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

[damianslaw]

Can only see a very slow rise in the CET in the next 10 days, going into the last third we will still be below the average, would need a major warm up to pull the CET up to average, not out of the question, but the odds of a below average May look higher than above, let's see where we are in a week's time, will be clearer whether those odds are changed.

 

[The PIT]

Sunny Sheffield up to 8.2C -1.9C below average. Rainfall unchanged.

Still a chance we will end up average to above we've been this far below average at mid point a few times and still had a very warm spell warmer than the cold spell. Local forecast shows a slow down in the rise but then they under estimate the high temps by a couple degrees normally. If that's the case then we still have a steady albeit slower rise.

[Stu_London]

Based on the current output, below average would be a strong favourite, at least as far as the current average goes anyway. 1961-1990 is not so certain.

 

[BornFromTheVoid]

Latest projections

 

The chances of finishing:
Close to average (11.4C to 12.4C) is to 10.8% (3 days ago was 18.5%)
Above average (>12.4C) is to 0.0% (3 days ago was 0.4%)
Below average (<11.4C) is to 89.2% (3 days ago was 81.1%)

The period of the 13th to the 18th is forecast to average 10.4C, 1.0C below the 91-20 average.

Assuming we're on 9.3C to the 18th, the remainder of the month would have to average 10.9C or higher to reach 10C. Assuming even a small 0.2C correction, the 19th to 31st average would have to be at least 11.4C to reach 10C overall. A sub 10C May still seems very much possible

[Summer Sun]

8.8c to the 12th

1.6c below the 61 to 90 average
2.0c below the 81 to 10 average

___________________________

Current high this month 8.8c on the 12th
Current low this month 6.6c on the 1st

[Don]

4 hours ago, BornFromTheVoid said:

Latest projections

 

The chances of finishing:
Close to average (11.4C to 12.4C) is to 10.8% (3 days ago was 18.5%)
Above average (>12.4C) is to 0.0% (3 days ago was 0.4%)
Below average (<11.4C) is to 89.2% (3 days ago was 81.1%)

The period of the 13th to the 18th is forecast to average 10.4C, 1.0C below the 91-20 average.

Assuming we're on 9.3C to the 18th, the remainder of the month would have to average 10.9C or higher to reach 10C. Assuming even a small 0.2C correction, the 19th to 31st average would have to be at least 11.4C to reach 10C overall. A sub 10C May still seems very much possible

Another month where my CET guess looks to be going out the window lol!  Still time for a warm up later in the month but will need to start showing up soon.

Edited May 13, 2021 by Don

[Roger J Smith]

Current EWP projection about 90-100 mm to 29th, based on 51 mm to 11th, 5 mm grid average yesterday (much larger amounts in the southwest up to 38 mm locally) and 30 mm grid average for next ten days. Not as wet a pattern towards days 11-16 but that keeps changing. This slow steady rise looks likely to continue with 10.5 to 11.0 the most likely outcome based on current model run. There could be a few reasonably warm days near the end but unless there's record heat, by 29th if we reach 10.5 then days like 14-16 can only bump the average up by about the same as the usual downward adjustment anyway. 

[SummerShower]

Now looking at a possible northerly again later next week!  This will probably mean colder nights again, giving a better chance at sub 10c.

I wonder how the April and May combined cet will end up in historical context..

Still early days yet admittedly, but could be quite significant I feel

[Man With Beard]

On 12/05/2021 at 15:08, Summer Sun said:

8.6c to the 11th

1.6c below the 61 to 90 average
2.1c below the 81 to 10 average

___________________________

Current high this month 8.6c on the 11th
Current low this month 6.6c on the 1st

We've had milder Decembers. Horrifically low. Can't see any huge increase soon.

[Roger J Smith]

A 10.0 C finish would give 2021 an average of 8.2 C for April-May. 10.6 C would give 8.5 C.

Years that have finished 8.5 or lower, in reverse chronological order (with some slightly warmer ones until past 1971) ...

