April 2017 – Mean pressure

Figure 1 – Data courtesy of NCEP/NOAA Reanalysis (anomalies wrt 1948-2014 long-term average)

I’ve just been looking at the mean pressure chart for April 2017, and it was certainly an anticyclonic month with a large +12 hPa anomaly to the west of Ireland which produced a sizeable 1025 hPa anticyclone at 50°N 12°W, and a northwesterly flow across the British Isles. This made April 2017 a very dry and rather mild month across the British Isles, which although cloudy in the far west, was rather sunnier than average elsewhere. April 2017 does look to have a fairly strong resemblance to the April’s of 1967, 1980, 1982, 1995, 2015 and 1997.

Monthly Weather Report – April 2017

Monthly weather summary – April 2017

Images and data courtesy of the Met Office

Final rainfall totals for April

Figure 1

Sorry I’m a bit late on this one, but here are my best estimates of the total precipitation for April 2017 from the SYNOP reports. If you want them for Scotland, or anywhere else for that matter, as ever I’m only an email away.

April warmth cancelled out by late cold spell

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.

Figure 1 – Data courtesy of the Met Office

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.

Figure 2 – Data courtesy of the Met Office

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