A huge water spout has been sighted off Castor Bay on Auckland's North Shore. Video / Conrad Gair
Humidity, warm temperatures, thunder, heavy rain and even a waterspout - a mixed bag of weather swept across the country in recent days with more “liveliness from Mother Nature” on the way.
But what’s driving the weather? And what is a waterspout?
Yesterday afternoon, an Auckland resident captured footage of a waterspout about 500m off the coast of Castor Bay on the North Shore. The resident said it was tracking down the middle of the harbour.
Niwa’s principal scientist, forecasting and media, Chris Brandolino, said a waterspout was a funnel of air that touches the water rather than one that touches the ground, which would be a tornado.
“You get a thunderstorm and the air is rotating within the thunderstorm - that’s a very simple way to explain it - but that’s what gives you the spinning finger of air or a funnel and if that funnel touches the ground, it’s a tornado, if it touches the water it’s a waterspout.”
MetService meteorologist John Law said a waterspout involved not water but moisture being sucked up into the sky that is condensing as it rises, similar to how clouds form.
“When we look at the waterspout we can see [a] spinning cloud-filled funnel-shaped column. Around the base of the funnel, you can sometimes see spray being generated by the strong winds.”
A waterspout formed off the coast of Auckland's Castor Bay on Sunday afternoon. Photo / Sarah Robbins
Waterspouts were typically short-lived, tending to be over in less than 30 minutes, while impacting only a small area.
The waterspout was linked to the recent warm, humid conditions, he said.
“That extra humidity is one of the factors that helps the waterspouts form. We’ve seen air arriving from the north and west, from up in the subtropics. That has been the main reason for the muggy-feeling weather we’ve had.”
The warm air with extra moisture had also helped spark off the large number of thunderstorms recorded over the weekend. New Zealand was not “out of the woods just yet” with an unsettled start to the week. More thunderstorms were possible this afternoon and on Tuesday.
Brandolino said a 36-48 hour period of “liveliness and activity” from Mother Nature was expected from Tuesday to early Thursday.
“There will be some rocking and rolling, weatherwise,” he said.
Our weather was being influenced significantly by La Niña - a phase of the naturally occurring global climate cycle known as the El Niño Southern Oscillation.
“We tend to get more north-easterly / easterly winds. What it also does is … give higher than normal air pressure to the east and southeast of the country, and lower than normal air pressure to the west of the country.”
To describe the weather event affecting New Zealand right now, he said to picture two cogs spinning in opposite directions.
“Low pressure is a cog that spins clockwise. High pressure [is] another cog, that spins anti-clockwise. Those two cogs working in tandem … helps to induce that warm airflow from the subtropics and tropics.”
Brandolino said it has been an unusually warm first three weeks of November across the whole country. However, by Thursday or Friday, it will be noticeably cooler and less humid.
“Last I checked, there was close to 60 locations that were on track to have the warmest or near-warmest November.”
Ocean temperatures around New Zealand were also running very warm for this time of the year, with marine heatwave conditions across much of the coastal water around the country, he said.
“When we have warmer than average ocean temperatures, that does have an upward influence on our air temperatures. Because we are an island nation, we are kind of linked at the hip with our air temperatures.”
The most severe weather warning MetService had issued as of Monday afternoon was for the Bay of Plenty, east of Opotiki, and the ranges of Gisborne, north of Ruatoria.
The “orange” heavy rain warning is in place from Tuesday afternoon to early Wednesday morning. During this time, between 90-140mm of rain and thunderstorms are expected with possible peak rates of up to 35mm per hour.
Meanwhile, heavy rain is predicted for Northland, especially the north and east, all day tomorrow.
Strong winds are expected to set in along the upper east side of the central North Island, including across Auckland and down to the Bay of Plenty and Gisborne, from tomorrow evening.
Further south, strong northwest winds are forecast for the Canterbury High Country and heavy rain for the Westland ranges south of Otira, from tomorrow morning.
