16 Aug 2022 | 02:42 AM UTC
New Zealand: Adverse weather forecast for northwestern South Island and western North Island through at least Aug. 19 /update 1
Severe weather forecast across northwestern South Island and western North Island, New Zealand, through Aug. 19. Disruptions possible.
Event
Heavy rainfall and strong winds are forecast across northwestern South Island and western North Island through at least Aug. 19. A low-pressure system over the Tasman Sea is forecast to track over the country Aug. 16, remain almost stationary Aug. 17, and move slowly eastwards across the South Island Aug. 18-19. Flooding is possible, especially in areas with already saturated soils from recent rain. As of early Aug. 16, the New Zealand National Meteorological Service (MetService) has issued the following weather warnings:
Red Heavy Rain Warning (the highest level on a three-tier scale): Buller and Westland. 35-55 cm (14-22 inches) of rainfall is likely about the Buller ranges south of Little Wanganui and 15-28 cm (6-11 inches) over the rest of Buller. An additional 30-50 cm (12-20 inches) of rainfall is forecast to accumulate over the Westland ranges, especially between Bruce Bay and Otira, with 12-20 cm (5-8 inches) likely over the Westland coast.
Orange Heavy Rain Warning: Marlborough Sounds, Bryant and Richmond ranges, Rai Valley, Mount Taranaki, Nelson Region, Northland, and Tasman District west of Motueka.
Orange Strong Wind Warning: Northland.
Yellow Heavy Rain Watch: Auckland, Great Barrier Island, headwaters of the Canterbury lakes and rivers, Marlborough northwest of the Inland Kaikoura Range and south of the Richmond Range, North Taranaki away from the mountain, Waikato, Waitomo, Taumarunui, Taupo, Taihape, and Tasman District from Motueka eastwards excluding Nelson Region.
Yellow Strong Wind Watch: Auckland, Great Barrier Island, Buller, Nelson, Tasman, Taranaki about and south of the mountain, and Taihape.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Authorities have advised residents to ready emergency supplies, be prepared for power outages, and keep up to date with the latest weather warnings. Residents are also advised to clear drains and gutters of leaves and debris and to consider using sandbags. Properties in low-lying areas or near water bodies should prepare for flooding.
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 delays and cancellations at regional airports. Authorities may temporarily suspend port operations 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.
