The North Island’s big wet summer shows no sign of abating, with more heavy rain warnings and watches for Coromandel, Bay of Plenty and Gisborne today - and showers for Auckland, Northland and Hawke’s Bay. And Fiji Met now says it expects a tropical low in the Pacific to form into a cyclone tomorrow - weather authorities are keeping a close watch on that and any potential impact on New Zealand over the coming week.
MetService has this morning issued an orange heavy rain warning for Gisborne from Tolaga Bay north until 4am tomorrow while heavy rain watches have been issued for Coromandel (until 4pm) and Bay of Plenty (until midnight). On the east coast, 70 to 100mm of rain is expected on top of what has already fallen, with possible localised downpours of 25-40mm an hour.
MetService meteorologist Ciaran Doolin said there was also a low risk of heavy rain for Auckland and Hawke’s Bay. Northland, Auckland, and the Coromandel Peninsula should expect a few showers in the morning, with the chance of thunderstorms and some heavy showers. This will be unwelcome news for the already battered Northland and Auckland regions, which experienced another deluge on Friday.
Mōrena! Today Auckland is likely to get light to heavy showers once again🌧️ It is always better to be prepared so make sure you:
🚨Review your evacuation plan ⚠️Know the warning signs so you can act quickly if needed 👂Stay informed
— Auckland Emergency Management (AEM) (@AucklandCDEM) February 26, 2023
A severe thunderstorm watch stretches from Northland to Manawatu and MetService says there is a high chance this could bring hail, localised downpours and flooding.
“These thunderstorms are expected to be slow-moving, and consequently there is a moderate risk that these storms could become severe, generating localised downpours of 25 to 40 mm per hour, or possibly more.”
The affected areas are Northland, Auckland, Waikato, the Kaimai Range, inland Waitomo, Taumarunui, southern Rotorua, Taupo, Taihape, northern Manawatu and inland Hawke’s Bay.
However, Niwa reported this morning that ensemble forecasting showed it’s likely the cyclone will move past New Zealand.
Niwa meteorologist Ben Noll told the Herald ensemble forecasting involves running multiple instances of a forecast model, or “members” repeatedly to see if a pattern emerges.
“There are inherent uncertainties in forecasting and over time those can compound. NIWA runs an ensemble system with 18 different members, you can understand if they’re vastly different or similar - for example, if we have 18 members in agreement, then the forecaster confidence can be higher but if they disagree we can understand how they diverge.”
Noll said at the moment, Niwa expects a tropical cyclone - the fourth of the season - to form over Vanuatu.
“As we go towards to the late stages of the week that cyclone will travel south of Vanuatu- what forecasts tell us is while its travelling south there’s an atmosphere of high pressur - an atmospheric stop sign – sliding in over the South Island and that may help keep it away.”
He said given the storm is still almost a week out, it will be monitored closely and while most members point to it missing New Zealand, there is a chance that could change.
“There may still be an ensemble monitor or two that tracks it a little closer.”
Doolin earlier said there was a low risk on Sunday of the tropical low forming a cyclone. That risk would pick up to “moderate” in the coming days, though.
Doolin also noted the existence of another low over the Coral Sea that was “poorly organised at the moment” and had a potential to intensify into a tropical cyclone.
But it was still too far off to make solid predictions on either weather system, or their movements.
“We’re talking quite long range now for a system that’s not even being called a tropical cyclone.
“The really long-range projections at the moment have this system kind of moving east of the country a bit, quite far east ... but we need to emphasise a lot of uncertainty. Over the next several days we will have a lot more certainty.”
Northland, Auckland flooding
More than 200 people were stranded on Friday at schools, camps, in their cars and strangers’ homes as torrential rain and plunging temperatures brought hailstones, slips and flooding in Mangawhai.
The Brynderwyns detour via Kaiwaka-Mangawhai Rd was closed due to massive slips and flooding, causing Northland to be left essentially isolated from the rest of the country.
Doolin said this week would be a “seesaw” across the nation, with rain in the north today and tomorrow, and sunshine in the south. The South Island was “continuing to see largely pretty nice weather” and that was going to continue for the early part of the week.
“However, they are going to see, in sort of the middle of next week, a front push across them, which means conditions are going to deteriorate.”
The West Coast was most likely to be affected, he said.
The weather will start to improve for the North Island at that time. Wellington would be neither the best off, nor the worst off, he said, and would experience a little bit of everything.
Meanwhile, fears are mounting in a rural community for residents who are still “uncontactable” 12 days after the deadly Cyclone Gabrielle as cleanup in Hawke’s Bay continues.
The surging flood floods, silt and muck brought by the cyclone devastated areas like Esk Valley, Puketapu, Dartmoor, and Pakowhai. There have been 11 deaths associated with Cyclone Gabrielle, mostly in Hawke’s Bay.
A police spokesperson said that as of 9pm last night, eight people remained uncontactable after the floods.
“The remaining number of people includes those who, for a variety of reasons, do not engage with authorities,” the spokesperson said.
Scores of highways and local roads around the North Island have access issues as workers clean away debris, slips and other hazards left behind by one of the worst weather events to hit New Zealand.