20 Jul 2022 | 03:17 PM UTC
New Zealand: Adverse weather forecast for parts of northeastern South Island and eastern North Island through at least July 21
Severe weather forecast across northeastern South Island and eastern North Island, New Zealand, through July 21. Possible disruptions.
Event
A deep low developing off the eastern coast of central New Zealand late July 20 is forecast to bring heavy rainfall, snowfall over higher ground, and strong winds across northeastern parts of South Island and eastern parts of North Island through at least July 21. Winds gusting up to 130 kph (81 mph) and rainfall totals of 7-9 cm (2.8-3,5 inches) are possible in parts of the affected region July 21. Due to the anticipated high winds and rough seas, some ferry services between North and South Islands have been suspended July 21.
As of late July 20, the New Zealand National Meteorological Service (MetService) has issued the following weather warnings:
Orange Heavy Rain Warning (the middle level on a three-tier scale): Wairarapa south of Featherston; and the Kaikoura coast and ranges.
Orange Strong Wind Watch: Wellington and Wairarapa; and the Kaikoura Coast.
Yellow Heavy Rain Watch: Wellington; and the Banks Peninsula and Canterbury north Waipara.
Yellow Heavy Snow Watch: The Canterbury High Country north of the Rangitata River, and inland parts of the far south of Marlborough, including the Kaikoura Ranges.
Yellow Strong Wind Watch: Horowhenua, Kapiti, the Tararua District, Hawke's Bay, and Gisborne; and Canterbury north of Ashburton, and Marlborough, excluding the Kaikoura Coast.
Road snowfall and heavy swell warnings have also been issued for some mountain passes and coastal areas in the affected regions. Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Heavy rainfall across parts of South Island recently has led to disruptions to transport links and evacuations. Around 250 people remain stranded in the Lake Ohau area after flooding washed away a bridge on the only access road to the area. Around 60 people were evacuated from a holiday park in Omarama late July 18 due to the threat of flooding. At least six major roads and many smaller ones across South Island were closed overnight July 19-20 due to flood damage and landslides; however, authorities have been working to restore the road network throughout July 20.
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 delays and cancellations at regional airports, including but not limited to Christchurch International Airport (CHC) and Wellington International Airport (WLG). 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.
