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

[Weather-history]

A case history

8th May 1923 CET: 12.6C  --------> May 1923 CET: 9.2C

Only 0.1C above the May 1996 CET despite the very warm start.

The modern equivalent would be March 2013, that was 4.9C by the 9th and ended up as 2.7C

 

Edited May 4, 2021 by Weather-history

[Summer Sun]

7.2c to the 3rd

2.4c below the 61 to 90 average
3.3c below the 81 to 10 average

___________________________

Current high this month 7.2c on the 3rd
Current low this month 6.6c on the 1st

[Roger J Smith]

Let's say that 7.2 CET is probably 6.9, then that would rank t-28th coldest in 250 years of data (1772-2021). 7.2 itself ranks t-33rd coldest.

It would also be coldest since 1981 (colder than 1996) with only 1967, 1979 colder since 1961.

Only these years started colder than 7.2 (to 3rd) with daily values for coldest, and showing any recent (post 1980) sub-7.5 also: 

(_ 7.5 _ 1996 )

_ 7.2 _ 1954, 1991

_ 7.0 _ 1805, 1809, 1896,

_ 6.9 _ 1851, 1887

_ 6.8 _ 1779, 1952

_ 6.7 _ 1858, 1925

_ 6.6 _ 1773, 1817, 1855, 1874

_ 6.5 _ 1852, 1909

_ 6.4 _ 1850, 1857

_ 6.3 _ 1786, 1799, 1981

_ 6.2 _ 1892

_ 6.1 _ 1929

_ 6.0 _ 1879

_ 5.6 _ 1870

_ 5.5 _ 1876

_ 5.3 _ 1967 (6.4, 4.9, 4.7)

_ 4.9 _ 1782 (4.4, 5.2, 5.1), 1866 (4.2, 6.1, 4.4), 1877 (5.1, 6.4, 3.1)

_ 4.8 _ 1856 (4.3, 4.3, 5.7)

_ 4.7 _ 1945 (4.3, 4.9, 5.0)

_ 4.3 _ 1979 (4.4, 3.8, 4.7)

__________________________________________

(May 11-14 2020 averaged 6.8, means were 6.6, 6.3, 7.5, 6.3. )

[Roger J Smith]

EWP is around 15-20 mm now after grid average of 12-13 mm on 3rd (1 mm on 2nd). 

[Weather-history]

It will be interesting to compare the 5th April-4th May 2021 CET with the same period in past years.

In 1986, I think that period was about 6.7C and we will probably be lower than this. 

 

 

 

 

[BornFromTheVoid]

I'll do the usual update tomorrow, but...

The latest GFS has the CET at about 8.5C to the 15th (29th coldest on record). Assuming that's accurate, we'd need to average 11.3C or less for the 16th to 31st to finish below 10C.
For the whole record, 32% of years have achieved this. In the last 50 years, 13 years have achieved this - the most recent year was 2015, which averaged just 10.9C for the 16th to 31st. Downward corrections will help a lot too.

So, a sub 10C CET is well within the realms of possibility, close to a 1/3 chance at the moment.

[Weather-history]

12 hours ago, Weather-history said:

It will be interesting to compare the 5th April-4th May 2021 CET with the same period in past years.

In 1986, I think that period was about 6.7C and we will probably be lower than this. 

 

 

 

 

5th April-4th May 1917: 6.9C

5th April-4th May 1922: 6.3C

 

[Summer Sun]

7.4c to the 4th

2.2c below the 61 to 90 average
3.1c below the 81 to 10 average

___________________________

Current high this month 7.4c on the 4th
Current low this month 6.6c on the 1st

[BornFromTheVoid]

Latest projection for May

 

The chances of finishing:
Close to average (11.4C to 12.4C) is  to 22.9% (2 days ago was 19.3%)
Above average (>12.4C) is  to 3.6% (2 days ago was 3.2%)
Below average (<11.4C) is to 73.5% (2 days ago was 77.5%)

The period of the 5th to the 10th is forecast to average 8.9C, 2.5C below the 91-20 average.

[Roger J Smith]

EWP now around 22 mm, predicted to add about 30-40 mm over next two weeks. It's running a bit above normal but not excessive. Looks like most guesses above 50 mm have some chance of doing well, would not like to be too low or too high (although I am anyway). If I had this guidance to make a monthly forecast I would now be saying about 75-80. 

The CET indications are fairly bland, from this cold start, a more average period looms from this weekend through mid-week, then back to slightly colder conditions, followed by a gradual warming with above  normal temperatures likely for several days around the 15th-20th according to most models.

That could lead to a steady rise in the CET to reach about 10 C by the 20th. How much further it might go after that depends on whether the warm spell intensifies or is replaced by another cold spell. So I would say just about all guesses except maybe 5.9 are still in the hunt. 

[Summer Sun]

7.2c to the 5th

2.6c below the 61 to 90 average
3.3c below the 81 to 10 average

___________________________

Current high this month 7.4c on the 4th
Current low this month 6.6c on the 1st

[The PIT]

Sunny Sheffield at 6.5C -2.7C degrees below normal. Rainfall 29.4mm 49.3% of the monthly average.

