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?