April 2021 C.E.T. and EWP forecast contests

[North-Easterly Blast]

10 minutes ago, summer blizzard said:

Probably looking at March 13 in terms of 91-10 anomoly.

Not quite I do not think.  I think that March 2013 was around 3.9*C below the 1981-2010 mean and 3*C below 1961-90.  For April 2021 to have such a large anomaly from the most recent average, I think it would need a CET in the low 5s, of which there is no way that it will be that low.

[Roger J Smith]

Does anybody have a link to any list of official 1981-2010 CET normals? I have these calculated from averages of 30 monthly means ... but some could be rounded differently from the CET official data which is calculated from average max and min (I've found it only makes a difference if the monthly averages are very close to a rounding point like between x.45 and x.55.)

My version is 

__________ JAN _ FEB _ MAR _ APR _ MAY _ JUN _ JUL _ AUG _ SEP _ OCT _ NOV _ DEC _ YEAR 

__ 2 dec _ 4.44_ 4.39_ 6.58_ 8.52_11.66_14.48_16.71_16.41_14.03_10.69_ 7.14_ 4.63 _ 9.97

_>1 dec __ 4.4 __ 4.4 __ 6.6 __ 8.5 _11.7 _14.5 _16.7 __ 16.4 _ 14.0 _10.7 __ 7.1 _ 4.6 __ 10.0

____________________________________________________________________________

anyway, based on those the months that are 1.0 or more below 1981-2010 normals since Jan 2011 include these:

Jan 2021 (3.1) ______________________________________ -1.3

Feb 2013 (3.2) and Feb 2018 (2.9) __________________ -1.2, -1.5

Mar 2013 (2.7) Mar 2018 (4.9) ______________________ -3.9, -1.7

Apr 2012 (7.2) Apr 2013 (7.5) Apr 2016 (7.5) ________ -1.3, -1.0, -1.0

May 2013 (10.4) ____________________________________ -1.3

June 2012 (13.5) ____________________________________ -1.0

July 2011 (15.2) July 2012 (15.5) July 2020 (15.7) ____ -1.5, -1.2, -1.0

Aug 2011 (15.4) Aug 2014 (14.9) ____________________ -1.0, -1.5

Sep 2012 (13.0) Sep 2015 (12.6) ____________________ -1.0, -1.4

Oct 2012 (9.7) ______________________________________ -1.0

Nov 2016 (5.6) ______________________________________ -1.5

__________________________

(note that no Dec made the list, in fact no Dec was even below 4.6)

The coldest year was 2013 (9.6) followed by 2012 (9.7).  (-0.4 and -0.3)

___________________________

Obviously we're not going to be using 10-year normals, but if there was such a thing, this would be it for 2011-20:

4.8 _ 5.1 _ 6.6 _ 9.1 _12.0 _14.7 _16.7 _16.4 _14.1 _11.3 _ 7.6 _ 6.1 _ 10.4

 

 

 

[Relativistic]

On 26/04/2021 at 13:58, Relativistic said:

Ten days later and the provisional figure is 1.6C, so a mean of 4.6C for the remaining four days would take us to 2.0C. Current forecasts suggest that this is unlikely to happen now, and that April 2021 could join one of only four other Aprils to record a sub-2C minimum CET -- the first to do so in 99 years.

Precisely where we end up in the rankings will depend on the magnitude of the end-of-month correction.

The provisional figure to the 30th is 1.8C. Unless we get an upward correction this will put us comfortably in the top five since the record began. Last time we made the top five for any month was in March 2013 which placed joint-fifth. The last top-10 finish was in September 2015, placing joint-eighth.

[summer blizzard]

36 minutes ago, North-Easterly Blast said:

Not quite I do not think.  I think that March 2013 was around 3.9*C below the 1981-2010 mean and 3*C below 1961-90.  For April 2021 to have such a large anomaly from the most recent average, I think it would need a CET in the low 5s, of which there is no way that it will be that low.

I was speaking on reference to the most recent month to exceed our anomoly.

[Don]

3 hours ago, Froze were the Days said:

Amazing how the anomaly has stayed the same for the 61-90 series over the last few days...it's certainly been colder than average here by day and night. I think we'll see a downward correction for the final figure at the end of the month making it one of the coldest anomaly months over the last few years.

Defo going to be the coldest April since at least 1989 and maybe 1986.

