MetService had ten severe weather alerts in force for New Zealand on Saturday morning, with severe gales gusting to 120 kilometres an hour forecast on Sunday for a band of the country running from Stewart Island to the Tararua District, and heavy rain already building over the West Coast ranges.
A check of the MetService public alert feed at 8.21am on Saturday showed six wind alerts and four rain alerts active. Five of the wind alerts are orange warnings, which is the level the forecaster uses when weather is expected to meet its severe weather criteria and people need to prepare and act.
Almost all of the wind falls on Sunday. The orange strong wind warning for Wellington and the Marlborough Sounds runs from 1am to 10am. Canterbury High Country is covered from 1am to 1pm, the Wairarapa from 2am to noon, and the Tararua District has the longest window of any region at 16 hours, from 4am through to 8pm. Southland south of Gore, including Stewart Island, is warned from 6am to 4pm.
Every one of those five warnings carries the same forecast number, severe gales gusting 120 kilometres an hour in exposed places. That is well above the threshold MetService uses to classify wind as severe weather in the first place, which is gusts of 110 kilometres an hour or 60 knots. The agency’s standard impact wording for all five is that damage to trees, powerlines and unsecured structures is possible, and that driving may be difficult, especially for high sided vehicles and motorcycles.
Dunedin and Clutha sit under a strong wind watch rather than a warning, from 8am to 6pm on Sunday, with west to southwest winds that may approach severe gale in exposed places. That watch is the one most likely to be escalated. MetService rates the chance of it being upgraded to a warning as high, while the five orange warnings are all rated as having a low or minimal chance of going red.
MetService meteorologist Alwyn Bakker told RNZ the practical advice was straightforward. “Tie your trampolines down, that kind of stuff, and there’s a risk of damage to trees and power lines and driving might be difficult, especially for campervans,” he said.
The rain arrives first. An orange heavy rain warning for the ranges of the Buller and Grey districts starts at 3pm on Saturday and runs until 9am on Sunday, with 90 to 120 millimetres forecast and peak rates of 15 to 25 millimetres an hour expected on Saturday night and Sunday morning. MetService says thunderstorms are possible on Sunday morning on top of that. Anything at 25 millimetres an hour is itself enough to meet the severe weather criteria for heavy rain.
Three heavy rain watches sit around that warning. The ranges of the Westland District and the headwaters of the Canterbury lakes and rivers are both covered from 9am Saturday to 9am Sunday, and Nelson Lakes from 6pm Saturday to 8am Sunday. All three are rated as having a moderate chance of being upgraded to warnings, so the rain picture across the top and west of the South Island could still get worse rather than better.
Bakker warned that the run-off would be quick. “Streams and rivers might rise rapidly, there might be surface flooding, there might be slips,” he told RNZ, and suggested people check their drains and gutters before the heavy falls arrive.
The set-up behind all of this is a series of fronts pushing onto the South Island from the southwest, dragging warm northwesterly air ahead of them and then swinging the flow around to a colder southwest on Sunday. That is why the same weekend can deliver 120 kilometre an hour nor’westers to the Canterbury High Country and snow on the higher South Island roads within about a day of each other.
MetService head of weather news Heather Keats told 1News the weekend was “a bit of a taster of what spring is like”, and that “spring is a notoriously tricky season and full of all sorts of fun fronts and strong winds”. Winter officially has one more week to run.
The upper North Island escapes the alerts entirely. Napier is forecast to reach 20 degrees, and Christchurch, Ashburton and Dunedin around 17 to 18 degrees, which is the sort of split that catches people out. Warm, still weather in Auckland on Saturday tells you nothing about what a Wellington commuter or a Southland farmer is dealing with at dawn on Sunday.
The distinction between the three alert levels matters if you are deciding whether to travel. A watch means severe weather is possible but not certain, and MetService asks people to stay alert and keep checking forecasts. An orange warning means the bad weather is expected and there may be disruption and risk to people, animals and property. A red warning, which is not in play this weekend, is reserved for the most extreme events where immediate action is required. You can read the full MetService definitions here.
Practically, the exposure is worst for anything tall and light. Trampolines, garden umbrellas, wheelie bins, scaffolding and construction site fencing are the usual casualties of a 120 kilometre an hour gust, and powerline damage means the possibility of outages in the warned areas on Sunday morning. Anyone towing a caravan or driving a campervan over the Remutaka Hill Road, through the Manawatū corridor or across the Canterbury high country on Sunday morning would be sensible to check conditions before setting out rather than after.
Warnings are updated several times a day and the timings above are the ones issued on Friday evening. If you are travelling on Sunday, check the current position with MetService before you leave.
Are you in one of the warned areas this weekend? Tell us in the comments below what the weather is actually doing where you are.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂
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