July 2023 C.E.T. and EWP forecast contests

[Frigid]

It really does feel like a July 06/07 situation, though a lot less extreme. Other big contrasts within a year in recent times would be Dec 10/11, March 12/13, July 12/13, Feb 2018/19, April 20/21, May 20/21.

There's a chance that July could be 3.0C cooler (15.2C) than the one previous, quite the contrast indeed. Though I'd expect a figure around 15.2C if the final week is cool and we don't experience a July 2020 situation. 

 

[Addicks Fan 1981]

I think @Frigidthe final CET for this month will be between the 2009 value to the 1997 value.    

[Roger J Smith]

Top 20 differentials (colder) in July of consecutive years

It used to be quite common for warmest months of July to be followed by quite cool ones. But 1818 (18.2) was followed by three consecutive colder months of July eventually dropping 3.4 by 1821. The largest year to year differences 1659-1700 were 2.0 C so none made this list. 

Note August 1911 (18.2) to August 1912 (12.3) fell 5.9 deg. July 1911 (18.2) to July 1912 (16.1) was a less noteworthy drop but to July 1913 the total drop was 3.6 from 18.2 to 14.6. ... Note also three of these drops in six years 1874 to 1879 (and a fairly large drop 1870 to 1871 of 2.3). 

 

Rank _____ July A ______ July B ______ diff

_ 01 ______ 1921 18.5 _ 1922 13.7 __ 4.8 (1921 was also 4.4 warmer than July 1920 at 14.1)

_ 02 ______ 2006 19.8 _ 2007 15.3 __ 4.5

_ 03 ______ 1757 18.4 _ 1758 14.2 __ 4.2 (then 1759 was 18.2! up 4.0) (July 1818 was also 4.1 warmer than 1817)

_t04______ 1852 18.7 _ 1853 14.9 __ 3.8

_t04______ 1859 18.3 _ 1860 14.5 __ 3.8

_t06______ 1783 18.8 _ 1784 15.2 __ 3.6

_t06______ 1887 17.3 _ 1888 13.7 __ 3.6

_t08______ 1701 18.3 _ 1702 15.0 __ 3.3

_t08______ 1808 18.4 _ 1809 15.1 __ 3.3

_t08______ 1901 18.0 _ 1902 14.7 __ 3.3

_ 11 ______ 1878 16.6 _ 1879 13.6 __ 3.0

_t12______ 1794 18.1 _ 1795 15.2 __ 2.9

_t12______ 1976 18.6 _ 1977 15.7 __ 2.9

_t14______ 1801 16.1 _ 1802 13.5 __ 2.6

_t14______ 1983 19.4 _ 1984 16.8 __ 2.6

_t16______ 1714 18.0 _ 1715 15.5 __ 2.5

_t16______ 1762 17.8 _ 1763 15.3 __ 2.5

_t16______ 1874 17.3 _ 1875 14.8 __ 2.5

_t16______ 1876 17.2 _ 1877 14.7 __ 2.5

_t20______ 1870 17.5 _ 1871 15.2 __ 2.3

_t20______ 1999 17.6 _ 2000 15.3 __ 2.3

?? ________ 2022 18.2 _ 2023 ?? ?? __ ?? (needs to be 15.8 to become sole 20th, 15.7 t16, 15.6 t14, 15.3 to 15.5 sole 14th 15.3 t12, etc)

____________________________

The warmest July not to be followed by a cooler July was 18.0 1994 (1995 18.5);

2nd to 17.8 1933 (1934 was 18.2);

3rd to 17.7 1900 (1901 was 18.0);

4th to 17.6 1793 (1794 was 18.1). 

 

 

[Roger J Smith]

This may be the mildest November ever to happen in July. 

[richie3846]

I'm not convinced by this sea temperature anomaly, holding up temperatures in this setup. The sea temps are no longer extremely above average, and last Tuesday made no sense to me, with areas of the CET zone being stuck in low to mid double figures, even when it wasn't raining. One of the coldest July days this century for some, with warm seas and westerly dominated wind, and rainfall coming in from the west. I can't see the link between sea temperatures at the moment, and surface temperatures. 

[Shillitocettwo]

Is there a year in rhe CET series with June being the warmest month? Bar a 1 day heatwave this July so far feels like October is squatting in it weather wise. 

