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

[February1978]

8.7c and 73mm please

[Duncan McAlister]

A cold-ish month 2008-style. 7.9

[Don]

Despite some very cold model outputs currently, I'm not convinced April will be a cold month overall.

I will go with a CET of 9.1C and EWP of 75mm, please.

I think a cold start/first half will be more than offset by warmer weather later on.  It wouldn't surprise me if we get a very warm spell during the second half of the month with temperatures in the mid twenties, particularly but not exclusively in the south!

As always, we will see......

[damianslaw]

Please could someone post date low max temp records for 5th and 6th April. Good chance these could be smashed in Scotland at least. BBC going for max 2 degrees Aberdeen and widely much of the day below freezing on 5th. 

[Roger J Smith]

^^^ all on time

 

Whistle blows for extra time. 

 

vvv Extra time ...

_____________________________________________________

Not quite an answer to the above question, but the record low CET values for 5th and 6th are 0.4 and 0.8, both from 1911.

This is the weather map for April 5 1911 at 06z (wetterzentrale NOAA archives) -- more of an easterly in this case. 

https://www.wetterzentrale.de/reanalysis.php?map=1&model=noaa&var=1&jaar=1911&maand=04&dag=05&uur=0600&h=0&tr=360&nmaps=24#mapref

 

 

[Roger J Smith]

Since 1950, these are the coldest mean daily CET values (with 2.4 the cutoff): 

14th 1966 ___ 0.5 (broke a daily record of 0.6 from 1816)

 2nd 1968 ___ 1.1 (directly followed very mild end of March, cold first half, warm second half)

11th 1978 ___ 1.3

15th 1966 ___ 1.4

 3rd 1958 ___ 1.6

 9th 1973 ___ 1.7

 6th 2008 ___ 1.7 (mean first four days April was 10.3)

 7th 1986 ___ 1.8 (also 2.8 on 11th)

10th 1978 ___ 1.9

 1st 2013 ___ 1.9

 1st 1970 ___ 2.3 (also 2.5 on 9th)

 6th 1975 ___ 2.4

 5th 1989 ___ 2.4

 4th 1990 ___ 2.4

__________________________________________________________________________________________________________________

The only sub-zero CET daily means in April come from early (1st-2nd) 1917 (-0.2, -0.5) and (1st, 3rd) 1799 (0.0, -0.5), plus an outlier, 19th 1772 (-0.2). 

Very late April extremes are 0.7 (29th 1856) and 0.5 (24th 1908).  A notable cold week was 8th-14th 1837 (avg 2.0, min 0.5 on 10th).

[pegg24]

9.4c 85 mm please 

[Weather-history]

5 hours ago, damianslaw said:

Please could someone post date low max temp records for 5th and 6th April. Good chance these could be smashed in Scotland at least. BBC going for max 2 degrees Aberdeen and widely much of the day below freezing on 5th. 

In 1911 around those dates, it was reported that it was -2.1C at Hampstead Observatory at midday.

5th April 1911

Brighton: 1C 

Weybridge: 1.2C

Tunbridge Wells: -1C

Ulcombe Place: 0C

Southgate: 1.5C

Totland Bay: 1.4C

The CET daily mean
5th April 1911: 0.4
6th April 1911: 0.8

 

 

[BLAST FROM THE PAST]

8.1c and 50mm

 

BFTP

Edited April 1, 2021 by BLAST FROM THE PAST

[BornFromTheVoid]

First projections for April

  

The chances of finishing:
Close to average (8.5C to 9.5C) is 22.2% 
Above average (>9.5C) is 6.0% 
Below average (<8.5C) is 71.8% 

GFS for the 1st to 6th looks like averaging about 5.8C, or 2.3C above the 91-20 average

[damianslaw]

Colder air has arrived bang on cue first day of the new month. 

[Timmytour]

1 hour ago, BornFromTheVoid said:

First projections for April

  

The chances of finishing:
Close to average (8.5C to 9.5C) is 22.2% 
Above average (>9.5C) is 6.0% 
Below average (<8.5C) is 71.8% 

GFS for the 1st to 6th looks like averaging about 5.8C, or 2.3C above the 91-20 average

I look at the models and think below average.

