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

[Sunny76]

18 minutes ago, damianslaw said:

May is my favourite month, but not feeling it one bit this year..  feels a perpetual late winter.. year yet to get going especially after the misery of last 14 months. Really need June to kick things into touch.

Hopefully the last few days of May and early June will make up for it, but if the dull and cool weather persists into late June, it will be time to start worrying. The summer pattern tends to be locked in place by the time we reach late June and early July. 

[The PIT]

Sunny Sheffield back down to 9.1C -1.8C below normal. Rainfall up 111.8mm 187.6% of the monthly average.

Probably go back to 9.2C by tomorrow then not move much at all for the next few days at least.

[Roger J Smith]

EWP closing in on 100 mm, was 84 mm to 19th, then yesterday's downpours especially heavy in north Wales and northwest England, look to add 10-12 mm as smaller amounts fell in the southeast. The 10-day GFS outlook now about 20-25 mm mostly from this weekend's rainfall plus the tail end of today's portion of the event. That all adds up to around 120 mm but could go a bit higher, guidance would have to be seriously off to get us to the record but for what it's worth this is the top twenty of May rainfalls (precip if it snowed) in the past 255 tries (with their CET values for May and June to September in brackets): 

Rank _ Year _ May EWP _ (CET May to Sep)
 

01 _ 1773 __ 151.8 mm (10.3, 14.7, 15.9, 17.2, 12.4)

02 _ 1782 __ 142.4 mm ( 9.0, 14.9, 15.6, 14.2, 13.3)

03 _ 1967 __ 140.7 mm (10.4, 14.0, 16.7, 15.7, 13.5)

04 _ 1932 __ 129.6 mm (10.5, 14.1, 16.1, 17.1, 12.9)

05 _ 1843 __ 129.1 mm (10.4, 12.8, 14.8, 15.3, 14.4)

06 _ 1886 __ 123.1 mm (10.3, 13.6, 15.9, 15.8, 13.6)

07 _ 1924 __ 122.4 mm (11.6, 13.9, 15.3, 14.1, 13.3)

08 _ 1811 __ 121.9 mm (12.8, 14.1, 16.1, 14.4, 13.7)

09 _ 1869 __ 121.5 mm ( 9.6, 13.2, 17.3, 15.5, 14.4)

10 _ 1979 __ 119.1 mm (10.0, 13.9, 16.2, 14.9, 13.5)

11 _ 2007 __ 118.4 mm (11.9, 15.1, 15.2, 15.4, 13.8)

12 _ 1878 __ 117.6 mm (11.8, 15.1, 16.6, 16.2, 13.3)

13 _ 1969 __ 115.8 mm (11.2, 13.9, 16.8, 16.4, 13.9)

14 _ 1983 __ 115.2 mm (10.3, 14.4, 19.5, 17.3, 13.7)

15 _ 1807 __ 113.9 mm (11.8, 14.2, 17.1, 16.9, 10.5)

16 _ 2006 __ 111.8 mm (12.3, 15.9, 19.7, 16.1, 16.8)

17 _ 1796 __ 110.4 mm (10.3, 13.9, 14.7, 15.9, 14.6)

18 _ 1813 __ 110.1 mm (11.6, 13.6, 15.0, 14.5, 12.5)

19 _ 1797 __ 109.5 mm (11.3, 13.6, 17.3, 15.8, 12.5)

20 _ 1766 __ 108.1 mm ( 9.7, 13.7, 15.7, 16.6, 13.3) 

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

(averages for CET) __ (10.86, 14.15, 16.38, 15.77, 13.50)

... so as you might expect, rather cool May values, lingering cool into June, July quite a mix, Aug tending more seasonable and Sept rather cool also). 

... as to rainfalls in the summer seasons that followed these wet Mays, the tendency seemed to be for at least one month to be quite dry but it ranged from June to August, and one or two (like 2007 and also 1782) had quite a prolonged wet spell. 

