La Niña Summer Starts: Stormy September Ends – Scientist Says
- New Zealand is preparing for a period of unsettled weather in September as La Niña,a notable climate pattern,makes a return for the fifth time in six years.
- La Niña is a climate pattern characterized by cooler-than-usual ocean temperatures in the central and eastern tropical Pacific Ocean.
- The current return of La Niña is noteworthy because such frequent occurrences - five times in six years - have only been observed once before since 1900.
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La Niña returns: new Zealand Braces for Stormy September,Potential Summer Impacts
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New Zealand is preparing for a period of unsettled weather in September as La Niña,a notable climate pattern,makes a return for the fifth time in six years. This unusual frequency raises concerns about the potential impacts on spring and summer conditions.
What is La Niña and Why Does it Matter?
La Niña is a climate pattern characterized by cooler-than-usual ocean temperatures in the central and eastern tropical Pacific Ocean. This cooling influences global atmospheric circulation, leading to shifts in wind and rainfall patterns. For New Zealand, La Niña typically brings:
- Increased rainfall: Notably in the North Island.
- Westerly winds: More frequent and stronger westerly winds.
- Cooler temperatures: Generally cooler temperatures, although this can vary.
- More frequent cyclones: Increased risk of cyclones tracking towards New Zealand.
The current return of La Niña is noteworthy because such frequent occurrences – five times in six years – have only been observed once before since 1900. This heightened frequency suggests a potential for more pronounced and persistent impacts.
September Storms and the Sudden Stratospheric Warming Event
According to Earth Sciences New Zealand’s Chris Brandolino, September will be “exceptionally unsettled, stormy, dare I say.” This is due, in part, to a sudden stratospheric warming (SSW) event high above the Antarctic. SSW events can disrupt the polar vortex, leading to changes in atmospheric circulation that extend down into the troposphere, impacting weather patterns globally.
the combination of La Niña and the SSW event is expected to create a period of strong westerlies across New zealand, bringing frequent and intense storms.
Longer-Term Outlook: Spring and Summer Predictions
While September is expected to be particularly turbulent, the influence of La Niña will extend into spring and summer. The specific impacts will depend on the strength and duration of the La Niña event.
Potential summer scenarios include:
- Heavy rainfall: Especially in the North Island, perhaps leading to flooding.
- A heat dome: While less likely, a strong La Niña can sometimes contribute to the formation of a heat dome over New Zealand.
- Continued westerly winds: Maintaining a pattern of unsettled weather.
brandolino emphasizes that the situation is still evolving and ongoing monitoring is crucial.
Historical La Niña Events in New Zealand
| Year | La Niña Strength | Key New Zealand Impacts |
|---|---|---|
| 1973-74 | Strong | Extensive flooding in the North Island, unusually wet summer. |
| 1975-76 | Moderate | Increased rainfall in the west of the South Island, cooler temperatures. |
| 1988-89 | Strong | Prolonged drought in the east of the North Island, heavy rainfall in the west. |
| 2010-12 | Strong | Record rainfall in many regions, widespread flooding, significant agricultural impacts. |
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