Every single spring there’s one message WeatherWatch.co.nz frequently repeats “Spring is all about winter gradually fading and hints of summer slowly coming in”. Of course the warmer than average theme for 2016 makes some of us feel like the end of spring is already here – especially when sub-tropical air at the weekend pushed Northland to 23 degrees and many other places were a few to several degrees above average.
But the warmth is temporary.
As we say above, in spring winter weather “gradually” fades. So it’s not surprising that this week we go from seeing highs in Northland from 23 degrees yesterday to 13 degrees this coming Thursday.
The cold snap hits Southland on Wednesday with just single digit highs again.
Queenstown may even see a few snow flurries on Wednesday as the coldest, and wettest, of the air moves past. Temperatures will drop to -2 overnight, which isn’t too brutal. Conditions warm up a little in the days after, by a couple degrees.
The fast moving burst of cold air will bring wintry weather back to Dunedin too – for both Wednesday and Thursday and there may even be a few low level snow flurries around the city. Daytime highs are still getting up to 10 degrees though, so this isn’t a direct polar blast – but the air is coming from well south of New Zealand.
Wellington also has a cold mid to end week coming – with gale southerlies arriving on Wednesday and a high of only 9 degrees (with a feels like temp around 5 degrees!).
WHY WARM THEN COLD?
Just about every single warmer than average event this year has had something big in common – a large high just north of Northland which scoops sub-tropical air from around New Caledonia and spreads it down over the country as a northerly.
This week we have another big high – but this one is shaped more north to south and rather than being located to our north it’s located to our west, over eastern Australia This is a better recipe to dredge up colder air from the sub-Antarctic region, and is why the temperatures tumble this week across New Zealand.
Warmer Northerlies return this coming weekend to many places.
– Image / Noon Wednesday shows the incoming southerly south of New Zealand and the large high over eastern Australia and Tasmania to our west. Weathermap.co.nz