Edited April 30, 2021 by Don

[damianslaw]

1 hour ago, Don said:

Defo going to be the coldest April since at least 1989 and maybe 1986.

Chance will beat 1989 with downward corrections, never thought I'd say that given how mild April has been over many recent years, a month not prone to sustained cold I thought, but goes to show the variability of our weather.. oddities pop up unexpected..

Expect a final figure either 6.5 or 6.6 degrees, not much above the growing mean temp of 6 degrees, no wonder grass and leaf growth is so slow this year, suspect much of the north will return means below the 6 degree figure.. akin to many a winter month in recent years.

[Roger J Smith]

The EWP appears to have ended up near 13 mm, it was 12 mm to 29th and the grid average for 30th appears to be close to 1 mm. 

We never see a provisional update for the CET to last day of month because the final number replaces it, but that hasn't happened yet, looking at the temperatures around the CET region yesterday I would say the value of 6.91 to 29th hasn't changed much, even 8.0 (which is higher than I would expect) only changes that to 6.94 so it stays 6.9, while 6.0 reduces it to 6.88. Of course the more significant question is, what will the official value be? I will guess 6.7. 

[Weather-history]

Looks like it could be the coldest April on record that was so dry. There is only one in the list I posted a few days ago that is in the top 30 driest Aprils on record that had a CET was below 7.0C.

An unusual combination.

 

[Roger J Smith]

Yes was that 1806? Just going by memory because I had a bit of a similar post back in the middle of the month. Only two of the driest Aprils were much under 40 mm, one around 20 and one around 30. And of course 2007 and 2011 are in the list of dry Aprils, many of the others IIRC were average in CET for their time and would seem a bit cool nowadays (around 8-8.5 seemed to be popular). 

[Roger J Smith]

If the EWP tracker holds up later (5th May is when a final value will be declared), any value from 11.6 mm (2011) to 14.1 mm (1854) will fall into a gap to become 10th driest May. This was a list wx-history posted earlier of the 30 driest Aprils with their CET values ... I have bolded the ones that were colder than 7.2 C. ... I also added the 2021 provisionals which I will edit when possible. That makes the list 31 years. 

10 driest with 2021 _________ 10th to 19th driest before 2021 ___ 20th to 29th driest before 2021

 

1938: 7.6  (7.1mm) __________ 1854: 9.2  (14.1mm) ____________ 1852: 8.2  (20.1mm) 

1817: 7.6  (7.9mm) __________ 1842: 7.8 (14.3mm) _____________ 1870: 9.2  (21.5mm)

1912: 8.8 (9.0mm) ___________ 1974: 8.2 (14.3mm) _____________ 1801: 8.3  (21.6mm)

1957: 8.9  (9.7mm) ___________ 1783: 10.1 (15.2mm) ___________ 1776: 9.4  (22.4mm)

1893: 10.3 (9.9mm) __________ 1954: 7.6  (16.1mm) ____________ 1807: 7.7  (22.9mm)

1785: 8.4  (10.1mm) _________ 1844: 9.8  (16.6mm) _____________ 1778: 8.2  (23.0mm)

2007: 11.2 (10.4mm) _________ 1980: 8.8  (17.5mm) _____________1873: 7.7  (23.1mm)

1984: 8.1 (10.8mm) ___________ 1976: 8.1  (19.0mm) ____________ 1997: 9.0  (23.7mm)

2011: 11.8 (11.6mm) __________ 1855: 7.1  (19.9mm) ____________1840: 9.7  (24.2mm)

2021: 6.4 (c13.0 mm) _________ 2017: 8.9  (19.9mm) ____________ 1982: 8.6 (25.4mm)

and former 30th driest, now 31st _______________________________ 1806: 6.8 (26.8mm)

________________________________________

2021 also finds its way into this table, which is re-organized by ranks in terms of how much April went colder than March ... for now I have parked it in the middle of the table. There were only 14 Aprils colder than preceding March, now it looks like 15 (two more were equal CET). Now confirmed as 6.4 which moves 2021 up the table into a three-way tie for fifth largest drop in CET March to April.

