Meanders, loops in the jet stream stretching hundreds of miles, can prevent weather systems from their natural progression eastwards. This effect, known as blocking, can cause conditions to stay fixed for days or weeks, producing extreme weather. Blocking brought us the sweltering summer of 1976, the bitter winter of 1962-3, and contributed to the cold spell this March.
Such blocks are extremely hard to predict, but a new study from the University of Chicago published in this month’s Science magazine suggests that they can be treated, mathematically at least, as resembling traffic flow. The study, “Atmospheric blocking as a traffic jam in the jet stream” suggests that the jet stream has a limited capacity. When it gets close to this capacity the jet stream slows. Too many cars trying to get on to the motorway can bring the whole thing to a crawl. When the jet stream gets close to capacity it meanders, and blocking results.
The new model may not help to predict blocking in the short term, but should improve meteorologists’ models of how often blocking patterns occur. The researchers suggest that in some regions climate change will result in more blocks, and hence more spells of extreme weather.
