Sandy’s Garden ... Forecasting the weather

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We British are preoccupied with the weather.

While the standard Italian greeting is Bon giorno! and the typical American will greet you with a cheerful Hi!, the average Brit will say something along the lines of Nice day, or It’s a cold one, isn’t it? or Looks like rain. No news bulletin is complete without a weather forecast; and folklore is full of supposed links between natural occurrences and the weather that lies ahead. “Red sky at night is the shepherd’s delight; red sky in the morning is the shepherd’s warning,” is one of the best-known, but there are myriad others, ranging from, “Sounds travelling far and wide, a rainy day will betide,” through, “Clear moon, frost soon,” to, “A warm November is the sign of a cold winter.”

Now this last example is relatively rare in folklore, most of whose forecasts are very short term, claiming to foretell what the weather will be like a few hours ahead. And, while this may suffice for many everyday purposes, there are times when a forecast for days, weeks or even months ahead can be very useful, especially to the likes of farmers, highway engineers, transport operators … and gardeners. The Meteorological Office, which supplies the majority of the forecasts that we see, or read or listen to in the media, is … contrary to popular belief … pretty good at short-term forecasting. It’s not infallible, of course, and here in central Scotland we know only too well how difficult even the best professionals find it to forecast the timescale of approaching weather. “Rain will spread from the west later,” we learn … but exactly how much later can be very difficult for the meteorologist to determine. Long-term forecasting … looking at the weather we can expect in several months time … is a very much less exact science which, frankly, is more often wrong than right at present. Yet the Met Office strives tirelessly to develop its strategies to look into the future; and recent developments promise better long-term forecasts in future years.

A recently-published study in the journal Environmental Research Letters, describes the latest efforts being made to better warn the United Kingdom of extreme winter weather conditions. A new computer model, dubbed the “high top” system, takes into account phenomena known as sudden stratospheric warmings (SSWs), which have previously been shown to be responsible for cold conditions at ground level. Sudden stratospheric warmings occur when the usual westerly winds in the stratosphere … that is, between 10km and 50km above the earth’s surface … break down and ultimately reverse. This is of no immediate significance to us who live at ground level. But, over a period of several weeks, the effect of SSWs tracks earthwards through the stratosphere and into the atmosphere, where it interrupts the westerly winds that usually bring milder air in from the Atlantic to protect us in western Europe from the Arctic blasts from the north or the bitter winds from Siberia to the east. This means that northern Europe experiences cold conditions that can cause extreme low temperatures, as happened in the winter of 2009-2010.

David Fereday, lead author of this Met Office study, said: “This research demonstrates our investment in science is yielding results, but this is just one incremental step in our ongoing effort to improve long-range weather forecasts. In itself it’s not the silver bullet for long-range forecasting - there is still much more research to be done in this developing area of meteorology, and we’re continuing our work to stay at the forefront of that.” We shall do well to recognise his words, “It’s not the silver bullet”: but we might also welcome the promise of a probable improvement in the accuracy of long-range forecasting.

Sandy Simpson, Polmont Horticultural Society