A cold start to the meteorological winter looking likely
As we move towards the first month of the meteorological winter December with January and February been the other two months we are looking at some strong signals coming from some of the main forecast models that December will start of colder and yes many will think it December it gets colder generally anyway during the month but this year compared to the last number of years we are looking at a colder start than normal.
Tonights Ecmwf weather model longer range 42 day forecast is showing very high chance of strong or significant Scandinavia high pressure system sitting over Scandinavia. This in turn will open the door for a colder northeast or easterly airflow which will bring a colder start to the first week of December with cold nights and temperatures below freezing and also the risk of fog and freezing fog. This looks the most likely outcome at this stage with blocking in the Atlantic stopping the normal westerly airflow feeding in wet and windy weather.
After that anything could happen and it could lead to something even colder and wintry to develop moving into the second week of December but at this moment its a watch and wait to see what happens if or when that cold arrives but over the coming week we should have a better Idea. I'd expect day time temperatures to be in single figures over the first week of December possibly just above freezing any day fog lingers but over all it will be mainly dry.
Some showery could effect some areas which could be wintry but don't expect Snowmageddon. In these sort of set ups you normally get the cold in first and it can then lead to something more wintry down the road.
We then also have a possible SSW sudden stratospheric warming event which could occur at the end of the first week of December which can also lead to colder weather a few weeks later down the line.
December is going to be a interesting month weather wise especially if you are a person who monitors forecasts and the atmosphere as there is many changes that look set to occur over the coming weeks.
I will have updates over the coming weeks once we have a better understanding on the set up and what scenarios play out.
Kenneth from the Donegal Weather Channel