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

[The PIT]

Sunny Sheffield back to down 5.6C -0.1C below average, Rainfall 59.9mm 68.5% of the monthly average

[Roger J Smith]

 

Almanac for 19th December

 

The highest daily mean (1772-2020) was 13.1 in 2015; this remains the warmest daily mean for December and as a daily record it replaced 11.6 from 1993 which had replaced 11.2 from 1772. Other mild averages were 10.6 in 1932, 10.4 in 1924, 10.3 in 1797 and 1921, and 10.1 in 1827.

The lowest daily mean (1772-2020) was -6.8 in 2010 which replaced -5.7 from 1859.  Other low daily means include -4.4 in 1927, -4.0 in 1799, -3.8 in 1801, -3.3 in 1860, -3.0 in 1855 and 1981, -2.7 in 1935, -2.6 in 1938, -2.4 in 1978, -2.3 in 1917, -2.2 in 1961, -2.1 in 1890, -2.0 in 2009, -1.9 in 1841 and 1931, -1.8 in 1804 and -1.7 in 1886. Will cut off these cold lists at -2.0 from 20th Dec to mid-February.

The highest maximum (1878-2020) was 15.3 in 2015 which is also the December record high. Before that, daily records for 19th were set in  1993 with 13.3, which replaced 12.4 from 1991 which had replaced 12.1 set in 1932 and 1957. That was matched by 12.1 in 2019. It was 11.9 in 1959, and 11.8 in 1924 and 1958. 

The highest minimum (1878-2020) was 10.8 in 2015 which replaced 9.9 from 1993, before that the record was 9.2 from 1921. Other very mild readings include 9.1 in 1932, 9.0 in 1924 and 2020, and 8.0 in 1934. 

The lowest maximum (1878-2020) was -3.2 in 2010. This replaced -2.1 from 1927; other cold values were -2.0 (1938), -0.9 (1890), -0.2 (1978), 0.9 (1935), 1.0 (1963), 1.1 (1931 and 1961), 1.2 (1917), 1.3 (1916), 1.5 (1886), 1.6 (1999) and 1.8 (1896 and 1969). (2009 was 2.1).

The lowest minimum (1878-2020) was -10.3 in 2010 which replaced -8.9 from 1981 which had replaced -6.6 from 1927. Other cold minima include -6.1 in 2009, -5.7 in 1917, -5.5 in 1961, -4.8 in 1886, 1931 and 1955, -4.5 in 1978 and -3.8 in 1937. 

The wettest 19th of December (1931-2020) in the EWP data was 23.21 mm (2012), followed by 16.48 mm (1995), 14.22 mm (1982), 13.97 mm (2019), 12.55 mm (1959), and 11.27 mm (1980). 

The wettest week ending 19th December (13th - 19th Dec) was 90.90 mm in 1989, which is also a record for all of December and second highest all-time with only 27 Oct to 2 Nov 2000 (93.33 mm) ahead. This record amount for 19th Dec was followed by 51.63 mm (2012) and 48.48 mm (2019).

The least amount falling in a week ending 19th December was 0.43 mm in 2007, followed by 1.80 mm in 1931, and 1.98 mm in 1939. This is a sharp decrease in the number of dry weeks (under 2.0 mm) from previous entries.

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

(Today's map link is for 2015, with the monthly record warmth - tomorrow will feature 2010 as it reached its lowest readings.) 

https://www.wetterzentrale.de/reanalysis.php?jaar=2015&maand=12&dag=19&uur=1200&var=1&map=1&model=noaa

 

Edited December 19, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield down to 5.5C -0.1C below normal. Rainfall 60.2mm 68.8% of the monthly average

[Summer Sun]

6.4c to the 18th

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

[Roger J Smith]

Almanac for 20th December

 

The highest daily mean (1772-2020) was 11.1 in 1828; the warmest since then being 10.8 in 2015. Other mild averages were 10.5 in 1907, 10.3 in 1971, 9.9 in 1819 and 1974, 9.8 in 1912 and 1987, and 9.7 in 1772, 1792, 1851 and 1958.

The lowest daily mean (1772-2020) was -7.0 in 2010 which replaced -4.2 from 1938. Other low daily means include -4.1 in 1890, -4.0 in 1799, -3.7 in 1860, -3.3 in 1878 and 1886, -3.1 in 1855 and 1927, -2.7 in 1935, -2.6 in 1801, -2.2 in 1999, -2.1 in 1804 and 1808, and -2.0 in 1935 and 1981. 

