Better weather predictor on hand People are always curious about what the weather will be in the coming days, weeks and even months. So having a good forecast model to provide this information is important. The Met Office, the National Weather Service of the United Kingdom, has developed and launched a new mo... People are always curious about what the weather will be in the coming days, weeks and even months. So having a good forecast model to provide this information is important. The Met Office, the National Weather Service of the United Kingdom, has developed and launched a new model that can provide better forecasts months in advance. Presented in the journal Environmental Research Letters, a new study compared the latest seasonal forecast system to the one previously used. The results showed that this new model can provide the United Kingdom with better information about the extreme weather conditions for the coming winter season. Researchers call this system 'high-top'. What makes this model better than the one that is currently being used? The Met Office team said their latest tool includes phenomena like 'sudden stratospheric warmings' (SSWs), which experts say have triggered cold surface conditions. 'SSWs occur when the usual westerly winds in the stratosphere - between 10 and 50 kilometres altitude - break down,' said lead author David Fereday of the Met Office. 'This causes a reversal in the westerly winds in the stratosphere, generating a signal that can often burrow down to the Earth's surface over the course of a few weeks,' he added. 'This reduces the occurrence of surface westerly winds that bring mild air to northern Europe in winter from the North Atlantic. Instead, northern Europe experiences cold and blocked conditions that can cause extreme low temperatures, as happened in winter 2009/10.' GloSea4 can simulate weather conditions in higher parts of the atmosphere, the researchers said. This feature was not available in the forecast system used for the long-range outlook in 2009/10. Using a computer model, GloSea4 can simulate winds, humidity and temperatures on around a 150 km-spaced grid of points at a range of vertical heights from the surface, surpassing the stratosphere. This is why SSWs are represented more realistically. For the purposes of their study, forecasts made during the 2009/10 winter with the low-top model were compared to retrospective forecasts made with the high-top model, the researchers said. The high-top model made predictions that were more in line with the actual severe conditions in that period. 'By October 2010, the high top version of the GloSea4 system was indicating an increased chance of a cold start to winter,' said the Met Office's Jeff Knight, one of the authors of the study. 'That year December was the second-coldest in 350-years of records. It also highlighted the possibility that conditions in late winter were likely to be less harsh, which was indeed the case. In 2011, GloSea4 predicted that a mild, westerly winter was likely. This turned out to be the case - only the first two weeks of February 2012 were cold. The inclusion of the high top model is one of a series of planned improvements to long range forecasts.'For more information, please visit:Met Office:http://www.metoffice.gov.uk/Environmental Research Letters:http://iopscience.iop.org/1748-9326 Countries United Kingdom
