1News weather expert Daniel Corbett on the outlook for the coming Pacific cyclone season.
The start of the Southwest Pacific Tropical Cyclone season is nearly upon us, and this year could be interesting for several reasons.
We have a super charged El Nino that is yet to peak and continuing very warms seas around New Zealand.
The Tropical Cyclone season typically runs from November 1 to April 30 but tropical cyclones can occur outside of the seasonal dates too. An average to slight above average season is what the official forecast says.
Seven to eleven potential tropical cyclones across the Southwest Pacific Basin are expected, with four being in the severe category (Category three or above). There will also be a normal risk of tropical cyclone impacts for New Zealand (zero to potentially one).
How super El Niño will impact NZ this Pacific cyclone season - Watch on TVNZ+
That's the broad view, but let’s dive a bit deeper and explore why this could be a unique season.
First of all, take a look at the big red elephant in the room. The sea temperature anomaly map across the globe. That blood red area across the eastern equatorial Pacific is the growing Super El Nino.
Notice how those temperatures are literally off the scale. The warming seas that are upwelling in the region are even warmer. A good hint that the effects of this El Nino will intensify.
The developing Super El Nino has already had dramatic effects on the hurricane season to our northeast. The typical busy Atlantic Hurricane season went for the longest period without a named hurricane, whereas further west the eastern Pacific just experienced it’s most active season ever recorded.
Almost every hurricane attained cat 3 status with three reaching to top level category 5.
So, what has caused the increase storm activity in the eastern Pacific and almost nothing further east? In a nutshell it was the perfect conditions for hurricanes to develop in the eastern Pacific with very warm seas and favourable light winds to allow the storms to develop.
The seas were warm in the Atlantic Basin but the winds in the lower sections of the developing storms were much more hostile. This in turn tore the storms apart as they were trying to form - known as wind shear.
So how will it influence our tropical cyclone season?
The Super El Nino and it’s massive area of warming seas has a big impact on the typical east to west low level wind flow of the trade winds across the equatorial pacific.
More warm water helps create more lift in the atmosphere which weakens the typical high-pressure zone in the eastern Pacific. This coupled with more subsidence (air moving downwards in the atmosphere) further west in western equatorial Pacific, back across northern Australia and then to Indonesia.
That's the opposite of La Nina so, instead of clouds and developing storms here it will be mostly dry and settled. In El Nino those typical build-ups of cloud and storms move further east to just east of the international dateline.
This becomes the favoured area for tropical cyclone development. There can also be more shear further west.
This will play a part in how and where the Southwest Pacific Tropical cyclones develop this year. They typically develop along with the band of cloud and converging winds that bisects the region during the Cyclone season (the Southwest Pacific Convergence Zone).
In El Nino years with a weaker high-pressure zone in the east this convergence zone can shift a bit further east, closer to Tahiti. This in turn creates a slightly higher risk in the eastern regions to the northeast of New Zealand. There can also be more shear further west reducing the Cyclone risk.
As we know with many tropical cyclone seasons, they can all be a bit different.
Take last year, an La Nina Year, there were hardly any Tropical Cycloness but several devastating tropical lows, some of which impacted New Zealand.
Southwest Pacific could experience severe tropical cyclones reaching category 3 or higher this season. (Source: 1News)
Remember the intense tropical low that hit New Zealand in the third week of January 2026? It caused extensive slips and flooding across upper North Island. In particular Mt Maunganui and the Bay of Plenty.
On the other side of the scale in 2015-2016, an El Nino year, it was a quiet season in the west of the basin but one of the largest Tropical Cyclones (Winston) formed in recent memory and devastated parts of Fiji. It was a top end category 5 tropical cyclone.
So, in nutshell, despite the expected warm and dry forecast impacts from the growing super El Nino - don’t rule out the TC season.
We, on average, expect 1-2 fading Tropical Cyclones to come within 500km of New Zealand per season.
This season, even though the development region could be further east - closer to Fiji than Vanuatu, don’t think we are in the clear. The warmer seas and the odd wild card tropical low can be just as dangerous.
Get ready for the Summer!
How super El Niño will impact NZ this Pacific cyclone season - Watch on TVNZ+
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