03 Aug 2022 | 01:36 AM UTC
New Zealand: Heavy rainfall and strong winds forecast across South Island through at least Aug. 6 /update 1
Heavy rainfall, strong winds forecast across South Island, New Zealand through Aug. 6. Flash flooding, disruptions possible.
Event
Heavy rainfall and strong winds are forecast across most of South Island through at least Aug. 6. Heavy rain and strong winds are forecast to develop over the far south of New Zealand late Aug. 4 before spreading north over the rest of South Island Aug. 5
As of the afternoon of Aug. 3, the New Zealand National Meteorological Service (MetService) has issued the following warnings:
Orange Heavy Rain Warning (middle level on a three-tier scale): Fiordland; 18-22 cm (7-9 inches) of rain is likely to accumulate, with the heaviest rainfall likely the afternoon and evening of Aug. 5.
Yellow Heavy Rain Watch: headwaters of the Canterbury lakes and rivers south of Arthurs Pass, headwaters of the Otago lakes and rivers, and Westland south of Otira.
Yellow Strong Wind Watch: Banks Peninsula, Canterbury High Country, Canterbury Plains, Otago, and Southland.
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) 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.
