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

[Stu_London]

8 minutes ago, LetItSnow! said:

Curiosity strikes me as I wonder what we’d be looking at if a GEM scenario came off. Temperatures in the CET zone will be falling away quite quickly this week. I know some were worried about cloud but I think in the south the high pressure doesn’t look to be the type to bring in excessive damp, drizzly, frost inhibiting conditions. You tend to see that when there’s a more westerly/northwesterly element. I’ve been caught out before thinking a month was going cold (February 2021 ) only to not, but could we be seeing the coolest December since 2010 unfolding? It wouldn’t take much. Watch this space! 

Only need to get below 4.8C for the coldest month since 2010. I'd say that is probably marginally odds on at the moment, given the outlook.

Of similar interest is whether we can get to 3.7C ish - that would bring us our first sub 10C calendar year since 2013. I think we would definitely need that cold spell in the final third for that to happen, unless the high pressure becomes very cold with freezing fog during daytime, which would be another route.

[Summer Sun]

5.6c to the 12th

0.7c above the 61 to 90 average
0.5c above the 81 to 10 average

___________________________

Current high this month 7.3c on the 1st
Current low this month 4.9c on the 7th

[Roger J Smith]

Almanac for 14th December

The highest daily mean (1772-2020) was 11.8 in 1912. The highest since then was 11.7 in 1929 and more recently 11.5 in 2006. The record in 1912 replaced 10.5 from 1867. Other mild averages were 11.0 in 1948, 10.9 in 1972, 10.8 in 1985, 10.7 in 1998, 10.2 in 1922, and 10.1 in 1953 and 2016.

The lowest daily mean (1772-2020) was -5.3 in 1878 which replaced -4.2 from 1846. Other low daily means include -5.1 in 1890, -4.8 in 1899, -2.6 in 1801 and 1859, -2.2 in 1788, -2.1 in 1819, -1.9 in 1813, -1.7 in 1844, -1.4 in 1840, 1920 and 1943, -1.1 in 1805, and -1.0 in 1981.

The highest maximum (1878-2020) was 13.9 in 1912 with 13.8 in 1998 the highest since then. Other mild daily maxima include 13.6 in 1972, 13.2 in 1929, 12.9 in 1948 and 2016, 12.7 in 1941, and 12.6 in 1982, 1985 and 2006.

The highest minimum (1878-2020) was 10.5 in 2006 which replaced 10.2 from 1929 which had overtaken 9.7 from 1912. Other mild readings include 9.4 in 1922, 9.2 in 1894, 9.1 in 1948, 9.0 in 1985, 8.7 in 1938, 8.4 in 1953, and 8.2 in 1918 and 1972. 

The lowest maximum (1878-2020) was -2.2 in 1878; other cold values were -1.7 (1890), -1.4 (1899), 1.1 (1925), 1.2 (1943) and 1.3 (1950). 

The lowest minimum (1878-2020) was -8.4 in 1890 followed by -8.3 in 1878, -8.1 in 1899, -7.1 in 1981, -5.0 in 1920, and -4.6 in 1968.

The wettest 14th of December (1931-2020) in the EWP data was 15.94 mm (2012), followed by 13.26 mm (1936), 12.44 mm (1989), 10.83 mm (1993), 10.41 mm (1940), 10.35 mm (1955), and 10.27 mm (1983).  

The wettest week ending 14th December (8th - 14th Dec) was 70.31 mm in 1979, followed by 57.47 mm (1978), 54.56 mm (1993), 50.95 mm (1989) and 50.49 mm (2000).

The least amount falling in a week ending 14th December was 0.07 mm in 1991, then 0.66 mm in 2001, 1.38 mm in 1987, 1.46 mm in 1971, 1.62 mm in 1996, and 1.67 mm in 2005. 

-----------------------------

(The very cold December of 1890 was starting to go into a deep freeze on this date; more severe cold would follow in about a week). 

https://www.wetterzentrale.de/reanalysis.php?jaar=1890&maand=12&dag=14&uur=0600&var=1&map=1&model=noaa

 

Edited December 14, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield up to 5.2C -0.8C below average. Rainfall 59mm 67.4% of the monthly average.

[Summer Sun]

5.9c to the 13th

1.0c above the 61 to 90 average
0.8c above the 81 to 10 average

___________________________

Current high this month 7.3c on the 1st
Current low this month 4.9c on the 7th

[BornFromTheVoid]

Latest CET projection, based on the 06z GFS.

