September 2020 C.E.T. and EWP forecast contests

[mb018538]

Hasn’t been posted today, but another 0.2 chipped off. Down to 15.2c now, with further drops to come.

[Roger J Smith]

This is the daily update that didn't appear yesterday ... 

 

15.2c to the 24th

1.4c above the 61 to 90 average
0.9c above the 81 to 10 average

___________________________

Current high this month 15.6c to the 16th & 17th
Current low this month 13.8c to the 1st

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The EWP had made it to 36 mm by the 24th and looks to have added 2-3 yesterday, a blend of mostly zero or very low amounts, and huge falls in eastern Norfolk. Assuming it has reached 38 mm, the five-day addition from the 00z GFS was only about 5 mm with a dry core and some 10-20 mm amounts around the edges of the grid. Some heavier rain is coming in at the end of the month but looks like most of that will fall on the first of October. 

That being the case, 43 mm is the most likely outcome, and Polar Gael would be just a bit closer (at 40.2) than SummerShower at 47 mm, with nobody in between those guesses, and just two lower than 40. Will hold off on any scoring updates until I have final numbers but you can guess your score roughly by counting how many forecasts are below yours, and taking 0.2 away from the max of 10 for each of them (unless you're in the very lowest forecast zone, then you've probably scored about 9/10). 

This is the portion of the table of forecasts that contains the lower third of the forecasts which will score highest. 

.. 64_Earth ... 60_SB, BFTP ... 58.3_2010cold ... 58_Godb, mb  ... 55_B87,DT ... 50_Fre, dan^

... 48.2_wx26 ... 47_SumSh ... 40.2_PG ... 37_Bob, DRL ... 35_syed, wx-his 

With 56 forecasts, the scoring interval will be 0.182, so 11th place would be ten intervals lower than 10.0, at 8.18 (etc). I don't think we were totally out to lunch to suspect heavy rainfalls in the final segment, and they could still materialize if the models are off with timing. But as things have worked out, the long-running dry totals are not going to be greatly disturbed by this late activity mostly off or near the coasts. 

As to the question about coldest last third, I will work on that later this morning and give you a report. I would say this last third will likely come in pretty close to 10.5 or 11 C. Normally I notice in the 1981-2010 tracking the CET falls 0.5 from 21st to 30th. This month it may fall more like 1.0 to 1.5. 

 

Edited September 26, 2020 by Roger J Smith

[Roger J Smith]

Okay, so here's the scoop on cool last thirds of September in recent and historical times ...

For the period 21-30 September, the lowest average CET value is 9.1 from 1786 and since 1970 the lowest is 9.4 in 1974, since then the lowest values are 10.7 in 1993, then 10.8 in 2012 and 10.9 in 2018. 

The highest value was 16.7 in 2006. The average for 1981-2010 was 13.1 and for 1990-2019 it was 13.3 C.

The coldest eleven all-time were 9.1 (1786), 9.2 (1877), 9.4 (1919 & 74) and 9.5 (1793, 1871, 1889, 1928) and 9.6 (1932), 9.7 (1872, 1885). 

(added in later edit _ 2020 average for 21-30 is 11.6 C). 

Edited October 1, 2020 by Roger J Smith

[The PIT]

Sunny Sheffield at 14.5C +0.3C above normal. Rainfall up to 21.7mm 33.2% of the monthly average.

Local forecast suggesting that we will finish on 13.8C average for the month. Little sign of any significant rainfall bar a few light showers so likely to finish the 6th driest on record here.

[Summer Sun]

15.0c to the 25th

1.2c above the 61 to 90 average
0.8c above the 81 to 10 average

___________________________

Current high this month 15.6c to the 16th & 17th
Current low this month 13.8c to the 1st

[The PIT]

Sunny Sheffield down to 14.3C +0.2C above normal. Rainfall unchanged.

Landing zone for us looks to be between 13.6C and 14C.

[Summer Sun]

14.7c to the 26th

1.1c above the 61 to 90 average
0.5c above the 81 to 10 average

___________________________

Current high this month 15.6c to the 16th & 17th
Current low this month 13.8c to the 1st

[Kentish Man]

Wow a 0.3c drop is unusual at this late stage of a month. Could end up near to 1981 -2010 average of 14.2C.

[Dancerwithwings]

20 minutes ago, Kentish Man said:

Wow a 0.3c drop is unusual at this late stage of a month. Could end up near to 1981 -2010 average of 14.2C.

0.3c...I was surprised myself, but with forecasted temps over the next three days being mid to high teens and minima close to double figures I can’t see it dropping that far, but then again with the unpredictable corrections who knows

[Don]

28 minutes ago, Kentish Man said:

Wow a 0.3c drop is unusual at this late stage of a month. Could end up near to 1981 -2010 average of 14.2C.