I look at this, remember the last two months, and think something above 10.5C has to be the form horse!

[Roger J Smith]

April CET extremes and 1981-2010 averages, extreme values of running CET

 

DATE ___ MAX yr _________ MIN yr ________ CET __cum CET ____ Max CET __ Min CET

01 Apr ... 13.3 (1995) ........--0.2 (1917) _________8.3 _____ 8.3 ____ 13.3 (1995) __--0.2 (1917)
02 Apr ... 13.9 (1835) ........--0.5 (1917) _________8.1 _____ 8.2 ____ 13.1 (2011) __--0.35 (1917)

03 Apr ... 15.0 (1926,1946) ..--0.5 (1799) _______7.4 _____ 7.9 ____ 12.9 (1926) __--0.1 (1917)
04 Apr ... 15.6 (1946)......... 1.0 (1809&1830) ___ 7.1 _____ 7.7 ____ 13.6 (1946) __ 0.5 (1799&1917)
05 Apr ... 13.3 (1857) ......... 0.4 (1911) _________ 7.1 _____ 7.6 ____ 12.9 (1926) __ 1.2 (1917)

06 Apr ... 15.1 (2011) ......... 0.8 (1911) _________ 7.5 _____ 7.6 ____ 12.8 (1926) __ 1.4 (1917)
07 Apr ... 14.7 (1859) ......... 1.0 (1839) _________ 7.3 _____ 7.5 ____ 12.6 (1926) __ 1.7 (1917)
08 Apr ... 13.0 (2020) ......... 2.4 (1780) _________ 7.2 _____ 7.5 ____ 12.2 (1926) __ 2.0 (1917)
09 Apr ... 13.7 (2017) ......... 1.4 (1812) _________ 7.5 _____ 7.5 __ 11.8 (1926,2011) _ 2.2 (1917)
10 Apr ... 14.1 (2020) ......... 0.5 (1837) _________ 8.2 _____ 7.6 ____ 11.8 (2011) __ 2.1 (1917)

11 Apr ... 16.0 (1869) ......... 1.3 (1978) _________ 8.0 _____ 7.6 ____ 11.7 (2011) __ 2.1 (1917)

12 Apr ... 14.4 (1939) ......... 1.1 (1879) _________ 7.8 _____ 7.6 ____ 11.4 (2011) __ 2.3 (1917)
13 Apr ... 14.6 (1792) ......... 1.1 (1816) _________ 7.5 _____ 7.6 ____ 11.2 (1778) __ 2.4 (1917)
14 Apr ... 16.1 (1869) ......... 0.5 (1966)*_________8.0 _____ 7.7 ____ 11.0 (2011) __ 2.6 (1917) _ *(also 0.6 1816)
15 Apr ... 16.3 (1945) ......... 1.4 (1966) _________ 8.3 _____ 7.7 ____ 11.0 (2011) __ 2.6 (1917)

16 Apr ... 17.0 (1945) ......... 2.0 (1892) _________ 8.5 _____ 7.7 ____ 11.0 (2011) __ 2.8 (1917)
17 Apr ... 14.9 (1865) ......... 2.1 (1793&1812) ___8.4 _____ 7.8 __ 11.0 (1945.2011) _ 2.8 (1917)
18 Apr ... 17.0 (2018) ......... 1.7 (1807) _________ 8.1 _____ 7.8 ____ 11.2 (1945) __ 3.0 (1917)
19 Apr ... 17.6 (2018) .........--0.2 (1772) _________8.1 _____ 7.8 ____ 11.4 (1945) __ 3.2 (1837)
20 Apr ... 16.6 (1893) ......... 2.3 (1849) _________ 8.4 _____ 7.8 ____ 11.5 (1945) __ 3.3 (1837)

