The ifs and buts of long-term weather forecasting

Predicting the weather more than 30 days ahead is fraught with difficulty. But that doesn’t stop meteorologists trying

Ever since the Met Office was derided for predicting a barbecue summer, long-range weather forecasting for the season ahead has been avoided. The most that is attempted is 30 days, and the current forecast contains so many ifs, buts and possibilities that almost any weather might occur in November and no one could complain.

That does not mean that predicting the weather for the coming season is not the ambition of every meteorologist and scientist, especially as climate change makes extreme weather both more likely and economically important.

In Britain the track of depressions across the country that turn into winter storms and bring the threat of flooding are of increasing concern. The warmer atmosphere out in the Atlantic means more water in the clouds has to be deposited as rain.

The second threat, extreme cold, is posed by changes in the Arctic. According to the latest research, the jet stream, that is responsible for pushing the depressions towards us across the Atlantic, is developing a wavy habit. This has led to the current dry spell as long lasting high-pressure systems block the path of the lows that would normally bring autumn rain.

If the weather pattern persists, or returns in the winter, the weather will turn cold and could remain bleak for days and possibly weeks. Researchers say this has already happened in the past in the UK, and brought the winters that the Eastern United States has suffered recently with record snowfalls. And it may soon happen again.

On the other hand, as the Met Office would be careful to say, it might just rain a lot.

Contributor

Paul Brown

The GuardianTramp

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