Let’s hope it gets down to 14.2C  Probably a big ask though.

[JeffC]

9 hours ago, Don said:

Let’s hope it gets down to 14.2C  Probably a big ask though.

I concur!

[damianslaw]

Further cooling today, but temps will hold up a bit more Monday and Tuesday with milder maxima and minima so perhaps not so much of a drop thereafter, a finish probably in the 14.2-14.4 degree range expected, possibility may go below 14.2 degrees, but can't see a sub 14 degree finish unless we see a marked downward adjustment, not unheard of though. A near average month return. 

Possible values:

28 Sept 14.5

29 Sept 14.4

30 Sept 14.4

Downward adjustment ?

Edited September 27, 2020 by damianslaw

[Summer Sun]

14.6c to the 26th

0.9c above the 61 to 90 average
0.4c above the 81 to 10 average

___________________________

Current high this month 15.6c to the 16th & 17th
Current low this month 13.8c to the 1st

[mb018538]

Only down 0.1c today, with the last few days not looking as cold, maybe only another 0.1c will come off? 14.5c finish?

[Don]

21 minutes ago, mb018538 said:

Only down 0.1c today, with the last few days not looking as cold, maybe only another 0.1c will come off? 14.5c finish?

Before any adjustments could well be.  I think 14.2C to 14.5C range, the likely final figure.  So, not as warm as it looked to be a couple of weeks ago, courtesy of this cold week.

Edited September 28, 2020 by Don

[The PIT]

Sunny Sheffield down to 14.1C +0.1C above average. Rainfall unchanged.

Looking like 13.8C for us in Sunny Sheffield.

[Ultima Thule]

After adjustments something between 14.3 and 14.4 seems likely

[DAVID SNOW]

2 hours ago, Ultima Thule said:

After adjustments something between 14.3 and 14.4 seems likely

The after adjustments are a mysterious thing.

As for this month it could be 0.3 to 0.4, so a very slight chance of 14c or just below .

[damianslaw]

Not quite the drop I thought today, was a cold night for many though, this will be cancelled out somewhat by milder maxima. Key question will there be a downward correction, most likely as this seems the norm now, when was the last time we didn't have an adjustment.

[Daniel*]

2 hours ago, damianslaw said:

Not quite the drop I thought today, was a cold night for many though, this will be cancelled out somewhat by milder maxima. Key question will there be a downward correction, most likely as this seems the norm now, when was the last time we didn't have an adjustment.

I think because it was a mild night in SE the low was 10.6C here a sharp boundary to west of London much cooler with clear skies.

[The PIT]

Sunny Sheffield down to 14C +0.1C above normal. Rainfall unchanged.

[Roger J Smith]

Just for this year, the downward adjustments each month look like this in two and one decimal values ...

JAN __ -0.14 __ -0.1

FEB __ -0.17 __ -0.2

MAR __ -0.05 __-0.1

APR __ -0.33 __ -0.3

MAY __ -0.42 __ -0.4

JUN __ -0.24 __ -0.3

JUL __ -0.31 __ -0.3

AUG __-0.04 __ 0.0

The average downward adjustment is -0.21 for -0.2. 

These values do not have to correspond by rounding, as shown by June, it depends on the second decimals which in that case were 15.56 to 15.32 (0.24 but a difference of 0.3 to rounded one decimal result). 

I won't post all the values from 2019 but was able to see those as well, the range is similar although generally a bit larger, and the average adjustment was -0.29. 

There were some smaller adjustments in 2018 and even some slightly upward (in two decimals, they all stayed even in one decimal, for March, April and November of that year). 

 

[damianslaw]

8 hours ago, Daniel* said:

I think because it was a mild night in SE the low was 10.6C here a sharp boundary to west of London much cooler with clear skies.

This is an important comment, how the CET can be distorted when one of the three stations is markedly different to the other two. Rotherhithe on this occasion being the odd one out, hence the less marked drop than might have been expected.

Pershore is a bit of a frost hollow as well, so low temps there often distort the final value and it might be this station alone that results in the downward adjustments.

[Daniel*]

14 minutes ago, damianslaw said:

This is an important comment, how the CET can be distorted when one of the three stations is markedly different to the other two. Rotherhithe on this occasion being the odd one out, hence the less marked drop than might have been expected.

Pershore is a bit of a frost hollow as well, so low temps there often distort the final value and it might be this station alone that results in the downward adjustments.

One of other SE stations is Heathrow is it not? Which had a milder night. Last night was very mild too but more widely across England a minimum of 15C in London been cooler in daytime. With cloud only a diurnal range of 1-2C expected the smallest of the year it appears.

[mb018538]

Down to 14.4c now. Perhaps it'll settle here with it not being overly cold for the last couple of days. Chance of 14.3?