What the potential end of La Niña weather pattern means for Marlborough

A weather pattern that has been influencing wet and cloudy weather in Marlborough this summer, could be over by the second half of 2023, meaning potentially drier conditions by the end of the year.

Niwa meteorologist Ben Noll said La Niña, one of the phases of the El Niño Southern Oscillation global climate cycle, or ENSO, had persisted for the last three years, which was “pretty unusual”.

“What we call a triple-dip La Niña. . . It plays a very important role in our climate, and there’s an indication that by maybe the middle part of the year, if not sooner, perhaps during autumn, that we’ll be exiting La Niña, and we will be going to what we call ENSO neutral,” Noll said.

“It may be the case that the weather patterns that we’ve seen over the last several months, such as the heavy rain that has frequented the top of the south, including in Marlborough, there’s a chance that we could see a reprieve from those conditions maybe as we go a little bit later into the year.

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“But for the time being, La Niña is still with us, so there’s going to be an opportunity probably for some more heavy rain before we’re through with La Niña I think in the coming probably weeks and months.”

Noll said the weather pattern had been an influence on severe weather events affecting Marlborough in the last couple of years, as La Niña changed pressure patterns around the globe, including in the Southwest Pacific.

“The change in pressure patterns leads to more winds that are coming from the east and northeast, and those winds can kind of blow on shore into the Sounds, into Blenheim, into east-coastal Marlborough, and bring some pretty kind of cloudier, rainier, more humid weather, and also kind of limit the number of hot days as well,” he said.

Blenheim recorded its lowest sunshine hours in nearly a decade in 2022, and Noll said the town had only recorded eight days above 25C between the start of November last year and January 25, compared to 27 days above 25 the summer before.

“So it’s definitely made its presence, La Niña has, in Marlborough.”

He said weather in Marlborough for the rest of 2023 would depend on whether El Niño, the opposite phase of ENSO to La Niña, developed during the second part of the year.

“Right now we’re kind of in a wait and see mode, it doesn’t look like we’re going to have La Niña last through the whole year”.

El Niño tended to be associated with more westerly winds for New Zealand, which “dried out” by the time they crossed the Tasman Sea and reached the east coast of the South Island, Noll said.

“Historical drought events in New Zealand have been disproportionately associated with those El Niño events. It doesn’t mean that they can’t happen in neutral or La Niña, but we know that there’s a higher chance for those dry and drought episodes during El Niño.”