The outlook for the coming months of weather was just published. Here’s what it means for the different parts of the country.
El Niño is back, was the official ruling today from New Zealand’s experts. That much was expected. More remarkable is what it portends. As this El Niño pattern evolves, suggests the new seasonal climate outlook from Earth Sciences NZ, it is “expected to intensify into one of the strongest on record” as we move into spring.
Sea surface temperature readings in the east-central tropical Pacific, where El Niño originates, are already 1°C above average. If it hits 1.5°C that makes it a “strong” El Niño.
“We’re well on track for that to happen during the next three months, and that’s not even the end of it,” said Earth Sciences NZ meteorologist Jon Tunster, speaking to the Spinoff on the new podcast At Large with Toby Manhire. “Beyond that, we’re expecting even further increases.”
That would send it past the 2°C mark and into the “very strong” category, informally known as a “super El Niño”.
In assessing the likely impacts, scientists have studied the five strongest El Niño events on record, as experienced in 1972, 1982, 1991, 1997 and 2015. All measured a sea surface reading “near or slightly above 2.5°C”.
“We can group them together into a nice, somewhat coherent family of five, look at patterns that exist across those five … There’s a family resemblance among siblings, but each of them still has their own individual quirks and personalities.”
Historic data suggests El Niño heralds drier and windier than usual weather in northern and eastern parts of the country as winter moves into spring, with increased rainfall in western regions, especially the South Island. (The more detailed regional breakdown of probable impacts is included at the foot of this post.)
Despite the broader outlook, Earth Sciences is warning of a “significant rain event” in the coming week, expected to hit the east of the North and South Islands. That is “not really a characteristic El Niño type event – it’s a low pressure system expected to bring decent rainfall to eastern areas, which is actually the opposite to what is sort of the overriding pattern of El Niño,” said Tunster.
“Exactly where the rain will fall is going to be subject to exactly how the low configures itself, but it is starting to line up to look as though it’s going to give at least respectable rain to places like Canterbury, possibly Marlborough.”
El Niño’s regional impacts
Drier than usual conditions are expected for the top of the North Island – from Taranaki through to Bay of Plenty and up to Auckland and Northland. Reduced rainfall is also likely in the east of the North Island from Gisborne down and through the east of the South Island.
For Westland through to Southland, wetter conditions are on the cards.
Periods of high temperature are in the offing for Canterbury, Marlborough, Wairarapa, Hawke’s Bay and Gisborne, with warnings of increased wildfire risk for Canterbury, Marlborough, Wairarapa, Hawke’s Bay, Gisborne, Bay of Plenty and Northland.
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