December 2022 C.E.T. and EWP contests _ start of a new contest year

[Don]

17 hours ago, Roger J Smith said:

See if I listened to you I would be much further ahead ...

Indeed.  However, I doubt I will be advising you to go lower with your January CET forecast!!

[The PIT]

Tonight's run shows much milder conditions so it's going to be interesting too see how high CET gets.

[Don]

1 hour ago, The PIT said:

Tonight's run shows much milder conditions so it's going to be interesting too see how high CET gets.

Think my 3.8C could be in with a chance now!!

[ItNeverSnowsInWindsor]

1 hour ago, Don said:

Think my 3.8C could be in with a chance now!!

I’m thinking 3.4 - 3.5c before adjustments now!

Edited December 27, 2022 by prolongedSnowLover

[Don]

5 minutes ago, prolongedSnowLover said:

I’m thinking 3.4 - 3.5c before adjustments now!

End of month adjustments don't tend to happen since the update earlier this year.  I imagine mid 3's look to be the landing point now and suspect December will be the coldest month of winter, possibly by a considerable margin!

[The PIT]

Sunny Sheffield up to 3C -1.9C below average. Rainfall 61.4mm 70.2% of the monthly average.

The likely landing zone for us is 3.3C to 3.7C

Edited December 28, 2022 by The PIT

[snowray]

Sheffield once again milder that the CET.

 

[The PIT]

1 minute ago, snowray said:

Sheffield once again milder that the CET.

 

Yup lack of cold nights. Although last month the cet was 9.2 I believe we came in at 8.4C so no not again higher than CET. October we were also below the national CET. Probably were for other months.

[ItNeverSnowsInWindsor]

How is the CET determined ? Is it an area in the midlands ?

[snowray]

23 minutes ago, The PIT said:

Yup lack of cold nights. Although last month the cet was 9.2 I believe we came in at 8.4C so no not again higher than CET. October we were also below the national CET. Probably were for other months.

I noticed that at times this year Sheffield has been higher, and also a fair bit drier too. Maybe its the effect of having the Pennines just to the West. 

[Summer Sun]

2.7c to the 27th

1.8c below the 61 to 90 average
1.9c below the 81 to 10 average

[Roger J Smith]

8 hours ago, prolongedSnowLover said:

How is the CET determined ? Is it an area in the midlands ?

It is basically the average of three locations, only one (Pershore) is in the Midlands (even that one just perhaps as it's a bit southwest of where most would define the Midlands), the others are near Luton (Rothamsted) and in Lancs (Stonyhurst). The average is then reduced by 0.2 to account for a small urban effect which may actually be only a factor at one of these (so 0.6 there and zero at the other two but the math would be the same). This also helps to explain why v2.0 numbers jump around a bit in certain periods, there was an attempt made to adjust older CET data to match the current station grid which led to some different adjustments depending on what stations had been used in the legacy era. I don't know if the outcome would be a lot different if they took say one location like Birmingham airport. But it is what it is. And as I found out from Reef, it is when it is also. 

[Roger J Smith]

EWP continues to mount and is near 80 mm at this point, with 15-20 mm suggested as a grid average now to end of month. So 95-100 mm is looking like the most likely finish. 

I just wanted to add for the benefit of a few people who entered the December contest and may be reading the thread, this is an annual contest and there's a January contest thread open. We hope our new forecasters will decide to participate in the whole contest (or at least the winter season) and not just December. 

[damianslaw]

58 minutes ago, Roger J Smith said:

EWP continues to mount and is near 80 mm at this point, with 15-20 mm suggested as a grid average now to end of month. So 95-100 mm is looking like the most likely finish. 

I just wanted to add for the benefit of a few people who entered the December contest and may be reading the thread, this is an annual contest and there's a January contest thread open. We hope our new forecasters will decide to participate in the whole contest (or at least the winter season) and not just December. 

Up to the 17th we were on course for a very dry December, alas the recent atlantic conditions have helped raise levels immensely and we may well end up wetter than average.

4 days of CET values to go, a finishing mark between 3.3 and 3.6 degrees most likely.

[Don]

Just now, damianslaw said:

Up to the 17th we were on course for a very dry December, alas the recent atlantic conditions have helped raise levels immensely and we may well end up wetter than average.

4 days of CET values to go, a finishing mark between 3.3 and 3.6 degrees most likely.

All that good work from the cold spell largely undone!  However, at least it will still be comfortably below average.

[Dancerwithwings]

1 minute ago, Don said:

All that good work from the cold spell largely undone!  However, at least it will still be comfortably below average.

Lately it doesn’t seem that way Don

[summer blizzard]

Perhaps worth asking if we have any sub 4C December's that were above 100mm.

[Dancerwithwings]

Just now, summer blizzard said:

Perhaps worth asking if we have any sub 4C December's that were above 100mm.

Very good point, you’d think we would of had plenty of snowfall with a sub 4c and a 100mm….but not 🫣

[damianslaw]

4 minutes ago, Don said:

All that good work from the cold spell largely undone!  However, at least it will still be comfortably below average.

The depth of cold was very notable though, not many Decembers at least last 100 years shared same running 10 day mean between 7 and 17 Dec, something to applaud the month with. The change to very mild very similiar to both 2008 and 2012, I didn't expect such a sustained spell of very mild weather though, thought it may have been briefer and broke around christmas. 