... the only thing these wet Mays can say about summer forecast might be to expect one hot, dry month somewhere in the mix, it seemed to happen more often than not. also, some near misses (rank 21-30) included some other hot summers like 1955, so that perhaps 1983 and 2006 being in the set is not that big a fluke. 1925 fairly wet May (96.5 mm) was followed by driest June on record. 

[Stu_London]

2 hours ago, Roger J Smith said:

EWP closing in on 100 mm, was 84 mm to 19th, then yesterday's downpours especially heavy in north Wales and northwest England, look to add 10-12 mm as smaller amounts fell in the southeast. The 10-day GFS outlook now about 20-25 mm mostly from this weekend's rainfall plus the tail end of today's portion of the event. That all adds up to around 120 mm but could go a bit higher, guidance would have to be seriously off to get us to the record but for what it's worth this is the top twenty of May rainfalls (precip if it snowed) in the past 255 tries (with their CET values for May and June to September in brackets): 

Rank _ Year _ May EWP _ (CET May to Sep)
 

01 _ 1773 __ 151.8 mm (10.3, 14.7, 15.9, 17.2, 12.4)

02 _ 1782 __ 142.4 mm ( 9.0, 14.9, 15.6, 14.2, 13.3)

03 _ 1967 __ 140.7 mm (10.4, 14.0, 16.7, 15.7, 13.5)

04 _ 1932 __ 129.6 mm (10.5, 14.1, 16.1, 17.1, 12.9)

05 _ 1843 __ 129.1 mm (10.4, 12.8, 14.8, 15.3, 14.4)

06 _ 1886 __ 123.1 mm (10.3, 13.6, 15.9, 15.8, 13.6)

07 _ 1924 __ 122.4 mm (11.6, 13.9, 15.3, 14.1, 13.3)

08 _ 1811 __ 121.9 mm (12.8, 14.1, 16.1, 14.4, 13.7)

09 _ 1869 __ 121.5 mm ( 9.6, 13.2, 17.3, 15.5, 14.4)

10 _ 1979 __ 119.1 mm (10.0, 13.9, 16.2, 14.9, 13.5)

11 _ 2007 __ 118.4 mm (11.9, 15.1, 15.2, 15.4, 13.8)

12 _ 1878 __ 117.6 mm (11.8, 15.1, 16.6, 16.2, 13.3)

13 _ 1969 __ 115.8 mm (11.2, 13.9, 16.8, 16.4, 13.9)

14 _ 1983 __ 115.2 mm (10.3, 14.4, 19.5, 17.3, 13.7)

15 _ 1807 __ 113.9 mm (11.8, 14.2, 17.1, 16.9, 10.5)

16 _ 2006 __ 111.8 mm (12.3, 15.9, 19.7, 16.1, 16.8)

17 _ 1796 __ 110.4 mm (10.3, 13.9, 14.7, 15.9, 14.6)

18 _ 1813 __ 110.1 mm (11.6, 13.6, 15.0, 14.5, 12.5)

19 _ 1797 __ 109.5 mm (11.3, 13.6, 17.3, 15.8, 12.5)

20 _ 1766 __ 108.1 mm ( 9.7, 13.7, 15.7, 16.6, 13.3) 

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

(averages for CET) __ (10.86, 14.15, 16.38, 15.77, 13.50)

... so as you might expect, rather cool May values, lingering cool into June, July quite a mix, Aug tending more seasonable and Sept rather cool also). 

... as to rainfalls in the summer seasons that followed these wet Mays, the tendency seemed to be for at least one month to be quite dry but it ranged from June to August, and one or two (like 2007 and also 1782) had quite a prolonged wet spell. 

... the only thing these wet Mays can say about summer forecast might be to expect one hot, dry month somewhere in the mix, it seemed to happen more often than not. also, some near misses (rank 21-30) included some other hot summers like 1955, so that perhaps 1983 and 2006 being in the set is not that big a fluke. 1925 fairly wet May (96.5 mm) was followed by driest June on record. 

