07 Jul 2022 | 07:20 AM UTC
New Zealand: Adverse weather forecast over northern and western New Zealand through at least July 9 /update 1
Severe weather forecast over northern and western New Zealand, through at least July 9. Disruptions possible.
Event
Severe weather is forecast across portions of northern and western New Zealand through at least July 9. A low pressure system is forecast to track across New Zealand July 7-8, bringing strong to gale strength north to northeasterly winds and heavy rainfall to western and northern parts of North and South Islands.
As of July 7, the MetService has issued the following weather warnings across the affected region:
Orange (middle level on a three-tier scale) Heavy Rain Warning: Bay of Plenty ranges east of Opotiki, ranges of Gisborne north of Ruatoria, Mount Taranaki, Tasman west of Motueka, and ranges of Westland south of Otira; up to 23 cm (9 inches) of rain is forecast to accumulate.
Orange Heavy Snow Warning: Canterbury High Country south of the Rangitata River; rain is likely to turn into snow at elevations above 400 meters (1,312 feet). 5-10 cm (2-4 inches) of snow is forecast at elevations of 700-400 meters (2,296-1,312 feet) while 10-15 cm (4-6 inches) of snow is likely at elevations of above 700 meters (2,296 feet).
Yellow Heavy Rain Watch: Bay of Plenty about and west of Opotiki, Buller, Coromandel Peninsula, Northland, Rotorua, Tongariro National Park, and Westland from Otira northwards.
Yellow Heavy Snow Watch: Queenstown Lakes District.
Yellow Strong Wind Watch: South Taranaki, inland Whanganui and Taihape.
Road Snowfall Warnings: Crown Range Road, Lindis Pass (SH8), and Porters Pass (SH73).
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Hazardous Conditions
The storms could produce rounds of heavy precipitation (including rain and snow), strong winds, and isolated thunderstorm activity in affected areas. Where precipitation falls as rain, flash and areal flooding is possible. Such flooding is possible in low-lying communities near watercourses and other large bodies of water, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites located downstream of large reservoirs may be subject to flash flooding after relatively short periods of intense rainfall.
Precipitation could fall as snow in the higher elevations over the coming days. Wind gusts could cause blowing and drifting snow; decreased visibility is likely in mountainous areas. Rain-induced landslides cannot be discounted in areas of elevated terrain; there is also the possibility of avalanches in mountainous areas where the snowpack has become unstable due to heavy snowfall. Power outages could occur throughout the affected area.
Transport
Floodwaters and related debris may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around the affected area. Flooding in urban areas could also result in significant traffic congestion. Heavy snow will likely make driving hazardous in some areas; authorities could implement temporary road closures or detours in such locations. Mountain passes and tunnels could be closed as a precautionary measure during periods of intense snowfall.
The disruptive weather may cause some delays and cancellations at airports in the worst affected areas. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding or snow could block regional rail lines; freight and passenger train delays and cancellations are possible in areas that see heavy rainfall and potential track blockages.
Disruptions triggered by inclement weather and resultant hazards, such as flooding, landslides, or avalanches, 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-related updates and advisories. Confirm all transport reservations and business arrangements before traveling in affected areas. Seek updated information on road conditions before driving or routing shipments through areas where severe weather is forecast; plan for possible supply chain disruptions throughout the affected areas. Stay away from elevated streams, creeks, and other watercourses that are prone to flash flooding. Do not attempt to navigate flooded roadways. Exercise caution in elevated terrain due to the threat of landslides, as well as mountainous regions where avalanches pose a threat. Charge battery-powered devices in the case of prolonged electricity outages.
