CET

The Central England Temperature [CET] record is a meteorological dataset originally published by Professor Gordon Manley in 1953 and subsequently extended and updated in 1974, following many decades of painstaking work. The monthly mean surface air temperatures, for the Midlands region of England, are given in degrees Celsius from the year 1659 to the present.

This record represents the longest series of monthly temperature observations in existence. It is a valuable dataset for meteorologists and climate scientists. It is monthly from 1659, and a daily version has been produced from 1772. The monthly means from November 1722 onwards are given to a precision of 0.1 °C. The earliest years of the series, from 1659 to October 1722 inclusive, for the most part only have monthly means given to the nearest degree or half a degree, though there is a small ‘window’ of 0.1 degree precision from 1699 to 1706 inclusive. This reflects the number, accuracy, reliability and geographical spread of the temperature records that were available for the years in question (intro courtesy of Wikipedia).



Summer 2016 in Central England

Now that summer has finally drawn to a close I thought I would look at how the astronomical summer finished in the Central England Temperature [CET] series. The mean CET of the astronomical summer was slightly higher than that of the meteorological one (1st June – 31 August) at 16.70°C, or +1.36°C above the 1961-1990 long-term average, which made it the warmest since 2006, and the 19th warmest in the daily series that started in 1772. A couple of caveats to all this are (1) the values are based on September provisional values (2) I use fixed dates in my climate statistics for the seasons, so summer starts on the 21st of  June and ends on the 20th of September, and yes I do know that the date and time of the equinoxes varies.

daily-cet-summer-2016

Ranked on night-time minima the summer of 2016 was joint 3rd warmest. So it looks like the higher number of warm nights and the high mean minimum CET bolstered up the final mean CET of the summer. Not all years are like 2016 where the mean maximum anomaly is matched by the mean minimum anomaly. If you look at the above graph the blue diamonds indicate where four new highest minimum CET records were broken during the summer.

daily-central-england-temperature-summer-1772-2016

The table below shows a count of when maximum daily CET was equal to or exceeded 25, 26.7 or 28°C.  There were only 8 days when the maximum daily CET was 25°C or higher during the summer of 2016. Interestingly, the summer of 2013 had double that number of days but a slightly lower mean (16.24°C), but that again can be explained by the mean minimum in 2016 which was +0.93°C higher than in 2013.

daily-central-england-temperature-1-jan-1878-20-sep-2016

 

Warm start to September 2016 in central England

It’s been a very warm start to the first 13 days of September 2016 in the Central England Temperature [CET] daily series. Using provisional data it lies 10th warmest for the first 13 days in the daily mean series 1772 with a mean anomaly of +2.83°C,  warmer than even the great September of 1959.

daily-central-england-temperature-warmest-start-to-a-september-1772-2016

If you rank on daily maximum temperatures which dates back to 1878 rather than 1772, then 1959 is out at number one, with 2016 trailing by 2.26°C. The reason why September 1959 was so warm was that it was anticyclonic and very sunny.

daily-central-england-temperature-warmest-start-to-a-september-1878-2016

Interestingly, September 1906 – the year with the highest September temperature – appears prominently  in both tables.

 

Warmest Summer since 2006 in Central England

Daily CET Summer [JJA] 2016

Daily CET Summer [JJA] 2016

It looks like Summer 2016 was the warmest in Central England since 2006 with a mean temperature of 16.43°C which was +1.08°C above the long-term average (1961-1990). Surprisingly no maximum records were broken during the summer but two high minima were.

Warmest Summers 1659-2016

Warmest Summers 1659-2016

In the bigger scheme of things Summer 2016 was the joint 27th warmest since 1659 based on mean temperature.

Summer mean CET & anomaly 1659 - 2016

Summer mean CET & anomaly 1659 – 2016

 

Warmest August since 2004 in Central England

August 2016 looks like it was the warmest since 2004 with a mean CET of 17.12°C which was +1.38°C above the long-term average (1961-1990):-

Daily Central England Temperatures August 1772 - 2016

I make it the 27th warmest August since 1659 judging by its monthly mean temperature:-

August mean CET & anomaly

August mean CET & anomaly

Warmest daily anomalies since 1878

Someone on the Weather and Climate Google Group asked me to produce a list of the 50 warmest daily anomalies in the Central England Temperature [CET] series in a similar manner to how I produced a list of the 50 hottest days since 1878, and so here it is!

50 warmest daily CET anomalies since 1878

50 warmest daily CET anomalies since 1878

So there were nine entries in the top fifty that have occurred since 2001, but surprisingly to me, an April was in top spot, the 3rd of April 1946 to be precise, with an anomaly of +13.6°C for that day, closely followed by the 3rd July 1976 (+13.2) and the 9th of August 2003 (+12.8).  This is the chart of the 3 April 1946 courtesy of Wetterzentrale, so obviously a very warm spring day in an anticyclonic SE’ly.

Also noticeable was the 29th of March 1965, with a remarkable range in anomalies of -2.2°C minimum to +11.5°C maximum. The actual temperature range was 21.5°C from a minimum of +0.7°C to a maximum of 22.2°C in the day.

