May 2016 C.E.T. forecasts

[Roger J Smith]

From the record warm intervals in Nov-Dec I would say tendency for correction averages zero and will only kick in when the morning low is higher than the evening portion of the day. I have the theory (and it is mine) that part of correction process is to convert the provisional time frame to the calendar day midnight to midnight. So any cold day that gets colder after sunset is going to have a downward correction. Any mild day that gets a boost in the evening is set for an upward correction. These happen less frequently in the summer half-year than the winter half-year anyway. But I also think some part the correction process is to incorporate data not available earlier or maybe to reflect quality control. So it's complicated but whatever the 18.0 will probably settle close to that and comfortably break the old record.

[BornFromTheVoid]

1 hour ago, Relativistic Sting Jet said:

Glancing at a couple of Roger's posts, it seems that there are three daily records before the 8th of May that are higher than 18.0C. These are;

- the absurdly warm 29/4/1775 (19.7C),
- 4/5/1834 (18.0C),
- 6/5/1867 (18.8C).

I couldn't find any other years on these dates for which 18.0C or more was recorded.

We should also bear in mind that this may be subject to a slight downward correction. Are warm days more likely to be corrected upwards or downwards?

Cheers. Got my laptop now. Yup, just 3 previous occasions have averaged 18.0C or greater at an earlier date. This also means that since the last time we recorded a record cold Spring day (1996), we've recorded 10 record warm Spring days.

[BornFromTheVoid]

The minimum today is much higher than expected, and so the max only needs to be 22.2C or higher to set a new record for the day. A max of 23.0C will also give us another early 18.0C daily mean.

[The PIT]

A much warmer day than forecast Sunny Sheffield now on 12.1C could be as high as 12.6C tomorrow depending on tonight's low

[BornFromTheVoid]

Min today of 12.9C, while maxima were close to 22.5C, so an increase to 12.7C is likely on tomorrows update.

After that, the 06z GFS has the CET at:

12.9C to the 10th (14.8: +4.0)
13.2C to the 11th (15.8: +4.7)
13.4C to the 12th (15.6: +4.3)
13.3C to the 13th (12.7: +1.1)
12.9C to the 14th (7.2: -4.5)
12.7C to the 15th (10.0: -1.7)
12.6C to the 16th (10.5: -0.9)
12.5C to the 17th (12.2: +0.9)
12.4C to the 18th (10.6: -0.8)

Cool conditions have been delayed until the weekend, and have then been watered down substantially. We're likely to be about 1.5 - 2.0C above the 81-10 average by mid month

[Don]

2 hours ago, BornFromTheVoid said:

Cool conditions have been delayed until the weekend, and have then been watered down substantially. 

Familiar story!

[Roger J Smith]

The last three days of April 1775 averaged 18.0 and the highest running May CET on any day of May that I could spot was 16.75 on 4th May 1990.

The record month of May 1833 ran warmer than its end result (15.3) but the highest it achieved for a running CET was 15.6 on 25th.

[Relativistic]

18 hours ago, BornFromTheVoid said:

Cheers. Got my laptop now. Yup, just 3 previous occasions have averaged 18.0C or greater at an earlier date. This also means that since the last time we recorded a record cold Spring day (1996), we've recorded 10 record warm Spring days.

I suppose it makes sense. With 245 years of data, one would expect a record warm Spring day approximately twice every five years, and the same goes for record cold days. Since 1996 (21 years of data), we have had ten record Spring days, so approximately a record warm day every two years (on average). Putting it another way, two in every four years as opposed to every five. So not actually a huge deviation from what one would expect. However, one record cold day in 21 years of data obviously is. I suppose this is a reflection of how much more the Arctic has warmed relative to other air masses, the extra warmth making it very hard to achieve record cold days. Less dramatic warming of air masses south of us has meant an increase in the number of record warm days, but not by much.

Perhaps we may have seen a couple of record cold days in the last week of April had the Arctic been in the state it was, say, 50 years ago.

[Roger J Smith]

The extinction of record cold was well underway before the AGW period. There was no record low in May between 1935 and 1979.

Another factoid of interest, the year we just stole a record from (1867) has three cold records in a row from 22 to 24 May.