21 Apr ... 16.4 (1893) ......... 2.4 (1936) _________ 9.2 _____ 7.9 __ 11.5 (1945.2011) _ 3.3 (1837)
22 Apr ... 15.4 (2011) ......... 3.4 (1778) _________ 9.4 _____ 8.0 ____ 11.6 (2011) __ 3.5 (1837)
23 Apr ... 15.9 (1874) ......... 2.6 (1908) _________ 9.7 _____ 8.1 ____ 11.8 (2011) __ 3.6 (1837)
24 Apr ... 15.3 (2007) ......... 0.5 (1908) _________ 9.7 _____ 8.1 ____ 11.9 (2011) __ 3.7 (1837)
25 Apr ... 15.9 (1821) ......... 1.8 (1908) ________ 10.1 _____ 8.2 ____ 11.9 (2011) __ 3.9 (1837)

26 Apr ... 16.1 (1928) ......... 3.3 (1981) ________ 10.1 _____ 8.3 ____ 11.8 (2011) __ 4.1 (1837)
27 Apr ... 16.5 (1866) ......... 2.7 (1919) ________ 10.1 _____ 8.3 ____ 11.8 (2011) __ 4.2 (1837)
28 Apr ... 16.9 (1775) ......... 3.0 (1826) _________ 9.9 _____ 8.4 ____ 11.7 (2011) __ 4.4 (1837)
29 Apr ... 19.7 (1775) ......... 0.7 (1856) _________ 9.9 _____ 8.4 ____ 11.7 (2011) __ 4.5 (1837)
30 Apr ... 17.4 (1775) ......... 2.6 (1945) ________ 10.5 _____ 8.5 ____ 11.8 (2011) __ 4.7 (1701&1837)*

* Min CET on 30th from monthly averages, no daily data for 1701 otherwise. 

(14.7 on 11th 2020 not a record but warmest of the month, min daily mean was 4.9 on 1st)

===========================================================================

1991-2020 CET daily averages and running means

1 __ 8.3 _ 8.3 ___ _ 6 __ 8.3 _ 8.1 ___ _ 11 __ 8.4 _ 8.2 ______ 16 __ 8.6 _ 8.3 ___ _ 21 __10.0 _ 8.5 ___ _ 26 __10.0 _ 8.8

2 __ 8.5 _ 8.4 ___ _ 7 __ 8.0 _ 8.1 ___ _ 12 __ 8.3 _ 8.2 ______ 17 __ 8.8 _ 8.3 ___ _ 22 __10.2 _ 8.5 ___ _ 27 __ 9.7 _ 8.8

3 __ 8.0 _ 8.3 ___ _ 8 __ 8.1 _ 8.1 ___ _ 13 __ 7.8 _ 8.2 ______ 18 __ 8.6 _ 8.3 ___ _ 23 __10.5 _ 8.6 ___ _ 28 __ 9.6 _ 8.9

4 __ 7.7 _ 8.1 ___ _ 9 __ 8.5 _ 8.2 ___ _ 14 __ 8.4 _ 8.2 ______ 19 __ 8.8 _ 8.3 ___ _ 24 __10.6 _ 8.7 ___ _ 29 __ 9.7 _ 8.9

5 __ 8.0 _ 8.1 ___ _10__ 8.7 _ 8.2 ___ _ 15 __ 8.6 _ 8.2 ______ 20 __ 9.2 _ 8.4 ___ _ 25 __10.6 _ 8.8 ___ _ 30 __10.2 _ 8.95

(waiting to see if UK Met Office calls the 1991-2020 mean 8.9 or 9.0, calculations are right on the cusp)

... note the rather prominent warm spell in the 1991-2020 data from 21st to 25th, after which somewhat cooler

near end of April, although running mean continues a slow rise. 

[BornFromTheVoid]

Looks like the record minimum for the 6th could be within reach. It's currently -2.4C, and the forecast looks set to be about -2C.

[Roger J Smith]

These Aprils were colder than or same CET,  as March preceding them ... full list in reverse chronological order. 

The more notable cases are in the first of two columns.