The highest maximum (1878-2020) was 13.9 in 1971. This replaced 13.3 from 1900. The warmest since 1971 was 12.4 in 1989. Other mild days include 13.0 in 1957, 12.1 in 2008 and 2015, 11.8 in 1987 and 11.6 in 1907.  

The highest minimum (1878-2020) was 9.6 in 2015 which replaced 9.4 from 1907. Other very mild readings include 8.7 in 1958, 8.4 in 1912 and 1974, 7.9 in 1934, 7.4 in 1924. 

The lowest maximum (1878-2020) was -2.2 in 1938. This replaced -1.5 from 1890. Other cold values were -1.6 (2010), -0.3 (1927), -0.1 (1878), 0.0 (1935), 0.6 (1886), 1.0 (1904), 1.2 (1901), 1.3 (1933), 1.5 (1978) and 1.6 (1961). (2009 was 1.9).

The lowest minimum (1878-2020) was -12.4 in 2010 which replaced -7.2 from 1886. Other cold minima include -6.9 in 1999, -6.8 in 1981, -6.6 in 1890, -6.4 in 1878, -6.1 in 1938, -5.8 in 1927, -5.6 in 2009, -5.1 in 1978, -5.0 in 1917, -4.7 in 1909, -4.5 in 1891, -4.4 in 1901, -4.2 in 1963 and 1967, -4.1 in 1937 and -4.0 in 1935 and 1961.

The wettest 20th of December (1931-2020) in the EWP data was 18.34 mm (1989), followed by 12.51 mm (2003), 12.26 mm (2012), and 10.06 mm (1983). 

The wettest week ending 20th December (14th - 20th Dec) was 85.22 mm in 1989, followed by 61.67 mm in 2012, 52.86 mm in 2019, 52.41 mm (1993) and 50.81 mm (2018). 

The least amount falling in a week ending 20th December was 0.08 mm in 1961, followed by in 0.40 mm in 2007, 1.80 mm in 1939, 2.05 mm in 1972, 2.07 mm in 1933, 2.14 mm in 1931. 

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

(Today's map link is for 2010, with its coldest readings - although some places had lower minima on 25th than 20th, unlike CET data.) 

https://www.wetterzentrale.de/reanalysis.php?jaar=2010&maand=12&dag=20&uur=1200&var=1&map=1&model=noaa

 

Edited December 21, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield at 5.4C -0.1C below average, Rainfall 61.2mm 69.9% of the monthly average.

[Summer Sun]

6.3c to the 19th

1.5c above the 61 to 90 average
1.4c above the 81 to 10 average

___________________________

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

[johncam]

1 hour ago, Summer Sun said:

6.3c to the 19th

1.5c above the 61 to 90 average
1.4c above the 81 to 10 average

___________________________

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

Could be another above average month again ?

[damianslaw]

Mmm just like November these means seem high to me and am expecting a marked downward correction again. 

Edited December 20, 2021 by damianslaw

[Don]

3 hours ago, johncam said:

Could be another above average month again ?

Yes, could well be but too early to say even this late in the month!

[Roger J Smith]

EWP update _ still stuck on 52 mm but projections now call for 90 mm totals, about 30 mm more by 30th on GFS ten-day, and probably another 10 mm potential on 31st. Still a range of uncertainty, probably 80-110 mm covers it. 

Neither of the two leading models goes for a lot of cold intrusion although it will be a bit colder at times, that plus the probable adjustment leads me to think the finish will be around 5 C. It could go lower then come back up as 30th-31st now looking quite mild. However there's plenty of uncertainty in these outlooks and we have seen colder runs in previous days that might return to action. Cold and snow seem to be confined largely to northern high ground and parts of Scotland at this rate though. Last night's 00z run was a lot colder and would have seen a CET falling into the low 4s. But last night's ECM had a dartboard low northwest of Ireland 27th that has disappeared from the 12z run. 

GEM has been doing okay in recent comparisons and it is considerably colder through the 24th to 29th at least, with a slight warming at the end. It would suggest a 4.5 C outcome for CET (and probably closer to 80 than 110 mm EWP with a southern storm track). 

GFS ensemble spread at 120h to 168h is about average or even less than average indicating that not many ensemble members are buying into a southern track like the GEM and to a lesser extent the ECM. I think the "weighted average" prediction for CET assuming an adjustment of 0.3 is 4.9 C (unadjusted finish 5.2). 

