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).

It’s best to navigate all the articles by moving your mouse cursor over the ‘Look Back’ tabbed page and a drop down menu of items will appear for you to select from.



Summer days in Central England

IMG_9414

I reckon that a temperature of 26.7°C or 80°F is the threshold for a summer day in Central England. If you set the threshold any higher the number of occurrences drops off quite a bit. I analysed the data back to 1878 when the daily series started pushing out both maximum and minimum temperatures, and as you can see from the chart below there has been a 43.1% increase in the annual number of days with a maxima equal or higher than 26.7°C since 1878.

Daily Central England Temperature

Daily Central England Temperature – annual number of days with maxima >=26.7°C

The table below shows the results from three different thresholds (25, 26.7 & 28°C). The table is sorted and ranked on the 26.7°C column, and the year 1995 with 24 days with maximum temperatures of 80°F or higher tops the results, quickly followed by 1976 the year with the great summer.

Daily Central England Temperature 1 Jan 1878 - 18 Jul 2016

Daily Central England Temperatures – annual maximum temperatures 1878 – 2016

And here are the results grouped by decade:

Daily Central England Temperature 1 Jan 1878 - 19 Jul 2016

Daily Central England Temperature – maximum temperatures by decade 1878 – 2016

Of course some years are worst than others, 2012 had no days in Central England with a maxima above 80°F, so did 2012, and the very bad summer of 1954 (not in this list) only had one day with a temperature above 25.0°C!

Daily Central England Temperatures 1 Jan 1878 - 18 Jul 2016

Daily Central England Temperatures 1 Jan 1878 – 18 Jul 2016

 

Finally, here is a chart of the number of days with a slightly lower threshold of 25.0°C, which as you can see from the chart shows an even greater 59% increase in the annual number of such days since 1878.

Daily Central England Temperature

Daily Central England Temperature – annual number of days with maxima >=25°C

In conclusion the CET is showing a strong increase in warm or very warm days in the series back to 1878, the increase is of course erratic as you would expect, but the trend over the last 138 years is upwards, and that means whether we like it or there will be an increasing number of warm or very warms days in Central England in the years to come.

CET: June 2016

The June Central England Temperature [CET] values are now in, and I make the mean temperature for the month around 15.3°C with an anomaly of +1.08°C (wrt 1961-1990 LTA). June 2016 was warm for the first 10 days or so, but temperatures returned to near average for the remainder of the month as the westerlies returned, and it ended up being the #46 warmest in the monthly series back to 1659. One thing I did notice through June was the preponderance of warm nights.

June mean CET & anomalies 1659-2016

June mean CET & anomalies 1659-2016

Another warm spring

Daily CET Spring 2016

Daily CET Spring 2016

The astronomical spring of 2016 looks like it was the 37th warmest in the last 244 years in the Central England Temperature [CET] series, with a mean temperature of 10.97°C and anomaly of +0.76°C with respect to the 1961-1990 long-term average. On the 28th of April a new minimum record was set in a late spring frost. Two new daily maximum records were set in the early May warm spell on the 8th and 9th as were two new high minima. A warm spell in early June lasted for eight days but the high night-time minima went on for 13 nights. Spring, like all the other seasons are slowly warming, in the last 244 years the decadal warming trend is +0.14°C, and only one spring (2013) in the last twenty has been cold. The final values for spring 2016 may change very slightly because the data for June from the Met Office is still only provisional.

Daily Central England Temperature Spring 1772 - 2016

Daily Central England Temperature Spring 1772 – 2016

Start of June similar to the barbecue summer of 2009

Barbecue Summer with Darren Bett

I was just looking at the latest Lamb Weather Types [LWT] from the Climate Research Unit [CRU] and ran a comparison on the beginning of June in previous years. Interestingly on the 14 days between the 30th of May and 12th of June, 2009 tops the list of best analogs to 2016, with a match of 88.7% when you compare the indices from the objective LWT data for both years. I will stress at this point that my method is just a simple comparison using these indices, and drawing any conclusion on what the rest of the summer might bring from a short 14 day analog would be very foolish. Having said that so few people read my ramblings, and since I’m paying for the privilege of hosting the xmetman blog, I thought I would do it anyway, so if you’re reading this remember you heard it here first! Of course if you’re reading this in the future and it turned out that 2016 was a great summer, just put it down to those pesky analogs.

