22 Aug 2022 | 05:01 AM UTC
New Zealand: Further adverse weather forecast over southwestern and northwestern South Island through at least Aug. 25
Further severe weather forecast across western South Island, New Zealand, through at least Aug. 25. Flooding, evacuations possible.
Event
Adverse weather is forecast across parts of southwestern and northwestern South Island through at least Aug. 25. A weak low-pressure system is forecast to track eastwards across central New Zealand Aug. 22, bringing heavy rainfall to western Tasman. A front is likely to approach Fiordland from the southwest Aug. 23 and track northeastwards across southern New Zealand Aug. 24 before drifting southwards early Aug. 25 and weakening.
As of the evening of Aug. 22, the New Zealand National Meteorological Service (MetService) has issued the following weather warnings:
Orange Heavy Rain Warning (middle level on a three-tier scale): Fiordland; 10-12 cm (4-5 inches) of rainfall is forecast.
Yellow Heavy Rain Watch: Tasman west of Motueka and Westland south of Otira.
Yellow Strong Wind Watch: Fiordland, Central Otago, Queenstown Lakes, and Southland.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
As of the evening of Aug. 22, authorities are maintaining the local states of emergency across Marlborough, West Coast, and Nelson Tasman regions due to heavy rainfall since Aug. 17, resulting in flooding. Nelson City was the worst hit, with 1,200 people from 411 households displaced. At least nine homes in the area are inhabitable, and 11 other homes seriously unstable; assessments of other homes are still in progress. State Highway 6 is closed between Hira and Renwick in Marlborough and between the Haven Road and Tahunanui Drive/Bisley Avenue intersection in Nelson due to flooding, damage, and the risk of landslides while State Highway 6 from Atawhai to Hira has single-lane access only for residents due to a landslide and multiple road works; a temporary 30 kph (19 mph) speed restriction is in place. State Highway 63 is closed from Renwick to Saint Arnaud due to flood damage and washouts. Additional rainfall is likely to exacerbate the situation and hamper recovery and relief efforts.
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.
