Met Office better placed to predict 'big freezes' Since their technology was upgraded two years ago, forecasters have accurately predicted the cold start to December 2010 and the mild winter of 2011. It is too early to say what this winter's weather will be but any severely cold spells caused by the same conditions as the winter of 2009-10 can now be anticipated as early as November. A new study by the agency found that the unexpected nature of the "deep freeze" lay in the inability of its seasonal forecasting equipment to simulate phenomena known as sudden stratospheric warmings (SSWs). These happen when the usual westerly winds in the stratosphere of 10km to 50km above the ground stop or reverse, causing a knock-on effect at surface level. Westerly winds blowing warm air from the North Atlantic across Northern Europe are blocked, causing extended periods of extremely low temperatures. Since late 2010, the Met Office has been using a new long-range forecasting system to simulate winds, humidity and temperatures at a range of heights stretching beyond the stratosphere. Researchers say this means it can foresee the wind changes. However, they added that the technology would not lead to perfect predictions. While cold winters caused by the wind changes were now more predictable, other combinations of conditions could still cause freak cold spells. In the new study, published in the Environmental Research Letters journal, the team compares forecasts made ahead of the "deep freeze" against a new, retrospective prediction based on the same data but using the new technology. The new model was able to produce a more accurate forecast of the cold winter, especially the bitter conditions that took hold towards the end of the season. David Fereday, who led the study, said: "What the updated model showed was that there was an increased risk of SSWs towards the end of the winter, and this was what we had, a cold February in 2010. These events were not represented in the earlier forecasting system. Adam Scaife, his co-author, said: "This is a step forward but it is not a silver bullet in solving the problem. We have improved our ability to predict a certain class of winters, but it does not mean we can predict all classes of winters.