Storm and tornado warning for much of North Island

Tornadoes and storms could be on the way for large swathes of the North Island.

• First published on RNZ

MetService issued a severe thunderstorm watch for Auckland, Waikato, Coromandel Peninsula, Bay of Plenty and Rotorua, for early Sunday afternoon into Sunday night.

Thunderstorms could be severe and rainfall could reach 40mm an hour, causing flooding, slips and dangerous driving conditions.

There could also be hail and tornadoes, MetService said: "Tornadoes may cause some structural damage, including damage to trees and power lines, and make driving hazardous. If any tornadoes occur, they will only affect very localised areas."

A strong wind watch was also in place for the northernmost parts of Northland, from 11am Sunday into the evening, with forecasters cautioning that winds could approach severe gale force in places.

Tai Rāwhiti preparing for more heavy rain

Gisborne and Tai Rāwhiti are under a heavy rain watch, with work underway to stop a large landslide already blocking access between Wairoa and Gisborne from growing further.

A large section of Tiniroto Road collapsed on Tuesday, cutting off 1500 residents in the Hangaroa area. The slip was in the same place as a slip that happened during Cyclone Bola, which had formed a lake that locals had called Lake French.

The council estimated 25,000m3 of hillside above the road had come down and shunted about 100m of the road downhill, damming the Waikoko Stream.

MetService issued a Heavy Rain Watch for the Wairoa District and parts of Tai Rāwhiti, especially about the ranges, for Sunday morning through into Sunday night.

Gisborne District Council said river levels would be monitored, particularly near the bridges at Te Karaka and in the Hikuwai catchment.

And preparations were being made to prevent the landslide on Tiniroto Road from deteriorating further.

Mayor Rehette Stoltz said contractors were digging a spillway at the site to prepare for the weather.

"We will ... work on a managed release of the landslide dam of the Waikoko Stream by digging a spillway channel below there to make sure there is a natural release of that water."

A temporary track at the site of the slip would be used to restore access for local communities, and it was hoped they could have temporary access restored by the beginning of Labour Weekend.

"Our contractors have made great progress," Stoltz said. "They have cut a temporary track through the slip ... Power lines have been removed.

"What will happen next is that lots of trees will be cut down and will have to be removed. So a lot has happened."

Stoltz said the region has had nine major storms in the past 18 months.