New Zealand: Further adverse weather forecast across parts of North and South islands through at least Feb. 3 /update 4

Event

Heavy rainfall and thunderstorms are forecast across parts of North and South islands through at least Feb. 3. Further heavy downpours are forecast across northern parts of North Island, where rounds of heavy rainfall have been causing widespread disruptions since Jan. 27. Additional rainfall totals of 5-8 cm (2-3 inches) are forecast across parts of the affected area Feb. 1-2. Separate weather systems are expected to bring heavy downpours and thunderstorms across parts of South Island through Feb. 3, with rainfall totals of 20-30 cm (8-12 inches) possible over mountainous areas of western South Island Feb. 2-3. Heavy downpours could trigger flooding in low-lying areas and landslides on unstable slopes, especially in areas where the ground is already saturated from previous rainfall.

As of late Feb. 1, the New Zealand National Meteorological Service (MetService) has issued the following weather warnings:

• Orange Heavy Rain Warnings (the middle level on a three-tier scale): Bay of Plenty about and east of Kawerau, Gisborne north of Ruatoria, and Westland south of Otira.

• Yellow Severe Thunderstorm Watch: Canterbury High Country, North Otago, Central Otago, Dunedin, Clutha, Southland, and Fiordland.

• Yellow Heavy Rain Watch: The Hunua Ranges and the Coromandel Peninsula, and Bay of Plenty west of about Kawerau, including the Rotorua Lakes District, Western Bay of Plenty District, and Tauranga City, Tasman west of Motueka; and Fiordland north of George Sound.

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

Authorities in Auckland have declared a state of emergency after at least four fatalities occurred following heavy rainfall late Jan. 27. Hundreds of homes in the city have been damaged by the flooding. Auckland Airport (AKL) closed Jan. 27-29 due to flooding, widespread power outages were reported, and schools closed; however, most services have begun to return to normal as of Feb. 1. Heavy rainfall has continued across much of the north of North Island over recent days and has impacted numerous roads across the affected areas; full details on road closures can be found here. A landslide triggered by heavy rainfall at Orua Bay Beach near Auckland Jan. 31 caused three injuries and destroyed a building and a vehicle.

Hazardous Conditions
Sustained heavy rainfall could trigger 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. 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
NZ Transport Agency