April 2024 C.E.T. and EWP contests

[Derecho]

20 minutes ago, WYorksWeather said:

Perhaps 9.5C to 10.5C the favoured range?

EC00z control this morning has us finishing at 10.2C but this is on the mild side of the ensemble with a warm day on the 30th.

 EC 00z control

GFS 12z operational however...

Finishes at just 9.2C however this is on the cold side of the ensemble mean. 9.7C would be a more sensible option right in the middle.

[Don]

5 minutes ago, Derecho said:

Finishes at just 9.2C however this is on the cold side of the ensemble mean. 9.7C would be a more sensible option right in the middle.

Maybe, just maybe my 9.3C guess isn't out of the question after all!  However, still pretty unlikely.

[snowray]

 Don I think you would need some frosty nights to achieve this.

[reef]

If that came to fruition it would mean the first 15 days of the month were almost 4C warmer than the last 15 days. That would really be quite something in April, a warming month.

[Don]

 snowray definitely 

[damianslaw]

 reef April 2024 could go down as one of those classic switcharound months, where first and second half are complete opposites CET wise. Such months include Jan 13, Feb 05, 09, 12, Nov 05.. can't think of others but sure someone with stats will tell me. 

A finish in the 9s now looking a more and more possible outcome. It is unusual for April and May to see much colder second halves than first halves though.. 

[Roger J Smith]

So, on subject of April cooldowns, sam e list as I posted for record warm first 14 days, but now arranged not in order of CET but in order of size of cooldown. There could have been larger drops from less lofty starting points but as we are talking about warm  starts transforming to near average end points, only these seem relevant. 

 

YEAR ___ CET 1-13 _ CET 1-14 ___ end result __ CET drop 14 to 30 Apr

 

2024 ___ 11.53 ___ 11.39 ___ ___ ?? ?? ___ ___ ?? ??

 

1778 ___ 11.19 ___ 10.71 ___ ____ 8.2 ___ ___ 2.5

1815 ___ 10.42 ____ 9.93 ___ ____ 8.1 ___ ___ 1.8

1835 ___ 10.15 ___ 10.06 ___ ____ 8.6 ___ ___ 1.5

1926 ___ 10.59 ___ 10.47 ___ ____ 9.3 ___ ___ 1.2

1995 ___ 10.24 ___ 10.23 ___ ____ 9.1 ___ ___ 1.1

1803 ____ 9.93 ___ 10.07 ___ ____ 9.1 ___ ___ 1.0

1827 ____ 9.90 ____ 9.83 ___ ____ 8.9 ___ ___ 0.9

1894 ___ 10.42 ___ 10.29 ___ ____ 9.7 ___ ___ 0.6

1999 ___ 10.58 ___ 10.04 ___ ____ 9.5 ___ ___ 0.5

1792 ____ 9.95 ___ 10.16 ___ ___ 10.0 ___ ___ 0.2

2020 ___ 10.89 ___ 10.54 ___ ___ 10.5 ___ ___ 0.0

2014 ___ 10.35 ___ 10.31 ___ ___ 10.3 ___ ___ 0.0

1943 ___ 10.14 ___ 10.30 ___ ___ 10.5 ___ ___ up 0.2

1798 ____ 9.97 ___ 10.04 ___ ___ 10.3 ___ ___ up 0.3

1865 ___ 10.05 ____ 9.99 ___ ___ 10.6 ___ ___ up 0.6

2011 ___ 11.18 ___ 11.08 ___ ___ 11.9 ___ ___ up 0.8

 

[BlueSkies_do_I_see]

To fall from 11.39C on the 14th to 9.7C at month's end would require a cool down of 1.7C, a feat only achieved twice in 1778 and 1815.

Interesting times! Thanks for those stats Roger.

Edited April 17 by BlueSkies_do_I_see

[damianslaw]

Interesting stats, not many examples of significant falls as I thought the case for April, probably also May.

1995 keeps cropping up as a comparator month for 2024.. 

[Metwatch]

What would be quite peculiar is if the second half of April (15th - 30th period) could have a total lower CET than all of February or March, certainly possible I reckon and maybe the first time of such occuring since records began

[Summer Sun]

11.0c to the 16th

3.2c above the 61 to 90 average
3.2c above the 81 to 10 average

[raz.org.rain]

 Roger J Smith quite a few warm summer analogues there. 1995 of course, and 1778 was supposedly a notably warm summer at the time with a wet July. But 1815...

Edited April 17 by raz.org.rain

[The PIT]

Sunny Sheffield down to 9.9C +2.1C above average. Rainfall 65.2mm 116.2% of the monthly average.

[BruenSryan]

April 2024 a bit different to the other warm Aprils this century so far.. (though 2014 was somewhat different too)

 

[snowray]

Where do we stand so far this month for rainfall? I suspect it must be close to 70mm or just a bit over by now.

The rest of the month did look to be dominated by HP over or close to the UK, but a more unsettled end of the month now could be more likely, so might we be looking at another 100mm month by any chance?

Edited April 17 by snowray

[WYorksWeather]

 snowray

Currently at 59.4mm to the 15th. Seems pretty clear we'll go above average, making it ten months in a row, (63.2mm the target) but not necessarily by a huge amount.

[snowray]

 WYorksWeather

Thanks. Thought we had gone higher by now, it certainly seemed like it by just looking out of the window. 

Anyway if GFS is on the money we could be easily looking at another 40mm or so.

 

[WYorksWeather]

 snowray Yep, an increasing signal in the model output to retrogress the high towards Greenland allowing more lows to pass over the UK. 