YEAR ____ APR _ MAY ___ avg ___ rank (1659-2020) ___YEAR ____ APR _ MAY ___ avg ___ rank (1659-2020)

2013 ____ 7.5 __10.4 __ 8.95 ___ ---- _____________1817 ____ 7.6 __ 8.7 ___8.15 __ 20

1996 _____8.5 ___ 9.1 __ 8.80 ___ ---- ______________ 1816 ____ 6.6 __ 9.9 ___ 8.25 ___t27

1986 _____5.8 __11.1 __ 8.45 ___t37_______________ 1812 ____ 5.5 __10.9___ 8.20___t21

1984 _____8.1 ___ 9.9 __ 9.00 ___ ---- ______________ 1799 ____ 5.4 __ 9.6 ___ 7.50 ___t5

1983 _____6.8 __10.3 __ 8.55 ___t43 _______________1782 ____ 5.2 __ 9.0 ___ 7.10 ___ 1

1951 _____6.8 __10.1 __ 8.45 ___t37________________1772 ____ 6.4 __10.1___ 8.25 ___t27

1941 _____6.4 ___ 9.4 __ 7.90 ___t12________________1770 ____ 5.4 __10.0___ 7.70 ___ 7

1923 _____7.6 ___ 9.2 __ 8.40 ___ 36 ________________1756 ____ 6.7 __ 9.1 ___ 7.90 ___t12

1902 _____7.5 ___ 8.9 __ 8.20 ___t21________________1751 ____ 7.1 __ 9.3 ___ 8.20 ___t21

1891 _____6.2 ___ 9.5 __ 7.85 ___11 _________________1748 ____6.3 __10.4___ 8.35 ___ 35

1888 _____6.2 __10.7 __ 8.45 ___t37 ________________ 1741 ____ 7.1 __ 9.3 ___ 8.20 ___t21

1887 _____6.2 ___ 9.4 __ 7.80 ___t9 _________________ 1740 ____ 6.4 __ 8.6 ___ 7.50 ___ t5

1885 _____7.7 ___ 8.9 __ 8.30 ___t32_________________1713 ____ 5.5 __10.5___8.00 ___t15

1879 _____5.7 ___ 8.9 __ 7.30 ___t3 __________________1702 ____ 5.8 __10.6___8.20 ___t21

1877 _____7.0 ___ 9.1 __ 8.05 ___19 _________________ 1701 ____ 4.7 __10.9___7.80 ___ t9

1855 _____7.1 ___ 8.8 __ 7.95 ___14 __________________1699 ____ 6.4 __10.0___8.20 ___t21

1839 _____6.4 __10.2 __ 8.30 ___t32 _________________ 1698 ____ 7.5 ___ 8.5 __ 8.00 ___t15 

1838 _____6.1 __10.5 __ 8.30 ___t32 _________________ 1696 ____ 5.5 __10.5___ 8.00 ___t15

1837 _____4.7 ___ 9.9 __ 7.30 ___t3 __________________ 1695 ____ 5.5 __ 9.0 ___ 7.25 ___ 2

_____________________________________________________ 1694 ____ 7.5 __ 9.0 ___ 8.25 ___t27

_____________________________________________________ 1693 ____ 6.5 __ 9.0 ___ 7.75 ___ 8

_____________________________________________________ 1692 ____ 7.5 __ 9.0 ___ 8.25 ___t27

_____________________________________________________ 1691 ____ 6.5 __10.0___ 8.25 ___t27

_____________________________________________________ 1688 ____ 5.5 __10.5___ 8.00 ___t15

_____________________________________________________ 1680 ____ 6.5 __10.5___ 8.50 ___t40

_______________________________________________1665, 1667 ____ 7.0 __10.0 ___ 8.50 ___t40,t40

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

The table is arranged so the second column begins around the halfway point of data (1840 now).

Since there are some unranked recent outcomes above 8.50, the balance is even more tilted to the

past with the 1690s showing that in the late Maunder, this sort of cool spring was more or less the

normal outcome. But even so, only three years from 1659 to 1687 limped into this table, so even

back that far this seemed cold. 

... 42 years had averages of 8.50 or lower, the ranks for 8.00 are t15 coldest (this would require 9.6 from May 2021).

(the rank t43 for 1983 assumes there are other 8.55 outcomes, those and warmer were not tabulated)

 

 

Edited May 13, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield up to 8.5C -1.7C below average. Rainfall up to 83.9mm 140.8% of the monthly average

[Summer Sun]

9.0c to the 13th

1.4c below the 61 to 90 average
1.8c below the 81 to 10 average

___________________________

Current high this month 9.0c on the 13th
Current low this month 6.6c on the 1st

[Derecho]

With the model output hinting at a northerly early next week I think we have a good chance of a sub-10C month. A cold latter to half to Spring then overall. 

