Jamie Morton is the NZ Herald's science reporter.

Dial stuck on cold ... ish

Spring-like days are forecast to persist into August. Photo / Jason Oxenham
Spring-like days are forecast to persist into August. Photo / Jason Oxenham

Welcome to "sprinter".

That's the term that WeatherWatch.co.nz analyst Philip Duncan has used to brand this winter, which is blurring the boundaries with spring because of its milder temperatures.

Duncan said many people had been asking when winter weather would be truly arriving, with a few cold patches in an otherwise warmer season.

The neutral weather pattern New Zealand was experiencing had led to "enormous" high pressure systems over Australia, which were fuelling powerful westerlies in the Southern Ocean, he said.

"Basically, we've got a lot of high pressure over Australia and [it's pushing] a lot of air down into the Southern Ocean."

The air was then being redirected to New Zealand with strong westerlies, he said.

"It just gets caught up in the roaring forties and comes straight over us. The result of that is kind of like a leaf-blower against a hose, because the southerly is trying to come up to us, but is being cut off at the knees by the westerlies."

It was a different picture from the near- or below-average temperatures of last year's winter.

"Because we are two small, mountainous islands in the roaring forties, our weather every year is quite different, but the main difference [this year] is that we are not really getting the big southerlies."

How long will it last?

"I think this is what we will be seeing between now and, let's say the second week of August.

"It doesn't mean that we can't have brutally cold southerlies coming in August and September, but it does limit how cold it can really be across the country."

Between July and September, the National Institute of Water and Atmospheric Research (Niwa) predicted that temperatures had a 60 to 70 per cent chance of being above average in all regions, although it said that frosts and cold snaps would occur from time to time.

Seasonal rainfall was also about equally likely to be near normal or above normal for all regions.

Today's outlook

Auckland: Showers and strong southwesterlies, gales gusting to 90km/h. High: 15C

Whangarei: Fine breaks with the odd shower, strong southwesterlies. 17C

Hamilton: Few showers, fine breaks. Strong southwesterlies. 15C

Tauranga: Morning showers, strong southwesterlies. 16C

Wellington: Fine day, evening northwesterly. 13C

- NZ Herald

Get the news delivered straight to your inbox

Receive the day’s news, sport and entertainment in our daily email newsletter

SIGN UP NOW

© Copyright 2016, NZME. Publishing Limited

Assembled by: (static) on production apcf03 at 29 Sep 2016 16:54:27 Processing Time: 747ms