Emergency mobile alert sent out as Aucklanders warned of possible localized downpours

Aucklanders have been issued an emergency mobile alert (EMA) on possible localized downpours in Auckland overnight.

This is the first EMA since heavy rain battered Auckland on Friday, and caused significant flooding, claiming four lives.

Auckland Emergency Management issued the alert at 7.47pm on Sunday, to provide important safety messages ahead of the potential for extremely heavy rain to hit the Auckland region.

MetService has issued an orange heavy rain warning due to an active line of thunderstorms currently sitting over the Hauraki Gulf.

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Between now and 7am Monday, this line of thunderstorms could produce localized downpours of 50-90mm of rainfall.

The possibility of localized extreme downpours up to 150mm cannot be ruled out, with the larger totals likely north of the Auckland Harbor Bridge.

“Given recent rainfall, the ground is extremely saturated which changes how rainfall can affect the environment,” Auckland Emergency Management Controller Mace Ward said.

“The decision to issue this alert was made so people in the region can make the best decisions of how to remain safe, should this heavy rain eventuate.”

People in the area between Ōrewa/Waiwera and down to Papakura/Drury, from coast to coast including Aotea Great Barrier Island are advised to make sure they stay informed and watch the forecast.

Any further updates would be posted to the Auckland Emergency Management social media channels.

Meanwhile, emergency response teams are urging the top of the North Island to get ready for more extreme weather, with a second “atmospheric river” possible.

MetService earlier issued an orange heavy rain warning and thunderstorm watch for Northland, as the heavy rain or “atmospheric river” moves northwards.

Although rain has eased in some areas, MetService meteorologist Angus Hines said we are not out of the woods yet.

“Large rainfall figures are still expected, and this is in addition to the immense rain that has already fallen,” Hines said.

While this rain will spread across many areas, there are places of particular concern.

“Northland is going to get waves of impactful rain in the coming days, especially overnight tonight (Sunday), and again from Tuesday.

“An Orange Rain Warning is in place for that area for the first of these waves, and more weather warnings are likely to be issued in the coming days,” said Hines.

These further bouts of upcoming rain could put stress on already saturated soils, causing more flooding and road closures, he said.

Northland Civil Defense Controller Graeme MacDonald said Northland should take the warning seriously and be prepared. Slips, road closures, and surface flooding were all possible.

In a briefing, Niwa forecaster Ben Noll said it was likely another atmospheric river would hit the upper North Island next week.

Victoria University professor of physical geography James Renwick said an atmospheric river was what meteorologists called river-like torrential rain.

The atmospheric river that had fallen over Auckland had been caused by a slow moving storm in the north Tasman Sea.

In the meantime, meteorologist Georgina Griffiths told Aucklanders to “hang in there”, with a reprieve from the extreme weather likely for Monday.

“Use Monday to clean up and get yourselves sorted out.

There had been light rainfall in parts of Auckland on Sunday, but if the rain was to increase to 10mm or 15mm an hour there may be some brief, localized, ankle-deep type flooding.

Their main concern for the remainder of Sunday was the Northland region, she said.

“We are under heavy rain watch until 6am [Monday].”

A reprieve was coming for Monday, but a system of gales and rain would then come through from the north again, affecting Northland significantly and Auckland later Tuesday or Wednesday, she said.

Isolated thunderstorms were forecast for the rest of the North Island on Sunday afternoon, separate from the line of rain stretching across the upper-North Island.

Wellington and Wanganui had both been added to MetService’s severe thunderstorm watch too.

The watch lasts until 9pm on Sunday and also includes the Manawatu, Tararua, Kapiti-Horowhenua and Wairarapa.

“There is a possibility that some of the thunderstorms could become severe until about 9pm, producing localized downpours of 25 to 40mm per hour,” MetService said.

There was a possibility of hail larger than 20mm in diameter.

“Large hail can cause significant damage to crops, orchards, vines, glasshouses and vehicles, as well as make driving conditions hazardous,” MetService said.

Heavy rainfall could also spark surface or flash flooding, especially in low-lying areas such as streams, rivers, or narrow valleys.

“Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain,” MetService said.

The rain over Coromandel had not relented since starting on Thursday – feeding into the area’s rivers and catchments – until an orange warning was lifted about 6pm on Sunday.

The Bay of Plenty had also been hit hard over the last 36 hours, with one location seeing more than 302mm of rain.

In the Waitomo region, extensive flooding resulted in a state of emergency being declared on Saturday evening.

Although rain had eased in some areas, MetService meteorologist Angus Hines said humid, rain-laden air from the tropics showed “no sign of letting up any time soon”.

“Large rainfall figures are still expected, and this is in addition to the immense rain which has already fallen.”

These further bouts of upcoming rain could put stress on already saturated soils, causing more flooding and road closures, he said.

However, the worst should clear by noon on Thursday, although some rain may linger for the weekend, he said.

“For those down South, who have so far avoided most of the rain, there will be wet weather through much of the week, especially west of the Southern Alps.”

The risk of downpours was heavier around the Tararua district, Wairarapa, and the Ruahine range, with a risk of 25 to 40mm of rain for those areas.

Auckland was hit by torrential rain, with 245mm recorded at Auckland Airport in the 24 hours from 9am Friday, surpassing the previous record of 161mm by about 50%.

Some weather stations reported more than 80mm of rain in an hour.

MetService’s highest classification for intense rain is “torrential” – defined as 40mm of rain or more in an hour.

“That was truly record-breaking rain – the likes of which we very rarely see in New Zealand and it just happened to be right over Auckland,” Corrigan said.

People in areas facing rain warnings were advised to keep on top of forecasts and up to date with emergency investigations.