Lamb Weather Type Analog for the Last 14 days [30 May - 12 Jun] Match Average Indices method

Lamb Weather Type Analog for the Last 14 days [30 May – 12 Jun] Match Average Indices method

If you scan down the closest matches in the list many of them from recent years. Here’s a look at the daily charts for 2009 and 2016 just to see how alike they are.

30 May - 12 June 2009 (courtesy of The Met Office)

30 May – 12 June 2009 (courtesy of The Met Office)

30 May - 12 Jun 2016 (courtesy of The Met Office)

30 May – 12 Jun 2016 (courtesy of The Met Office)

Both were initially anticyclonic, with high pressure to the north of the country, before pressure fell and low pressure systems spread in from the southwest. This is how the summer of 2009 turned out as far as Central England Temperatures [CET] were concerned, a warm spell at the end of June and start of July, the rest of July was cool and August was only just slightly above average.

Daily CET Summer [JJA] 2009

Daily CET Summer [JJA] 2009

And below is a chart of how the England Wales daily precipitation looked through the summer of 2016. July did turn out a very cool and wet month indeed. Looking back in hindsight, the rainfall accumulations were only 120% of average for the whole summer, but I suppose that you have to set that against what a disappointment it was after all the euphoric hype and raised expectations that the seasonal forecast by the Met Office received back in the April.

HadUKP England & Wales 1 June 2009 - 31 August 2009

HadUKP England & Wales 1 June 2009 – 31 August 2009 (courtesy of the Met Office)

I don’t recall if the north Atlantic sea surface temperatures were as cool as they are this year so I can’t say if there was a similarity there. At the start of summer 2009 we had also just exited from a minor La Niña event and just entering an El Niño, so completely the reverse of what’s happening at the moment in summer 2016. We will just have to see what the next couple of months bring and hope for the best.

So you thought it’s been a warm start to June?

You may have thought it’s been quite a warm start to June, but it pales into insignificance when you look back at the Central England Temperatures [CET] for the first eight days of June over the last 244 years. So far the mean anomaly for the first eight days of June 2016 has been +2.15°C above average, making it the 32nd warmest start since 1772. The warmest first eight days of June occurred in 1982 when the mean anomaly was +5.68°C, over three degrees higher. I suppose we can console ourselves that 1976 had a cooler start than 2016 has had, but then again there looks like there is a distinct change of type in the offing if the NWP models are anything to go by.

Warmest 1-8 June 1772-2016

Warmest 1-8 June 1772-2016

Interestingly there has been a very, very slight cooling trend for the mean temperature for the first eight days of June in the last 244 years.

CET 1-8 June 1772-2016

CET 1-8 June 1772-2016

Tri weather data sets

A bit of a strange title I know, but I’ve recently written an application that displays climate data for the UK from three separate daily data sets for atmospheric circulation, temperature and precipitation, and hence the tri.

  • Daily Central England Temperature [CET]
  • Objective Lamb Weather Type [LWT]
  • UK regional precipitation series [HadUKP]

It’s not the first time I’ve merged weather data sets in a single application, but this is probably the first time I’ve managed to finish it and publish the results that it generates. The essential requirement of course is a source of regular daily weather data, and so the CET and LWT series were the ideal (and only) choice because they are both updated on a daily or weekly basis. The other daily weather set that fits was the HadUKP series that the Met Office maintain, but there are a couple of problems with this series, one being that is only updated on a monthly basis, and the other is that the series isn’t very long and only extends back to 1931, and not 1772 and 1861 as in the case of CET and LWT. The big plus for anyone interested in the climate of the British Isles is that you can explore the climate of a particular day, week, month or season very easily and quickly. Here is a screenshot of the application as it stands now:

LWT-CET-UKP application

LWT-CET-UKP application

Below are a few examples of some particular well-known periods and spells of weather from the past, starting with a look at last Autumn and Winter.

