New Zealand: Adverse weather forecast over northwestern parts of North Island through at least Jan. 29 /update 1

Event

Heavy rainfall accompanied by severe thunderstorms and strong winds are impacting parts of North Island as of late Jan. 27 and further severe weather is forecast through at least early Jan. 29 across much of North Island and far northern South Island. The severe weather is causing widespread disruption across Auckland and other surrounding areas. A subtropical low to the northwest of North Island is expected to bring further rainfall totals of up to around 15 cm (6 inches) on top of heavy rain that has already fallen in some areas. Winds gusting up to 110 kph (68 mph) are also possible across parts of the affected region, and there is a threat of severe thunderstorms across northern parts of North Island. Heavy downpours could trigger flooding in low-lying areas and landslides on unstable slopes and strong winds could cause property damage and power outages.

As of late Jan. 27, the New Zealand National Meteorological Service (MetService) has issued the following weather warnings:

• Red Severe Thunderstorm Warnings (the highest level on a three-tier scale): Rodney, Gulf, Auckland City, Waikato, Waitakere, Franklin, and Albany

• Red Heavy Rain Warning: Auckland about and south of Cape Rodney.

• Orange Heavy Rain Warnings: The Coromandel Peninsula; Waikato north of Te Awamutu; Bay of Plenty west of Whakatane; Bay of Plenty from Whakatane eastwards, and Gisborne north of Ruatoria; Mount Taranaki, and Wairarapa including the Tararua District

• Yellow Severe Thunderstorm Watches: Auckland, Great Barrier Island, Coromandel Peninsula, Bay of Plenty, and Rotorua

• Yellow Heavy Rain Watch: South Taranaki (excluding Mount Taranaki), Manawatu, and Whanganui; and Central North Island from southern Waikato across to Taihape and inland Hawke's Bay

• Yellow Strong Wind Watch: Auckland, and Horowhenua Kapiti Coast, Wellington, and the Marlborough Sounds.

Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

Evacuations are ongoing across parts of Auckland and authorities have reported at least one fatality after heavy rainfall triggered widespread flooding in and around the city Jan. 27. Flood waters have inundated homes, shops, and other buildings in the area. Auckland Airport (AKL) closed late Jan. 27 due to flooding impacting the terminal building and surrounding roads. Many roads across Auckland and its environs have been made impassable by flooding and landslides, including sections of State Highway 1. Further severe weather is forecast over the coming hours and additional heavy downpours will likely exacerbate the flood situation and hamper ongoing response and recovery efforts.

Hazardous Conditions
Further sustained heavy rainfall could trigger additional flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed or lack of stormwater drainage systems. Sites located downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides are possible in hilly or mountainous areas, especially where the soil has become saturated by heavy rainfall. Power outages could occur throughout the affected area.

Transport
Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters. The disruptive weather may cause delays and cancellations at regional airports. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding could block regional rail lines; freight cancellations are possible in areas with heavy rainfall and potential track blockages.

Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after conditions have improved - it could take days before any floodwaters recede and/or officials clear debris. If there is severe damage to infrastructure, repair or reconstruction efforts may result in residual disruptions.

Advice

Monitor local media for weather updates and related advisories. Confirm all transport reservations and business appointments before travel. Make allowances for localized travel delays and potential supply chain disruptions where flooding has been forecast. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.

Resources

New Zealand National Meteorological Service