17 May 2023 | 08:49 AM UTC
New Zealand: Adverse weather forecast over northern parts of North Island and southern and western South Island through at least May 19 /update 1
Severe weather forecast over parts of North Island and South Island, New Zealand, through May 19. Flooding and disruptions possible.
Event
Severe weather is forecast over northern parts of North Island and southern and western South Island through at least May 19. A weather front will continue to move over southern parts of South Island May 17-18, bringing further heavy downpours to the region and possible snowfall to elevated parts of Otago. Another weather front is forecast to pass over northern parts of North Island May 18-19, bringing heavy downpours and strong winds. Flooding is possible in low-lying areas following periods of intense rainfall, as well as landslides on unstable slopes. Strong winds could cause property damage and power outages.
As of late May 17, the Meteorological Service of New Zealand (MetService) has issued the following watches and warnings across the affected area:
Orange Heavy Rain Warning (the middle level on a three-tier scale): Fiordland about and north of Doubtful Sound; and Westland south of Harihari.
Yellow Heavy Rain Watch: Southland; Westland about and north of Harihari including the Grey District; Dunedin and Clutha; Northland; Auckland including Great Barrier Island; the Coromandel Peninsula; and Bay of Plenty.
Yellow Heavy Snow Watch: Central Otago and Queenstown Lakes District.
Yellow Strong Wind Watch: Northland; Auckland including Great Barrier Island; the Coromandel Peninsula; and Bay of Plenty and Rotorua.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
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. Additional power outages are possible in areas impacted by the weather system.
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 additional delays and cancellations at regional airports. Flooding could block regional rail lines; freight cancellations are possible in areas subject to heavy rainfall and track blockages.
Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after weather 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 or reported. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.