 

(0.5 or more colder) ___________________________ (0.0 to 0.4 colder)

YEAR ____ MAR __ APR __________________ YEAR ____ MAR __ APR

 

1780 ____ 7.9 ____ 6.3 _ (-1.6) ____________1790 ____ 6.4 ___ 6.1 _ (-0.3)

1938 ____ 9.1 ____ 7.6 _ (-1.5) ____________1957 ____ 9.2 ___ 8.9 _ (-0.3)

2012 ____ 8.3 ____ 7.2 _ (-1.1) ____________1990 ____ 8.3 ___ 8.0 _ (-0.3)

1989 ____ 7.5 ____ 6.6 _ (-0.9) ____________1978 ____ 6.7 ___ 6.5 _ (-0.2)

1809 ____ 6.0 ____ 5.2 _ (-0.8) ____________1998 ____ 7.9 ___ 7.7 _ (-0.2)

1936 ____ 7.1 ____ 6.3 _ (-0.8) ____________1981 ____ 7.9 ___ 7.8 _ (-0.1)

2021 ____ 7.2 ____ 6.4 _ (-0.8)

1903 ____ 7.1 ____ 6.4 _ (-0.7) ____________1702 ____ 5.8 ___ 5.8 _ (-0.0)

1750 ____ 8.2 ____ 7.7 _ (-0.5) ____________1991 ____ 7.9 ___ 7.9 _ (-0.0)

 

 

 

Edited May 1, 2021 by Roger J Smith

[Midlands Ice Age]

21 hours ago, Roger J Smith said:

Does anybody have a link to any list of official 1981-2010 CET normals? I have these calculated from averages of 30 monthly means ... but some could be rounded differently from the CET official data which is calculated from average max and min (I've found it only makes a difference if the monthly averages are very close to a rounding point like between x.45 and x.55.)

My version is 

__________ JAN _ FEB _ MAR _ APR _ MAY _ JUN _ JUL _ AUG _ SEP _ OCT _ NOV _ DEC _ YEAR 

__ 2 dec _ 4.44_ 4.39_ 6.58_ 8.52_11.66_14.48_16.71_16.41_14.03_10.69_ 7.14_ 4.63 _ 9.97

_>1 dec __ 4.4 __ 4.4 __ 6.6 __ 8.5 _11.7 _14.5 _16.7 __ 16.4 _ 14.0 _10.7 __ 7.1 _ 4.6 __ 10.0

____________________________________________________________________________

anyway, based on those the months that are 1.0 or more below 1981-2010 normals since Jan 2011 include these:

Jan 2021 (3.1) ______________________________________ -1.3

Feb 2013 (3.2) and Feb 2018 (2.9) __________________ -1.2, -1.5

Mar 2013 (2.7) Mar 2018 (4.9) ______________________ -3.9, -1.7

Apr 2012 (7.2) Apr 2013 (7.5) Apr 2016 (7.5) ________ -1.3, -1.0, -1.0

May 2013 (10.4) ____________________________________ -1.3

June 2012 (13.5) ____________________________________ -1.0

July 2011 (15.2) July 2012 (15.5) July 2020 (15.7) ____ -1.5, -1.2, -1.0

Aug 2011 (15.4) Aug 2014 (14.9) ____________________ -1.0, -1.5

Sep 2012 (13.0) Sep 2015 (12.6) ____________________ -1.0, -1.4

Oct 2012 (9.7) ______________________________________ -1.0

Nov 2016 (5.6) ______________________________________ -1.5

__________________________

(note that no Dec made the list, in fact no Dec was even below 4.6)

The coldest year was 2013 (9.6) followed by 2012 (9.7).  (-0.4 and -0.3)

___________________________

Obviously we're not going to be using 10-year normals, but if there was such a thing, this would be it for 2011-20:

4.8 _ 5.1 _ 6.6 _ 9.1 _12.0 _14.7 _16.7 _16.4 _14.1 _11.3 _ 7.6 _ 6.1 _ 10.4

 

 

 

Also of interest (to me)...

What would be the coldest annual year figure based upon the  coldest of the monthly figures?

My guess would be about 8.6C.

Which just goes to show what a year 2010 was to come in below 9.0C. (8.96C from memory).

MIA

 

[Roger J Smith]

Do you mean, what is the average of the coldest months quoted 2011-2021? That would be 8.6 as you say. 

[Midlands Ice Age]

11 minutes ago, Roger J Smith said:

Do you mean, what is the average of the coldest months quoted 2011-2021? That would be 8.6 as you say. 

Yep..

Your listing did not have the coldest figure for Dec (so I assumed) 2.0C) and used that.

I looked and saw you were still logged on,  so I used your brain, rather than sorting it out for myself.

PS Are you still in Canada? In case what time do you go to bed?

