April sunshine totals 1981-2010

Figure 1

The sunniest place on average in the UK in the period between 1981 and 2010 is Shanklin on the Isle of Wight with 201.4 hours. In fact most of the climate stations in the top 17 can be found on the English Channel coast somewhere. On the southwest peninsula the fall off in sunshine the further away from the coast you are looks to be around 10%. The Met Office provide these 1981-2010 average in their DataPoint web service and are not neither straightforward to download or to parse, because they’re all in XML format and come as individual files for almost 300 locations. The things I have to go through for a climate story.

Figure 2

I contacted the Met Office at Jersey yesterday and asked them what their record highest April sunshine total and got this tweet back.

Figure 3

I make their total for the same period 249.5 hours, yesterday they had another 2.5 hours taking them up to 252.0 hours. I’ve tweeted the Met Office at Jersey and asked them to check their total, but so far have had no response. As far as I can see I’ve done the maths correctly, and my old maths teacher Mr Brightmoor I’m sure would have been proud of me. The 1981-2010 average for Jersey is 196.5 hours in April, so that makes the latest anomaly just over 28% above the average.

Figure 4

Recent April circulation patterns

Figure 1

Another product that I can generate from my reanalysis application is a 4×3 grid of charts for monthly mean pressure and anomalies. Here are the circulation patterns for the last 12 years of April’s (2006-2017). If I ever do acquire a monitor that is larger than my Dell 24″, I may be able to pack more into a single screenshot! There is a broad similarity between 2015 and this April. April 2015 was the sunniest on record in many regions across the UK, and a comparison between it and the incomplete chart for this year show that although the mean pressure anomalies were not as large, the centre of the positive anomaly was further east at around 1° west (+7 hPa) rather than 10° west (+11 hPa) as it is this year (fig 1).

I’ve added extra functionality to the application to allow the selection of any area at any zoom level from around the world, as this example shows for Australia in 2016 (fig 2).

Figure 2

I’ve had a quick look at some of the results that I have generated and compared them with those from the IRICS, which is part of the Earth Institute, at the University of Columbia, and they seem to be in reasonable agreement, where they might not agree so well is when comparing monthly anomalies, because I use some extra long long-term averages when I calculate anomalies for my charts.

You may ask why I bother to write a bespoke application to do this when you can access anomaly charts from this great site, and my answer is, I have the time and resources, I love climate and weather maps, and because that’s what I do.

A sunny month in the south and east

Figure 1

A very sunny month especially across more southern and eastern areas of both Scotland, Wales and England, but always cloudier the further northwest that you went, and more generally over Ireland (fig 1). The sunshine figures are for some reason always more reliably reported in a SYNOP report from a AWS than are rainfall totals, as you can see from the Rx column (fig 2) most stations are at 100%. Jersey is still miles out in front this month, with over 240 hours of sunshine, being an Island in a relatively cold English Channel does help a bit in that department. There are several other chasing stations who also might crack the 200 hour barrier this month, and today might help in that regard at Camborne.

Figure 2

These sunshine totals are high but they don’t look high enough to beat the April of 2015 which was exceptionally sunny across the country (fig 3). ‘Sunniest since 2015’ doesn’t make much of a headline I’m afraid.

Figure 3 – Data courtesy of the Met Office

The Met Office do provide monthly climate statistics for Jersey, so it looks like this April they are currently around 122% of the average, with four days left of the month. I’ve Tweeted the Jersey Met Office to try and find out if they know what the sunniest April on record there, hopefully they will reply, and not by Tweeting ‘yes we do but we are not telling you’.

Figure 4 – Courtesy of the Met Office

A dry month apart from the last day?

Figure 1 – SYNOP data courtesy of OGIMET

Some of these plotted totals (fig 1) may be misleading due to missing SYNOP reports from some stations such as Edinburgh, but most of the others are more complete, but until the Met Office finally release their stranglehold on the daily NCM climate data, there is nothing I can do about it. Putting the Met Office monopoly on climate data in this country to one side (what ever happened to the free data campaign?), this may well end up being one of the driest April across some regions of the UK since 1938 (fig 2).

Figure 2 – Data courtesy of the Met Office

Having said that, Sunday is looking like a wet old day in the southwest, and may (excuse the slight pun) help redress the balance there (fig 3). I think a spell of heavy rainfall after a drought on dry cracked earth (like it is in our garden at the moment) can bring its own kind of problems with run off.

