Most forecasts call for lower pressure than normal in the North Atlantic, and higher pressure over Europe, which means generally milder winter in Europe. But, if you are a winter lower, do not despair! These forecasts are an average picture over 3 months (Dec-Jan-Feb), and show the general prevailing weather pattern. Even if the models would be completely accurate, it does not mean that such milder weather would last for 3 months. There can still be cold fronts and snowfall in between such milder patterns. The difference is that instead of the usual 20 snow days for example, you only get 8 or 10 snow days. So the models dont suggest what the weather will be like for 3 months straight, but just how it might look 40-60% of the time.
We still have the stratosphere as a major factor. Long range forecasts are generally not as good at forecasting stratospheric dynamics in detail, which means they tend to underestimate any potential sudden stratospheric warming events (SSW’s), since the final forecast is made out of many individual calculations, which have different ideas about the stratospheric development. An SSW event can have a major impact on the circulation and can cause major pattern changes in the Northern Hemisphere. So a potential SSW event is an important factor that can change the course of winter in either way across the North Hemisphere.
We will keep you updated on any important stratospheric development, and we will also check the long range models again, when they update in October.