17 Aug 2022 | 10:13 AM UTC
New Zealand: Adverse weather forecast for western and northwestern South Island and most of North Island through at least Aug. 19 /update 3
Severe weather forecast across parts of South and North Island, New Zealand, through Aug. 19. Evacuations and road closures ongoing.
Event
Heavy rainfall and strong winds are forecast across western and 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 ongoing in some areas and likely to occur across much of the affected area, especially in areas with already saturated soils from recent rain. Rainfall totals of 10-25 cm (4-10 inches) are expected across the affected areas, on top of heavy accumulations that have already fallen in some areas.
As of late 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, Nelson Region, and Westland.
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, 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 regional state of emergency over the West Coast region in South Island late Aug. 16 in anticipation of the adverse weather. In parts of Buller District around 160 residents of Westport, Seddonville, and Mokihinui have been asked to self-evacuate by authorities Aug. 17 due to the possibility of flooding in the early hours of Aug. 18. A local state of emergency has also been declared in Nelson Aug. 17 after the Matai River burst its banks. Around 223 homes threatened by the river have been evacuated by authorities from the Nile Street Bridge to the Golf Course in Nelson East. Power outages were reported in parts of Nelson; however, authorities have largely restored services as of late Aug. 17. In Tasman District, reports indicate that some people in Takaka, Golden Bay have been forced to evacuate due to sewage pump stations overflowing. Boil water notices have been issued for people on Eight-eight Valley and Dovedale roads.
Several roads in the affected parts of Nelson, Tasman, and West Coast districts are closed due to flooding and landslides. State Highway (SH) 6 is closed at Hira to Havelock and Russell Street to Bisley Avenue; SH 60 between Haldane Road and Pupu Valley Road; and SH 63 between Anglesea Street and Alma Street. Some Auckland Gulf Harbour ferry services are canceled Aug. 18 due to forecast hazardous weather conditions.
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 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.
