17 Mar 2023 | 09:15 AM UTC
New Zealand: Severe weather forecast over parts of North Island and northwestern South Island through at least early March 18 /update 2
Severe weather forecast over northern and western New Zealand through at least early March 18. Flooding and associated disruptions possible.
Event
Severe weather is forecast over parts of North Island and northwestern South Island through at least early March 18. A broad trough of low pressure containing several weather fronts is forecast to move over central New Zealand late March 17-early March 18. Ahead of the trough, moist air will generate heavy rainfall and thunderstorms across parts of the affected area. Rainfall accumulations of up to 9 cm (3.5 inches) are possible in places on top of rain that has fallen in recent days. Heavy downpours could trigger flooding in low-lying areas and landslides on unstable slopes, especially in areas where the ground is saturated from previous rainfall.
As of late March 17, the Meteorological Service of New Zealand (MetService) has issued the following watches and warnings:
Orange Heavy Rain Warnings (the middle level on a three-tier scale): Bay of Plenty east of Whakatane, Mount Taranaki, and the Tararua Range.
Yellow Severe Thunderstorm Watch: Auckland, Great Barrier Island, the Coromandel Peninsula, and Waikato.
Yellow Heavy Rain Watches: Bay of Plenty from Whakatane westwards including Rotorua, the central plateau of the North Island from Tongariro National Park to the Kaimanawa Range, and Buller.
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. 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.