[Roger J Smith]

EWP goes back to 1766 so the overlap with CET is for 257 years counting this year. This table lists all cases of CET below 4.0 and EWP above 98 mm for those 257 years (final values 102.0 mm and 3.4 C for this month) ... the order is chronological to give any perspective on changes over time in this correlation.

Only 23 of the 100 years with that much December precip (counting 2022) were sub 4.0 despite a similar number being available, so most of them ended up dry. As I worked down the list from wettest EWP, the first year to qualify was 9th wettest 1978 (3.7 C). The second and third that made the list were 21st and 22nd wettest 1886 and 1779, and of the top 29 (around 140 mm or higher), only three were colder than 4.0 C. 

The proportion rises gradually after that. Four in a row were cool Decembers from EWP ranks 30 to 33. Even so, the proportion was still rather small by 50th place EWP ( 9/50). 

You'll notice that a lot of these "cold" Decembers were in the 3.0 to 3.9 range also, so not necessarily cold enough for a lot of snow. Only four of the 23 years identified were colder than 3.0, with two others at 3.0 ... and the highest EWP in a really cold December was 96.6 mm in 1874.

(recent near misses as the proportion of cold Dec drops off ...) 2012 and 2017 (both 4.7 C) were in this EWP range also. 2012 was 7th (175.2 mm) and 2017 was 62nd (113.4 mm). 1982 at 4.1 was just outside this list and was ranked 69th EWP. Also 2003 (4.6 C) had 100.3 mm (94th).

Also outside the CET portion was 1938 which had pre-Christmas cold and snow, 4.4 avg CET and 72nd EWP (108.6 mm). 

So here's the list which would be very small indeed if the cutoff was 3.0 instead of 3.9. 

 

YEAR ___ CET __ EWP (rank)

1770 ___ 3.6 ___ 116.9 (55)

1773 ___ 3.8 ___ 101.2 (90)

1779 ___ 3.1 ___ 144.4 (22)

1787 ___ 3.8 ___ 109.1 (t70)

1810 ___ 3.6 ___ 134.4 (33)

1816 ___ 3.1 ___ 102.6 (87)

1817 ___ 2.5 ___ 107.7 (t74)

1839 ___ 3.7 ___ 103.5 (t83)

1869 ___ 2.8 ___ 124.7 (44)

1881 ___ 3.9 ___ 103.3 (85)

1882 ___ 3.9 ___ 125.5 (42)

1886 ___ 1.9 ___ 145.2 (21)

1896 ___ 3.9 ___ 137.3 (30)

1901 ___ 3.4 ___ 136.1 (31)

1909 ___ 3.9 ___ 135.4 (32)

1923 ___ 3.8 ___ 100.0 (95)

1937 ___ 3.0 ____ 98.5 (99)

1960 ___ 3.9 ___ 117.2 (54)

1961 ___ 2.2 ___ 106.1 (78)

1964 ___ 3.6 ____ 99.8 (97)

1978 ___ 3.7 ___ 172.8 (9)

2009 ___ 3.0 ___ 109.1 (t70)

2022 ___ 3.4 ____102.0 (89) confirmed

_____________________

The flip side of this correlation is illustrated by the mildest dry December which was 1843 (7.4 C, 18.2 mm third driest). Most of the notable cold Decembers were around 20th to 50th driest. 1796 must have had some heavy snow because it managed to reach 73.1 mm (the equivalent of 73.1 cm of snow). The precip in cold Dec 1981 was 93.5 mm. 

Edited January 12, 2023 by Roger J Smith

[Don]

2 hours ago, damianslaw said:

The depth of cold was very notable though, not many Decembers at least last 100 years shared same running 10 day mean between 7 and 17 Dec, something to applaud the month with. The change to very mild very similiar to both 2008 and 2012, I didn't expect such a sustained spell of very mild weather though, thought it may have been briefer and broke around christmas. 

Indeed, I expected a cold Christmas to New Year period at least!

[Don]

2 hours ago, Dancerwithwings said:

Lately it doesn’t seem that way Don

I know! 

[Roger J Smith]

Well at least the daily records for 31 Dec and 1 Jan are probably safe thanks to last year at this time. 

[The PIT]

Sunny Sheffield up to 3.2C -1.6C degrees below average. Rainfall 72.1mm 82.4% of the monthly average.

[Roger J Smith]

14 hours ago, summer blizzard said:

Perhaps worth asking if we have any sub 4C December's that were above 100mm.

 

14 hours ago, Dancerwithwings said:

Very good point, you’d think we would of had plenty of snowfall with a sub 4c and a 100mm….but not 🫣

Just to let you know I researched this and reported on it (a few hours ago), should have quoted you then so you would know the answer but maybe you spotted it -- there were a few below 4C but very few below 3C that exceeded 100 mm (or 98 mm as that is 100th place if 2022 hits that value or higher).

There were only 4 out of that 100 with a mean below 3.0 and two more at 3.0, then another 15 in the 3.1-3.9 range. It seems like most wet Decembers are not the very mildest but those with means in the 4s and 5s, they quite often seem to end up rather wet. The milder ones become hit or miss, some are wet, some are dry. 

I was not surprised by the trend but the almost complete lack of examples of cold, wet Decembers is striking. Dec 1874 came fairly close to this year's probable outcome and was much colder (-0.2) so that must have had a lot of snow.