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

[summer blizzard]

Here's a question, when was the last time we had two consecutive months that were 2C or more below the 1991-2020 average.

Off the top of my head I'd be guessing Jan-Feb 10.

Edited May 15, 2021 by summer blizzard

[Chesil View]

Not strictly cet related but just an interesting sidenote. I have been recording temperature and rainfall in south Dorset for the last 29 years. So far this year I have not yet registered a temperature of 20c or above.  This sets a new record. Every other year has seen 20c reached or breached well before todays date date. Even previous late years got there no later than 7th May. That is quite something for a lowland location within 5 miles of the south coast.

[LetItSnow!]

42 minutes ago, summer blizzard said:

Here's a question, when was the last time we had two consecutive months that were 2C or more below the 1991-2020 average.

Off the top of my head I'd be guessing Jan-Feb 10.

Feb/Mar. 2018 was very close

2.9   4.9

-2.0 -1.8

Otherwise, yes, 2010. 

1.4   2.8

-3.3 -2.1

Before that, Dec. 1996/Jan. 1997

2.9   2.5

-2.1 -2.2

(which I think is a fair comparison since by 1997 the climate in this country had warmed to similar if not same levels as now)

Edited May 15, 2021 by LetItSnow!

[Roger J Smith]

Just for my own interest, is there any official release of 1991-2020 normals yet? I worked out some averages in a thread here but found a couple of cases that were very close to rounding points so I wasn't sure of those two being up or down. 

[Roger J Smith]

Today's 12z GFS run had a somewhat warmer look by fourth week and would probably allow May 2021 to escape the 9s eventually, would estimate 10.5 C as the outcome from this run. We keep seeing this back and forth in the longer term, and I won't be too surprised if the chilly fourth week shows up again in another run or two. The most likely EWP outcomes are in the range of 110 to 130 mm. If we do exceed 110 mm this will definitely be similar to the eventual top 35 in the annual contest (showing May forecast and rank to give an idea of how outcomes between 90 and 110 might shake up the order, davehsug and I would drop down a few ranks if the outcome is much below 110, most others would just jostle the next person possibly as almost all these forecasts are close to those of similar points totals annually:

 1. Feb1991Blizzard ____ 44.77 ____ 83 mm (17th)

 2. snowray ____________ 43.33 ____ 86 mm (14th)

 3. Reef ________________ 40.72 ____ 91 mm (10th)

 4. virtualsphere _______ 38.50 ____ 37 mm (53rd)

 5. Don _________________38.09 ____101 mm (4th)

 6. Federico ____________ 37.53 ____ 60 mm (45th)

 7. bobd29 _____________ 37.32 ____ 58.8 mm (46th)

 8. The PIT _____________ 36.01 ____ 50 mm (51st)

 9. Godber1 ____________ 35.74 ____ 87 mm (13th)

10.  Roger J Smith ______ 35.33 ___ 127.2 mm (1st)

11. Relativistic __________34.99 ___ 55 mm (49th)

12. Blast from the Past _ 34.83 ___ 75 mm (28th)

13. davehsug ___________ 34.68 ___109 mm (2nd)

14. Midlands Ice Age ____33.45 ___ 79 mm (24th)

15. noname_weather ___ 33.19 ___ 84 mm (15th)

16. February 1978 ______ 32.06 ___ 81 mm (20th)

17. Polar Gael __________ 31,20 ___ 68 mm (36th)

18. Mulzy _______________ 30.64 ___ 83 mm (18th)

19. seaside60 ___________ 30.59 ___ 79 mm (22nd)

20. JeffC _________________ 30.27 ___ 62 mm (43rd) 

21. J10 __________________ 29,24 ___ 75 mm (27th)

22. Norrance ___________ 28.55 ___ 75 mm (26th)

23. Stationary Front ____ 28.49 ___ 72 mm (t30th)

24. Frigid _______________ 28.37 ___ 95 mm (9th)

25. Leo97t ______________ 28.29 ___ 70 mm (34th)

26. General Cluster (EdS) 27.94 ___ 69 mm (35th)

27. Emmett Garland ____ 27.67 ___ 83 mm (16th)

28. Jonboy ______________ 27.29 ___ 65 mm (40th)

29. coldest winter _______ 27.16 ___101.3 mm (3rd)

30. Kirkcaldy Weather __ 26.67 ___ 65 mm (38th)

31. SteveB ______________ 26.69 ___ 64 mm (41st)

32. sundog _____________ 26.59 ___ 90 mm (11th)

33. MrMaunder ________ 26.44 ___ 82 mm (19th)

34. summer blizzard ___ 25.46 ___ 60 mm (44th)

35. DR(S)NO ___________ 25.37 ___100 mm (5th)

________________________________________________________________________

If you were below that cut-off, the points only fall off gradually and all other regulars are in the range of 16 to 25 points now. The only regular entrants who had a higher than 20th May finish were daniel* (96 mm, 7th) and I Remember Atlantic 252 (98 mm, 6th). They both moved up in ranking and have reached 52nd (from 74th) and 43rd (from 55th). 

