Now that we’re 136 days into the year 2017, I thought that it was about time I looked to see just how this year was shaping up as regards temperatures in Central England. And as you can see from the table (fig 1), this year is already exceptionally mild, with a mean CET so far this year of 7.47°C which is +1.54°C above the 1961-1990 long-term average. This makes it currently the eleventh mildest start to a year since 1772, but as you can see many of the mildest years in the top 12 have also occurred in recent years.
The early April warmth was cancelled out a little by the late cold spell in Central England, which although lasted no more than 5 days, did manage to limit the mean temperature to just 8.9°C for the month. The final mean anomaly, which had been running at almost +3°C earlier in the month, ended up at +0.97°C. It was the warmth of the days that help produce the +0.97°C anomaly, the mean maximum anomaly was +1.57°C, whilst the mean minimum anomaly was only +0.39°C. Eleven of the last 12 months have been warmer than average. I still calculate all my anomalies with respect to the 1961-1990 long-term average.
One notable extreme maximum record was set during the month on Sunday the 9th, which had a maximum of 21.4°C which was +10.5°C above the average for that day.
Easter in 1908 fell late, so the snow that fell over much of southern England must have come as a big surprise on the Easter Sunday on the 19th of April (fig 1). The following week was intensely cold for late April, and there were periods of heavy snow across much of southern England. In an article in the Met Mag of May 1908, Fred J Brodie said this about the snow at Oxford:
The conditions at Oxford are interesting in a special degree on account of the length of the meteorological records at the Radcliffe Observatory which run from 1853. The depth of snow there was 17 inches, and the only instance of a greater amount being recorded at any time of year was on February 13th and 14th, 1888, when 24 inches of undrifted snow was measured.
I love the comment that Fred went onto make a few lines further on…
The practice of comparing, for the purpose of record making, observations made in two different localities is not to
He of course is completely right in what he says, but he must be spinning in his grave these days, on the goings on in the early 21st century with extreme temperature records I would have thought, because no one, and that includes myself seems to give a hoot these days about comparing extremes from weather stations without knowing thinking much about their actual location. You can find an article about the events of April 1908 on the Weather Outlook forum, which includes details of snow depths recorded at the time, plus a lot of other information and photographs about the blizzard. The Weather Magazine of December 1981 also had an article about April 1908 in which it linked it to the April of 1981 and said:
The marked similarity of the graphs for 1908 and 1981, especially in the second half of each, is confirmed by a correlation coefficient of 0.93 for the last 15 days of the month. For the full month the correlation coefficient is 0.65. The weather of late April was remarkably similar in these years.
Since 1981, the daily CET series may well have undergone some slight modifications, but there is most definitely a cold spell that occurred during at the second half of each month, the minimum CET in 1908 was a couple of degrees colder than it was in 1981 though, and those on the 24th and 25th still hold the record for lowest minimums on those two days (blue stars). Personally I only see a broad similarity between the two, I’ll have to spend some time and write some code to generate a correlation coefficients between these two months and see what I come up with. If you look closely at the graph of CET (fig 2), you’ll notice that in just over a week, maximum anomalies rose from around -8°C to +8°C. The resultant rapid thawing of lying snow from the week-long cold spell lead to great flooding in places along rivers in the southeast especially the Thames, and the Great Ouse at Buckingham.
Synoptically, the 25th of April in both 1908 and 1981 were slightly similar in that they were both cyclonic in nature.
But up aloft in the atmosphere the cold air of 1908 was much deeper than it was in 1981 (figs 4 & 5).
It seems cold outbreaks towards the end of April are not at all uncommon, I’ve just picked on probably two of the more extreme events. Next week promises its own cold outbreak (fig 6), but synoptically, if the GFS model is correct, it will be more of a cold northerly rather than cyclonic as it was either in 1908 or 1981.
The Met Office beat me to a story about extreme Easters of the past, but undaunted, and without the masses of climate data they have at their disposal, I pressed on with a bit of research of my own.
