New Zealand: Heavy rainfall forecast in western parts of South Island through at least Feb. 4

Event

Heavy rainfall is forecast in portions of western South Island through at least Feb. 4. An active front is forecast to track northwards across the South Island Feb. 2-4, bringing heavy rain to the western regions, especially in Buller and Westland. The heavy rain is likely to cause rapid water level rises in streams and rivers. Localized flooding and landslides are likely. The rain might result in hazardous driving conditions. As of Jan. 31, the New Zealand National Meteorological Service (MetService) has issued the following warnings:

• Heavy Rain Warning: Buller and Westland; forecast models indicate rainfall of 30-40 cm (12-16 inches) about the Buller ranges, 40-55 cm (16-22 inches) over the Westland ranges, and 15-30 cm (6-12 inches) near the coast.

• Heavy Rain Watch: Tasman west of Motueka, the headwaters of the Canterbury and Otago lakes and rivers, and Fiordland.

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

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 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 some delays and cancellations at regional airports. Authorities may temporarily suspend port operations along the Tasman 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 that see 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