 

Also the big l SST anomaly seems to have evaporated back to a broad everywhere is 1.C above average status

[Derecho]

1 hour ago, richie3846 said:

I'm not convinced by this sea temperature anomaly, holding up temperatures in this setup. The sea temps are no longer extremely above average, and last Tuesday made no sense to me, with areas of the CET zone being stuck in low to mid double figures, even when it wasn't raining. One of the coldest July days this century for some, with warm seas and westerly dominated wind, and rainfall coming in from the west. I can't see the link between sea temperatures at the moment, and surface temperatures. 

Well last Tuesday saw cool uppers and low cloud and heavy rainfall, the kind of synoptics that deliver low maximums.

The high SSTs will have encouraged troughing initially but sea temperatures are also pretty sensitive to atmospheric circulation because the mixing layer is shallow at this time of year (the part of the ocean that mixes with the atmosphere). It doesn't surprise me that they have dropped fairly quickly.

They will have added an extra degree of warmth, despite the unsettled weather the CET is still running above the old 61-90 average. Would it have been running above if we had been surrounded by colder then average SSTs? 

Edited July 11, 2023 by Derecho

[Roger J Smith]

1 hour ago, Shillitocettwo said:

Is there a year in rhe CET series with June being the warmest month? Bar a 1 day heatwave this July so far feels like October is squatting in it weather wise. 

 

Also the big l SST anomaly seems to have evaporated back to a broad everywhere is 1.C above average status

These 20 years (out of 354) had their warmest months in June. I list them by margins of "victory" over second place (and what second place was) ...

RANK ____ YEAR ____ JUNE ____ 2nd warmest ____ margin

_ 01 _____ 1676 ____ 18.0 ____ July 16.0 ___________ 2.0

_ 02 _____ 1846 ____ 18.2 ____ Aug 16.6 ___________ 1.6 (July was 16.5)

_ 03 _____ 1822 ____ 17.1 ____ July 15.6 ___________ 1.5

_t04_____ 1672 ____ 16.0 ____ July 15.0 ___________ 1.0

_t04_____ 1786 ____ 16.1 ____ Aug 15.1 ___________ 1.0

_t04_____ 1817 ____ 15.1 ____ July 14.1 ____________ 1.0

_t04_____ 1858 ____ 16.8 ____ Aug 15.8 ___________ 1.0

_t04_____ 1960 ____ 16.1 ____ July 15.1 ___________ 1.0

_ 09 _____ 1940 ____ 16.4 ____ Aug 15.6 ___________ 0.8

_ 10 _____ 1755 ____ 15.7 ____ July 15.0 ___________ 0.7

_ 11 _____ 1845 ____ 14.9 ____ July 14.3 ___________ 0.6

_t12_____ 1683 ____ 16.0 ____ July 15.5 ___________ 0.5

_t12_____ 1798 ____ 16.9 ____ Aug 16.4 ___________ 0.5

_t14_____ 1726 ____ 16.4 ____ July 16.0 ___________ 0.4

_t14_____ 1966 ____ 15.4 ____ July 15.0 ___________ 0.4

_t14_____ 1970 ____ 16.4 ____ Aug 16.0 ___________ 0.4

_t17_____ 1920 ____ 14.4 ____ July 14.1 ___________ 0.3

_t17_____ 1950 ____ 16.2 ____ July 15.9 ___________ 0.3

_ 19 _____ 1804 ____ 16.1 ____ July 15.9 ___________ 0.2

_ 20 _____ 1922 ____ 13.8 ____ July 13.7 ___________ 0.1 

__________________________________

In addition, these 8 years saw June equal one or two other months as warmest of the year:

1662 (15.0 tied both Jul, Aug)

1685 (14.5 tied Aug)

1711 and 1866 (15.5 tied July)

1785 (16.1 tied July), similar 1896 (16.2 tied July)

1877 (15.2 tied Aug)

1889 (15.3 tied July)

______________________________________

It used to be not so rare, but no year since 1970 has produced a warmest June, 1993 was 0.1 below (15.0 vs 15.1 in July). 

Note: in only one year is September the warmest month, 1890 (14.6 vs 14.5 July and 14.1 Aug).

In 1729 Sep (16.6) was 0.2 below July, same margin as in 1961 (15.2 tied July but Aug was 15.4);

in 1865 Sep (16.3) was 0.3 below July (16.6).

