MET ÉIREANN’S HEAD of forecasting Evelyn Cusack has said the “unseasonably warm” weather being experienced in Ireland at the moment is due to a warm air mass from the south but that this is likely to be replaced by a polar front over the weekend.
Cusack said Ireland’s global latitude at about 50 degrees north means the country’s weather is significantly influenced by the polar front.
The polar front is the transition zone between colder northern air and warmer southern air and Cusack says the interplay between them means that it’s “all to play for” in terms of temperatures at Ireland’s latitude.
Temperatures in the country today are expected to be mild with highs of between 12-16 degrees Celsius, the long-term averages for November in different parts of Ireland range between 7-9 degrees Celsius.
Asked about this yesterday at the launch of the government’s Be Winter Ready campaign, Cusack said that it was indeed “unseasonably warm” but that this is likely to change.
“While it is going to stay very fine over the next couple of days, our medium range models are giving it colder by Sunday and into next week. But that’s not a sign of a cold winter ahead,” she said.
As for January and February, it could be anything. The weather is very variable at our latitude. So we’ve been blessed really the last two winters, we haven’t had that very severe weather. So hopefully we won’t this winter, but the message is to be prepared.
Explaining further how the weather is likely to change over the coming week, Cusack said:
The reason it’s warm is because the air mass is coming up from the south, it’s coming up from Africa and southern parts of the Atlantic. The polar front is to the north of Ireland. So what’s happening over the weekend is that the polar front is moving south, so we’re getting into a northerly wind.
“This happens all the time at our latitudes, it’s an interplay between warm southerly winds and cold polar northerlies. We know sometimes at Christmas you can get temperatures up to 14 or 15 degrees Celsius on Christmas Day, and that’s because we’re in the southerly wind. In the northerly wind like we had for Christmas 2009/2010 we’re into the Arctic airmass. So it’s really all to play for at our latitude.”
Cusack says she wouldn’t directly explain the current unseasonably warm temperatures as being a product of climate change.
“No, at our latitudes, that’s about 50 degrees north, the whole way around the globe, that’s the average position of the so called polar front, which is the boundary between arctic air and a very mild tropical air, it’s always either moving up and down and undulating,” she said.
Cusack said, however, that the lasting snow and icy conditions seen during the so-called ‘Big Freeze’ in 2009/10 and ‘Storm Emma and the Beast from the East’ in 2018 are related to the changing climate and are “a very likely” to be more frequent in the future.
Now with global warming and the increase in temperature, what it’s doing is it’s causing this polar front sometimes to ‘lodge’, it’s like a fast moving river if there’s a big rock in it kind of slows down and diverges the flow. So that’s what we think is happening to the jet stream. So for example, when we hear of really bitter winters over North America lasting weeks and weeks and weeks, that’s due to the polar front maybe slowing down.
“We can get the same effect, that’s what happened with us in 2009/10, we were on the cold side of jet stream, and that stayed over us for a couple of weeks, so that’s a very likely scenario going forward. Whether that happens this winter, we don’t know and that’s why we’re getting prepared.”
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