Warmest Central England Temperatures for the 29 March

Warmest Central England Temperatures for the 29 March

Hottest days since 1878

Daily Central England Temperatures

For a bit of fun I thought that I would graph the hottest days in the daily Central England Temperature [CET] series since 1878. My graph is a copy of one that I saw on the Met Office web site, so it’s not particularly unique. As you can see the hottest day in Central England is tied between the 3 August 1990 and the 3rd July 1976 with a composite maximum of 33.2°C. The colour of the bars indicate that seven of the top fifty warmest days have occurred since 2001, in fact last month’s maximum of 30.9°C (19 July 2016) has now become the 22nd hottest day in the last 138 years.

I’m not that satisfied with the graph though as it fails to highlight clearly in which twenty year period the extreme occurred, even though I’ve added a colour code for each bar that corresponds to the specific twenty year period that it occurred. It maybe the colours that I’ve chosen are wrong, but it might also be the fact there is very little difference between each extreme record. I also realise that the sort needs to be a little more sophisticated, so that records with equal maximum temperatures are also sorted a second time on their means so that the day with the higher mean is also ranked higher. So I may revisit this application to fix both that and also to add extra functionality to filter on warmest day by month and season, as well as year.

Daily extremes in Central England Temperatures

Here is a table and chart that display the daily extremes in the Central England Temperature [CET] series from 1878. When I say daily extreme, what I mean is the difference between the highest and lowest temperatures that have occurred on that particular day since 1878. It was a little surprising when I added a best fit curve and noticed that it wasn’t as seasonal as I would have thought, with the highest extremes in the summer and the lowest in the winter. Instead the lowest extremes seem to occur in November with the highest extremes in May and June. It does of course depend on what kind of best fit curve you employ, the one I used in this graph were to the 5th polynomial according to my charting component, which produces a very smooth curve than a higher polynomial would do.

Daily Central England Temperatures

Extreme Daily Range from 1878

Daily Central England Temperatures Largest Daily Range 1 Jan 1878 - 10 Aug 2016

Largest Daily Range from 1878

Summer 1954 – worst in living memory?

In a recent article about the Summer Index  in Central England, summer 1954 came in at the bottom of the table with the worst possible scores for temperature, rainfall and sunshine since at least 1929. In researching for this article by looking back in the online archives of the Royal Meteorological Society, I did find that 1931, 1922 (mental note to find out why the summer of 1922 was so cold) and 1912 all rivalled 1954 as the worst summer on record, but I have a special affection for 1954 because it was in the summer of that year I was born.  Here are the headlines for the months of the extended summer of 1954 that I’ve grabbed from the Monthly Weather Report for each month that the Met Office make available online (they are Crown copyright – so I hope they don’t mind).

  • May 1954 Mainly dull and wet, with frequent thunderstorms; large variations of temperature.
  • June 1954 Mainly dull and cool; periods of rain, heavy at times.
  • July 1954 Notably cool and dull; wet in some areas.
  • August 1954 Cool and dull, mainly wet in England, Wales and southern Scotland.
  • September 1954 Cool and unsettled; wet in most areas; sunny on the whole.

To begin with I thought that I would just look back at the circulation patterns of the summer using the reanalysis MSLP data from NOAA, so the next three charts are the mean pressure for each meteorological month of the summer, followed by three more anomaly charts for June, July and August.  As you can see from the first three charts the summer was dominated by a west or northwesterly flow, which during July was quite strong.

Mean Sea Level Pressure 1 Jun - 30 Jun 1954

Mean Sea Level Pressure 1 Jun – 30 Jun 1954

Mean Sea Level Pressure 1 Jul - 31 Jul 1954

Mean Sea Level Pressure 1 Jul – 31 Jul 1954

Mean Sea Level Pressure 1 Aug - 31 Aug 1954

Mean Sea Level Pressure 1 Aug – 31 Aug 1954

The monthly anomaly charts for each month all show an anomalous low to the northeast or east of the British Isles, with mean pressure between -5 and -9 hPa lower than the monthly long-term average.

Mean Sea Level Pressure Anomalies 1 Jun - 30 Jun 1954

Mean Sea Level Pressure Anomalies 1 Jun – 30 Jun 1954

Mean Sea Level Pressure Anomalies 1 Jul - 31 Jul 1954

Mean Sea Level Pressure Anomalies 1 Jul – 31 Jul 1954

Mean Sea Level Pressure Anomalies 1 Aug - 31 Aug 1954

Mean Sea Level Pressure Anomalies 1 Aug – 31 Aug 1954

And here are the 1200 UTC surface temperature anomalies also from reanalysis data which show how cool, if not cold it was, not just across the British Isles but also the near continent through each of the summer months.

Air Temperature Anomalies 01 Jun to 30 Jun 1954

Air Temperature Anomalies 01 Jun to 30 Jun 1954

Air Temperature Anomalies 01 Jul to 31 Jul 1954

Air Temperature Anomalies 01 Jul to 31 Jul 1954

Air Temperature Anomalies 01 Aug to 31 Aug 1954

Air Temperature Anomalies 01 Aug to 31 Aug 1954

Here for good measure are the mean temperature anomalies for the entire summer courtesy of the Met Office.