Despite going for another below average month, I may have guessed too high yet again...

[Frigid]

Well the 12z GFS would definitely guarantee a sub 10c CET. 

[Roger J Smith]

Agreed, that run is quite cold looking, the 00z GFS last night was a bit warmer than some runs recently, models struggling a bit past seven days at the moment. EWP is already at or about 65 mm (55 mm to 12th, 10 mm possibly added yesterday), and latest 10d guidance goes for 40-50 mm more, well up towards 110 mm by 24th and some potential for more shown on maps to end of the month now. If this holds for a day or two longer I will post the updated scoring on a provisional basis, for 120 mm it shows Feb91blizzard taking the lead with snowray right behind, Reef moves to third and virtualsphere back to fourth, then Don in fifth. 

I think this would likely be the case for any outcome much above 90 mm which seems almost locked in now. 

[Derecho]

5 hours ago, Quicksilver1989 said:

With the model output hinting at a northerly early next week I think we have a good chance of a sub-10C month. A cold latter to half to Spring then overall. 

Despite going for another below average month, I may have guessed too high yet again...

* later next week

[Stu_London]

Were the GFS 12z pattern to verify, the CET would struggle to get very much higher than where it is now. Certainly a few days where there would be downward movement. 

I suspect however, that a few warmer days will creep into the output towards the end of month. Still likely to be a fairly noteworthy cool spring however, certainly by 20th and 21st century standards. 

If the CET does stay suppressed then there is a reasonable chance that the CET for the period Jan-May 2021 will be below the 1961-90 average.

2013 (benefiting from the coldest spring in over 100 years) was the last year that achieved that and managed to keep the run going into August. 

[Weather-history]

Last April was the coldest April that was so dry, that was very unusual but to be possibly followed by a cooler and wetter than average May that could be possibly unique in the records.

April 2021: 6.4C and 13.8mm

May is up to 59mm (up to 13th)

 

 

 

 

[Roger J Smith]

It's true, in that list I had the other day of cold April-May combinations, 1817 is the only one with similar precip, and that is in the list because of a very cold May (8.7) with April only moderately cool (7.6). The 1817 EWP values are 7.9 mm and 101.4 mm. Also in the list 1984 had a dry April but only an average amount of rain in May. 1812 is a very distant second closest analogue at 43.0 mm, 87.6 mm and the temps are not a super good fit (5.5, 10.9).

Maybe one of those more distant years was like 2021, we only have rainfall from 1766 on. If we were to finish 9.6 this month, then it would rank t15 coldest all time Apr-May and the closest analogues would be 1941 and before that 1891. If we somehow had the coldest May on record (8.4) it would go to 3rd coldest Apr-May and the closest analogue would be 1740 (6.4, 8.6) which leads one to ask, where was our winter of 1740? (answer, up north). 

[The PIT]

Sunny Sheffield up to 8.6C -1.7C below normal. Rainfall up 84.3mm 141.4% of the monthly average.

[Summer Sun]

9.1c to the 14th

1.4c below the 61 to 90 average
1.8c below the 81 to 10 average

___________________________

Current high this month 9.0c on the 13th
Current low this month 6.6c on the 1st

[LetItSnow!]

22 minutes ago, Summer Sun said:

9.1c to the 14th

1.4c below the 61 to 90 average
1.8c below the 81 to 10 average

___________________________

Current high this month 9.0c on the 13th
Current low this month 6.6c on the 1st

With the upcoming week to ten days looking average at best & mostly cool, is it fair to suggest we may not get above 10 until very late in the month... or perhaps might not at all?

[Shillitocettwo]

  Crikey I now feel I've gone too HIGH with my 9.9.C prediction for the month!

[Frigid]

35 minutes ago, Shillitocettwo said:

  Crikey I now feel I've gone too HIGH with my 9.9.C prediction for the month!

With what the models are showing currently, I feel 9.7 to 10.2 is the most likely range. You should be fine with 9.9c

[Godber 1]

1 hour ago, Frigid said:

With what the models are showing currently, I feel 9.7 to 10.2 is the most likely range. You should be fine with 9.9c

And here's me thinking 9.6c was in with a shout?