Aussie heatwave cause of Auckland thunderstorm

Lightning strike from the thunderstorm in Auckland. Taken from Massey looking towards the city. Photo / Logan Pratt

The spectacular thunder and lightning storm that roared over Auckland on Saturday night can be blamed on Australia's soaring temperatures.

The thunderstorm, which raged from 11.55pm to 12.20am, and at various times throughout the early hours of Sunday morning boomed overhead, waking Aucklanders out of their sleep and providing a bright lightning show as bursts of white streaked across the sky.

It followed a day of rainfall, soaking Fleetwood Mac fans at the band's outdoor gig at a packed Mt Smart stadium.

Around 10,000 lightning strikes were recorded during the storm - 1300 of them over the Auckland region land mass, which was "a bit unusual for this time of year", MetService meteorologist Georgina Griffiths said.

"Usually the land's too cold. And these thunderstorms weren't actually triggering at the bottom, near the land, they actually started up in the atmosphere where there was nice, warm juicy air from Australia actually, from the heatwave," she said.

"So they [thunderstorms] are kind of like mushrooms, they need the moisture and the warmth."

Australia sweltered in a heatwave last week, with temperatures in Sydney soaring to 41C.

The hot air from Australia hit a cold front coming up New Zealand, and created the thunderstorms.

It comes as new graphics from MetService show the scale of the thunder and lightning storm.

The image shows bands of lightning recorded across the Auckland region from 12am to 2am on Sunday - with the blue rainfall markers almost obscured by the sheer amount of lightning markers.

The lightning is represented by X, and are colour-coded for the time they occurred - those between 1.30am and 2am are in red; strikes between 1am and 1.30am are in orange; between 12.30am and 1am are in purple; and those between 12am and 12.30am are in blue.

The red and purple X's appear to be the most prevalent.

Despite the scale of the storm, it was not classified as an extreme event, and was not unusual for the City of Sails, Ms Griffiths said.

Auckland gets such storms about two to three times a year, she said, "more than people think".

"But the reason I think it was quite noticeable was because there were these three lines - normally there will be one line going across Auckland quite quickly - [on Saturday] there were three lines that were quite slow moving," she explained.

"It took from about 11pm to about 5am for these three lines to shuffle past, and I think that's probably the slow moving nature of it, the long-winded nature."

The three lines of thunderstorms were "training", she said - the term meteorologists use for when thunderstorms follow "the same flight path as the one before them".

It would have made the storm seem bigger than it was, as the three bands of thunder and lightning moved slowly over the same areas.

Saturday night's storms created "beautiful lightning" and loud thunder, she said, but "no, they didn't qualify as severe".

"Severe storms need large hail, or tornadoes, or wind in excess of 110km/h and rain rates of 25mm an hour or more.

"None of those things were met. Rain rates peaked at about 12mm an hour, in fact it wasn't that wet an event, so there was nothing exceptional from a severe thunderstorm point of view. But obviously a beautiful lightning storm for Auckland."

What was notable was the slow moving nature of the storm, and the time of year it occurred, she said. It had also been a while since Auckland had experienced a thunderstorm.