Weather: Atmospheric river to bring 140km/h winds and heavy rain to South Island

An upgraded red warning has been issued for Canterbury high country as an atmospheric river bears down on New Zealand, bringing damaging winds, heavy rain and dangerous driving conditions to much of the country.

MetService meteorologist Mmathapelo Makgabutlane told the Herald the alert level had been lifted from orange to red - the highest level - with winds expected to reach up to 140km/h between 10pm Saturday and 3pm Sunday.

“That red warning indicates quite significant and widespread impacts,” Makgabutlane said.

“We’re talking about damage to property, falling trees, power outages, and dangerous driving conditions- particularly concerning as the school holidays kick off this weekend.”

Almost the entire South Island is now under orange wind warnings, with gusts of up to 120km/h forecast in exposed areas.

Wellington has also been upgraded from a watch to a warning for strong winds, while new watches have been issued for South Taranaki and inland Manawatū.

Heavy rain is expected on Sunday for the West Coast and the headwaters of lakes and rivers east of the Southern Alps, with bursts of intense downpours possible.

Government forecaster Niwa is predicting above normal rainfall next week for almost the entire country, except for the east coasts of the North and South Island.

Wind and rain forecast this weekend

Aucklanders are set to have a chilly start today, with a minimum temperature of 5C, but are likely to dodge any significant rain until next week.

“Midway through Saturday and the latter part of the day, we have our next weather system approaching,” Makgabutlane said.

On Saturday, winds will start to increase in speed for the South Island and the lower North Island.

“The real weather really comes in on Sunday, where we’re seeing that heavy rain moving into Sunday. That heavy rain arrives over the western part of the South Island and then continues to make its way up the island throughout Sunday.”

She said the rain would arrive in central New Zealand by the end of Sunday.

“Particularly for the Canterbury high country, we could see some possibly damaging winds. Those wind gusts could get up to about 140km/h,” Makabulane said.

On Sunday, there is a possible risk for thunderstorms for Fiordland and Stewart Island.

Wet month ahead

Much of the South Island will take a battering for the remainder of the month, with the western parts of the island being the wettest part of the country “probably for the rest of the month, maybe even to the first few days of October”, said Niwa’s principal scientist Chris Brandolino.

“There will probably be a wet period for the North Island, maybe the 21st to the 28th [of September], so that week could be an unsettled and wet week.”

Things might start to look up in October, with drier conditions predicted because of the low-pressure system in the Southern Ocean disappearing.

“Some days it’ll feel almost like summer, and then it goes back to winter. And that’s kind of quintessential with spring.

“It’s quite variable and quite moody. I call it the teenager of seasons because lots of ups and downs,” Brandolino said.

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