 

[Roger J Smith]

Almanac for 21st December

 

The highest daily mean (1772-2020) was 11.4 in 1971 which narrowly edged out 11.2 set back in 1828. Other mild averages were 10.6 in 1974, 10.5 in 1842, 10.2 in 1985, 10.0 in 1989, 9.9 in 1857 and 1868, 9.8 in 1776 and 2008, and 9.7 in 2015.

The lowest daily mean (1772-2020) was -5.9 in 2010 which replaced -4.7 from 1855. Other low daily means include -4.1 in 1890, -3.8 in 1808, -3.7 in 1816, -3.6 in 1891, -3.2 in 1874 and 1935, -2.8 in 1878, -2.7 in 1935 and 1938, -2.6 in 1886 and 1901, -2.4 in 1807 and 1870, -2.2 in 1799, 1860, 1909.

The highest maximum (1878-2020) was 13.7 in 2015. This replaced 13.2 from 1971. Other mild days include 13.0 in 1991, 12.7 in 1942 and 2014, 12.0 in 1974, 11.9 in 2011, 11.8 in 1986 and 11.6 in 2008 and 2013, 11.5 in 2020 and 11.4 in 1987 and 1989.  

The highest minimum (1878-2020) was 9.6 in 1971 which replaced 8.1 from 1907. Other very mild readings include 9.2 in 1974, 8.6 in 1985 and 1989, 7.9 in 2008, 7.8 in 1908 and 7.6 in 1936, 1987 and 2017.

The lowest maximum (1878-2020) was -1.5 in 1891. Other cold values were -1.2 (2010), -0.9 (1890), -0.1 (1901), 0.6 (1904), 0.8 (1938), 1.0 (1886), 1.1 (1981), 1.3 (1935 and 1956), 1.4 (1895 and 1950), 1.6 (1896) and 1.7 (1878). 

The lowest minimum (1878-2020) was -10.6 in 2010 which replaced -8.2 from 1909 and 1946. Other cold minima include -7.7 in 1935, -7.3 in 1878, -7.2 in 1890, -6.2 in 1886 and 1963, -6.1 in 1938, -5.6 in 1891, -5.1 in 1901 and 1999,-4.4 in 1927, -3.9 in 2009 and -3.8 in 1967. 

The wettest 21st of December (1931-2020) in the EWP data was 24.63 mm (2002), followed by 19.19 mm (1995),  12.90 mm (2012), 11.58 mm (1985), and 10.73 mm (1968). 

The wettest week ending 21st December (15th - 21st Dec) was 75.39 mm in 1989, followed by 58.63 mm in 2012, 53.13 mm in 1968, 52.85 mm in 2018, 51.46 mm in 2013. and 50.77 mm (2019). 

The least amount falling in a week ending 21st December was 0.08 mm in 1961, followed by in 0.46 mm in 2007, 1.23 mm in 1939, 1.41 mm in 1933, 1.75 mm in 1931 and 1.95 mm in 1972. 

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

(Today's map link is for 1909, a cold spell eclipsed by 2010.) 

https://www.wetterzentrale.de/reanalysis.php?jaar=1909&maand=12&dag=21&uur=0600&var=1&map=1&model=noaa

 

Edited December 21, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield down to 5.2C -0.3C below normal. Rainfall 61.3mm 70.1% of the monthly average

[Summer Sun]

6.1c to the 20th

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

___________________________

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

[johncam]

10 hours ago, The PIT said:

Sunny Sheffield down to 5.2C -0.3C below normal. Rainfall 61.3mm 70.1% of the monthly average

Hi Mate , how come the Sheffield avg is above the CET average , I thought it would be the other way round 

[Roger J Smith]

3 hours ago, johncam said:

Hi Mate , how come the Sheffield avg is above the CET average , I thought it would be the other way round 

Actually his report says it is 0.9 deg lower (5.2 vs 6.1). 

[johncam]

1 minute ago, Roger J Smith said:

Actually his report says it is 0.9 deg lower (5.2 vs 6.1). 

Sorry didn't convey that correctly , I meant the normal,  sheffield normal would be 5.5C and CET 4.8C if I am reading it right 

 

 

[Roger J Smith]

Sorry, you were maybe clearer than I thought, the reason then is probably that the PIT is in an urban area and the CET average is adjusted down somewhat to remove urban effects. The PIT is reporting vs end of month average so the differential may get even larger as the CET report is against a running mean 1st to 20th at present. Also maybe the PIT will let us know this, but his "normal" could be 1991-2020 rather than 1981-2010 which would make it warmer. But I think it's mostly the urban setting that accounts for the difference, which as you say should probably be running in the other direction. 