    

Before corrections, the chances of finishing:
Close to average (4.5C to 5.5C) is 45% (3 days ago was 44%)
Above average (>5.5C) is 50% (3 days ago was 43%)
Below average (<4.5C) is 5% (3 days ago was 13%)

The period of the 9th to the 14th is forecast to average 7.9C, 3.0C above the 91-20 average.

Here's the change in projections

[Roger J Smith]

EWP update ... about 52 mm has fallen so far (49 mm to 12th, about 3 mm grid average 13th). The ten-day GFS projection is zero, with just very small amounts around coastal fringes and the entire grid inland at zero. That implies we remain at 52 mm to the 24th. From then to end of the month (current GFS runs to 12z 30th) the maps appear to have more dry conditions in store with a 5-10 mm event starting up on the 30th, so this would suggest a finish near 60 mm. Only four of our fifty-eight forecasts lie below that mark. Lengthy dry spells are quite rare at this time of year, the smallest amount of total precip that has fallen from 14th to 30th (projected to be almost zero this year) in the EWP records since 1931 is 7.5 mm in 1939 with 8.6 in 2008 and 9.9 mm in 1972. In 1961 there was virtually no precip 14th-27th but heavier amounts 28th-30th took that year well above the 1939 minimum. Note that it turned quite cold at the start of Jan 1962 and of course Jan 1940 was a very cold month. Jan 2009 also had quite a cold start and snowfalls near the end of the month. The 19th to 31st in 1992 was also quite dry (but about 20 mm fell 14th to 18th).

As to the CET, with the mild anticyclonic pattern looking to be subject to a slow transition to colder and perhaps some inversion fog chill at times, I think the most likely outcome taking the projections above from BFTV would be through the bottom third of the spectrum and out around 4.5 C before corrections but with some potential for lower if the nearby arctic chill gets more fully involved around 24th-28th. Probably any outcome from about 3 to 6.5 after corrections is still within reach depending on how this plays out, I am only confident of the mild air remaining in control to about Friday with the chill perhaps setting in gradually over the following week. 

[Roger J Smith]

Almanac for 15th December

The highest daily mean (1772-2020) was 11.2 in 1985 which narrowly edged out 11.1 from 1867. Other mild averages were 10.2 in 1998 and 2015. This is a sharp decline in the number of 10+ days compared to the previous week.

The lowest daily mean (1772-2020) was -5.4 in 1788. Other low daily means include -4.2 in 1846, -3.5 in 1840, -3.4 in 1859, -3.3 in 1878, -3.2 in 1899, -3.0 in 1813 and 1890, -2.6 in 1950, -2.3 in 1801, -1.5 in 1928, and -1.3 in 1925 (1981 had a brief break from the extreme cold, at 0.8 but only 1990 at 0.5 has been colder since then).

The highest maximum (1878-2020) was 13.2 in 2015 which replaced 13.1 from 1982, which had pushed out 12.6 from 1962. Other mild daily highs include 13.0 in 2013, 12.6 in 1985, 12.4 in 1971.

The highest minimum (1878-2020) was 9.8 in 1985 which replaced 7.6 from 1900 (7.4 in 1941 and 7.3 in 1912, 1942). Other very mild readings are recent and include 9.7 in 1998, and 8.7 in 2006. 

The lowest maximum (1878-2020) was -0.3 in 1890; other cold values were +0.3 (1950), 0.8 (1925), 0.9 (1920), 1.0 (1899), 1.1 (1928), 1.3 (1946) and 1.8 (1878 and 1981). 

The lowest minimum (1878-2020) was -8.4 in 1878 followed by -7.4 in 1899, -5.6 in 1890,-5.4 in 1950, -4.2 in 1968 and -4.0 in 1928; -3.6 in 1994 was the lowest since 1968. 

The wettest 15th of December (1931-2020) in the EWP data was 15.17 mm (1989), followed by 14.84 mm (2018), 13.05 mm (1956), and 10.16 mm (1987).  

The wettest week ending 15th December (9th - 15th Dec) was 65.94 mm in 1989, followed by 65.16 mm (1979), and 51.59 mm (1978).

The least amount falling in a week ending 15th December was 0.96 mm in 2001, then 1.34 mm in 1971, 1.56 mm in 1947, and 1.91 mm in 1943 and 2005. 