Because Easter is not at a fixed time each year it’s difficult to compare one with another. Easter Sunday can fall as early as the 22nd of March or as late as the 25th of April. I’ve used the daily CET series from 1772 (now there’s a surprise), and calculated a five-day mean, from Maundy Thursday to Bank Holiday Monday to do my comparison with. Because of the time range that easter can fall, I have base it on mean temperature anomalies rather than the mean temperature. So from what I’ve found the coldest Easter period since 1772 occurred in 1892 (fig 3). The Easter Sunday that year fell on the 17th of April so it was by no means early.
The mean temperature for the five days between Maundy Thursday and the Bank Holiday Monday in 1892 was 2.1°C, which was -6.4°C below the long-term average for that period (fig 3). The weather chart for the Sunday (fig 1) shows just what a bleak and cold Easter that must have been in eastern parts.
I couldn’t resist including the Monthly Weather Report for April 1892 after using it to check out my story because I was taken with some of the phrases that were used by whoever wrote the report. I have highlighted some of them from the PDF that I accessed courtesy of the Met Office (fig 4). The remark about Vapour Tension exceeding 0.25 on the south coast of Ireland and England was a real charmer, I bet sixpence was a lot of money in 1892, and what happened to the Weekly Weather Report?
Conversely, the warmest Easter using the same method, fell in 1926 in Central England at any rate. Easter Sunday that year fell on April 4th, and the five-day mean was +6.5°C above today’s long-term average, and if you look at the synoptic situation (fig 5) you can understand why. I did look for any weather related news for Easter 1926, and mistakenly thought that this was the year of the Easter Rebellion in Ireland, but I was 10 years too late, that occurred in 1916.
A fascinating battle is going on at the moment in the climate statistics of Central England temperatures, well at least it is for people who have the time to notice these things. In the last 30 day period (the 10th of March to the 9th of April), 2017 currently has the second highest mean temperature in the CET series since at least 1772, sandwiched as it is between two other very memorable periods in 1957 and 1938. If you are interested, 2017 is currently joint 9th warmest year since 1772, which is a reflection of just how mild it’s been so far this year.
The Met Office finally got there act together today, and fixed their web service and updated their CET web page with the latest data. As expected, March 2017 was a very mild month, and when the temperatures were finally confirmed today, it turned out that it had been the 3rd mildest since the monthly series started in 1659. I make the mean temperature for the month 8.68°C, which was exactly 3°C above the 1961-1990 long-term average. It couldn’t quite beat the CET of either March 1938 or 1957, so it ended up being the warmest March since 2012.
The month saw four new high minimum temperature records set and one highest maximum record on the 30th.
With 28 days of the month now gone, March 2017 provisionally stands as the 7th warmest March in Central England back to 1772, with a mean temperature of 8.11°C which is +2.55°C above the 1961-1990 long-term average. Maximum anomalies are a little higher than minimum anomalies this month, indicating that the days have been a little milder than the nights. Mild has it’s been, there was little chance that it would catch the exceptionally mild March of 1957 though.
Now that I’ve discovered the VEI database from the NCEI, I can now overlay volcanic eruption events on top of the monthly CET anomalies and chart the results. In the above chart (fig 2) I’ve overlaid all the VEI 4 events or greater from 1980, and was surprised to find that there seemed little in the way of correlation between them. The Pinatubo eruption of the 15th of June 1991 for example was the first VEI 6 event since Tambora in 1815 (fig 1), and lifted more than 5 cubic kilometres of material 25 miles straight up into the stratosphere, coincidentally a typhoon that was passing close by to the Philippines at the same time scattered the ash from the volcano to the four winds. I thought the effects of this would have had a dramatic cooling effect on CET in 1992, but not that you would notice. Of course any cooling in a local temperature series may well be masked by other regional and global factors that influence CET that are going on at the same time, global climate is complicated.
This chart is of 365 day centred rolling daily mean CET temperature anomalies for the last 30 years. Just to complicate things, I’ve overlaid a 14 day moving average on top of this just to smooth things out a bit. The LTA that I have used to calculate the anomalies is the latest possible 30 year period that I could use i.e. 1987-2016. The decadal linear trend for the last 30 years is just +0.08°C per decade. Of course, things would look different if I had used a longer period or an earlier LTA, but such is the way with statistics.