 

[Roger J Smith]

Almanac for 22nd December

 

The highest daily mean (1772-2020) was 11.6 in 1991 which like the previous day's (1971) record narrowly edged out 11.2 again set back in 1828. Other mild averages were 10.8 in 1857, 10.7 in 1974, 10.2 in 1789, 1795 and 2008, 10.1 in 2015, 9.9 in 1842 and 2011, 9.8 in 1776 and 1988, and 9.7 in 1872.

The lowest daily mean (1772-2020) was -6.8 in 1890 which replaced -5.5 from 1874. Other low daily means include -5.3 in 1870, -4.9 in 1816, -3.8 in 1891, -3.5 in 1901, -3.3 in 1860, -2.5 in 1779, -2.4 in 1878, and -2.1 in 2010.

The highest maximum (1878-2020) was 13.8 in 2015. This replaced 13.2 from 1991 which had replaced 12.1 from 1967. Other mild days include 12.7 in 2012, 12.3 in 2014, 12.0 in 1980, 11.9 in 1974, 11.8 in 1985, 11.7 in 2004, 11.6 in 2008 and 2011, and 11.5 in 1977.

The highest minimum (1878-2020) was 10.0 in 1991 which replaced 9.5 from 1942 and 1974. Other mild minimum readings were 8.9 in 2008, 8.6 in 1988, 8.3 in 2011, 7.8 in 2017, and 7.5 in 1908.

The lowest maximum (1878-2020) was -1.5 in 1891. Other cold values were -1.0 (1901), -0.9 (1890), 0.2 (1904), 0.3 (2010), 0.4 (1981), 1.2 (1887 and 1950), and 1.7 (1878 and 2009). 

The lowest minimum (1878-2020) was -12.6 in 1890. Other cold minima include -7.0 in 1946, -6.5 in 1878, -6.1 in 1935, -6.0 in 1891, -5.9 in 1901, -4.8 in 1963, -4.5 in 2010, -4.4 in 2009, -4.2 in 1886 and -4.1 in 1938.

The wettest 22nd of December (1931-2020) in the EWP data was 16.48 mm (1965), followed by 15.63 mm (2012), 13.79 mm (1967), and 12.15 mm (1995). 

The wettest week ending 22nd December (16th - 22nd Dec) was 71.93 mm in 2012, followed by 62.59 mm in 1989, and 58.43 mm in 1995. 

The least amount falling in a week ending 22nd December was 0.24 mm in 1961, followed by 0.62 mm in 1972, 0.81 mm in 1933, 0.84 mm in 1931, 1.00 mm in 1939, 1.42 mm in 2007, and 1.70 mm in 1948. 

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

(Today's map link is for 1890 for a second time, with that month's coldest day.) 

https://www.wetterzentrale.de/reanalysis.php?jaar=1890&maand=12&dag=22&uur=0600&var=1&map=1&model=noaa

Edited December 22, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield down to 5.1C -0.3C below normal. Rainfall unchanged.

[Summer Sun]

6.0c to the 21st

1.2c above the 61 to 90 average
1.2c 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]

EWP last reported at 53 mm, looks to add around 35 mm on average to end of month, outcome near 90 mm. 

After some hints of colder weather on model runs, latest guidance looks very mild at times so perhaps a finish near 6.5 C before corrections, maybe they will just say 5.9 and end the wait. 

[summer blizzard]

Yikes, much milder than I thought. Very uneventful too.

[Don]

37 minutes ago, Roger J Smith said:

EWP last reported at 53 mm, looks to add around 35 mm on average to end of month, outcome near 90 mm. 

After some hints of colder weather on model runs, latest guidance looks very mild at times so perhaps a finish near 6.5 C before corrections, maybe they will just say 5.9 and end the wait. 

Think my 4.7C guess is down the bog now!

[Roger J Smith]

Well the 12z GFS is colder again, would support a finish in the low 5 area, so high fives all around. 

They still bring in the very mild air on the 31st but most of the period 24th to 30th is fairly cool -- it has been a nightmare coming up with forecasts for the Christmas week out of these constantly changing model runs and lack of consensus. 

The EWP rise looks a bit more nailed on, cold or mild it's likely to rain or sleet a fair amount of the time.