Shillitocettwo had 168 mm which in this estimate is tied 30th and leaves Shil in 41st just below DR(S)NO with 25.33 points. Every mm that is added on to the outcome is probably worth 0.2 points to shillitocettwo, to a maximum of 5 so a very wet outcome won't change any scores except that one (most would fall by 0.2), and the highest that shil can reach in the table would be 20th. It would require a total rainfall of 130 mm to get to 28 points in total. 

Worth noting that coldest winter has reached their points total on three of six contests entered, prorated that would be ten points higher than first place in the contest. Norrance, sundog and Frigid in the table above have five of six entries. 

Also first time entrant rwtwm had 95 mm (8th in this provisional, and could be higher if outcome is closer to 100 mm). Well done. 

I am going to add the excel file with this provisional scoring, there is one new feature that wasn't there in April, all of the EWP historical data have been added (scroll down below all scoring info), before there was just 1981 to 2021, but now I've added 1766 to 1980 to all of that. Also have updated the seasonal scoring with this May provisional scoring data included. All subject to adjustments at end of the month. 

EWP2020_21_May.xlsx

Edited May 15, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield remains at 8.6C -1.8C below normal. Rainfall up 92.2mm 154.7% of the monthly average.

A rise for today and a slow rise next week for us. Probably around 9C to 9.2C by Friday. ECM hinting a very warm end of the month although it maybe too late to bring the month to average values it could still reduce the difference by a notable margin. GFS keeping us on the cool side through out.

[Summer Sun]

9.2c to the 15th

1.3c below the 61 to 90 average
1.8c below the 81 to 10 average

___________________________

Current high this month 9.2c on the 15th
Current low this month 6.6c on the 1st

[Roger J Smith]

EWP now around 75 mm, was 62 to the 14th, then added about 10-15 mm yesterday and early today, 12z GFS suggesting 40 mm average for the grid to 26th and some further rainfall shown to 31st -- all adds up to around 115-125 mm. 

The latest 12z GFS run is cool but probably does get the CET past 10.0 slowly and would say 10.2 to 10.6 the eventual outcome from that run. The ECM might be a touch warmer with hints of a more substantial warming trend by the 27th. If we were at 10 by 26th and had a few very warm days (16-18) it could end up going through the 10s to about 11.0. That looks like the upper limit for any realistic forecast now. 

[The PIT]

Sunny Sheffield up to 8.8C -1.7C below normal. Rainfall unchanged.

Looked like it may rise quicker than I thought as very mild nights will be making the biggest change to the average figure so guessing will be around 9.6C by Friday.

[summer blizzard]

After the coolest opening third since 2010 we now have the coolest first half since 2012.

Next target is the 1st-20th.

[Summer Sun]

9.3c to the 16th

1.3c below the 61 to 90 average
1.7c below the 81 to 10 average

___________________________

Current high this month 9.3c on the 16th
Current low this month 6.6c on the 1st

[damianslaw]

Mmm nothing warm on the horizon, odds of a below average May return against 61-90 mean increasing by the day, even though just past half way mark of the month, would require a very warm spell latter part of the month to nudge it just above average, but this doesn't look likely based on current output. Things may change by the end of the week still..

[BornFromTheVoid]

Latest projections

 

The chances of finishing:
Close to average (11.4C to 12.4C) is  to 8.4% (4 days ago was 10.8%)
Above average (>12.4C) is remains at 0.0% (4 days ago was 0.0%)
Below average (<11.4C) is to 91.6% (4 days ago was 89.2%)

The period of the 17th to the 22nd is forecast to average 11.1C, 1.1C below the 91-20 average.

Edited May 17, 2021 by BornFromTheVoid

[Scorcher]

This is going to end up a cool month but perhaps nothing particularly notable- the CET should continue to rise throughout this week with night time temps holding up.

Certainly no chance of matching 1996 now without a really remarkable cold spell.

[damianslaw]

1 hour ago, Scorcher said:

This is going to end up a cool month but perhaps nothing particularly notable- the CET should continue to rise throughout this week with night time temps holding up.

Certainly no chance of matching 1996 now without a really remarkable cold spell.

Average maxima could be quite a bit down on the May average, whilst minimal might be closer to average with the cool start cancelled out by slightly milder minima rest of the month. This often happens in the warmer half of the year under Atlantic airstreams, westerly or north westerly, perhaps more so the summer months which can end up being near average thanks to mild nights but such months feel cool with suppressed maxima.

[snowray]

Could still turn out relatively mild in the last week of May, recent runs have been hinting at this, and possibly even quite dry as HP moves in.

Edited May 17, 2021 by snowray

[Roger J Smith]

EWP around 74 mm now, was 67 mm to 16th and yesterday had heavy rainfalls in Thames valley, estimate 7 mm for the grid average. Ten day grid average is about 25 mm so now looking closer to 100 mm than 120 mm as last few days indicated as dry. However, looking back at GFS predictions from 7th to today, the grid average was a bit lower than reality and their day 11-16 projection then looked like 5-10 mm (that is now day 1-6, looks more like 20 mm). So that says GFS can underestimate total rainfalls. We have seen a few relatively settled spells showing up on past GFS runs then they disappear in a day or two, so not that convinced we would get this dry end to the month. But verbatim the GFS run pushes the CET steadily up in the last week and it could break into the 10.5 to 11.0 range then. 