Could go one of a number of way I guess. There is often a significant period of rather unsettled weather in May or June (sometimes nicknamed the June monsoon) - from a personal point of view, hopefully we are getting this out of the way now as June does have the potential to deliver my favourite summertime weather of warm, dry, sunny days without significant humidity. 

[Summer Sun]

9.6c to the 20th

1.1c below the 61 to 90 average
1.5c below the 81 to 10 average

___________________________

Current high this month 9.6c on the 18th, 19th & 20th
Current low this month 6.6c on the 1st

[BornFromTheVoid]

Latest projections

 

The chances of finishing:
Close to average (11.4C to 12.4C) is  to 0.0% (4 days ago was 8.4%)
Above average (>12.4C) is remains at 0.0% (4 days ago was 0.0%)
Below average (<11.4C) is to 100% (4 days ago was 91.6%)

The period of the 21st to the 26th looks like averaging about 9.6C, 3.3C below the 91-20 average.

I'd say odds are now in favour of a sub 10C finish after corrections, and not far off 50/50 before.

[Weather-history]

On 12/05/2021 at 13:42, Weather-history said:

April-May CET combinations

2013 CET: 8.95C  (A May CET < 11.5C will beat this)

1996 CET: 8.8C (A May CET < 11.2C will beat this)

1986 CET: 8.45C (A May CET < 10.5C will beat this)

1941: CET: 7.9C (A May CET <9.4C will beat this)

 

 

I think it looks likely it will be the coldest April-May CET period since 1941.

Edited May 21, 2021 by Weather-history

[Relativistic]

Yes, looks like we'll be trundling along in the 9s for the foreseeable future. If the month ends in the same vein then there's a chance we'll end up in the top-five coldest Mays of the past century. In reverse-chronological order, we have the following:

1996: 9.1C
1984: 9.9C
1975: 9.9C
1968: 9.8C
1955: 9.7C
1941: 9.4C
1935: 9.9C
1923: 9.2C

A remarkable decadal consistency for sub-10C Mays until the 2000s (someone else may have already pointed this out). Thanks to the cluster in the upper 9s, we don't have to finish that far below 10C to rank well on this list.

[Don]

1 hour ago, BornFromTheVoid said:

Latest projections

 

The chances of finishing:
Close to average (11.4C to 12.4C) is  to 0.0% (4 days ago was 8.4%)
Above average (>12.4C) is remains at 0.0% (4 days ago was 0.0%)
Below average (<11.4C) is to 100% (4 days ago was 91.6%)

The period of the 21st to the 26th looks like averaging about 9.6C, 3.3C below the 91-20 average.

I'd say odds are now in favour of a sub 10C finish after corrections, and not far off 50/50 before.

Time to big farewell to my 11.4C guess.  However, my precipitation guess should be closer to the mark at least!  The warmer second half of the month has failed.....

[Roger J Smith]

With the EWP heading for an outcome well into the 120-140 mm range, the only unknown about scoring now is where shillitocettwo might finish with a 168 mm forecast. This was tied 30th when I scored provisionally for 120 mm. But every mm gained on 120 will move shil up the table, as shown here: 

125 mm _  t19th

130 mm _ 10th

135 mm _  4th

140 mm _ 2nd

147.7 mm _ 1st

This will impact the "best combined" forecast where coldest winter looks quite strong unless shil can pass cw's current 3rd place EWP or even make it to perhaps 5th (shil is slightly colder).

[BornFromTheVoid]

Assuming a post corrections May CET of ~9.8C, the next big target becomes an April to June average of under 10C. This was last achieved in 1923, and would require a June CET under 13.7C this year (June <13.7C was reached quite recently too, in both 2012 and 2013)

[Stu_London]

23 minutes ago, BornFromTheVoid said:

Assuming a post corrections May CET of ~9.8C, the next big target becomes an April to June average of under 10C. This was last achieved in 1923, and would require a June CET under 13.7C this year (June <13.7C was reached quite recently too, in both 2012 and 2013)

9.8 would also leave us needed June to be sub 14.9C for the period 01.01.21-30.06.21 to be below the 1961-90 average.

