How bad is the 'drought'?

Now the hose-pipe ban been implemented the rain has started to fall, albeit in small amounts, so far! Comparisons have been made with the 'drought' of 1975/6. Comparing the rainfall figures for Kew in 1975 and Morden 2011 the totals are as follows:- Annual total Kew 1975 was 558mm. Annual total Morden 2011 was 510mm. Total from July to December (Kew) 1975 (6 months) 263mm (this included 51mm in just 1 day during September!). Total from July to December (Morden) 2011 (6 months) 268mm. For the last 3 months of 1975 the total was 108mm, in 2011 it was 123mm. The first 3 months of 1976 produced just 46mm. January to March this year has given 73mm. The '75/76 drought did not really become serious until the summer months of 1976 when days of unbroken sunshine accompanied by brisk winds, heat and low humidity conspired to reduce reservoir levels dramatically. Yes, some of the reservoirs this year are down below 50% capacity, and yes leaks from pipes are unacceptably high, but it remains to be seen if the the widespread ban on hoses is a justified precaution against water shortages, or a cynical political ploy to soften us up for the compulsory use of water meters!

Today marks the 15th consecutive day without measurable rain (defined as 'no daily rainfall equal to, or exceeding, 0.2mm/0.01 ins.'). Up until the 1980s this 15-day period was known as a 'drought'. However, the rise of the mocking tabloid press, the general decline in exactitudes, and comparisons with life-threatening water shortages in the Third World quite correctly brought about the abandonment of the term 'drought' by all but a few diehards.

Nevertheless, it's interesting to examine these lengthy dry spells. The previous one occurred here from the 16th September to 2nd October 2009 (a total of 17 days), but lack of rain is generally less common during the Autumn and Winter months. A good Summer often produces a prolonged period of dry weather. In 1959 this area had 37 consecutive dry days (15th August to 20 September) and in 1976 parts of southwest England had no measurable rain for 45 days. Perhaps surprisingly there was no 15-day dry spell in 2003, but the rainfall deficit for the period February to October in that year was well over 50%.

The Spring months seem to have the most frequent dry spells. In recent years there have been several in mid Spring. In 1995 there were 19 dry days (29th March-16th April), in 1997 it was dry from the 25th March to 17th April (24 days). A total of 27 dry days occurred between 21st March and 16th April 2002, and in 2007 there was dry weather between 31st March and 22nd April (23 days).

Is there any way of connecting dry Aprils to the following Summer? Fortunately the answer is no. In 1912, parts of London had no measurable rain during April and the following Summer was one of the coldest and wettest on record! By the way, the previous 4 mid Spring dry spells were equally divided between good Summers and decidedly indifferent ones.

'Snow Breaks the Drought'... but not any more

The light snow that fell overnight and early this morning marked the end of a 16-day period without measurable rain. In the old days, when City gents wore bowler hats and Christmas crackers only came from Woolworths, a spell of 15 days, or more, without 'significant' rain (less than 0.01 inches, or 0.25 millimetres) was known universally as a 'drought'. It was a term reluctantly used by meteorologists but regularly dug up by the media. Fortunately, since the real droughts, especially in Africa and Australia, have been vividly portrayed on our television screens, a lack of rainfall has been taken more seriously. However, to get back to the quirky old 'drought'. There have only been 3 occasions during the last 20 years in this part of London when a 15-day dry spell has encompassed the winter months (December, January and February) and not at all when the majority of dry days occurred during December! The 16 consecutive 'dry' days is nowhere near a record. In 1959, http://www.london-weather.eu/article.99.html central London had no measurable rain from the 24th January to 20th February, a total of 28 days.