17 Aug 2022 | 02:35 AM UTC
New Zealand: Adverse weather forecast for northwestern South Island and most of North Island through at least Aug. 19 /update 2
Severe weather forecast across northwestern South Island and most of North Island, New Zealand, through Aug. 19. Disruptions possible.
Event
Heavy rainfall and strong winds are forecast across northwestern South Island and most of North Island through at least Aug. 19. A low-pressure system over New Zealand is forecast to remain almost stationary Aug. 17, and move slowly eastwards across the country late Aug. 18-19. Flooding is possible, especially in areas with already saturated soils from recent rain. As of early Aug. 17, 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. A further 20-30 cm (8-12 inches) of rainfall is likely about the Buller ranges south of Little Wanganui and 10-20 cm (4-8 inches) over the rest of Buller. An additional 20-30 cm (8-12 inches) of rainfall is forecast to accumulate over the Westland ranges, especially between Bruce Bay and Otira, with 8-15 cm (3-6 inches) likely over the Westland coast. Thunderstorms are possible in southern Westland Aug. 17.
Orange Heavy Rain Warning: Auckland, Bay of Plenty west of Edgecumbe, Great Barrier Island, Mount Taranaki, Northland, North Taranaki away from the mountain, Tararua Range, Tasman District west of Motueka, Tongariro National Park, Marlborough Sounds, Richmond and Bryant ranges, Rai Valley, Nelson District, Taumarunui, Waikato south of Raglan, and Waitomo.
Orange Strong Wind Warning: Northland.
Yellow Heavy Rain Watch: Bay of Plenty about and east of Edgecumbe, headwaters of the Canterbury lakes and rivers, Coromandel Peninsula, Marlborough northwest of the Inland Kaikoura Range and south of the Richmond Range, Waikato about and north of Raglan, Taupo, Taihape west of Tongariro National Park, and Tasman District from Motueka eastwards excluding Nelson District.
Yellow Strong Wind Watch: Auckland, Great Barrier Island, Buller, Nelson, Tasman, Taranaki about and south of the mountain, Taihape, and Whanganui.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Civil Defence declared a State of Emergency over the West Coast region in South Island late Aug. 16. SH 60 is closed between Haldane Road and Pupu Valley Road intersection and SH 63 is closed between Anglesea Street and Alma Street due to flooding. SH 6 is closed between Russell Street and Bisley Avenue intersection due to a landslide. Some Auckland Gulf Harbour ferry services are canceled Aug. 18 due to hazardous weather conditions. Reports indicate that some people in Takaka, Golden Bay have been forced to evacuate due to sewage pump stations overflowing. Authorities are strongly recommending residents in portions of Seddonville, Mokihinui, and Westport to voluntarily evacuate.
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.