Figure 3 – Courtesy of OGIMET

April 1-23 northern hemisphere temperature anomalies

The recent cold weather seems to have cancelled out the earlier warmth in the month of April, because temperature anomalies up until the 23rd are quite close to average across most of Europe, although Iberia has been unusually warm. The Arctic has been its exceptional mild self once again, and is probably one of the reasons why this recent ‘Arctic blast’ has been so relatively innocuous.

Figure 1

Late April cold spells and the Easter Snowstorm of 1908

Figure 1 – Lymington High Street – April 25th 1908 (courtesy of lymington.org)

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
be commended…

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.

Figure 2

Synoptically, the 25th of April in both 1908 and 1981 were slightly similar in that they were both cyclonic in nature.

Figure 3 – Courtesy of NCEP/NOAA reanalysis

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.

Figure 6 – Courtesy of OGIMET

 

Q: Just why has April been so dry & sunny?

Q: Just why has it been so dry and sunny and dry this April?

Figure 1 – Data courtesy of NCEP/NOAA reanalysis

A: Because for the first 18 days of the month there has been a large (+11 hPa) positive MSLP anomaly sat just to the west of Ireland (fig 1). As I reported earlier this month (never thinking that the first half of April would turn out as anticyclonic as it has), 1938 was the most anticyclonic in records that started in 1871 (fig 2). The two April’s are indeed very similar, but the anomaly chart for 1938 was for the entire month, and not just the first 18 days, and were larger and even more pronounced. That’s not to say that the second half of April 2017 won’t continue to be just as anticyclonic as was the first.

Figure 2 – Data courtesy of NCEP/NOAA reanalysis

I’ve just put quite a lot of programming effort into the program that I use to download, parse and visualise reanalysis MSLP data from NOAA, so hopefully I’ve got things right. The LTA that I have used to calculate the anomalies for years 2012 or earlier is for the whole of the 20th Century i.e 1901-2000. For the years after 2012 the LTA is for the 66 year period 1948-2013. This is because the older reanalysis data uses a 2 x 2° grid, whilst the data after 2012 is from the 20th Century reanalysis on a 2.5 x 2.5° grid.

Jersey the sunny Channel Island

Figure 1 – Courtesy of vintagerailposters.co.uk

Jersey have taken over at the top of the sunshine league this April, with almost 9 hours of sunshine each day for the first 20 days of the month. Their total of 178.6 hours so far is I estimate 66.1% of the possible maximum total. It’s not been sunny everywhere across the British Isles, but without detailed climate statistics to produce anomaly values it’s impossible to be precise, but as usual, it seems to have been duller the further west and north that you are so far this month (fig 2).

Figure 2

The driest Aprils since 1910 by region

I’ve spent a bit of time today creating an infographic of driest April’s. I’ve used the free data set maintained by the Met Office, which started in 1910 and is produced from gridded data for ten regions across the country. Hopefully one day the Met Office will extend this series to cover all the rainfall data that they inherited from the British Rainfall Organization in 1919 and just sat on for the last 98 years. I knew about the very anticyclonic and dry April of 1938 from a previous article that I had written earlier this month, but hadn’t realised that it was only driest in three out of the ten regions, even though it was the driest April in the EWP monthly series that started in 1766. The 1.0 mm in East Anglia in 2007 tops the list of driest region by region, which is something else I missed. I’ve borrowed the regional map from the Met Office, I’m sure that they won’t mind, let me know if you spot any issues.

Data courtesy of the Met Office

Later….

What’s slightly puzzling about these figures for April is why the UK value is the highest April value for all regions at 14.1 mm, when it’s made up of the value for Wales 8.8 mm, and the value for England 6.7 mm. Both values are for the same year 1938, I would have thought that the combined UK value should be some kind of mean of the two, but obviously not. It must have something to do with the gridding I suppose.

April in pictures

Images courtesy of the Met Office and EUMETSAT

Here in Devon, we just about got away with five consecutive sunny days at the start of this April, but even today it’s still very pleasant, and unofficially the air temperature is around 17.5°C at 15 BST. A number of stations won’t be that far short of a 100 hours of sunshine in the first 11 days by close of play today I would have thought, Lyneham most certainly will have a ton up (fig 2).

Figure 2