Weather: Thunderstorms, severe gales to lash parts of the country bringing threat of damage and power outages

Thunderstorms, heavy rain and strong 120km/h gales are bearing down on Auckland, with the rapidly approaching storm prompting MetService to issue a top priority severe thunderstorm warning.

The warning, valid until 10.30am on Wednesday, affects people in the local government areas of Rodney, Gulf, Thames Coromandel, Kaipara, Auckland City, Waikato, Hauraki, Waitakere, Franklin and Albany.

At 9:30am, MetService’s weather radar detected a line of severe thunderstorms lying off the West Coast.

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The weather agency said this line of thunderstorms is moving towards the northeast and are expected to be accompanied by damaging wind gusts.

MetService said very strong wind gusts can break branches from trees, damage roofing, and make driving hazardous especially for high-sided vehicles and motorcycles.

The National Emergency Management Agency is advising people to take shelter as the storm approaches, preferably indoors and away from windows.

It’s also asking people to avoid sheltering under trees if outside; to get back to land if outdoors on the water; to move cars under cover or away from trees; to secure any loose objects around the house; check drains and gutters are clear; and be ready to slow down or stop if driving.

Once the storm passes it’s also asking people to beware of fallen trees and power lines, and to avoid streams and drains that may be flooded.

This morning, MetService issued a strong wind watch for Auckland and Great Barrier Island. Wind gusts of 120km/h are possible in exposed places from 10am until 2am tomorrow.

Drivers using the Auckland Harbour Bridge are being warned it could close temporarily if wind gusts reach threshold levels.

Potentially destructive gusts are forecast to begin at lunchtime and last until early Thursday morning.

NZTA is urging drivers to take extra care travelling over the bridge with the likelihood of reduced speed limits and some lanes on the bridge closing if wind gusts reach threshold levels.

It said the strongest wind gusts were predicted from 10am until midday and during rush hour at 6pm.

“If threshold levels are reached during this time, there is a possibility that all lanes on the bridge could close temporarily,” said the transport agency.

Auckland Emergency Management (AEM) last night advised Aucklanders to stay indoors and avoid going outside unless necessary.

“Drive carefully if you’re on the road, reduce speed and keep both hands on the wheel. Watch for fallen branches and do not drive through floodwaters,” the post read.

A Severe Thunderstorm Watch is also in place for Auckland, northwestern Waikato, and western parts of the Coromandel from 10am to 7pm, while the strong wind watch for Northland up to Kaikohe is in place from noon until 3am tomorrow.

Further strong wind watches are in place for the bottom of the South Island and western Taranaki, and would expire from late afternoon until early evening.

Forecaster Niwa said the strongest gusts were likely over coastal and higher areas. Localised power cuts and damage were possible.

People should prepare ahead of time by securing any loose objects that could be lifted or moved by the wind such as trampolines and wheelie bins, MetService said.

MetService meteorologist Mmathapelo Makgabutlane said thunderstorms are predicted to accompany the strong winds, with a chance of showers passing through.

“The wettest part of the country is forecast to be north of Whanganui, along the western parts, into Waikato and the Northland region.”

MetService says an unstable southwesterly flow will cover the country this morning, with an embedded cold front moving north to affect western parts of the North Island and South Island.

The cold front brings a moderate risk of thunderstorms about western areas from Taranaki to southern Northland and Auckland, with a low risk spreading across other areas from Northland to western Bay of Plenty and Horowhenua.

MetService predicts these thunderstorms will bring brief heavy rain, small hail, and squally wind gusts of 80-100km/h. A severe thunderstorm watch is in effect from 10am until 7pm.

In the South Island, there is a moderate risk of thunderstorms about Fiordland before dawn, and about northern Westland and Buller, mainly near the coast, through much of the morning.

A low risk covers other western and southern areas from western Tasman to Southland. Wind gusts could reach 80-90km/h near the coast.

Small amounts of snow fell overnight and through to early this morning on the Lindis Pass, Crown Range Rd, Milford Rd and Desert Rd.