In 1895 Sep (15.4) was 0.4 below August (15.8), a margin equalled by 2011 (Sep 15.1 vs 15.5 in Aug but July was also warmer at 15.3).

If you could trade 1-5 Oct 2011 for 1-5 Sep, then the "month" of 6 Sep to 5 Oct 2011 would be warmer by 0.1 like 1890 (15.6 vs 15.5 in Aug). 

 

 

[richie3846]

2 hours ago, Derecho said:

Well last Tuesday saw cool uppers and low cloud and heavy rainfall, the kind of synoptics that deliver low maximums.

The high SSTs will have encouraged troughing initially but sea temperatures are also pretty sensitive to atmospheric circulation because the mixing layer is shallow at this time of year (the part of the ocean that mixes with the atmosphere). It doesn't surprise me that they have dropped fairly quickly.

They will have added an extra degree of warmth, despite the unsettled weather the CET is still running above the old 61-90 average. Would it have been running above if we had been surrounded by colder then average SSTs? 

Thanks for the info, so it seems specific situations such as cold uppers and rain, can pretty much counteract any extra warmth, but generally speaking there may be an uptick in temperature from the warmer seas. That makes a lot of sense to me, because I was very confused by last Tuesday. Little Rissington only hit 12.5c, an extraordinary temperature for July, but as you suggest, other days in the month may have been a little warmer than they otherwise would have been. 

[richie3846]

2 minutes ago, Roger J Smith said:

These 20 years (out of 354) had their warmest months in June. I list them by margins of "victory" over second place (and what second place was) ...

RANK ____ YEAR ____ JUNE ____ 2nd warmest ____ margin

_ 01 _____ 1676 ____ 18.0 ____ July 16.0 ___________ 2.0

_ 02 _____ 1846 ____ 18.2 ____ Aug 16.6 ___________ 1.6 (July was 16.5)

_ 03 _____ 1822 ____ 17.1 ____ July 15.6 ___________ 1.5

_t04_____ 1672 ____ 16.0 ____ July 15.0 ___________ 1.0

_t04_____ 1786 ____ 16.1 ____ Aug 15.1 ___________ 1.0

_t04_____ 1817 ____ 15.1 ____ July 14.1 ____________ 1.0

_t04_____ 1858 ____ 16.8 ____ Aug 15.8 ___________ 1.0

_t04_____ 1960 ____ 16.1 ____ July 15.1 ___________ 1.0

_ 09 _____ 1940 ____ 16.4 ____ Aug 15.6 ___________ 0.8

_ 10 _____ 1755 ____ 15.7 ____ July 15.0 ___________ 0.7

_ 11 _____ 1845 ____ 14.9 ____ July 14.3 ___________ 0.6

_t12_____ 1683 ____ 16.0 ____ July 15.5 ___________ 0.5

_t12_____ 1798 ____ 16.9 ____ Aug 16.4 ___________ 0.5

_t14_____ 1726 ____ 16.4 ____ July 16.0 ___________ 0.4

_t14_____ 1966 ____ 15.4 ____ July 15.0 ___________ 0.4

_t14_____ 1970 ____ 16.4 ____ Aug 16.0 ___________ 0.4

_t17_____ 1920 ____ 14.4 ____ July 14.1 ___________ 0.3

_t17_____ 1950 ____ 16.2 ____ July 15.9 ___________ 0.3

_ 19 _____ 1804 ____ 16.1 ____ July 15.9 ___________ 0.2

_ 20 _____ 1922 ____ 13.8 ____ July 13.7 ___________ 0.1 

__________________________________

In addition, these 8 years saw June equal one or two other months as warmest of the year:

1662 (15.0 tied both Jul, Aug)

1685 (14.5 tied Aug)

1711 and 1866 (15.5 tied July)

1785 (16.1 tied July), similar 1896 (16.2 tied July)

1877 (15.2 tied Aug)

1889 (15.3 tied July)

______________________________________

It used to be not so rare, but no year since 1970 has produced a warmest June, 1993 was 0.1 below (15.0 vs 15.1 in July). 

Note: in only one year is September the warmest month, 1890 (14.6 vs 14.5 July and 14.1 Aug).

