Despite a heavy dump of rain over the long weekend – and more coming this week – meteorologists say the Auckland region still faces a long recovery from its six-month drought.

And those hoping for an end to the region's worst dry spell in a quarter-century won't be happy to hear this month will bring yet more long stretches of rainless weather.

With no clear climate driver predicted over New Zealand throughout winter, forecasters say it's difficult to say what relief the region might get in the medium term.

But, at the end of the season, there's potential for a reverse version of the same system that fuelled Australia's bushfires, and kicked off drought conditions here, to form up and bring some much-needed moisture for spring.


In its latest seasonal outlook, Niwa reported a 71 per cent chance that ENSO-neutral conditions – meaning there was no El Nino or La Nina in the mix to play with our weather – would persist for the next three months.

"When you're looking at multiple months ahead of time, you really want to understand who is at the steering wheel of Mother Nature's car," Niwa forecaster Chris Brandolino said.

"If you can, then you have a pretty good idea about which direction we'll be gravitating toward.

"ENSO-neutral means things can be a bit muddy – and the predictability of things becomes more challenging."

As it stood, the same climate conditions that had contributed to dryness over much of New Zealand were expected to influence our weather for at least the first half of the winter season.

Across winter, air pressure was forecast to be higher than normal to the north of, and sometimes over New Zealand.

As a whole, air temperatures were most likely to be above average in the east of the South Island and about equally likely to be near average or above average in all other regions.

Rainfall levels, meanwhile, were most likely to be below normal in the east of both islands, near normal in the west and north of the South Island, and about equally likely to be near normal or below normal in the north and west of the North Island.


At the close of winter, however, came the possibility of an Indian Ocean Dipole (IOD) – a seesaw-like system that typically has three phases - neutral, positive and negative.

In a positive state, it created a temperature difference across the tropical Indian Ocean, with cooler than normal water in the east and warmer than normal water in the west.

Last year brought an IOD that reached one of the most intensely positive states in modern history which, when coupled with an unusual El Nino, set the stage for catastrophic fires across Australia.

Yet the IOD that could form up this year was expected to be negative, potentially bringing rain to typically dry areas of New Zealand.

"The intensity of this IOD is still up in the air – but it doesn't look like it will be as intense, or the polar opposite, of what we saw last year," Brandolino said.

But there was still the chance a negative IOD would embed tropical moisture into weather systems reaching New Zealand – and the country was getting a taste of that with the current downpours.

"So, we can expect that what we're getting [currently] will become more common as we head into spring."

As for drought relief in the short-term, Brandolino didn't have much good news to offer.

"People are going to be saying, 'look at all of this rain'. Well, I can tell you, after this, and a bit rain throughout the week, it's going to go dry again for much of June."

And there was a long way to go to make up a rainfall deficit that was running at 250mm at the start of last week – or top up Auckland dam levels that were still sitting at only 43 per cent of capacity today.

"Getting some rain now is good, obviously. If you're $100,000 in the hole, and you win $20,000 on a scratchie, that's great, but you still need 80,000 bucks."

Auckland's 'bad luck summer'

The run of dry weather that's plunged the upper north into the worst drought seen in the region since 1994 comes down to bad luck, scientists say – but that doesn't mean a warming climate hasn't played a part as well.

The drought has been driven by several factors including persistent, blocking high pressure systems in the northern Tasman Sea and north of the North Island, suppressing rain-bearing weather systems to the south.

There was also a lack of moist, northerly air flows and a persistently positive Southern Annular Mode early in the year which was associated with more tranquil weather in the New Zealand region.

Kiwi climate scientist Dr Luke Harrington said the drought would almost certainly go down as one more severe than simply a one-in-25-year event.

"To have the initial rainfall deficits across the summer requires a certain amount of bad luck, but having a 'bad luck' summer has been made more likely because of climate change," said Harrington, a research fellow in climate extremes at Oxford University's Environmental Change Institute.

Source / Niwa
Source / Niwa

Research he'd carried out with Victoria University's Professor Dave Frame had found that, although there'd been no major changes in average summer rainfall over the last 150 years, the chances of seeing unusual summers had grown higher.

"That means a greater chance of experiencing both wetter-than-normal summers and drier-than-normal summers," he said.

"So once there has been a 'bad luck' dry summer, the next opportunity for some decent rain normally comes from ex-Tropical Cyclones, as summer changes into autumn."

At the same time, there was also evidence suggest that autumn rain wouldn't be there to save the day.

"In fact, some studies suggests the chances of drier-than-average autumns are also becoming more common."

Harrington added that, while the coming months will hopefully bring the needed rain, there remained the risk of drought behaviour emerging in Auckland, as being seen elsewhere in the world.