An outcome closer to 100 mm for EWP would not change very much in the provisional scoring that I showed earlier, I would drop about five ranks and davehsug about three, otherwise most others would stay close to their current ranking, at 105 mm the changes are even slighter than that. There is heavy rain falling now and I wonder if the modelling on Thursday-Friday is all that accurate, so will hold off revising the scoring file until I see how the EWP actually responds next four days and also what the models are then showing for last few days of the month (GFS ten-day will go to end of month by this Friday). 

[BLAST FROM THE PAST]

Anyone seeing the chance of a lovely HP getting sat over us as we approach June....#hopefulforflamingjune

[The PIT]

Sunny Sheffield up to 8.9C -1.7C below normal. Rainfall up to 99.7mm 167.3% of the monthly average.

[Summer Sun]

9.5c to the 17th

1.2c below the 61 to 90 average
1.5c below the 81 to 10 average

___________________________

Current high this month 9.5c on the 17th
Current low this month 6.6c on the 1st

[Stu_London]

I think mid 10s might still be a bit of a stretch, particularly if the latest output is anything to go by.

Granted the models tend to underplay the max temps by a degree or so, but even allowing for that, there is not really much significant upward movement until the last few days of the month. 

If I'd entered this tournament, I would rather be sat on a guess of 9.5 than 10.5 right at this moment. 

 

 

[damianslaw]

7 hours ago, Stu_London said:

I think mid 10s might still be a bit of a stretch, particularly if the latest output is anything to go by.

Granted the models tend to underplay the max temps by a degree or so, but even allowing for that, there is not really much significant upward movement until the last few days of the month. 

If I'd entered this tournament, I would rather be sat on a guess of 9.5 than 10.5 right at this moment. 

 

 

Next week could deliver quite cold nights with chilly uppers and clear skies, much will depend on cloud cover which incidentally would bring suppressed maxes, either way either a cool minima, slightly milder or just average maxima combo or average, slightly milder minima and slightly below or average maxima latter end to the month, both of which will not help push the CET that much.

[Roger J Smith]

Agreed with both previous posters, high pressure builds in a fairly bad place for warming to occur, at least it may stop raining. EWP to 80 mm currently (74 mm to 16th and about 6 mm on map for 17th), shows another 25-30 mm to 28th and dribs/drabs at the end, looks like about 110 mm for a finish. 

CET might barely limp past 10 at some point but maybe pulled back to 9.9 by Mr D.A. at the end of play. 

Our current warmest day is shown as 12.8 C, even if we get perhaps a 14 around Friday, that is well below the average, I looked back and found that the last time no May day exceeded 14.0 was 1986 (max was 13.9). Since then the lowest values for the maximum daily CET have been 14.2 in 2013 and 14.5 in 2015.

If we stayed around 12.8 one would have to go back to 1975 for 13.0 as the max, and then to 1957 for 12.8. Before that the low max benchmarks are never lower than 12.8 (1887, 1894 also) until the absolute minimum of 12.0 for May, 1810. So at the moment we are tied with second lowest 12.8 from those three past years for low May maximum daily CET. 

Edited May 18, 2021 by Roger J Smith

[damianslaw]

2 hours ago, Roger J Smith said:

Agreed with both previous posters, high pressure builds in a fairly bad place for warming to occur, at least it may stop raining. EWP to 80 mm currently (74 mm to 16th and about 6 mm on map for 17th), shows another 25-30 mm to 28th and dribs/drabs at the end, looks like about 110 mm for a finish. 

CET might barely limp past 10 at some point but maybe pulled back to 9.9 by Mr D.A. at the end of play. 

Our current warmest day is shown as 12.8 C, even if we get perhaps a 14 around Friday, that is well below the average, I looked back and found that the last time no May day exceeded 14.0 was 1986 (max was 13.9). Since then the lowest values for the maximum daily CET have been 14.2 in 2013 and 14.5 in 2015.

If we stayed around 12.8 one would have to go back to 1975 for 13.0 as the max, and then to 1957 for 12.8. Before that the low max benchmarks are never lower than 12.8 (1887, 1894 also) until the absolute minimum of 12.0 for May, 1810. So at the moment we are tied with second lowest 12.8 from those three past years for low May maximum daily CET. 

So we could from a notably low minima April mean to a notably low maxima May mean, quite unusual!

[Stu_London]

5 hours ago, damianslaw said:

So we could from a notably low minima April mean to a notably low maxima May mean, quite unusual!

Yes quite different to the last cold spring of 2013, where the SSW effects kept us in a similar pattern for most of March and April.

We have had several pattern changes, but aside from the last 3 days of March, all of them have led to average or below average temps.