New Zealand: Heavy rainfall forecast in northern and central regions through at least March 25 /update 1

Event

Heavy rainfall, thunderstorms, and strong winds are forecast in northern and eastern North Island as well as far northwestern South Island through at least March 25. Forecast models indicate that a low-pressure system will develop northeast of North Island March 22 before tracking south March 23 and remaining to the east of North Island through March 25. As of March 22, the New Zealand National Meteorological Service (MetService) has issued the following warnings:

• Orange Heavy Rain Warning (the middle level on a three-tier scale): Bay Of Plenty, Gisborne, and Hawke's Bay; up to 23 cm (9 inches) of rainfall could occur in the area, especially in the Bay of Plenty and Gisborne.

• Yellow Heavy Rain Watch: Taupo and Tasman west of Motueka.

• Severe Thunderstorm Watch: Auckland and Northland; heavy showers and isolated thunderstorms affecting southern Northland and western Auckland are likely to cause surface or flash flooding in low-lying areas and landslides. Surface flooding and poor visibility in heavy rain are likely to result in hazardous driving conditions.

Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days. Recovery efforts are underway in Auckland following surface flooding March 21.

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. The disruptive weather may cause flight disruptions at airports in the region including Auckland International (AKL) 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