 

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

YEAR _______ MAR __ APR __________________ YEAR _______ MAR __ APR

 

2012 _______ 8.3 ____ 7.2 _ (-1.1) ____________ 1998 _______ 7.9 ___ 7.7 _ (-0.2)

1989 _______ 7.5 ____ 6.6 _ (-0.9) ____________ 1991 _______ 7.9 ___ 7.9 _ (-0.0)

1938 _______ 9.1 ____ 7.6 _ (-1.5) ____________ 1990 _______ 8.3 ___ 8.0 _ (-0.3)

1936 _______ 7.1 ____ 6.3 _ (-0.8) ____________ 1981 _______ 7.9 ___ 7.8 _ (-0.1)

1903 _______ 7.1 ____ 6.4 _ (-0.7) ____________ 1978 _______ 6.7 ___ 6.5 _ (-0.2)

1809 _______ 6.0 ____ 5.2 _ (-0.8) ____________ 1957 _______ 9.2 ___ 8.9 _ (-0.3)

1780 _______ 7.9 ____ 6.3 _ (-1.6) ____________ 1790 _______ 6.4 ___ 6.1 _ (-0.3)

1750 _______ 8.2 ____ 7.7 _ (-0.5) ____________ 1702 _______ 5.8 ___ 5.8 _ (-0.0)

__________________________________________________________

So only fourteen times out of 362 saw a decrease, two more stayed on the same value, and long intervals without any cases at all, such as 1810 to 1902, and all years before 1702. 

The phenomenon has become more common recently, and occurred three times in a row 1989 to 1991. Of the 16 cases, half were in the recent past (1957 to 2012). Two more were in the 1930s.

1743 only warmed by 0.1 (5.3 to 5.4) which is the coldest March to see that small an increase into April.

The two warmest Marches (1957, 1938) are in the list, along with other warm cases like 2012, 1990 and 1750.

Edited April 1, 2021 by Roger J Smith

[summer blizzard]

It is interesting to see that it has become more common (though i doubt it will occur this year with March being closer to average). It perhaps reflects changes to the late season polar vortex/final warming caused by climate change.

[Kentish Man]

A one day late 7.2C please

[feb1991blizzard]

Must admit i always have reservations about losing my order of entry for small changes late, sort of regretting my change now for only half a degree but no way am i doing another change and getting a late penalty on top of losing my place, realistically i need it to be significantly below average (around 7c) after the first half of month just to keep me even in with a shout.

Edited April 2, 2021 by feb1991blizzard

[Summer Sun]

8.8c to the 1st

1.9c above the 61 to 90 average
0.5c above the 81 to 10 average

___________________________

Current high this month 8.8c on the 1st
Current low this month 8.8c on the 1st

[BornFromTheVoid]

The current FI GFS outlook would have the CET in the low 5s (~5.3C) by mid month. Something that hasn't happened since 1986.
As remarkably cold as that sounds, it still wouldn't even enter the top 20 coldest first halves of April.

[damianslaw]

Could someone post the date maximum lows for England and Wales, and also Scotland for April. Chance might see date record on Monday go in Scotland I think.. normally we are speculating about date max records rather than minimum records..

[Roger J Smith]

This was posted during the last few days of March in the March CET thread to keep the flow of forecasts here going, but now I think it's safe to put it here. This is a table of the colder first half CET values for Aprils since 1950. 

 

