El Niño ... what to expect
Updated: 22 hours ago
There's a lot of talk about an impending El Niño weather event unfolding this Spring. This El Niño could match or exceed the strongest we have seen in modern history. What is it and how might it affect our fishing this coming season?
An El Niño occurs when the Pacific Ocean off the South American coast warms above average, and east-west trade winds around the Equator weaken or sometimes even reverse. This causes the sea in the western Pacific Ocean to cool down as the temperature rises in the eastern Pacific.
During El Niño, New Zealand experiences stronger and more frequent westerly winds. Because of our topography, our El Niño signature is one of the most distinctve in the world, producing a sharp east-west divide. As the westerly winds strengthen, moisture-laden air from the Tasman Sea hits the Southern Alps and releases heavy rain on the West Coast. The West Coast and Southern Alps get above-normal rainfall (≈150%), while eastern regions (Canterbury, Otago, Hawke's Bay, Marlborough) become drier and more drought-prone (≈65% of normal).
The most recent El Niño occurred from summer 2023 into early spring 2024. This year's event is already comparable with the powerful 1997 El Niño, and has shown the strongest warming trend on record. Current record sea-surface temperatures mean the atmosphere is already carrying considerably more moisture than during previous El Niño events. Pundits are forecasting an unusually windy and changeable spring, with dry spells across much of the north and east, and heavy rain and stormy weather in parts of the west and south. Temperatures are expected to be around or above average overall, but temperature swings between warm and cold are expected to be larger than usual. The greatest risk of nationwide unsettled weather is currently expected during mid-to-late spring.
El Niño also changes New Zealand's tropical cyclone risk. As warmer Pacific waters near the International Date Line shift the cyclone genesis-region eastward, fewer cyclones are forecast for Australia and Fiji, but there is an increased chance of some ex-tropical cyclones reaching New Zealand waters, particularly during late summer (February-March). Ex-tropical cyclones are among New Zealand's most damaging storm types. The concern for 2026-27 is statistical: a strong El Niño in the western Pacific tends to increase the probability that decaying tropical cyclones will track southward toward New Zealand, arriving as intense mid-latitude storms carrying extreme rainfall and damaging winds. For this 2026-27 El Niño, NIWA is forecasting heightened chances of summer drought in eastern regions, more ex-tropical cyclones reaching New Zealand waters, and increased wildfire risk in the dry east. Above-normal rainfall with increased flood risk is forecast for the West Coast, North West Nelson, and Fiordland.
Because Nelson is generally sheltered from westerly rain there should be a reduced likelihood of above-average rainfall east of the Tasman Mountains, with more settled weather and sunshine. Tasman, Nelson, Marlborough and Buller are however, expected to experience an especially changeable spring, with a tendency towards southwesterly flows from October. Anglers should therefore expect to be confronted with some challenging fishing conditions at times this coming season. The predicted increase in the frequency and strength of winds from the west, equates to potentially strong downstream winds on the majority of our rivers.
However, El Niño years generally bode quite well for the productivity of local Nelson fisheries, especially for the Motueka, Wangapeka and some smaller streams. With a bit of forethought, there are a number of strategies we can employ in planning our fly-fishing for better success during the coming season.
There is likely to be significant spill-over from the heavy westerly rains into the headwaters of the Wangapeka River and possibly the Baton Rv. This will very likely cause more high-water events flowing out of these rivers and produce higher river flows in the Motueka River, especially prior to Christmas, below the confluence with the Wangapeka.
Because river levels are likely to be high early season ... spend time checking out the smaller streams. Smaller streams also have the benefit of being more sheltered. On bigger waters, seek out bends and tree lined stretches which provide some respite from the wind.
Get ahead of the game, and work on improve your casting! Take the time to learn the Elliptical Cast for fishing with strong tailwinds, and the Ping Cast when confronted with challenging headwinds. While both initially take practice to adjust from your regular casting stroke, they are not difficult to master, and open up a lot more opportunity on windy days.
If a headwind wind proves too difficult to handle, don't give up ... re-rig with some small wet-flies or a streamer, turn and face downstream, and start swinging flies, down-and-across through the ripples. The Tug-is-the-Drug ... and this can be a very productive technique, especially on parts of the Motueka and Wairau.
As water levels fall and water temperatures inevitably rise in early and mid-summer, make sure to get up early to beat the wind and take advantage of the cooler morning temperatures. Mowing the lawns can wait until the wind gets up in the afternoon!
One way or another, this coming season promises to be pretty interesting. Whether this El Niño ultimately proves to be the 'Godzilla' event some pundits predict, we'll have to wait and see. One thing for sure however, is ... the best time to go fishing ... is when you can!
“The rhythm of a river is the heartbeat of the earth.” - Joan Wulff