 

[damianslaw]

Very poor May on the temperature front. Can't see the CET rising much in the days ahead. It feels cold out there this eve under cloud and wind. Tomorrow looks cold for late May, just scraping into double figures in the sunshine. Probably coldest May since 96 on the cards.

[Don]

4 hours ago, damianslaw said:

Very poor May on the temperature front. Can't see the CET rising much in the days ahead. It feels cold out there this eve under cloud and wind. Tomorrow looks cold for late May, just scraping into double figures in the sunshine. Probably coldest May since 96 on the cards.

Indeed and will May 2021 be a colder month than December 2015?  I don't think it will quite make it but could well be a close run thing!

Edited May 21, 2021 by Don

[Roger J Smith]

Shillitocettwo may be a big winner as the EWP takes one more spin of the wheel (the whirling wheels of wetness) mid-week apparently, which could more or less guarantee a finish no worse than second and possibly first if there's enough rain from it, at the moment we are near 102 mm with 94 mm to 20th, about 8 to 10 mm from yesterday's rather soggy outcome across the south, and the ten-day forecast (which ends with the month) looking like 40 mm at least, a total of about 140-145 mm. Shil needs 147.7 for the win but is guaranteed second after we pass 138.5 mm. As shown in the table of 20 wettest Mays that I posted yesterday, the month would finish second wettest at any value above 1782's 142.4 mm. 

The latest guidance looks just warm enough to get the CET above 10.0 before corrections but then probably back down below afterwards. 

[The PIT]

Sunny Sheffield at 9.1C -1.9C below normal. Rainfall up to 119.4mm 200.3% of the monthly average.

[Summer Sun]

9.6c to the 21st

1.1c below the 61 to 90 average
1.6c below the 81 to 10 average

___________________________

Current high this month 9.6c on the 18th, 19th, 20th & 21st
Current low this month 6.6c on the 1st

[Roger J Smith]

12z GFS not quite as strong for mid-week additional rainfall, gives a further 30 mm for outcomes around 130 mm. 

[Man With Beard]

On 21/05/2021 at 11:43, Summer Sun said:

9.6c to the 20th

1.1c below the 61 to 90 average
1.5c below the 81 to 10 average

___________________________

Current high this month 9.6c on the 18th, 19th & 20th
Current low this month 6.6c on the 1st

Still colder than a recent December month, then. Woeful.

[The PIT]

Sunny Sheffield back up to 9.2C -1.9C below normal. Rainfall 119.4mm 200.3% of the monthly average.

[Summer Sun]

9.7c to the 22nd

1.1c below the 61 to 90 average
1.5c below the 81 to 10 average

___________________________

Current high this month 9.7c on the 22nd
Current low this month 6.6c on the 1st

[Britneyfan]

We may actually end up with over 10 CET especially with the outlook, could get a few days above 20° to end the month! 

[Roger J Smith]

EWP update 102 mm to 22nd, plus about 25 mm rest of the month, would give 127 mm as outcome. Slightly warmer looking guidance might get us to around 10.2 by end before adjustments, could be back to 9.9 after them though. 

[Relativistic]

Provisionally, the highest daily mean of the meteorological Spring is still the 31st March's value of 14.3C. Can we make it to the end of May without recording a higher daily mean? Can't have been many years where the highest was in March.

Edited May 23, 2021 by Relativistic

[SummerShower]

1 hour ago, Relativistic said:

Provisionally, the highest daily mean of the meteorological Spring is still the 31st March's value of 14.3C. Can we make it to the end of May without recording a higher daily mean? Can't have been many years where the highest was in March.

I feel there's a fair chance of this happening.  Even if we get some warmer days under high pressure at the end of the month the nights could still be chilly