21 Sep 2021 | 02:43 AM UTC
New Zealand: Heavy rainfall forecast in northern and western regions through at least Sept. 23
Heavy rainfall forecast in northern and western New Zealand through at least Sept. 23. Flash flooding, disruptions possible.
Event
Heavy rainfall is forecast in portions of northern and western New Zealand through at least Sept. 23. The affected areas include far southwestern Canterbury, Nelson, Northland, far western Otago, western Tasman, and West Coast regions. As of Sept. 21, the New Zealand National Meteorological Service (MetService) has issued the following warnings:
Heavy Rain Warning: The headwaters of Canterbury lakes and rivers south of Arthur's Pass, the headwaters of Otago lakes and rivers, and Westland; additional 6-10 cm (2.5-4 inches) of rainfall could occur in the area.
Heavy Rain Watch: Buller, Nelson, Northland, and Westland from Greymouth northwards.
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 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 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.
