According to the New Scientist the last 10 months were the driest July to April for southern England in records stretching back more than 100 years, or so say the Centre for Ecology and Hydrology, which I must say is the first time that I’ve ever heard of them.
Possible discrepancy in latest July to April total
When I first read this I didn’t quite believe the claim that this arbitrary 10 month period between July 2016 and April 2017 had been the driest since 1910. I could remember the dry spell of 1976, and thought that this current dry spell couldn’t match it. I’ve now added code to my Met Office 1910 climate application, which I assumed used the same Met Office 1910 gridded rainfall data, so that I could graph any user defined period that I chose, and here are the results (fig 2).
As you can see 1976 was the driest July to April period since 1910, as I suspected it was, and there were four other years drier than 2016-17. So I went back to the CEH site and dug out the PDF of this April’s hydrological summary. I would include the relevant table from the summary in this article but I may well end up in prison if I did so because of the copyright clauses in it, suffice it to say they get a total of 446 mm for this period which I calculate 454.7 mm. Even if you look at the rainfall data for the ‘southern’ region, 1976 is still the driest period since 1910 for July-April rainfall and the latest total, 489.4 mm still don’t tally (fig 3).
Likely reason for the discrepancy
From reading the Hydrological summary, I assume that the Met office use the same gridded data set to create bespoke monthly rainfall totals for most of the regional water companies around the country, and one of them is Southern Water. I guess that the ‘southern‘ in the table of the Hydrological summary doesn’t exactly equate to the Met Office’s ‘southeast and central southern England‘ (fig 5) that they produce for their 1910 monthly climate series, in fact looking at the map from the Southern Water website (fig 4) it could be a combined area that includes Southeast Water.
So the difference in ‘catchment areas’ so to speak undoubtedly explains the small difference in totals that I found. But creating bespoke areas is confusing, the 1910 series that you can freely download from the Met Office includes 17 regions, some of which overlap and combine sub-regions, which makes it difficult to decide which area the climate data is for.
There is one thing that I have learnt from writing this article, and that is what an interesting website the CEH have, and what an invaluable publication the Hydrological summary is. Now why can’t the Met Office publish something similar in PDF format which they could email out to subscribers that’s full of climate data, perhaps they could call it the Monthly Weather Report?