-----------------------------

(Another ongoing cold spell was during mid-December of 1899). 

https://www.wetterzentrale.de/reanalysis.php?jaar=1899&maand=12&dag=15&uur=0600&var=1&map=1&model=noaa

 

Edited December 15, 2021 by Roger J Smith

[damianslaw]

Chance we may experience our driest second half to December on record. Nil amounts of rain forecast for many after tomorrow for possibly 10 days or more at least. 

[Dancerwithwings]

1 minute ago, damianslaw said:

Chance we may experience our driest second half to December on record. Nil amounts of rain forecast for many after tomorrow for possibly 10 days or more at least. 

LOL... and my first go at the EWP competition as well  

[Summer Sun]

6.1c to the 14th

1.2c above the 61 to 90 average
1.1c above the 81 to 10 average

___________________________

Current high this month 7.3c on the 1st
Current low this month 4.9c on the 7th

[The PIT]

Sunny Sheffield up to 5.4C -0.5C below average. Rainfall unchanged.

At the present time the run up to Christmas looks to turn cold so we are likely to drop below 5 degrees once again.  However after xmas if the GFS is right we pass winter into spring with another very mild spell possible.

[damianslaw]

Mmm perhaps not the driest second half to December.. lots of uncertainty but we might see a fair amount of precipitation of the snow variety for some.. perhaps..

[Roger J Smith]

Almanac for 16th December

 

The highest daily mean (1772-2020) was 11.4 in 2015 which replaced 10.8 from 1842. Other mild averages were 10.4 in 1849, 10.2 in 1867, 10.1 in 1951 and 1971, and 10.0 in 1873. 1985 had 9.7 to go with the high minimum noted below (9.1).

The lowest daily mean (1772-2020) was -6.6 in 1859. Other low daily means include -5.7 in 1788, -2.3 in 1916, -2.2 in 1981, -2.1 in 1805 and 1812 and -1.9 in 1878 with -1.6 in 1801.

The highest maximum (1878-2020) was 13.9 in 2015 which replaced 13.1 from 1897. Other mild daily highs include 12.5 in 1904, 12.2 in 1902, and 12.1 in 1989.

The highest minimum (1878-2020) was 9.1 in 1985 which replaced 8.6 from 1971 (before that 8.4 from 1951). Other very mild readings include 9.0 in 2015, and 7.5 in 1942. 

The lowest maximum (1878-2020) was -0.3 in 1890 although possibly closer to -3 in 1859; other cold values were 0.0 (1927 and 1981), 0.7 (1916), 0.8 (1878), and 1.6 (1946). 

The lowest minimum (1878-2020) was -5.5 in 1899 (although likely closer to -8 to -10 in 1859). Other cold minima include -5.3 in 1916 followed by -4.5 in 1878, -4.4 in 1981, and -3.9 in 1950 and 1957 with -3.8 in 1946. 

The wettest 16th of December (1931-2020) in the EWP data was 17.19 mm (1944), followed by 11.59 mm (1989), and 11.10 mm (2014).  

The wettest week ending 16th December (10th - 16th Dec) was 77.36 mm in 1989, followed by 51.40 mm (1979).

The least amount falling in a week ending 16th December was 0.88 mm in 2007, followed by 0.92 mm in 1943, 1.09 mm in 2001, then 1.38 mm in 1971, 1.41 mm in 1988, 1.55 mm in 2005, 1.76 mm in 1931, 1.90 mm in 1951, and 1.94 mm in 1947. 

-----------------------------

(A severe cold spell produced records around this date in 1859). 

https://www.wetterzentrale.de/reanalysis.php?jaar=1859&maand=12&dag=16&uur=0600&var=1&map=1&model=noaa

 

 

Edited December 16, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield at 5.6C -0.2C below average, Rainfall 59.1mm 69.5% of the monthly average.

[Roger J Smith]

For continuity ...

6.3c to the 15th

1.4c above the 61 to 90 average
1.3c above the 81 to 10 average

1.0 above the 91 to 20 average

___________________________

Current high this month 7.3c on the 1st
Current low this month 4.9c on the 7th

________________________________________________________

EWP at 52 mm, some changes to outlook though with 10 mm now added by 26th, could be more after that but with the low confidence in model output at this point, all speculative. Seems likely to go past 60 mm now, where it stops anyone's guess (as it was before we started). 

