Peter Lennon edits The Monthly Weather Bulletin. This slender booklet of some 20 pages is published by Met Eireann, as its name suggests, a dozen times a year, and is an essential vade mecum for the serious weather buff. One of Peter's tasks around this time of year is to calculate for publication in the Bulletin a number called the Poulter Index. It tells us what we know from experience already - how good or bad the recent summer was - but it provides a measure which allows us to compare it in a quantitative way with others in the past. But it is not easy to encapsulate a season in a single number. A bright summer that is characterised by chilly winds is no less mediocre than a warm one that is wet and dull. The Poulter Index, however, is based on the assumption that the character of a particular summer depends mainly on three specific parameters - temperature, rainfall, and sunshine. Other features, such as cloudiness, windiness, or the frequency of thunderstorms, are assumed to be related to these elements, and in any event they are known to have a smaller impact on our collective memory. The score assigned to each summer is calculated by a special formula carefully devised to give due weight to each of these three elements. For example, summer 1995 of blessed memory scored about 440, making it the highest scoring summer for a century or more. The summer of 1976, too, was very good, if you remember, and had a Poulter Index just above 400, and that of 1975 was not too far behind. By contrast, the summers of 1993 and 1994 were mediocre, achieving Poulter Indices in the region of 300; that of 1985 scored a miserable 249, with those of 1986 and 1980 not much better.
Not surprisingly, perhaps, the ranking provided by these calculations agrees quite well with the impressions of their relative merits held by most of us.
So how did we fare in 1997? The figures show it to have been a poorer than average summer except in the north of the country. The Index was about 4 per cent below normal at Valentia Observatory in Co Kerry and in Dublin, and at 290 a whopping 12 per cent below normal at Birr in Co Offaly. But Donegal fared well; with a Poulter index of 391, the summer of 1997 at Malin Head was much better than average, and was, in fact, the sixth best summer there since the index began to be calculated around 1915.