A lot of people are asking us this question at the moment “When is the winter weather arriving?”. It’s a tricky one to answer this year with the warmer than average weather pattern across the country. Since El Nino died away in Autumn we’ve seen a return to a neutral weather pattern – this encourages far more chaos. So is this warm weather just climate change? Or something more local? It may be a bit of both.
When it comes to Climate Change we can’t just look at one winter in isolation – we need to see a trend year after year, over a number of decades, but there is clearly a global trend to warmer than average conditions. Just look at the heat records being broken across the USA – and also here in New Zealand at the same time. Not just this month – but across the past several months. This also isn’t the first winter in recent years where we’ve seen warmer than average conditions.
However, New Zealand is so small we can buck the global trend at any time – in fact we can pinpoint why conditions are so warm at the moment, it’s mostly due to the northern placement of the air pressure systems.
Put it this way: Many of the warmer than average conditions around New Zealand this year have been caused by large highs east of Northland – this placement gives the high a huge reach into the sub-tropics. With the highs to our east and the wind flow anticyclonic it means the high can reach up to near Fiji and New Caledonia and then pull that humid warm air down across New Zealand as a northerly quarter airflow.
But if you placed that exact same high over Tasmania (now to the west of Fiordland and not to the east of Northland) and move the low east of the country (switching the current set up basically) we end up with a much colder than average wind flow across the country with southerlies dredged up from near Antarctica. It’s really as simple as that.
As to *why* are the highs tracking further north, that might be something the scientists may be able to help with – or not. There’s still a huge unknown about the chaos of air pressure systems – and how climate change may be playing a part. New Zealand is mainly comprised of two mountainous small islands in the roaring 40s and surrounded by ocean – the highs and lows dwarf our entire nation so they influence our entire weather pattern much easier than they do the bigger nations that have much greater landmasses.
Image / Next Wednesday shows a high to our east, once again reaching up into the subtropics and bringing that air down over New Zealand – working in tandem with a sub-tropical low in the Tasman Sea / WeatherMap