05 Aug 2022 | 11:48 AM UTC
New Zealand: Heavy rainfall and strong winds forecast across much of South Island and southern and western parts of North Island through at least Aug. 7 /update 2
Severe weather forecast across South Island and parts of North Island, New Zealand, through Aug. 7. Flooding and disruptions possible.
Event
Heavy rainfall and strong winds are forecast across most of South Island and southern and western parts of North Island through at least Aug. 7. An active weather front is forecast to move northwards over South Island Aug. 6 and reach southern parts of North Island early Aug. 7. The system is forecast to bring heavy rainfall to western parts of South Island and strong winds to southern and eastern parts.
As of late Aug. 5, the New Zealand National Meteorological Service (MetService) has issued the following warnings:
Orange Heavy Rain Warning (the middle level on a three-tier scale): Westland north of Otira and Buller; Westland about and south of Otira; the headwaters of the Canterbury lakes and rivers about and south of Arthur's Pass; the headwaters of the Otago lakes and rivers; and Fiordland.
Orange Strong Wind Warning: The Canterbury Plains, Christchurch and the Banks Peninsula; Fiordland, Southland, Stewart Island, and Otago; and Canterbury High Country.
Yellow Heavy Rain Watch: Taranaki; Tasman District west of Motueka; Tararua Range; and Richmond and Bryant ranges.
Yellow Strong Wind Watch: The ranges of Marlborough; and Wellington and Wairarapa south of Carterton.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days. The heavy rain is likely to lead to rapid water level rises in rivers and streams. Surface flooding, landslides, and hazardous driving conditions are possible.
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 airports in the region, including but not limited to Christchurch International Airport (CHC), Wellington International Airport (WLG), and Queenstown International Airport (ZQN). 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.