[Summer Sun]

12.8c to the 9th

2.5c above the 61 to 90 average

2.1c above the 81 to 10 average

[Relativistic]

34 minutes ago, Roger J Smith said:

The extinction of record cold was well underway before the AGW period. There was no record low in May between 1935 and 1979.

Another factoid of interest, the year we just stole a record from (1867) has three cold records in a row from 22 to 24 May.

Impressive! Something interesting I noticed when looking at 18C days in May is that it seemed to me as if these had actually become less common during the 20th century (like cold records), although I didn't crunch any numbers to back this up. The weather seemed to have huge mood swings during the LIA.

Edited May 10, 2016 by Relativistic Sting Jet

[Matthew.]

I think there's the potential of this being quite a warm month. The ECM is wanting to bring high pressure from the Sw closer over the uk next week and there a draw of mild Sw. The GFS still has the Jet further south as a rule with cooler potential longer term

[BornFromTheVoid]

It's another provisional record for the 9th. If the records remain after corrections, it will be the earliest that we've seen 2 consecutive days averaging at least 18C.

I've been working on an analysis of trends in record breaking CET days lately (which I'll post in full soon) so I happen to have a lot of relevant stats to hand. May is an odd month in that it's one of the few where we've had a similar number of record cold and record warm days since 1800 (71 record cold and 74 record warm, excluding the last 2 days). This is likely thanks to some very warm May months early in the CET record, with 6 of the 7 warmest Mays since 1772 (when the daily records began) occurring before 1868.
Spring as a whole shows the smallest seasonal record warm to record low ratio over the past 50 year, with just 2.4 record warm days for every record cold day. On the other end of the scale, Autumn has seen 16 record warm days for every record cold day in the last 50 years.

[Roger J Smith]

This is the full list of 18.0+ days in May (and the one in April) by decades ... within decades the list is also chronological.

1772-80 __ 19.7 (29 Apr 1775) .. 18.3 (29 May 1776) ... 18.5 (24 May 1779) ... 19.5 (28 May 1780), 21.2 (29 May 1780)

1781-90 __ 18.2, 20.2 (30-31 May 1781) ... 18.5, 18.7 (23, 26 May 1784) 18.0,18.9,18.5,19.0,18.5 (24-28 May 1788)

1791-1800- 19.0 (23 May 1795)

1801-10 __ 18.1, 19.8 (23-24 May 1807) ... 18.3, 20.0 (15-16 May 1808) ... 18.4 (18 May 1809)

1811-20 __

1821-30 __

1831-40 __ 20.0, 18.4, 19.7 (15-17 May 1833) ... 18.0 (4 May 1834)

1841-50 __ 18.6 (27 May 1841) ... 18.9, 20.6 (23, 28 May 1847)

1851-60 __ 18.9 (31 May 1858)

1861-70 __ 18.2, 18.5 (19-20 May 1864) ... 18.8 (6th, 1867) ... 18.2, 20.4 (18-19 May 1868) ... 18.3 (21 May 1870)

1871-80 __ 18.6 (24 May 1871)

1881-90 __ 18.4 (18 May 1888)

1891-1900- 18.3 (28 May 1892) ... 18.3 (30 May 1895)

1901-10 __ 18.2 (29 May 1901) ... 18.4 (20 May 1904) ... 18.0 (31 May 1908)

1911-20 __ 18.2 (30 May 1913) ... 18.8 (21 May 1916) ... 18.6, 19.5 (21-22 May 1918) ... 18.5 (25 May 1920)

1921-30 __ 18.7, 18.4, 19.5, 18.1 (21-24 May 1922) and 18.6 (31 May 1922) ... 18.2 (23 May 1929)

1931-40 __

1941-50 __ 21.1, 21.0 (29-30 May 1944) ... 18.8 (12 May 1945) ... 20.8, 19.9, 20.5 (29-31 May 1947)

1951-60 __ 19.0, 19.1 (17-18 May 1952) ... 18.8, 21.0 (24-25 May 1953) ... 18.2, 18.3 (10, 12 May 1959)

1961-70 __ 18.0 (14 May 1965)

1971-80 __ 19.4 (31 May 1978)

1981-90 __ 18.1 (23 May 1989)

