“La Niña has only just ended, but there are indications that we’ll see a rapid flip to El Niño,” says Jon Tunster from Earth Sciences New Zealand. This winter, New Zealand is preparing for a significant El Niño that could reshape weather patterns across the nation.
The forecast predicts a greater than 60% chance that this El Niño event will be classified as ‘strong’ by spring. Warm ocean temperatures in the central and eastern tropical Pacific are driving this shift, leading to expectations of varied rainfall across different regions.
Expected impacts this winter:
- Increased rainfall is anticipated for Southland, parts of Otago, and western-facing areas of the South Island.
- Much of the remainder of New Zealand may experience reduced rainfall.
- Dry conditions might become concerning as spring approaches in areas with less winter precipitation.
- Occasional cold snaps could occur, lasting a few days at a time.
Tunster emphasizes the importance of monitoring these changes: “Given the projected strength of this event, it will be very surprising if New Zealand doesn’t feel some impacts.” The atmospheric response from El Niño may also strengthen high-pressure systems over Australia during the winter months.
This year marks a notable shift after an extended period of La Niña conditions. For six months, scientists have monitored signs of developing El Niño. The Relative Oceanic Niño Index (RONI) shows a rapid rise consistent with its onset. Warm water beneath the surface of the tropical Pacific Ocean is moving eastward—an indicator that significant changes are on the horizon.
Key indicators include:
The atmospheric response expected as warm sub-surface waters reach the surface. and Potential dramatic impacts on large-scale global weather systems, including the Indian monsoon and North Pacific storm track.
As winter approaches, communities across New Zealand are advised to prepare for these potential shifts in weather patterns. While some regions may benefit from increased rainfall, others might face challenges due to dryness. The next few months will be crucial in understanding how these changes will unfold.
