Looking at the SYNOP rainfall totals for May 2016 over the British Isles it looks like the month has been below average for many parts. Wettest were Lusa in Skye (152.9 mm 24 hour total), and Capel Curig in Wales (127.8 mm 24 hour total). Parts of eastern Scotland and NE England were also very dry with Inverbervie driest with only 11.8 mm (24 hour total) and Aberdeen 14.9 mm (12 hour total). I don’t always get 100% of the possible SYNOP reports during the month although usually I do receive 98% or more from most stations. The other thing that can introduce differences is the fact that you can build an accumulation from 12 or 24 hour totals.
Of course there has also been the recent flooding of the last week in France and Germany from that small but intense low pressure system. Wettest place in northern France for the whole month appears to have been Trappes from the SYNOPs that I receive with 201.7 mm of rain (24 hr totals).
The wettest day seems to have been the 30th of May and overnight into the 31st. Here are the 24 hour totals up to 06 UTC on the 31st for most of France.
I can’t comment much on Germany because there’s a big hole of missing rainfall data in the middle of Europe this month by the looks of things.
Not clear what’s going on with the Germans, who seem to have joined the Danes in not reporting rainfall totals this month, either 6, 12 or 24 hourly which is a great shame. I’ll have to investigate, it could all be down to my parsing of course, but it maybe that the Germans have now switched to BUFR and OGIMET aren’t doing the conversion to SYNOP very well. There’s certainly a lot of blocks in a BUFR SYNOP as you can see in this example but no rainfall. I’ll email OGIMET about the problem but I’ve never received a reply for them before so the death by a thousand cuts continues as far as quality SYNOPs and climate data are concerned.
The annual trend in rainfall indicated by the England Wales Precipitation [EWP] series maintained by the Met Office is upward since 1766 when the series started. I have been studying this data for a few years now and I think the best way of looking at the individual monthly totals is by using a 12 month running mean. This removes a lot of the noise you get from any one dry or wet month or season. After that you can add a linear trend through the results to identify what the real trend over time reveals. The first chart does just that and shows that in the last 250 years the annual rainfall for England Wales has increased by 46.5 mm. We do moan at times about the rain and the occasional floods that we have to endure but looking at the record of the last 250 years, the one thing you can’t say is that we’ve ever gone without! In fact for all the oscillating the trace does it never ever drops below 650 or climbs much above 1250 mm a year.
If we zoom in a little to the last 50 years (see chart below) the wetter trend has increased to 65.2 mm. The dry years of 1975 and 1976 are clearly discernible along with the recent wet years and flooding that occurred in 2000, 2007 and 2012. Conversely the last 50 years have also had some noticeable dry spells, notably in 1976 but more recently in 2011.
At the moment we are in a wet streak as the Americans like to call it, with an accumulated total of 1,128.9 mm in the 12 months to April, this is +23.4% above the 1961-1990 long-term average for 12 months. There is a definite pulse in the annual rainfall totals, its erratic and at times incoherent. I just wonder what the rest of 2016 will bring in the way of rainfall for England Wales?
PS Don’t forget I have static pages setup to display monthly rainfall charts and table from the EWP series and which I’ll endeavour to keep updated. I also keep tabs on the Met Office HadUKP site.