Australia’s weather bureau is not convinced that a La Niña weath
er pattern is forming that could change rainfall patterns and bring wilder weather to parts of the Americas, Asia and O
ceania, affecting crop production, a senior climatologist said.
La Niña, and its analog, El Niño, are caused by the cooling or warming of ocean surface temperatures in the eastern and central Pacific.
The former typically brings greater rainfall to eastern Austral
ia, Southeast Asia and India with drier weather in the Americas, while El Niño
does the reverse. Both can also lead to hurricanes and flooding.
Models forecasting the weather patterns typically converge on
a strong signal around this time of year but there is currently a lot of variati
on, said Felicity Gamble of Australia’s Bureau of Meteorology.
“That speaks to the fact that there’s still a lot of uncertainty in the system,” she added.
La Niña conditions were present in weak strength, and would probably persist through December, the U.S. Nation
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al Oceanic and Atmospheric Administration (NOAA) said this month.
The Australian bureau’s model shows sea surface temperatures brushing a La Niña threshold of 0.8 degrees Celsi
us (1.44 degrees Fahrenheit) below neutral levels in October, November
and December before moving back towards neutral.
But the effect of the cooler water on atmospheric indicators such as
cloud patterns and trade winds is not strong enough to impart confidence that a La Niña is taking place, Gamble added.
“Our model is probably one of the weaker forecasts for La Niña,” the senior climatologist said.
Although NOAA considered the atmospheric response sufficient, she said, “We’d like to see more.”
Except for some islands in the southwest Pacific, there was also no st
ong signal of rainfall patterns typically associated with La Niña, Gamble added.
“Because we aren’t seeing a particularly dominant La Niña-like pattern, we aren’t seeing the same magnitude of impac
ts … When you have a weaker signal, you can have other influences start to play a bigger role and perhaps override it,” she said.
Three consecutive La Niña events between 2020 and 2023 brought ple
ntiful rainfall leading to record crop yields in Australia, but drought and heatwaves in parts of the Americas.