National Institute of Water and Atmospheric Research (Niwa) has officially confirmed the arrival of La Nina conditions, which means we are in for another record-breaking hot, dry summer in Otago and Southland.
The agency also confirmed New Zealand’s coastal waters were already unusually warm, and has warned another marine heatwave may develop between November 2020 and January 2021.
La Nina is an ocean-driven phenomenon that traditionally brings moisture to the North, dryness to the South, and warmer-than-average temperatures to most places.
For Southland and inland Otago, temperatures are "very likely" to be above average; rainfall totals are about equally likely to be near normal or below normal; and soil moisture levels and river flows are most likely to be near normal.
Coast Otago temperatures are also "very likely" to be above average; rainfall totals are about equally likely to be below normal or near normal; and soil moisture levels and river flows are "very likely" to be below normal.
Meteorologist and forecaster Ben Noll believed this La Nina could prove to be the strongest in nearly a decade.
"This La Nina overall, is tracking on the borderline of moderate to strong.
"The strongest one we had in the last decade occurred in late 2010, early 2011.
"So there is some indication that this event could be near that event in terms of intensity.
"It’s looking to be a stronger one than the one we experienced in 2017-18."
He said the 2017-18 La Nina brought New Zealand’s hottest summer on record, and given its similarities to the present La Nina system, it was likely temperature records would tumble again this summer.
He said the news may not be welcomed by North Otago and South Canterbury farmers because the area was already very dry.
"That is probably going to persist, so we’re keeping a very close eye on that area," Mr Noll said.
"Meteorological drought conditions are not in place yet, but if the dryness were to persist, that could be something that we’re talking about in, say, a month’s time."
He said the marine and fisheries sectors should also keep an eye on the evolving situation, because the rising sea surface temperatures (SSTs) could damage sea life.
The La Nina of 2017-18 coincided with the strongest marine heatwave ever observed around New Zealand.
It pushed SSTs to 1.5degC above average — and as high as 6degC above normal in some spots off the West Coast — and mussel beds, seaweeds and phytoplankton around Southland and Otago suffered cascading losses.
Mr Noll said our waters were already running warmer now than at this point in 2017.
"If current ocean and atmosphere trends continue, marine heatwave conditions will be possible in November and/or December."
— Additional reporting The New Zealand Herald
