19 Aug 2022 | 11:08 AM UTC
New Zealand: Further adverse weather forecast over western and northern South Island and western and northwestern North Island through at least Aug. 20 /update 4
Further severe weather forecast across parts of South and North Island, New Zealand, through Aug. 20. Evacuations and road closures ongoing.
Event
Further adverse weather is forecast across parts of western and northern South Island and western and northwestern North Island through at least Aug. 20. Heavy rainfall and strong winds have impacted much of the affected regions since Aug. 17 and have caused flooding and landslides in multiple areas, leading to evacuations and road closures. Further heavy rainfall is forecast over affected regions late Aug.19-Aug. 20 , with rainfall totals of 14-19 cm (5.5-7.5 inches) expected across mountainous areas and 7-11 cm (2.8-4.3 inches) across the rest of the affected area. The additional downpours are likely to trigger additional flooding and landslides in areas where the ground is already saturated from previous rainfall and river levels are already dangerously high, as well as hamper ongoing response and recovery operations.
As of late Aug. 19, 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): nelson District and the Bryant Ranges.
Orange Heavy Rain Warning: Buller; the Marlborough Sounds, Rai Valley, and the Richmond Range; Mount Taranaki; Northland; the Tasman District west of Motueka, and Westland.
Yellow Heavy Rain Watch: Marlborough northwest of the Inland Kaikoura Range and south of the Richmond Range, and the Tasman District from Motueka eastwards, excluding Nelson District.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Heavy rainfall has been impacting western and northwestern South Island since Aug. 17, before moving over parts of southern, western, and northwestern North Island Aug. 18-19. The intense downpours have caused several rivers across the affected area to burst their banks and triggered widespread flooding and multiple landslides in many areas. 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 and local state of emergencies have also been declared in Nelson Aug. 17 and Malborough Aug. 19 amid the ongoing severe weather. Flooding and landslides have led to authorities evacuating over 400 people in Nelson since Aug. 17. In parts of Buller District around 160 residents of Westport, Seddonville, and Mokihinui were asked to self-evacuate by authorities Aug. 17; however, many have now returned home. Dozens of landslides have been reported in the Wellington area Aug. 18-19, leading to property damage and road closures. Several people have voluntarily evacuated in Taranaki Region amid intense downpours in the region. Around 350 homes in the Far North District of Northland were without power as of late Aug. 19 and the town of Kaitaia has been largely cut off due to inaccessible roads. Dozens of other roads across the affected area have been closed due to flooding and landslides caused by the adverse weather conditions, including several sections of state highways. The latest information on closures and restrictions on state highways across the country can be found here.
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 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.