40mm does look quite high - even if we assume that there's another 5mm or so for yesterday and to lunchtime today to take us to about 65mm, this doesn't look close to a grid average of 35mm to me. Maybe 25mm, which would give a finish around 90mm or so.

My hope is that the models are overdoing the retrogression so we hang onto the dry weather, but of course the weather will do what it wants!

[Roger J Smith]

Okay, I took a look at all cases of late April temperature drops relative to first fourteen days (only the warmest 8% of early Aprils were in first sample, granted they would stand a better than average chance of seeing a drop of 1.0+, just about the entire 50% below average first fourteen days would likely be excluded by seasonal trend alone) ...

 ... that leads to following table of all cases with drops of 1.5 C or more (a total of 51 out of 252 dropped by at least 0.1 C and 11 stayed level). ...

 

YEAR ___ CET 1-14 _ CET 1-30 _ decrease

1778 ___ 10.7 ___ ____ 8.2 ___ ___ 2.5

1815 ____ 9.9 ___ ____ 8.1 ___ ___ 1.8

1884 ____ 8.9 ___ ____ 7.2 ___ ___ 1.7

1859 ____ 9.1 ___ ____ 7.5 ___ ___ 1.6

1906 ____ 8.9 ___ ____ 7.3 ___ ___ 1.6

1835 ___ 10.1 ___ ____ 8.6 ___ ___ 1.5

1981 ____ 9.3 ___ ____ 7.8 ___ ___ 1.5

This list adds only four cases (1884, 1859, 1906, 1981) to identify all drops of 1.5+, now working on a program that can isolate cases where second half of April was colder than Feb - march. I wouldn't be surprised to find one or two. 

 

 

[snowray]

April can certainly deliver quite a cold burst in the 2nd half of the month, even after a mild or very mild 1st half. 

I remember reading about years like 1908 when even on the south coast places were seeing frosts and snowfall, there are pictures of Southampton, fuzzy black and white, and showing a foot of snow in the last week of April. I personally can remember some very cold spells of weather late in the month, this would be quite a contrast this year as compared to the very mild first half, and producing possibly a record breaking colder 2nd half if some of recent model runs are to be believed.

[BlueSkies_do_I_see]

 snowray it's hard to believe, until you read about it.

The Great Snowfall – 25 April 1908 – Historic Southampton

HISTORICSOUTHAMPTON.CO.UK

 

Edited April 17 by BlueSkies_do_I_see

[snowray]

 BlueSkies_do_I_se

Thats it, well done.

I personally have experienced very heavy snow when I was a young child in the early 70's in Mid April, it was on a Good Friday but cant remember the year and some extreme cold with snowfall in the west country back in the mid 70's right at the end of the month.

[Don]

 snowray Those were the days!

[snowray]

 Don Indeed they were, 1975 seems to have been particularly snowy, and 1981 had a massive blizzard and snowdrifts in and around the Midlands later in the month.

Also Just spotted 1950, well before my time, that produced 15cm of snow in the south around the 25th/26th of April.

April can be the most unpredictable of all of the months of the year, like early summer one day and like late winter the next.

Edited April 17 by snowray

[Roger J Smith]

The 1908 late April cold spell set three daily CET records including 0.6 on 24 April; only 1856 (0.7 on 29 April)  has any reading lower than 1.0 after the --0.2 of 19 April 1772. 

Anyway, I looked into the question of a colder second half of April than Feb-Mar combined, and found six cases: 1809, 1815, 1859, 1884, 1903 and 1989. (note, Feb-Mar average is a daily average, only one of these cases (1903) actually yielded a late April decrease relative to both monthly means, as noted). 

This was the top 12 of (otherwise) smallest increases, and the six actual decreases heading the list. 

 

Least CET Increases second half April vs FEB -MAR

 

YEAR ____ 16-30 APR ____ FEB -MAR ______ difference  __ FEB CET _ MAR CET

1903 _____ 6.0 ______________ 7.1 ___________ --1.1 _______ 7.1 _______ 7.1

1815 _____ 6.6 ______________ 6.9 ___________ --0.3 _______ 6.5 _______ 7.3

1884 _____ 5.6 ______________ 5.9 ___________ --0.3 _______ 5.3 _______ 6.5

1859 _____ 6.3 ______________ 6.5 ___________ --0.2 _______ 5.7 _______ 7.3

1809 _____ 5.8 ______________ 5.9 ___________ --0.1 _______ 5.7 _______ 6.0

1989 _____ 6.7 ______________ 6.8 ___________ --0.1 _______ 6.0 _______ 7.5

1938 _____ 7.4 ______________ 7.2 ___________ +0.2 _______ 5.1 _______ 9.1

1877 _____ 5.9 ______________ 5.5 ___________ +0.4 _______ 6.2 _______ 4.9

1849 _____ 6.5 ______________ 5.9 ___________ +0.6 _______ 5.7 _______ 6.1

1981 _____ 6.2 ______________ 5.5 ___________ +0.7 _______ 3.0 _______ 7.8

2017 _____ 8.2 ______________ 7.5 ___________ +0.7 _______ 6.2 _______ 8.8

Despite record cold 23-25 April, 1908 was +0.9 (Apr 16-30 5.7, Feb 5.3, Mar 4.3 avg 4.8), 12th place for smallest increases. 

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

So, it has happened six times that second half of April was colder than Feb-March average, but only one of those was colder than both Feb and March averages, the other five beat March but not Feb; of the other six in the list, with small increases, one beat Feb, three beat March, and two were slightly warmer than both. 

 

 

Edited April 17 by Roger J Smith