In 1729 Sep (16.6) was 0.2 below July, same margin as in 1961 (15.2 tied July but Aug was 15.4);

in 1865 Sep (16.3) was 0.3 below July (16.6).

In 1895 Sep (15.4) was 0.4 below August (15.8), a margin equalled by 2011 (Sep 15.1 vs 15.5 in Aug but July was also warmer at 15.3).

If you could trade 1-5 Oct 2011 for 1-5 Sep, then the "month" of 6 Sep to 5 Oct 2011 would be warmer by 0.1 like 1890 (15.6 vs 15.5 in Aug). 

 

 

I believe 1st October 2011, Lyneham weather station recorded its warmest day of the year. It doesn't surprise me that 6th September to 5th October was a warmer period.

[Relativistic]

12 hours ago, Roger J Smith said:

Top 20 differentials (colder) in July of consecutive years

It used to be quite common for warmest months of July to be followed by quite cool ones. But 1818 (18.2) was followed by three consecutive colder months of July eventually dropping 3.4 by 1821. The largest year to year differences 1659-1700 were 2.0 C so none made this list. 

Note August 1911 (18.2) to August 1912 (12.3) fell 5.9 deg. July 1911 (18.2) to July 1912 (16.1) was a less noteworthy drop but to July 1913 the total drop was 3.6 from 18.2 to 14.6. ... Note also three of these drops in six years 1874 to 1879 (and a fairly large drop 1870 to 1871 of 2.3). 

 

Rank _____ July A ______ July B ______ diff

_ 01 ______ 1921 18.5 _ 1922 13.7 __ 4.8 (1921 was also 4.4 warmer than July 1920 at 14.1)

_ 02 ______ 2006 19.8 _ 2007 15.3 __ 4.5

_ 03 ______ 1757 18.4 _ 1758 14.2 __ 4.2 (then 1759 was 18.2! up 4.0) (July 1818 was also 4.1 warmer than 1817)

_t04______ 1852 18.7 _ 1853 14.9 __ 3.8

_t04______ 1859 18.3 _ 1860 14.5 __ 3.8

_t06______ 1783 18.8 _ 1784 15.2 __ 3.6

_t06______ 1887 17.3 _ 1888 13.7 __ 3.6

_t08______ 1701 18.3 _ 1702 15.0 __ 3.3

_t08______ 1808 18.4 _ 1809 15.1 __ 3.3

_t08______ 1901 18.0 _ 1902 14.7 __ 3.3

_ 11 ______ 1878 16.6 _ 1879 13.6 __ 3.0

_t12______ 1794 18.1 _ 1795 15.2 __ 2.9

_t12______ 1976 18.6 _ 1977 15.7 __ 2.9

_t14______ 1801 16.1 _ 1802 13.5 __ 2.6

_t14______ 1983 19.4 _ 1984 16.8 __ 2.6

_t16______ 1714 18.0 _ 1715 15.5 __ 2.5

_t16______ 1762 17.8 _ 1763 15.3 __ 2.5

_t16______ 1874 17.3 _ 1875 14.8 __ 2.5

_t16______ 1876 17.2 _ 1877 14.7 __ 2.5

_t20______ 1870 17.5 _ 1871 15.2 __ 2.3

_t20______ 1999 17.6 _ 2000 15.3 __ 2.3

?? ________ 2022 18.2 _ 2023 ?? ?? __ ?? (needs to be 15.8 to become sole 20th, 15.7 t16, 15.6 t14, 15.3 to 15.5 sole 14th 15.3 t12, etc)

____________________________

The warmest July not to be followed by a cooler July was 18.0 1994 (1995 18.5);

2nd to 17.8 1933 (1934 was 18.2);

3rd to 17.7 1900 (1901 was 18.0);

4th to 17.6 1793 (1794 was 18.1). 

 

 

Not relevant to this thread strictly speaking, but the jump from January 1795 (-3.1C; coldest on record) to January 1796 (7.3C; third-mildest on record) is very hard to imagine. A differential of 10.4C!

Edited July 11, 2023 by Relativistic

[Summer Sun]

16.4c to the 10th

0.4c above the 61 to 90 average

0.2c above the 81 to 10 average

[Addicks Fan 1981]

If I'm honest @Summer SunI think the CET now will be flat for the rest of this month, not going one way or the other.   

