Online Briefing report 5.9 Storm tracks, wind & anticyclones
Figure 21 shows changes in both the latitude and the strength of the centre of the North Atlantic storm track near the UK, by the 2080s under the Medium emissions scenario, from 17 variants of the Met Office Hadley Centre global model, chosen to sample a wide range of uncertain model parameters, and from 20 similar alternative climate models. The Met Office Hadley Centre models (red dots) have a tendency to project the storm track weakening slightly and moving further south. The alternative models show, in general, less change in the position of the track, but a wide range of changes in strength. Furthermore, a comparison of each model’s current storm track with observations shows an equally wide range of differences between model simulations and reality. These differences between individual models, and also between different types of model ensemble, indicate that robust projections of changes in storm track are not yet possible.
Anticyclones can persist over the UK for days or even weeks. They are associated with low wind speeds and, often, clear skies, conditions which can lead to high levels of pollution. In winter they can lead to cold spells at night and in summer they are responsible for heatwaves. Unfortunately, just as with storm tracks, model projections do not give a clear picture of changes to anticyclones. There is no compelling evidence that the frequency, duration or intensity of those affecting the UK will change markedly either way, although neither can it be ruled out.