September 2015 CET forecasts

[Stu_London]

I'm not in the competition but if I was, I would be very happy with something between 12.5C and 13.0C as things stand currently

[Stu_London]

13.2C to the 17th 

 

The timings of various areas of rain forecast in the next week will be a factor. If they arrive in the evening to the CET area they will likely keep temps from falling - daytime rain bands will suppress maxima.

 

Either way I don't see it moving more than 0.1C to 0.2C from where it is currently during this timeframe.

Edited September 18, 2015 by Stu_London

[Stu_London]

The rolling annual CET is likely to dip below 10C for the first time in a while during the next fortnight also!

[Summer Sun]

13.2c to the 17th

0.9c below the 61 to 90 average

1.4c below the 81 to 10 average

[BornFromTheVoid]

Minimum today of 8.7C, with maxima likely to reach the low 18s, so remaining on 13.2C on tomorrows update.

 

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

 

13.2 C to the 19th (13.2: -0.4)

13.3 C to the 20th (14.5: 0.4)

13.3 C to the 21st (12.6: -1.1)

13.2 C to the 22nd (11.4: -2.4)

13.2 C to the 23rd (13.6: +0.1)

13.2 C to the 24th (12.8: +0.0)

13.2 C to the 25th (13.7: +1.0)

13.2 C to the 26th (14.4: +1.6)

13.3 C to the 27th (15.0: +2.1)

 

Slightly below average in the near term, slightly above in the medium term. Even a very mild finish would only leave us in the high 13s, possibly 14.0C. So no real chance of finishing above the 81-10 average after corrections.

[Gael_Force]

 

Minimum today of 8.7C, with maxima likely to reach the low 18s, so remaining on 13.2C on tomorrows update.

 

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

 

13.2 C to the 19th (13.2: -0.4)

13.3 C to the 20th (14.5: 0.4)

13.3 C to the 21st (12.6: -1.1)

13.2 C to the 22nd (11.4: -2.4)

13.2 C to the 23rd (13.6: +0.1)

13.2 C to the 24th (12.8: +0.0)

13.2 C to the 25th (13.7: +1.0)

13.2 C to the 26th (14.4: +1.6)

13.3 C to the 27th (15.0: +2.1)

 

Slightly below average in the near term, slightly above in the medium term. Even a very mild finish would only leave us in the high 13s, possibly 14.0C. So no real chance of finishing above the 81-10 average after corrections.

 

The chap that runs the CET competition on TWO posted that the CET was running too high. Do you think there will be a big downward correction this month?

 

The provisional Hadley data is a heap of rubbish. As often happens with the provisional data it has failed to properly pick up the cold night time minimums we have had this month. On the 8th my CET reading was as low as 12.06C whereas Hadley was at 12.8C. So expect some huge downward adjustments at the end of the month.

http://www.theweatheroutlook.com/twocommunity/default.aspx?g=posts&m=720911#post720911

[BornFromTheVoid]

The chap that runs the CET competition on TWO posted that the CET was running too high. Do you think there will be a big downward correction this month?

http://www.theweatheroutlook.com/twocommunity/default.aspx?g=posts&m=720911#post720911

 

Can't really say. I don't track the actual max and min readings from the stations used. Many of the recent daily averages have been cooler than the GFS predicted though...

[Summer Sun]

13.2c to the 18th

0.9c below the 61 to 90 average

1.4c below the 81 to 10 average

[Lettucing Gutted]

Good to see a decent chance of a pretty cool September.

Let's not count our chickens just yet!

Edited September 20, 2015 by Goodbye Cold Weather! :(

[Summer Sun]

13.2c to the 19th

0.9c below the 61 to 90 average

1.3c below the 81 to 10 average

[Summer Sun]

13.2c to the 20th

0.8c below the 61 to 90 average

1.3c below the 81 to 10 average

[The PIT]

Bumping along on the bottom no change here at 12.3C can't see any real change and a chance this will be the final figure for us.

If it stays the same it will be coolest September since 1986

Edited September 21, 2015 by The PIT

[damianslaw]

CET unlikely to change much over the coming days, perhaps a slight upturn end of the month, high chance now we will come in below the 61/90 average, by how much who knows, but certainly going to end up one of the colder Septembers of the last 30 years.

[Summer Sun]

13.2c to the 21st

0.7c below the 61 to 90 average

1.3c below the 81 to 10 average

[March Blizzard]

13.2c to the 21st

0.7c below the 61 to 90 average

1.3c below the 81 to 10 average

Is it stuck on that?!

[Summer Sun]

Is it stuck on that?!

 

Not likely to see much change over the coming days + / - 0.2c or so max

Edited September 22, 2015 by Summer Sun

[Costa Del Fal]

Hopefully my 13.3c punt will come close again and be the 2nd consecutive very close estimate. However I do think there could be fairly large downward revision going by others.

[damianslaw]

Good chance we will end up below the 13 degree mark helped by the usual downward adjustments even though there is an expected warm up for the latter part of the month, higher maxima could though easily be cancelled out by low minima.

 

When the last sub 13 degree CET September?

[Weather-history]

Good chance we will end up below the 13 degree mark helped by the usual downward adjustments even though there is an expected warm up for the latter part of the month, higher maxima could though easily be cancelled out by low minima.

