Winter 2010/2011 update: Cold and dry?
A number of you have been in touch regarding precipitation levels this winter which I didn't mention in the previous blog.
All models seem to be in agreement that next winter will be drier than average. A vivid illustration of this can be seen below showing the European model. The red colour is indicative of higher pressure than normal.
If we take this at face value, it suggests the area of highest pressure to be positioned across Southern parts of the UK and into Central Europe. This would mean not especially cold temperatures, as the wind direction would not be from the North or East. So it's no surprise that the European model is expecting temperatures this winter to be close to normal.
But it wouldn't take much for the centre of gravity of the high pressure area to be in a different position. Indeed, the fact that the American model signals colder temperatures than the European model this winter illustrates this point, suggesting a bias to air from a colder direction, on average.
The forecast shown on my previous blog, showing 3 monthly temperature means from the American model, are relative to the 1981-2006 average and if correct for the winter period of Dec, Jan and Feb indicate a colder than average winter, but not as cold as last winter.
Having seen computer model output from the 3 main centres - the Met Office, the European Centre for Medium Range Forecasting (ECMWF) and the American centre (NCEP) - the conclusion is that this winter is likely on average to be dominated by High pressure, with below average rainfall and temperatures colder than average. Moreover a mild and wet winter, with West or Southwest winds, which have been such a feature of our climate for much of the last 20 years, again seems unlikely.