1991-2000- 18.8 (14 May 1992) and 18.1,18.5,18.1 (24,26,28 May 1992) ... 18.5 (15 May 2000)

2001-10 __ 18.3, 18.9 (30-31 May 2003) ... 18.3 (27 May 2005) ... 18.6 (11 May 2008) ... 18.1 (23 May 2010)

2011-16 __ 18.3, 18.4 (25-26 May 2012), ??? (8-9 May 2016)

_____________________________________________________________________

78 such days before the two possible new additions, plus the one in April 1775 ... these occurred in 48 (49 counting 1775) years before 2016, or about 20% of the 245 years in question. The longest spell was five days way back in 1788. The second longest was four days in 1922. The three days at end of May 1947 were followed by four more above 18.0 in early June 1st to 4th, which suggests that a seven-day spell is sustainable. There are very few cases where one spell was followed by any later days at 18.0 or higher, it seems that normally we get one kick at the can so to speak.

Noted in passing: No day in May 1885 exceeded 9.7 until the 26th !!

[Roger J Smith]

Note above that the longest spells without a May 18.0 reading were 23 years (1810 to 1832 inclusive) and 16 years (1872 to 1887 inclusive), also 14 years (1930 to 1943 inclusive).

[Summer Sun]

13.0c to the 10th

2.6c above the 61 to 90 average

2.3c above the 81 to 10 average

[BornFromTheVoid]

Minimum today is 12.4C, while maxima look like reaching about 19C, so an increase to 13.2C is likely on tomorrows update.

After that, the 06z GFS has the CET at:

13.4C to the 12th (15.8: +4.5)
13.2C to the 13th (11.2: -0.4)
12.8C to the 14th (7.0: -4.7)
12.5C to the 15th (8.8: -2.9)
12.5C to the 16th (11.5: +0.1)
12.5C to the 17th (12.3: +1.0)
12.4C to the 18th (11.9: +0.5)
12.5C to the 19th (12.9: +1.1)
12.4C to the 20th (12.3: +0.0)

A possible peak of 13.4C occurring tomorrow, before quickly dropping towards mid month and leveling off. Anything from a top 5 warmest month to about 1C below average is still possible at this stage.

[Roger J Smith]

Assuming that the 12z GFS has maintained that trend, I would say the output from 21st to 28th suggests a mean of 14.5 through that period which would bring the projection to 13.0 C. Would put my money more on the top five than the below normal at this point.

[Matthew.]

I wonder if this year will follow the pattern of 1947 bringing a May of 13c + and a Summer which is in the top 10 warmest Summers of all time( 7th or 8th if I remember correctly). Sadly not too many May's in the 13's have led to this though. Another encouraging thought is the Great El Niño of 83 gave a top 10 Summer also, holding 6th position I believe.

[DAVID SNOW]

14 minutes ago, Matthew Wilson said:

I wonder if this year will follow the pattern of 1947 bringing a May of 13c + and a Summer which is in the top 10 warmest Summers of all time( 7th or 8th if I remember correctly). Sadly not too many May's in the 13's have led to this though. Another encouraging thought is the Great El Niño of 83 gave a top 10 Summer also, holding 6th position I believe.

You maybe forgetting the record cold and snow of early 1947? No pattern what so ever compared to 2016.

[Chris.R]

Crosby is on 14.0°C so far for May. This is thanks to the 8th and 9th which have daily means of 18.9°C and 19.9°C respectively. 

[Summer Sun]

13.2c to the 11th

2.7c above the 61 to 90 average

2.5c above the 81 to 10 average

[Summer Sun]

13.5c to the 12th

2.9c above the 61 to 90 average

2.7c above the 81 to 10 average

[Roger J Smith]

Current 12z GFS output (and actual today) appears fairly normal today and tomorrow through 22nd, so using 11.5 as estimate for that period, we would be on 12.6 by then ... rest of month appears closer to 15 (less reliable time frame, 11-16 days out) ... that would bring the mean back up to about 13.3, 14 in that period to 13.0 ... so the trend continues to point to something around 13 which is higher than most but not all predictions (and previous Mays).

 

[Summer Sun]

13.4c to the 13th

2.8c above the 61 to 90 average

2.6c above the 81 to 10 average