[The PIT]

Sunny Sheffield down to 16.4C +1.1C. Rainfall 47.6mm 74.5% of the monthly average.

[Summer Sun]

16.5c to the 11th

0.5c above the 61 to 90 average

0.3c above the 81 to 10 average

[Don]

19 minutes ago, Summer Sun said:

16.5c to the 11th

0.5c above the 61 to 90 average

0.3c above the 81 to 10 average

A slight rise yesterday, CET hanging on in there!

[ItNeverSnowsInWindsor]

Looking interesting this month!

[Frigid]

3 hours ago, Don said:

A slight rise yesterday, CET hanging on in there!

I suspect the CET dropping from now, though a gradual decline. Could probably see it in the 15s by next week, weekend looks particularly cool. Who knows where it'll be by months end.. 

[The PIT]

Sunny Sheffield still at 16.3C +0.9C above average. Rainfall 51.3mm 80.3% of the monthly total.

[Addicks Fan 1981]

4 hours ago, Frigid said:

I suspect the CET dropping from now, though a gradual decline. Could probably see it in the 15s by next week, weekend looks particularly cool. Who knows where it'll be by months end.. 

Or it could stabilise.   

Edited July 12, 2023 by Addicks Fan 1981

[Addicks Fan 1981]

Have looked at Pershore as a template for the CET for the next days and it looks like we will have three cool days before the average temperatures return.   

[Roger J Smith]

Keep in mind also that the CET people take off 0.2 from the average of the three locations to adjust for urban heat island, I think actually what they are doing is taking 0.6 off the station near Luton and keeping the other two static (since there is no real urban effect there), but it has the same outcome. I looked at Stonyhurst on google earth, looks to be a very small village well removed from urban areas, and Pershore of course is in rural terrain. Rothamsted is suburban and 0.6 would be a conservative estimate for its urban effect, I won't be surprised if CET gives us a memo of an increase to 0.3 indiciating they rate it as 0.9 there. The point of doing that is that the CET is meant to be a climate index for non-urbanized locations. I have a study of Toronto downtown and NYC (Central Park) data in the climate change forum and I have been taking off 1.1 C or 2.0 F from the data since 1980, working up to that from 0.1 in the 1881-1890 decade and increasing by 0.1 each decade. At some point in a very large city like those or like London, the urban heat island flattens out and can reverse a little if parks are improved, but the total size and magnitude of the heat island spread out over larger areas. This is not supposed to contaminate climate change studies but of course if a large percentage of the earth is urbanized then it's more difficult to separate out the two forms of human caused (to whatever extent) increases, urban heat islands are supposed to reset during windy weather but that heat escapes somewhere into the larger atmosphere and is probably a part of the reason why there is a recent temperature increase as well as the more obvious reasons. It's a little more complex than just reducing a temperature series, for example, a cloudy and wet month may have a smaller urban increase than a calm, dry month. Most of the urban heat island's effects are seen in overnight temperatures and in particular when skies are clear and winds are light. So this 0.2 adjustment over a data set is only giving an approximate picture of the actual urban effect. (in my opinion) ... It is probably accurate on the macro scale but it may be a different story month by month. This is the same issue that is driving the discussion around changes from legacy to v2.0 and now v2.0.1.0, various adjustments are made after assessing impacts of station and site changes. It was realized at some point that data around 2000 to 2005 had perhaps not been adjusted correctly when there were station changes for the CET, and that's why those years in particular got larger adjustments than a lot of the modern data did. 

[Addicks Fan 1981]

Thanks @Roger J Smithfor the info.   

[Summer Sun]

16.4c to the 12th

0.4c above the 61 to 90 average

0.2c above the 81 to 10 average

[Roger J Smith]

EWP update, now at around 33 mm, the 00z GFS had a real soaker with over 100 mm more to come, but 06z has returned to previous moderate increases adding 35-40 mm to reach 70 mm or so. Both runs were rather cool, the 00z suggested a return to the 15s eventually, the 06z stays in the low to mid 16 range. The 00z run had a deep low moving across the south around day 15 (obviously not that credible at that time frame) with daytime readings at record low levels on 27th (only 10-13 C) in parts of Wales and Severn valley. That feature is gone from the 06z run. Will see how the 12z run looks within an hour or two (just starting in now).