In today's headlines with Susie Nordqvist, Hamas says its top political leader has been killed in an Israeli airstrike and nursing graduates were sent job offers in error.
Niwa is giving two in three chances of this decade’s fourth La Nina forming over spring – but not before a cold and dry start to August.
The agency’s just-issued climate outlook has offered a mixed bag of weather trends over the next three months, with rainfall and temperature patterns expected to take a turn later in August.
Meteorologist Ben Noll said New Zealand was experiencing the chilly influence of a disturbed polar vortex at present, resulting from a rare stratospheric warming event over Antarctica.
That phenomenon, which has seen a remarkable jump in temperatures in the polar stratosphere, was expected to continue for the next seven to 10 days – with New Zealand likely to see colder, drier conditions.
MetService reported temperatures around the country were set to drop overnight, amid a building ridge of high pressure.
Nearly all of the South Island main centres could expect freezing nights for the next few days, with only Dunedin and Westport remaining above zero.
“While Kaikōura’s forecast minimum temperature of minus 2C isn’t the lowest around, that’s eight degrees lower than its average at this time of year,” MetService meteorologist Alwyn Bakker said.
While it’d be somewhat warmer in the North Island, most locations south of Auckland would still see low single digits overnight.
Noll said the cool start to August wasn’t likely to define the wider three-month period, with a trend toward much more unsettled conditions later this month.
“And that may bleed into the spring season with more frequent lows and rain.”
For the whole period, the outlook picked above-average temperatures for the north of the North Island, with near- or above-average temperatures elsewhere.
Source / Niwa
More northerly flows would pick up from mid-August – likely bringing spells of “unseasonable warmth” – as would rainfall levels, which were predicted to be normal to above normal for all regions.
That was all coming against the backdrop of a developing La Nina, with Niwa giving a 60 per cent odds of the big climate driver forming in spring.
For much of the North Island, the pattern is known to bring northeasterly flows, muggy weather and regular visits from big rainmakers over the warmer months.
But that didn’t mean we could expect this summer to be a repeat of the disastrous La Nina summer of 2022-23, which also marked the end of an unusual three-year run under the pattern.
Source / Niwa
“At this point, we’re not looking at anything like that,” Noll said, adding that early indicators suggested the coming system would be of weaker intensity.
At the same time, however, a vast area of ocean that’s proven a potent source of energy and moisture for storms over recent La Nina years – called the West Pacific Warm Pool – was building.
“How intense that becomes is something that will help to shape the weather that we’ll experience later in the year.”
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