27 Sep 2015 - 20 Mar 2016

27 Sep 2015 – 20 Mar 2016

You can certainly see the lovely anticyclonic spell that we had in September 2015, and the record mild November and December that followed, in this six month overview. Next a four-month window and a look at the Winter of 1946-47, you can clearly see how the cold started with an anticyclonic spell in the second half of January 1947, with the snow following along at the start of February.

1 Dec 1946 - 23 Mar 1947

1 Dec 1946 – 23 Mar 1947

Here’s the summer of 1976 and the record warmth of late June and early July, notice also the preponderance of anticyclonic types up until the start of September, then the breakdown into more cyclonic weather and the rains that brought an end to the drought.

18 Apr 1976 - 17 Oct 1976

18 Apr 1976 – 17 Oct 1976

Here’s the great winter of 1962-63, in comparison to 1946-47 it’s clear that winter 1962-63 started much earlier (before Christmas) and finished earlier, but was also drier and more anticyclonic.

16 Dec 1962 - 24 Mar 1963

16 Dec 1962 – 24 Mar 1963

Improvements

I could maybe add an extra chart in the shape of a ‘barograph’ because I hold all the mean pressure points in the LWT data. I could present that as a scatter graph of all the 16 MSLP grid values for 12 UTC and then plot a moving average. I could also highlight with a star the named storms, but that would only work for the very latest years. I could also colour the precipitation bar chart blue to indicate snow rather than rain when the CET was less than 1 or 2 °C (I have in fact now implemented that idea as you can see if you look at the screenshot of the application!). I do plan to add functionality to show a grid of archived weather charts for the selected period from Wetterzentrale. The one element that I think it does miss is daily sunshine data, but there is no source that I know of for daily sunshine values for a region, let alone for a single station, so that’s a non-starter. I must say that this really is an excellent tool for any climatologist with an interest into the weather of the British Isles over the last 150 years or so.

Central England Temperatures: May 2016

As far as I can make out, May 2016 was the 37th warmest in the Central England Temperature [CET] series that started in 1659. It had started coolly but warmed up significantly between the 4th and the 12th when two maximum CET records were broken (8th and 9th), but a colder week followed and wiped out a lot of the positive anomalies that had been gained.

Daily Central England Temperature - May 2016

Daily Central England Temperature – May 2016

Here are the May rankings since 1659, it certainly was the warmest since the exceptionally warm May of 2008, with a mean anomaly of +1.46°C. So although global temperature records are being broken on a monthly basis, CET records certainly aren’t.

Warmest May CET

Here is a look at all May’s since 1659.

May mean CET & anomaly

May mean CET & anomaly

And finally looking back over the last 62 years of CET monthly anomalies.

Central England Temperature Mean Anomalies 1954 - 2016

Central England Temperature Mean Anomalies 1954 – 2016

Possibly the warmest May on record?

I have read reports that this month will end up being the warmest May on record thanks to a heat wave in the last 10 days of the month. Going by the latest provisional values of the Central England Temperature [CET] series, so far this month (up until the 20th) that looks a total impossibility. A quick bit of calculation to see just how hot the last 11 days of the month would have to be to beat May 1833 reveals that the daily mean would have to exceed 20.1°C for every remaining day of the month. The people who are making these predictions obviously didn’t realise just how exceptionally warm May 1833 was, +4.64°C above the long-term average. Currently May 2016 is tracking just inside the top twenty warmest at #19, with a mean anomaly of +1.97°C, which in itself is very high. Even if the short cold spell between the 14-16th hadn’t occurred it still wouldn’t have been anywhere close to beating 1833.