[Timmytour]

23 hours ago, BornFromTheVoid said:

Latest projection for May

 

The chances of finishing:
.....
Below average (<11.4C) is to 73.5% (2 days ago was 77.5%)

 

I can hear Mama Cass singing "it's getting better"!

[Roger J Smith]

Rather warm looking 12z GFS run, would estimate that CET will average 13 C during its sixteen day run, so if we take 7.0 for first six days as the adjusted outcome, then we would be at 11.4 C by the 22nd. 

[Don]

3 hours ago, Roger J Smith said:

Rather warm looking 12z GFS run, would estimate that CET will average 13 C during its sixteen day run, so if we take 7.0 for first six days as the adjusted outcome, then we would be at 11.4 C by the 22nd. 

Hope my 11.4C isn't going to be too low after this very cold start to the month! 

[damianslaw]

Another cold day for May which will do nothing for the CET in terms of a warm up, looks like though we will bottom out tomorrow and a rise will take hold thereafter, though nothing particularly warmer than average on offer for the foreseeable meaning a notably cold first half to May most likely.

[feb1991blizzard]

14 minutes ago, damianslaw said:

Another cold day for May which will do nothing for the CET in terms of a warm up, looks like though we will bottom out tomorrow and a rise will take hold thereafter, though nothing particularly warmer than average on offer for the foreseeable meaning a notably cold first half to May most likely.

2 well above average days the weekend according to this - 2 x 13c days.

[Weather-history]

To gauge how unusually cold the last 31 days had been, if we start from the date of when the Arctic blast struck on the 5th of April

 

5th April -5th May 2021: ~6.4C

5th April-5th May 1986: 6.8C  (April: 5.8C)

5th April-5th May 1941: 7.1C  (April: 6.4C)

5th April-5th May 1936: 6.7C  (April: 6.3C)

5th April-5th May 1922: 6.4C  (April: 5.5C)

5th April-5th May 1917: 7.0C (April: 5.4C)

5th April-5th May 1908: 6.9C (April: 6.0C)

5th April-5th May 1903: 7.0C (April: 6.4C)

5th April-5th May 1891: 6.8C (April: 6.1C)

5th April-5th May 1888: 6.9C (April: 6.2C)

5th April-5th May 1887: 6.5C (April: 6.2C)

5th April-5th May 1879: 5.9C (April: 5.7C)

5th April-5th May 1877: 6.3C (April: 7.0C)

5th April-5th May 1860: 6.5C (April: 5.7C)

5th April-5th May 1847: 7.2C (April: 6.6C)

5th April-5th May 1839: 7.7C (April: 6.4C)

5th April-5th May 1838: 7.4C (April: 6.1C)

5th April-5th May 1837: 5.8C (April: 4.7C)

5th April-5th May 1812: 5.5C (April 5.5C)

5th April-5th May 1809: 6.0C (April 5.2C)

5th April-5th May 1808: 7.4C (April: 5.8C)

5th April-5th May 1793: 7.0C (April: 6.2C)

5th April-5th May 1790: 7.2C (April: 6.1C)

5th April-5th May 1784: 7.2C (April: 5.7C)

5th April-5th May 1782: 5.3C (April: 5.2)

5th April-5th May 1780: 6.3C (April: 7.4C)

5th April-5th May 1772: 7.2C (April: 7.2C)

 

 

 

 

Edited May 7, 2021 by Weather-history

[The PIT]

Sunny Sheffield down to 6.4C -3.0C below normal. Rainfall up to 33.8mm 56.7% of the monthly average.

[BornFromTheVoid]

Latest projections

 

The chances of finishing:
Close to average (11.4C to 12.4C) is  to 21.7% (2 days ago was 22.9%)
Above average (>12.4C) is  to 1.6% (2 days ago was 3.6%)
Below average (<11.4C) is to 76.7% (2 days ago was 73.5%)

The period of the 5th to the 10th is forecast to average 10.4C, 1.0C below the 91-20 average.

[Summer Sun]

7.0c to the 6th

2.8c below the 61 to 90 average
3.6c below the 81 to 10 average

___________________________

Current high this month 7.4c on the 4th
Current low this month 6.6c on the 1st

[Don]

3 hours ago, Summer Sun said:

7.0c to the 6th

2.8c below the 61 to 90 average
3.6c below the 81 to 10 average

___________________________

Current high this month 7.4c on the 4th
Current low this month 6.6c on the 1st

Low point of the month and will only rise now.  Question is, how high will it go by month end?

[Roger J Smith]

Today's 12z GFS run has slightly cooler outcome than yesterday with a few rather cold looking days and this would revise my estimate from 11.4 to 10.8 as likely end of run value (also one day later into the month, 23rd now). The EWP evolution continues to look somewhat above normal in general with 65-70 mm projected for 23rd. Currently EWP is 25 mm (22 to 5th, about 3 mm yesterday) and ten day grid average is 30-35 mm. Some light falls indicated days 11-16. 

[The PIT]

Sunny Sheffield back to 6.5C -3.0C below average. Rainfall 38mm 63.8% of the monthly average.

If the rain keeps coming down like it is I wouldn't be surprised to be reaching average rainfall by the end of the day.

[Summer Sun]

7.0c to the 7th

2.9c below the 61 to 90 average
3.7c below the 81 to 10 average

___________________________

Current high this month 7.4c on the 4th
Current low this month 6.6c on the 1st