MIA   

Edited May 1, 2021 by Midlands Ice Age

[Roger J Smith]

The coldest for DEC was 4.8, just a straight average of the twelve coldest values 2011-21 was 8.55, a weighted average may be different. (I edited in was 8.55 because now it's 8.48 thanks to Apr 2021) And yes I'm in the Pacific time zone where it is eight hours behind BST, currently about 0300h. On the night of the first of each month I am often up all night scoring U.S. contest that I run, and updating other things, which is okay because I often sleep a few hours in the evening here and have rather short sleeps anyway (pushing 72 years of age). But it gets really off schedule around contest deadlines. 

Edited May 1, 2021 by Roger J Smith

[damianslaw]

Touch and go whether we equal 1989 or go below.. will depend on extent of any downward corrections, a reduction of 0.4 degrees is needed, not an easy task but not unheard of.. think we've had 0.5 drops.. Oct 2019 springs to mind.. 

[Weather-history]

Crikey

CET minimum is down as 1.0C!

Coldest ever recorded, well since at least 1878

https://hadleyserver.metoffice.gov.uk/hadcet/mly_cet_min_sort.txt

 

Edited May 1, 2021 by Weather-history
.

[Weather-history]

2 minutes ago, damianslaw said:

Touch and go whether we equal 1989 or go below.. will depend on extent of any downward corrections, a reduction of 0.4 degrees is needed, not an easy task but not unheard of.. think we've had 0.5 drops.. Oct 2019 springs to mind.. 

6.4C it is

https://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat

[snowray]

So is that 0.4c downward correction then. Wow.

[damianslaw]

2 minutes ago, Weather-history said:

6.4C it is

https://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat

Well, a significant correction then.. not unexpected has to be said. Coldest since 1986.. long time since we've had a month at least 30 years colder than previous ones.. March 2013 last time I think... correct if wrong.

Puts 1986 into perspective, the persistent clear skies whilst allowing exceptionally sustained cold nights also helped to boost temps by day.. but most places failed to see many days topping out above average maxima..

A highly abnormal April in all respects.. did anyone see such a dry sunny cold April on the cards... wonder if we can put it down to effects of SSW, and coming out of solar minima combined with weak la Nina state which often promotes northerlies in April.. think 2008.

[snowray]

Was thinking in terms of SSW effect, in fact went cold for both Feb and March but gave up on that for April and went way too mild in the end.

[Weather-history]

First April at least 1.0C below the 1961-90 mean average since that average came into existence, 30 years ago. 

And it is all down to the minimum, that was nearly 3.0C below the average. 

 

[Derecho]

32 minutes ago, Weather-history said:

6.4C it is

https://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat

Nice! Thought there would be a decent downwards correction this month. 

[BornFromTheVoid]

At 6.4C, April 2021 was the 36th coldest in a record dating back to 1659. It was also:
2.6C below the 91-20 average
1.5C below the 61-90 average
1.7C below the 20th century average
1.5C below the 18th century average

Compared with 1991-2020 average, 3 days were above average and 27 days were below. Three days were in the top 10 coldest, but no daily records were set.

At 1.0C, the mean minimum for April was the coldest on record, beating the previous record of 1.4C in 1917. Three daily low minima records were set, -3.3C, -2.0C and -2.3C on the 7th, 12th and 13th (previous records were -3.0C, -1.7C and -1.4C). At ten, April 2021 had the 2nd most sub 0C minima on record, beaten only by 1917 with 12.

No daily maxima records were set

Edited May 1, 2021 by BornFromTheVoid

[Walsall Wood Snow]

At 6.4c April 2021 shares the same mean CET with April's:

1699

1700

1740

1772

1839

1849

1903

1941

 

 

 

 

 

 

 

[North-Easterly Blast]

Well last month was a cause of celebration in that it has given us the first significantly below average April (first sub 7*C) in 32 years.  The absence of cold Aprils in recent times is certainly a remarkable statistic when you consider that between 1990 and 2020 the April CET was never lower than 7.2.  A 32 year run without the April CET going under 7*C (or 7.2 to be precise) is unprecedented in the 360+ year long record.  The April 2021 CET was 6.43*C to be precise.  The mean minimum was also the coldest in the list since 1878, although prior to that in the CET record we cannot be certain that it was the lowest ever.  The absence of cold Aprils must be the most remarkable of most if not any month in the year in the last 30 odd years, and congratulations that we have finally cracked it.