[Roger J Smith]

Almanac for 17th December

 

The highest daily mean (1772-2020) was 12.5 in 2015 which replaced 11.6 from 1904. Other mild averages were 11.0 in 1987, 10.9 in 1897, 10.7 in 1828, 10.6 in 1857, 10.4 in 1902, and 10.0 in 1932 with 9.9 in 1806. 

The lowest daily mean (1772-2020) was -7.7 in 1859. Other low daily means include -3.2 in 1878, -3.0 in 1818, -2.7 in 1981, -2.6 in 1801, 1805 and 1840, -2.4 in 1864, -2.3 in 1935, -2.1 in 2010, -2.0 in 1788, -1.9 in 1791 and 1874, -1.7 in 1916. and -1.5 in 1886.

The highest maximum (1878-2020) was 14.1 in 2015 which replaced 13.6 from 1987 which in turn had replaced 13.1 from 1965. Before that the record was 13.0 from 1936. Other mild daily highs include 12.8 in 1902 and 1921, 12.6 in 1911, 12.5 in 1897 and 1904, 12.4 in 1932, and 12.3 in 2014.

The highest minimum (1878-2020) was 11.0 in 2015 which replaced 10.7 from 1904. Other very mild readings include 9.3 in 1897, 9.2 in 1945, 8.4 in 1987, 8.3 in 1942, 8.0 in 1902 and 1989, and 7.6 in 1932. 

The lowest maximum (1878-2020) was -0.5 in 1981 although possibly closer to -3 or even -4 in 1859; other cold values were 0.0 (1886, 1927 and 2010), 0.9 (1969), 1.0 (1878 and 1879), 1.2 (1890), and 1.4 (1880 and 1916). 

The lowest minimum (1878-2020) was -7.3 in 1878 (although likely closer to -8 to -10 in 1859). Other cold minima include followed by -4.9 in 1981, -4.8 in 1916, -4.5 in 1927, -4.3 in 1967, -4.2 in 2010 and -4.1 in 1957. 

The wettest 17th of December (1931-2020) in the EWP data was 13.16 mm (1965), followed by 11.86 mm (1994), and 11.14 mm (1968).  

The wettest week ending 17th December (11th - 17th Dec) was 81.67 mm in 1989, followed by 49.37 mm (1936).

The least amount falling in a week ending 17th December was 0.60 mm in 2007, followed by 1.40 mm in 1971,  1.41 mm in 1988, 1.64 mm in 1931, 1.70 mm in 2001, 1.73 mm in 2005, and 1.88 mm in 1939. 

-----------------------------

(Today's map link is for 1927, see also a thread from weather-history in the historical weather forum, on cold and snow from this set-up a few days later around Christmas 1927). 

https://www.wetterzentrale.de/reanalysis.php?jaar=1927&maand=12&dag=17&uur=1200&var=1&map=1&model=noaa

 

Edited December 17, 2021 by Roger J Smith

[Summer Sun]

6.5c to the 16th

1.6c above the 61 to 90 average
1.5c above the 81 to 10 average

___________________________

Current high this month 7.3c on the 1st
Current low this month 4.9c on the 7th

[Don]

1 minute ago, Summer Sun said:

6.5c to the 16th

1.6c above the 61 to 90 average
1.5c above the 81 to 10 average

___________________________

Current high this month 7.3c on the 1st
Current low this month 4.9c on the 7th

Should start to ease down after today, I would think?

[summer blizzard]

A milder than expected first half, do we know when we last had a warmer.

[Don]

58 minutes ago, summer blizzard said:

A milder than expected first half, do we know when we last had a warmer.

2018?  That was a very mild December at 6.9C  I recall it being mild most of the way apart from a slight blip around mid month?  If not 2018, 2016 and if not 2016, most definitely 2015!! 

Edited December 17, 2021 by Don

[Roger J Smith]

Almanac for 18th December

 

The highest daily mean (1772-2020) was 12.5 in 2015 which replaced 11.8 from 2014 which had replaced 11.5 from 1932. Other mild averages were 11.3 in 1827, 11.0 in 1873, 10.6 in 1779, 10.3 in 1987, 10.2 in 1828 and 1965, 10.1 in 1921 and 10.0 in 1911. 

The lowest daily mean (1772-2020) was -7.1 in 1859. Other low daily means include -3.6 in 1801, -3.2 in 1981, -3.0 in 2010, -2.8 in 1808, -2.7 in 1841 and 1935, -2.3 in 1886, -2.2 in 1961, -2.1 in 1776, -2.0 in 1846, and -1.6 in 1788.