YEAR ___________ 1-15 Apr CET _____ March CET _ April CET

2013 ____________ 5.8 _________________ 2.7 _______ 7.5

2012*____________6.6 _________________ 8.3 _______ 7.2

2008 ____________ 6.7 _________________ 6.1 _______ 7.9

2000 ____________ 5.6 _________________ 7.6 _______ 7.8

1998*____________6.7 _________________ 7.9 _______ 7.7

1996 ____________ 6.5 _________________ 4.5 _______ 8.5

1994 ____________ 5.8 _________________ 7.7 _______ 8.1

1990 ____________ 6.7 _________________ 8.3 _______ 8.0

1989*___________ 6.5 _________________ 7.5 _______ 6.6

1986 ____________ 4.4 _________________ 4.9 _______ 5.8 

1984 ____________ 5.6 _________________ 4.7 _______ 8.1

1983 ____________ 5.6 _________________ 6.4 _______ 6.8

1978 ____________ 5.4 _________________ 6.7 _______ 6.5

1977 ____________ 6.2 _________________ 6.9 _______ 7.2 

1975 ____________ 5.6 _________________ 4.8 _______ 8.3

1973 ____________ 6.3 _________________ 6.2 _______ 7.0

1970 ____________ 4.7 _________________ 3.7 _______ 6.7

1968*____________4.9 _________________ 6.3 _______ 8.1

1967 ____________ 6.6 _________________ 7.0 _______ 7.7

1966 ____________ 6.0 _________________ 6.5 _______ 7.2

1964 ____________ 6.8 _________________ 4.3 _______ 8.7

1962 ____________ 6.5 _________________ 2.8 _______ 7.7

1958 ____________ 4.6 _________________ 3.7 _______ 7.4

1953 ____________ 6.5 _________________ 5.6 _______ 7.3

1951 ____________ 6.1 _________________ 4.1 _______ 6.8

averages ________ 5.95 ________________ 5.8 _______ 7.5

_________________________________________________

* had a warm spell in late March (see table of those in March thread)

25 of the past 70 Aprils have begun with a first half of 6.8 or colder. 

They tended to follow the colder Marches in general with a few exceptions like 1990, 2012.

The frequency has dropped off, only 4 of the past 21 (7.5 expected from the 25/70 rate).

The severity has also dropped, with most sub-6.0 cases in the first half of the interval. 

1986 was the most recent sub-5.0 first half of April. 

The all-time lowest first half (since 1772) was 2.6 in 1917 followed by 2.9 in 1837. 

A recent benchmark is a running mean CET of 3.8 on 8th of 1986. (3.7 to 8th of 1968).

 

 

[summer blizzard]

I don't recall the first half of 2013 being that cold, at least compared to 2012.

That said our targets are simple. 2013, 2000, 1986.

[Roger J Smith]

Many but not all from the deeper past of the CET records, these are the bottom 15 first half CET values ... added some very cold Aprils from years before 1772 without daily values, these were quite likely within the range of a bottom 15-20 list at the midway point too.

Rank __ Year ___ CET 1-15 __ CET 1-30

_ 01 ___ 1917 ____ 2.6 _______ 5.4 (tied 5th coldest)

_ 02 ___ 1837 ____ 2.9 _______ 4.7 (tied coldest)

_ 03 ___ 1784 ____ 3.8 _______ 5.7 (tied 16th coldest)

_ 04 ___ 1816 ____ 3.9 _______ 6.6 (tied 49th coldest)

_ 05 ___ 1839 ____ 4.0 _______ 6.4 (tied 32nd coldest)

_ 06 ___ 1799 ____ 4.2 _______ 5.4 (tied 5th coldest)

_ 07t___ 1780 ____ 4.4 _______ 6.3 (tied 29th coldest)

_ 07t___ 1986 ____ 4.4 _______ 5.8 (tied 18th coldest)*

_ 09 ___ 1924 ____ 4.5 _______ 6.9 (tied 68th coldest)

_ 10t___ 1790 ____ 4.6 _______ 6.1 (tied 23rd coldest)

_ 10t___ 1809 ____ 4.6 _______ 5.2 (tied third coldest)

_ 10t___ 1824 ____ 4.6 _______ 7.4 (tied 110th coldest)

_ 13t___ 1958 ____ 4.7 _______ 7.4 (tied 110th coldest)

_ 13t___ 1970 ____ 4.7 _______ 6.7 (tied 53rd coldest)

_ 15 ___ 1922 ____ 4.8 _______ 5.5 (t 7th coldest with six other years)

______________________________________________-

1701 finished 4.7 (tied coldest), 1782 (t 3 coldest at 5.2) had a first half CET of 4.9

1743 and 1770 5.4 (t 5th coldest).

Seven years were tied 9th coldest at 5.5 ... 1688, 1695, 1696, 1713, 1771, 1812, 1922 _

... the last two were in the daily era and their first half CET values were 5.5 (1812) and 4.8 (1922).

* 1986 was tied with 1702 and 1808 which had a first half CET of 7.1, very cold second half.

(no further pre-1772 listed)

1879 (t16 coldest) finished 5.7, the mid-month CET was 5.2 C. 

(no further daily era non-qualifiers listed)

[Don]

2 hours ago, summer blizzard said:

I don't recall the first half of 2013 being that cold, at least compared to 2012.

That said our targets are simple. 2013, 2000, 1986.

I do remember falling snow in April 2013 (not sure what dates), albeit it didn't settle.