Forecasting to the power of 7


THE number seven has had a mystical significance in almost every human culture. The creation of the world, after all, took seven days; in the Apocalypse there were seven candlesticks, seven stars; and seven trumpets, seven horns, seven plagues, and a seven headed monster. In the Hebrew tradition, every seventh year was a sabbatical and Christianity has its seven sacraments, seven virtues, seven deadly sins, and seven essential gifts of the Holy Ghost. Man's finest achievements are summed up in the Seven Wonders of the World and there are even seven days' in every week.

The search for sevens can be extended into meteorology. If you think about it, the popular weather lore on which our ancestors used to base their notions about future weather can be conveniently divided into seven separate categories. Let me provide you with a list.

First come sayings based on the current behaviour of the elements or the appearance of the sea and sky. "Red sky at night, the shepherd's delight" is a typical example. In the second category are those sayings concerned with plants and animals - the assumption being that certain living things can intuitively predict the weather by some means that we cannot understand: the recent well publicised arrival of the Kerry dolphins is a case in point. And a third type of weather saying deals - with the aches and pains of those afflicted with arthritis, rheumatism or less serious ailments. Jonathan Swift provides a good example here: "A coming shower your shooting corns presage".

The fourth and fifth categories are almost contradictory. The former might be called "persistence" - the notion that a series of rainy days must be a sign of yet more rain to come or that good summers always come in twos. The fifth, on the other hand, brings into play the law of averages: adherents would argue, for example, that if we suffer a harsh winter, we will be rewarded by a fine warm summer later in the year, or that a good summer one year must be paid for by a dreary season 12 months later.

The sixth class contains the cycles. Over the years many people have looked for and, indeed, claimed to have discovered, repeating patterns in our weather related, for example, to sunspots, to the phases of the moon, or to a number of years with no astronomical significance. And finally, in category seven, we have the multitude of proverbs related to saints days or other notable features of the calendar of these the legend of St Swithin, is, perhaps, most widely known.