Severe thunderstorms possible for upper North Island overnight

Waka Kotahi says speed restrictions and lane closures on the Harbour Bridge are likely, and a full closure is possible, if winds become too strong. Photo / Sylvie Whinray

Auckland has been under severe thunderstorm watch overnight - with earlier warnings that the Harbour Bridge could close if winds became strong enough.

Metservice says severe thunderstorms were possible across parts of the upper North Island overnight, and wind gusts could reach 110km/h.

Waka Kotahi said strong winds had been expected to affect the Harbour Bridge between 9pm on Tuesday and 4am Wednesday.

Speed restrictions and lane closures were likely and a full closure was also possible, the transport agency said on Twitter.

WEATHER WARNING - 6:30PM
Strong winds are expected to affect the #SH1 Harbour Bridge tonight between 9pm and 4am. Speed restrictions and lane closures are likely, a full closure is possible. Check our Traffic Map for the most up to date information: https://t.co/nOInjQdgUj ^LB https://t.co/bTWYiayNrt

— Waka Kotahi NZTA Auckland & Northland (@WakaKotahiAkNth) May 31, 2022

On Tuesday night, MetService issued a "severe thunderstorm watch" for Northland, Auckland, Great Barrier Island, Coromandel Peninsula, Waikato, Waitomo, Bay of Plenty, Rotorua and Taranaki.

The warning was in force until 6am on Wednesday.

A "severe thunderstorm watch" means conditions are favourable for severe thunderstorms in and close to the watch area, MetService said.

The forecast for these areas includes an intense front with embedded thunderstorms that were expected to move east across the upper North Island overnight.

There was a chance some of these thunderstorms could become severe, with damaging wind gusts reaching 110km/h.

MetService said there was also a possibility of one or two localised damaging tornadoes but they were expected to only affect very small areas.

"Wind gusts of this strength can cause some structural damage, including trees and power lines, and may make driving hazardous.

"If any tornadoes occur, they will only affect very localised areas."

MetService has issued different weather warnings for much of the country – including a severe thunderstorm watch that was issued for Nelson, Buller, Westland, Canterbury High Country and Fiordland tonight.

The watch is in place from 3am to 3pm on Wednesday. In it, MetService says an air mass with rapidly moving thunderstorms was expected to affect the west of the South Island overnight and during Wednesday.

There was a risk of severe thunderstorms bringing damaging wind gusts of more than 110km/h and localised tornadoes.

Weather warnings and watches have also been issued for Taihape, and the ranges of Hawke's Bay north of Kereru (strong winds), Taranaki (strong winds), Mount Taranaki (heavy rain), Wellington, Wairarapa about and south of Featherston, inland Marlborough and the Marlborough Sounds (strong winds), Kapiti-Porirua Coast - Otaki to Cape Terawhiti (heavy swells), Canterbury High Country (strong winds), Tasman west of Motueka (heavy rain) and Fiordland, Westland south of Fox Glacier (strong winds).