Long, dry spells loom beyond another messy week of spring weather

• A rainy front moving on to southern New Zealand on Monday is forecast to reach the North Island on Wednesday, bringing widespread cloud and showers.
• MetService is also forecasting warm temperatures for much of the country at the end of the week, with Hastings potentially hitting 28C on Friday.
• The National Institute of Water and Atmospheric Research (Niwa) is meanwhile flagging the possibility of long and widespread dry spells later in November, with 50/50 odds of La Nina officially forming by 2025.

New Zealand is in for another week of variable spring weather, courtesy of more westerly flows driving rainy and cloudy fronts on to the country.

However, beyond that, Niwa is flagging the potential for long and widespread dry spells in the final weeks before summer begins.

After a cool but settled Sunday for much of New Zealand, a ridge of high pressure is expected to keep North Island skies generally clear throughout Monday.

But further south, a rainy front was forecast to roll into Fiordland during the morning, MetService meteorologist Ngaire Wotherspoon said.

“From there, it’s going to creep up the West Coast of the South Island. Because it will be slow-moving, we do have potential for heavy rain.”

There was a “moderate” chance a heavy rain watch – currently in place for Westland south of Hokitika from 12pm on Monday to 9am on Tuesday – would be upgraded to a warning.

On the other side of the island, Wotherspoon said the westerly flow could bring a dramatic swing in early week temperatures for Canterbury.

“A lot of places in Canterbury didn’t get higher than 12C or 13C [on Sunday], but they’re looking at temperatures of 20-21C on Monday – that’s quite a jump.”

The westerly front was forecast to reach the North Island on Wednesday, bringing widespread cloudy and showery conditions about the middle of the week.

But there was also some late-week warmth in store for most of the country, she added.

Auckland temperatures weren’t forecast to climb above 17C on Monday, but by Thursday and Friday, the city was in for highs pushing into the early 20s.

It was a similar picture for Hamilton (hitting 23C on Thursday), Tauranga (22C on Friday), Whangārei (23C on Friday) and Thames (23C on Thursday and Friday).

The hottest spot of the week looked to be Hastings, which was forecast to hit a summery 28C on Friday; Alexandra was not far behind with a predicted high of 26C for Thursday.

Meanwhile, Niwa is picking 50/50 odds of another La Nina climate pattern officially developing by the end of the year.

If the pattern did form up, it was likely to be weak and short-lived, Niwa meteorologist Chris Brandolino said.

In any case, he said Kiwis could still expect to see some “La Nina-like” conditions – including potentially widespread dry conditions in the west of both islands later this month.

Niwa’s just-issued outlook for the November-to-January period predicted near normal rainfall for the east of the North Island, and near or below normal levels everywhere else.

Brandolino said the emerging La Nina pattern was likely to come with anti-cyclones helping to block rainmakers from the north throughout November.

“Whether that continues into December, January and February, we’ll see,” he said.

“At this point, the modelling is suggesting that this high pressure may relax a little and shift a bit further south as we move into January.

“That could certainly elevate the odds for our weather to be influenced from the north over summer.”

Temperatures were also likely to be warmer than average over the three months, with frequent northwesterly winds leading to more days above 25C.

“November certainly looks consistently warm and dry for a good chunk of the country.”

Also raising the odds for hot summer weather was the potential for marine heatwave conditions – already occurring in seas to the east of New Zealand – to expand and intensify.

“Once we get into mid-November, I think that people visiting the beach will notice ocean temperatures are warmer than they usually are,” Brandolino said.

“And as we get into December and January, when ocean temperatures will have really increased, those marine heatwave conditions are going to be making the days feel a lot more humid.”

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.

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