The highest maximum (1878-2020) was 15.1 in 2015 which was a new December record high, broken the next day (15.3 19th 2015). As a daily record it replaced 13.6 from 1993 which had replaced 12.5 set in 1898 and tied in 1991. 13.3 in 2014 was not a record. Other mild daily highs were 12.8 in 2020, and 12.3 in 1932.

The highest minimum (1878-2020) was 10.5 in 1932 which replaced 9.3 from 1898. Other very mild readings include 10.3 in 2014, 9.9 in 2015, 9.2 in 1987, 9.1 in 1911, 8.8 in 1965, 8.4 in 1892 and 1921.

The lowest maximum (1878-2020) was -1.3 in 1927; other cold values were -1.1 (2010), -0.5 (1961), -0.2 (1938), 0.4 (2009), 0.8 (1916, 1969 and 1981), 0.9 (1935), 1.0 (1886), 1.2 (1890) and 1.5 (1896). 

The lowest minimum (1878-2020) was -7.2 in 1981. Other cold minima include -5.6 in 1886, followed by -4.9 in 2010, -4.4 in 2005, -4.3 in 1937, and -4.0 in 1927 and 1967. 

The wettest 18th of December (1931-2020) in the EWP data was 15.40 mm (1993), followed by 15.06 mm (1943), 13.71 mm (2018), 13.49 mm (1989), 13.43 mm (2013), 13.10 mm (1965), 12.61 mm (1952), 11.83 mm (1967), 11.69 mm (1996), 11.50 mm (2019), 11.13 mm (1958), 10.84 mm (2004) and 10.56 mm (1997). This was an increase of ten (above 10 mm) from the previous day. 

The wettest week ending 18th December (12th - 18th Dec) was 88.58 mm in 1989, followed by 59.22 mm (1993), 50.71 mm (1965), and 50.33 mm (1936).

The least amount falling in a week ending 18th December was 0.50 mm in 2007, followed by 1.53 mm in 1990, 1.57 mm in 1939, 1.63 mm in 1931, and 1.89 mm in 2001. 

-----------------------------

(Today's map link is for 1932, which had a mild spell -- will feature 2015 tomorrow when the all-time December record is featured.) 

https://www.wetterzentrale.de/reanalysis.php?jaar=1932&maand=12&dag=18&uur=1200&var=1&map=1&model=noaa

 

Edited December 18, 2021 by Roger J Smith

[Roger J Smith]

1 hour ago, summer blizzard said:

A milder than expected first half, do we know when we last had a warmer.

They now say 6.5 but as we learned last month, that could mean 6.0. Anyway, I will play along and these are the relatively recent (1941 to present) Decembers that were at 6.0 or higher on the 16th, with eventual outcomes in brackets:

9.1 __ 2015 (9.7) (note 1934 was at 9.0, fell to 8.1 and 1898 at 9.0 fell to 7.3) 

8.7 __ 2000 (5.8)

8.6 __ 1979 (5.8)

8.4 __ 1948 (5.7), 1956 (5.7) 

8.2 __ 1985 (6.3), 2006 (6.5)

8.1 __ 1953 (6.9)

7.8 __ 1994 (6.4)

7.7 __ 1974 (8.1)

7.4 __ 1942 (6.7)

7.2 __ 1941 (5.6)

7.0 __ 2016 (6.0)

6.9 __ 1972 (5.8) 

6.7 __ 1986 (6.2), 1988 (7.5), 2013 (6.3)

6.6 __ 2018 (6.9)

6.5 __ 1971 (6.6)

6.4 __ 1993 (5.5)

6.1 __ 1992 (3.6), 1999 (5.0)

6.0 __ 1954 (6.8), 1955 (5.4)

So there were twenty out of eighty Decembers at or above 6.4 and 24 at or above 6.0. Only one of them fell below 5.0 at the end (1992 fell to 3.6 from 6.1). 

Hopefully we can make it two this time around. 

 

[damianslaw]

A mild first half but not exceptionally so and I wont be surprised to see another marked downward correction so we could be on 6 degrees which feels right as the opening to the month was chilly and it has only been the last 6 days or so that have been more appreciably mild. This should be the high mark a gradual fall now.. though south part of CET zone may take a while to cool down.

[Summer Sun]

6.5c to the 17th

1.6c above the 61 to 90 average
1.6c above the 81 to 10 average

___________________________

Current high this month 7.3c on the 1st
Current low this month 4.9c on the 7th