 

When the last sub 13 degree CET September?

1994

[Summer Sun]

13.2c to the 22nd

0.8c below the 61 to 90 average

1.2c below the 81 to 10 average

[BornFromTheVoid]

The minimum today is 7.3C, while maxima look like reaching the high 17s, so a decrease to 13.1C is likely on tomorrows update. 

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

 

13.1C to the 24th (12.9: +0.0)

13.1C to the 25th (11.6: -1.1)

13.0C to the 26th (11.4: -1.4)

13.0C to the 27th (11.8: -1.1)

12.9C to the 28th (12.5: -0.8]

12.9C to the 29th (12.7: -0.4)

13.0C to the 30th (14.0: +1.2)

 

So somewhere between 12.8 and 13.2C is likely before corrections, then 12.3 to 13.2C after corrections. 12.3C, if it happened, would be the coldest since 1986 and the joint 4th coldest in the last 50 years.

Edited September 23, 2015 by BornFromTheVoid

[Stu_London]

In 2015, it looks entirely possible that one or more of the first few days in October will record a daily value higher than every day recorded in September.

 

Not sure how remarkable this is - but I would imagine it's a pretty rare occurrence. 

[The PIT]

Sunny Sheffield up 12.4c rounded up. A very dry month as well but not as dry as last year. 

[Roger J Smith]

I just ran a filter on daily CET values for the above and found 19 cases out of 243 (1772-2014) where this happened (October had a warmer daily mean CET than any day in September). It last happened in 2011 but only by 0.1 degree (1st Oct 20.1, 30th Sept 20.0). The largest increase was in 1985 also on the 1st (20.2) from the 30th of Sept (17.4). Before that it had been 1921 when 17.3 on 7th Sept was eclipsed by 19.0 on 6th of October.

 

These are the top 20 that we might be challenging:

 

YEAR ___ SEPT MAX ___ OCT MAX ______ difference

 

1985 ____ 17.4 (30) _______ 20.2 (01) ______ 2.8

1921 ____ 17.3 (07) _______ 19.0 (06) ______ 1.7

1888 ____ 15.3 (05) _______ 16.7 (27) ______ 1.4

1873 ____ 15.5 (20) _______ 16.8 (03) ______ 1.3

1995 ____ 16.5 (01) _______ 17.7 (08) ______ 1.2

 

1910 ____ 15.2 (02) _______ 16.1 (02) ______ 0.9

1997 ____ 16.9 (01) _______ 17.7 (01) ______ 0.8

1909 ____ 14.8 (24) _______ 15.6 (04) ______ 0.8

1863 ____ 14.1 (18) _______ 14.9 (03) ______ 0.8

1845 ____ 14.3 (10,17) _____15.1 (02) ______ 0.8

1897 ____ 15.0 (24) _______ 15.6 (17) ______ 0.6

1983 ____ 17.1 (01) _______ 17.6 (04) ______ 0.5

 

1830 ____ 14.6 (02) _______ 15.0 (22) ______ 0.4

1986 ____ 15.4 (02) _______ 15.7 (07) ______ 0.3

1965 ____ 15.8 (25) _______ 16.1 (16) ______ 0.3

1920 ____ 16.3 (06) _______ 16.5 (05) ______ 0.2

2011 ____ 20.0 (30) _______ 20.1 (01) ______ 0.1

1807 ____ 14.9 (04,05)_____ 15.0 (14) ______ 0.1

1793 ____ 14.8 (18) _______ 14.9 (05) ______ 0.1

1886 ____ 17.9 (01) _______ 17.9 (05) ______ 0.0

 

You might guess that the above list contains many of the cases of lowest max for September (as well as record highs in October). So I had a look at that, and the top 11 for lowest max are:

 

1863 ___ 14.1 (18)

1912 ___ 14.1 (04)

1845 ___ 14.3 (10, 17)

1834 ___ 14.5 (14)

1860 ___ 14.5 (16)

1830 ___ 14.6 (02)

1831 ___ 14.6 (02)

1793 ___ 14.8 (18)

1909 ___ 14.8 (24)

1807 ___ 14.9 (04,05)

1963 ___ 14.9 (17)

 

1912 must have been quite a grim autumn, note that 14.1 on 4th September was the warmest day for the remainder of that year and 11.8 on 14th December was the fourth warmest day in the period October to December 1912 and the tenth warmest following the max in early September.

 

The average for the September daily max over the entire period is 17.5 and the average since 1980 has been 18.0. (readers will realize these are daily means not absolute maximum daily temps).

Edited October 4, 2015 by Roger J Smith

[Lettucing Gutted]

I'm very surprised to see 2011 in that list Roger.  That was a very mild September. 

 

So somewhere between 12.8 and 13.2C is likely before corrections, then 12.3 to 13.2C after corrections. 12.3C, if it happened, would be the coldest since 1986 and the joint 4th coldest in the last 50 years.

 

If this comes off then September will beat May to be the coldest month of the year anomaly wise.  If the last 4 months don't record a greater cold anomaly than September, then 2015 will have September as the coldest month of the year anomaly wise for the first time since 1994 and only for the second time since 1957.

Edited September 24, 2015 by Goodbye Cold Weather! :(