Daily Central England Temperature Warmest start to a May 1772 - 2016

Daily Central England Temperature Warmest start to a May 1772 – 2016

Remember you can keep an eye on the latest CET values in these special static pages dedicated to them.

Ice Saints

As Wikipedia points out – Ice Saints is a The Ice Saints is a name given to St. Mamertus (or, in some countries, St. Boniface of Tarsus), St. Pancras, and St. Servatius in Austrian, Belgian, Croatian, Czech, Dutch, French, German, Hungarian, North-Italian, Polish, Slovene and Swiss folklore. They are so named because their feast days fall on the days of May 11, May 12, and May 13 respectively, known as the “black-thorn winter”.

The period from May 12 to May 15 was noted to bring a brief spell of colder weather in many years, including the last nightly frosts of the spring in the Northern Hemisphere under the Julian Calendar. The introduction of the Gregorian Calendar in 1582 involved skipping 10 days in the calendar, so that the equivalent days from the climatic point of view became May 22–25.

Ignoring the spanner in the works that the change of calendar introduces – I decided to rework the code in my Central England Temperature [CET] application just to see if there was any evidence in the CET series to justify this singularity. Below is the list since 1970 (let me know if you want more), and as you can see Ice Saints do happen and more often than you might think, but by now the effort in just writing the extraction and plotting routines had got to me. It’s obvious to me from the scatter graph that you can’t say for certain that this singularity does exist and can be relied on for those specific dates in May, certainly H.H.Lamb didn’t think a lot of it in his book “The English Climate”, even though it does coincide with one of Buchan’s infamous cold spells, but it does coincide nicely with what Lamb calls the “Spring Northerlies” (16 April to 20th May).

The way I investigate it was to look at three five-day periods 6-10 May, 11-15 May and the 16-20 May. I then calculated the anomaly of each of these three pentads, calling them A, B and C, and then compared the difference between A and B and then B and C for each year since 1772.

Daily Central England Temperature Ice Saints Singularity Comparison 1772-2016

Daily Central England Temperature Ice Saints Singularity Comparison 1772-2016

Daily Central England Temperature SubTitle

Daily Central England Temperature Ice Saints Singularity Comparison 1772-2016

The most striking Ice Saints of recent years in the CET series was in 2010 and here are the analysis charts for that time. As you can see a northerly outbreak very similar to the one occurring this year (2016) was responsible. This period is after all when the peak frequency of N’ly types in the Lamb Weather Type [LWT] series occur. It certainly put paid to the unusual early warm spell that we had been experiencing up until the 13th, and ruined any real chance of an Ice Saints for 2016.

8 May -21 May 2010 (courtesy of the Met Office)

8 May -21 May 2010 (courtesy of the Met Office)

Daily CET Spring 2010

Daily CET Spring 2010

Probably the most severe examples of Ice Saints since 1772 occurred in 1830 and 1816 as you can see in the scatter plot chart.

CET Spring 1830

CET Spring 1830

CET Spring 1816

CET Spring 1816

The eagle-eyed amongst you may have noticed just a very slight cooling in the daily CET graphs (above) of the 1961-1990 long-term average (the green filled area series) between the 13th and 18th of May.

Warmest 8th of May since 1878

Warmest Central England Temperature for the 8th of May

Warmest Central England Temperature for the 8th of May

Provisionally yesterday – Sunday the 8th of May 2016 – was the warmest 8th of May in Central England since at least 1878. The maximum temperature anomaly was +10°C warmer than the 1961-1990 long-term average for that day and was a full 2°C warmer than the previous warmest that occurred in 2008. The mean temperature was the highest since at least 1772 at 18.0°C and exceeded the previous highest mean of 1867 by 1.1°C. Quite an exceptionally warm day for early May.

03772 London Heathrow - United Kingdom 24 AMSL 2 May-8 May 2016

03772 London Heathrow – United Kingdom 24 AMSL 2 May-8 May 2016