1954_14_MeanTemp_Anomaly_1961-1990

Summer 1954 – mean temperature anomalies

The British Isles were in quite deep (for the time of year) cold air for long periods during the summer of 1954. I count 49 of the 92 days of that summer when sub 552 dm partial thicknesses (the green blobs) covered all or some part of the British Isles.

North Atlantic MSLP & 500 gh [WZ] Summer [JJA] 1954

North Atlantic MSLP & 500 gh [WZ] Summer [JJA] 1954 (courtesy of Wetterzentrale)

Of all the information and graphics that I have packed into this article, none of them conveys as much as the next graphic just how exceptional the Summer of 1954 was. It’s a chart of daily Central England Temperatures [CET] and anomalies for the entire Summer. The fifth chart from the top displays cold or warm spells that have lasted for four days or longer and were +/- 2°C  above the long-term average for that day, and as you can see in the entire summer there were only three warm spells, and all of them spells of high night-time minima rather than day time maxima.

Daily CET Summer [JJA] 1954

Daily CET Summer [JJA] 1954

Here is a list of the coldest summers in the CET monthly series since 1659. Although 1954 was cold, coming in at the 17th coldest with a mean anomaly of -1.19°C, there have been colder summers including that of 1922 with an anomaly of -1.72°C.

Coldest Summers (1659-2016)

Coldest Summers (1659-2016)

And finally a look at the daily rainfall totals for England and Wales from the UKP data series that are maintained and made available by the wonderful Met Office yet again. It was a wet summer and according to the figures it was over 40% wetter than average. It looked very wet from the 5th of June for at least ten days or so, with wet spells again in late July and again through the first three weeks of August.

HadUKP England & Wales 1 June 1954 - 31 August 1954

HadUKP England & Wales 1 June 1954 – 31 August 1954

In writing this article I’ve finally come to realise that I have developed an amazing set of applications to display climate data, but charts, tables and maps aren’t the be all and end all of what makes an interesting article about past weather events. To glue all those disparate images together you need meaningful textual information about whatever event your article is about, and if that event happened over sixty years ago like this one did, when you were either perhaps too young or not even born, then you can’t always write about it with the benefit of first hand experience.

How summer 2016 is doing so far

In Central England the mean temperature of the Summer [JJA] so far is 1°C above the long-term average, which currently makes it the 17th warmest of the last 138 summers for the period from 1 June to 22 July. So pretty warm, but not in the same league as 1976 or 2003 for the same time, but of course there is still almost six weeks left to run of the meteorological summer and August might be a sizzler! Below is a chart comparing maximum temperatures of 2016 with the summer of 1976 forty years before, of course the data for July is still provisional but there’s still no missing the recent hot day of Tuesday the 19th. The way the anomalies for this summer are currently (maximum +0.71°C minimum +1.35°C) it points to warm nights being the main driver rather than warm days, in fact maximums ran below average for much of the period between the 24th of June and 15th of July.

Daily Central England Temperature Warmest start to a Summer [JJA] 1878 - 2016

Daily Central England Temperature  – Warmest start to a Summer [JJA] 1878 – 2016

Ten degree anomaly days

Daily Central England Temperature

Daily Central England Temperature – Annual number of days with maximum anomaly >=+10°C

The other day I was listening to a BBC forecast and heard John Hammond say that hot days like Tuesday (19th of July 2016) were not as unusual as you might think (or words to that effect). That got me thinking about just how rare or common exceptional days were in the Central England Temperature [CET] series, so I delved into the statistics to find out…

As far as I can make out there have been around 95 days which had an anomaly of +10.0°C or greater since 1880 ((extreme high maximum events) in the CET series. That may sound a lot, but don’t forget that’s over a period of 135 years, or almost 50,000 days, so that makes the average interval between exceptional warm days at once every 17 months or so, and don’t forget this type of event is not just limited to summer months, they can and do occur in any month between March and October.

Below are a couple of tables. The upper table is of totals that are grouped by decade, and the highlighted column is of warm days with anomalies >=10°C. The lower table is a list of all extreme warm events from 1970 to 2016, and as you can see first and latest entry is Tuesday’s event (19 July 2016) with a provisional CET of 31.5°C or +11.35°C above the long-term average for that particular day.  Tuesday’s event  wasn’t the first  ten degree event of 2016, the first one was occurred in a warm spell on the 8th of May, but I bet the majority of people will hardly remember that one. Last year there was only one ten degree event which of course is the one that occurred on the 1st of July 2015. Before that you have to go back almost four years to find the previous ten degree plus event which was also fairly notable as being the warmest October day on record if memory serves.

Annual number of extreme Anomalies

This application is still not finished, but already it’s thrown up some interesting statistical results. The 1941-1950 period has the record number of extreme high maximum +10 degree events in any decade which surprised me, and what about the period between 1976 and 1990, almost 14 years without a ten degree anomaly event. Also the table lists no ten degree high mean events, but around 37 extreme low mean events. Perhaps I’ve screwed up somewhere, I would have expected there to have been an equal number of hot and cold extreme mean events – but not none and 37!