New Zealand: Heavy rainfall forecast in northern and central regions through at least March 23

Event

Heavy rainfall and strong winds are forecast in northern and central North Island as well as far northwestern and northeastern South Island through at least March 23. The affected areas include portions of Auckland, Bay of Plenty, far northeastern Canterbury, northern Gisborne, northern Manawatu-Wanganui, northern Taranaki, northwestern Tasman, and Waikato regions. As of March 21, the New Zealand National Meteorological Service (MetService) has issued the following warnings:

• Orange Heavy Rain Warning (the middle level on a three-tier scale): Auckland including Great Barrier Island, Bay of Plenty west of Opotiki, Coromandel Peninsula, and Waikato; up to 10 cm (4 inches) of rainfall could occur in the area, especially in the Bay of Plenty.

• Yellow Heavy Rain Watch: Bay Of Plenty east of Opotiki, Gisborne north of Tolaga Bay, the Kaikoura coast and ranges, Taranaki about and north of the mountain, Tasman west of Motueka, Taumarunui, Taupo, and Waitomo.

• Yellow Strong Wind Watch: Auckland.

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

Reports indicate that parts of central Auckland are flooded. Several Countdown supermarkets across Auckland closed early March 21 due to heavy rain, flooding, and damage. Authorities have also closed several schools on Auckland's North Shore and West Auckland due to the heavy rain, surface flooding, and power outages.

Hazardous Conditions
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 a 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. Authorities have advised residents across Auckland to delay travel early March 21 and to drive with extra caution, especially in areas with surface flooding. All public transports services in Auckland are running as scheduled the afternoon of March 21 as the flooding has partially eased. Officials have reopened all lanes of Mt Wellington Highway and State Highway 1. The disruptive weather may cause flight disruptions at airports in the region including Auckland International (AKL), Taupo (TUO), and Gisborne (GIS) airports.

Authorities may temporarily suspend port operations along the Bay of Plenty, South Pacific Ocean, and Tasma Sea 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
Waka Kotahi NZTA Auckland & Northland Twitter