers in the first third of the 20th century were generally a bit milder than the mid-century period, means as high as 4.73 were reached in 1893-1922 and 1907-36. The lowest since those peaks was 4.33 for 1923-52. The last time that the running mean was 4.5 was 1957 to 1986. The table above tracks the changes since then, but worth noting that the cold December of 2010 dropped the running mean from 4.84 to 4.63 but it then went back up to 4.82 for 1982 to 2011 as that period dropped the cold December of 1981 (mean 0.3). 1981-2010 was the only 30-year mean at 4.6 after 1960-89. 

_______ _ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _ ________

 

Optional EWP (Precip) Contest -- details

The EWP contest now enters its fifth year. It remains entirely optional, in the first four years more than two-thirds of the regular temperature forecasters entered this second contest. (there were no precip-only forecasters). 

The contest asks you to predict an amount in mm (not a percentage) for this statistic. Any forecasts entered as percentages are converted using 1991-2020 averages.

After using the 1910-2017 "NCIC" precip values for the first contest, and scoring Hadley as an alternative, I went with the somewhat later appearing Hadley values for the second contest year, to reduce the complexity of scoring and reporting. You will have to be patient as Hadley posts their numbers around the 5th of each month. Preliminary numbers are available on the 2nd of each month and they rarely change much when given a decimal. Then the practice is to tweak the numbers through the following several months, which led me to start an "ultimate scoring" alternative table that adjusts the contest scores by these later amended values. However, the first reported values are what we use for the official contest results. In any case, most people stay within one rank or at the most two ranks of where they were in the immediate scoring. There was no appreciable differences in the ultimate scoring so I dropped that after 2019.

For December, here are the averages and extremes for your guidance. Data (from the Hadley EWP tables) go back to 1766.

The last twelve December EWP amounts appear in the table below. Both 2010 and 2012 qualified as min and max values for the period 1981-2020.

... the average of these past twelve Decembers is 111.7 mm. It can be seen from the 30-year normals and that last figure, that a general increasing trend is underway for Dec EWP.

 

Max on record ____193.9 mm (1876)

Max since 1981 ___ 175.2 mm (2012)

____2020 _______ 159.2 mm

____2015 _______ 145.9 mm

____2013 _______ 134.2 mm

____2019 _______ 121.4 mm

____2018 _______ 116.0 mm

____2011 _______ 113.6 mm

____2017 _______ 113.4 mm

____2009 _______ 109.1 mm

_ mean 2009-20 __ 111.7 mm

Mean 1991-2020 __103.6 mm

Mean 1981-2010 __ 97.4 mm

Mean 1766-2020 __ 88.9 mm (all 255 years of data)

____2014 ________ 77.3 mm

____2016 ________ 41.3 mm

Min since 1981 ____34.1 mm (2010)

Min on record _____ 8.9 mm (1788)

____________________________________________________

Note, the highest 30-year mean of December EWP was 106.6 mm (1896-1925). The lowest was 67.5 for 1864-1893. 

Since the peak value the lowest was 84.8 mm (1925-54). It has been gradually increasing since then and is now within 3 mm of the earlier peak. 

 

Your forecast should be in mm with one decimal allowed. If you enter a percentage, that will be applied to 1991-2020 mean of 103.6 mm to derive your contest entry. Any number that appears without a % sign or mm, will be taken as that number of mm, with .0 added. It will be up to you to clarify your contest entry.

Deadlines are the same as the temperature contest. EWP late penalties are 0.3 points per day (scoring runs from zero to 10.0 points each month).

______________________________________________________

Note that in both contests, there is a scoring deduction applied to forecasts of similar rank submitted later. 

We encourage you to enter each month as the contest year results depend on entering at least ten of the twelve contests. There are seasonal sub-contests which is why we start the contest year in December rather than January. Once you have missed three contests, you are no longer scored in the main CET scoring table, and while the EWP does not divide into two tables, effectively by scoring no points for three contests you are probably not going to finish among the top 20-25 totals. 

Good luck !!

 

Hi

4.8C and 81.6mm for me please….oh and let’s make it a very happy Christmas this December 

[Earthshine]

3.3C and 45mm please

[jonboy]

Going early 3.7c and 84mm

[Frigid]

3.9C and 75mm please, hoping for a blocked and snowy end to 2021!

[Stationary Front]

Every year the same punt, so here we go again 5.9 please with 132mm

[I remember Atlantic 252]

last few GFS runs suggesting warm start, 7.6C and 140mm

[Polar Gael]

4.0°C and 100.2mm for me please. 

[SteveB]

4.8c and 79mm please. 

[Weather26]

5.3C and 120mm please.

Edited November 21, 2021 by Weather26

[Summer18]

4.6C and 96mm thanks 

Edited November 24, 2021 by Summer18

[LetItSnow!]

early guess so may change if output changes but i’m currently feeling a colder and snowier december than what we’re used to. 

3.2 and 90mm

[Ross Andrew Hemphill]

3.5C and 45mm

[Mapantz]

4.4°C / 110mm

[Typhoon John]

5.9C / 115mm

[virtualsphere]

5.1C and 89mm please

[BlueHedgehog074]

Gonna go for 4.3*C and 50mm rain/snow, please. Just have a feeling it will be a pretty dry month overall. Quite chilly too, but with some milder periods thrown about at times.

[DR(S)NO]

Thanks to you both for running the competition. Always good fun.

5.5c and 85 mm thank you please

[Roger J Smith]

5.4 C and 118.8 mm, much of that after mid-month in a rather stormy pattern, will probably see the mean temp in the high 6 area to mid-month, think it will come under some pressure but too active to allow cold to settle very long, that's my story and I'm sticking to it. 

[Shillitocettwo]

  I am going to also go for 5.9.C about time we had one.

 

   Although it will often be cool and snowy, a ridiculously mild spell at some point in the month with mid teens temperatures will more than wipe out any below average ness.

 EWP 59mm

[stewfox]

4.8c 125mm

Edited November 26, 2021 by stewfox

[JeffC]

4.5 degrees C and 85 mms ppn please

[syed2878]

6C and precipitation 120 mm

[John88B]

5C and 100 mm please.

[reef]

Slightly cooler and wetter than average:

4.7C and 119mm