Emergency management teams meet as West Coast prepares for a month’s worth of rain in one day

Parts of the West Coast can expect “a month’s worth of rain in one day” as an “atmospheric river” washes over the area.

MetService has warned parts of Westland could be hit with a “significant” amount of rain over the next day or two, with up to 800mm forecast in the ranges.

A neighbouring district mayor said his thoughts went out to the West Coast and the “hammering” it was about to get.

Meanwhile Niwa said the level of rain expected is equivalent to a month’s worth, as “an atmospheric river of moisture” tracks into the district.

New Zealand gets about 40 atmospheric rivers per year, Niwa said.

Emergency management groups are in meetings today to prepare for the deluge, which could get as heavy as 25-30mm per hour at times. MetService classifies rainfall over 25mm per hour as torrential.

The forecast has prompted MetService to put out a red warning for Westland, while neighbouring areas are also on high alert with orange and yellow rain warnings. Westland can expect 600-800mm of rain, with isolated areas possibly accumulating even more.

Meteorologist Juliane Bergdolt said MetService normally issued warnings if an area was expected to get about 200mm of rain over a 24-hour period. Westland is expecting to get 300-400mm on average over 24 hours.

The red warning has been in place since 9am today and runs until 8am Saturday.

MetService has issued a red rain warning for Westland. File photo / Richard Robinson

“We are expecting quite a lot of rain from today and into Saturday, so that’s quite a prolonged time,” Bergdolt said.

“It is a significant amount of rain which is why we did send out that red warning. We know from experience that can make the rivers rise quite significantly in that area.”

She said they were conscious there were likely to be quite a few holidaymakers in the region who might not be as familiar with how quickly or how high the rivers could rise.

The Westland ranges, encompassing popular tramping and camping spots, are anticipated to experience the highest accumulations, while the coast may witness lesser amounts.

She also warned there was a risk of thunderstorms, which could cause even heavier hourly rainfall, possibly up to 30-35mm per hour.

“That’s like one of those big school ruler’s worth of rain.”

The heaviest rain is expected from late Friday morning, with heavy rain expected to ease from the south from early Saturday morning.

“This rain is expected to cause dangerous river conditions and significant flooding. Slips and floodwaters are likely to disrupt travel, making some roads impassable and possibly isolating communities,” MetService warned on its website.

MetService meteorologist Mmathapelo Makgabutlane also emphasised the need for caution as this red warning bears similarities to the damaging flooding from March 2019 in which the Waiho bridge was washed away.

“Red warnings are our highest warning level; they mean significant weather impacts are expected. People need to take immediate action to ensure they are safe, especially those camping near a waterway as there is a danger of flooding.

“For those planning a trip down south this weekend, be aware that this is a significant event and may affect travel plans. Stay up to date with the latest information on the MetService website and have alternative plans if needed.”

MetService red warnings are reserved for the most disruptive weather events and are only issued after consultation with the local regional council and civil defence.

West Coast Emergency Management posted on social media warning locals it was time to prepare for “extreme weather”.

Grey District Mayor Tania Gibson said they were under an orange warning, and would know more about emergency preparations after a meeting at 2pm.

“We’ve had, actually, dry weather here and people do actually need some water, but we don’t quite need this much.”

“There’s a lot of people still out there travelling at the moment. We just advise people to keep up to date with the weather reports.”

Southland Mayor Rob Scott said Fiordland was expecting about 250-350mm of rain, which was a “reasonable amount”, but that the area was used to heavy rainfall.

He said the peak rates were only about half of what they were in 2020, when torrential rain caused floods that stranded hundreds of people in Milford Sound.

“My thoughts are going to the West Coast, who are going to be bearing the brunt of it. We’re just getting the tail end of it on our end.

“The West Coast are going to get a hammering by the sound of it.”

Westland Mayor Helen Lash has been contacted for comment.

How to prepare for extreme weather

• Clear drains and spouting around your house
• Check on neighbours or anyone who may need assistance
• Have an emergency bag ready to go if needed
• Bring pets indoors
• Expect possible power outages
• Move livestock to higher ground
• Avoid driving, but have emergency supplies in your vehicle if you must travel

Melissa Nightingale is a Wellington-based reporter who covers crime, justice and news in the capital. She joined the Herald in 2016 and has worked as a journalist for 10 years.