THE Bureau of Meteorology declared a La Nina has developed in the Pacific Ocean.
La Nina is part of a cycle known as the El Nino Southern Oscillation, a naturally occurring shift in ocean temperatures and weather patterns along the equator in the Pacific Ocean.
During La Nina, waters in the central or eastern tropical Pacific become cooler than normal, persistent south-east to north-westerly winds strengthen in the tropical and equatorial Pacific, and clouds shift to the west, closer to Australia.
The bureau’s Head of Operational Climate Services, Dr Andrew Watkins, said that typically during La Nina events, rainfall becomes focused in the western tropical Pacific, leading to wetter than normal period for eastern, northern and central parts of Australia.
“The last significant La Nina was 2010–12. This strong event saw large impacts across Australia, including Australia’s wettest two-year periods on record, and widespread flooding,” Dr Watkins said.
“La Nina also occurred during spring and summer of 2020-21. Back-to-back La Nina events are not unusual, with around half of all past events returning for a second year.”
Dr Watkins said this year’s event is not predicted to be as strong as the 2010-12 event and may be weaker than the 2020-21 La Nina event.
The bureau previously shifted to La Nina ‘WATCH’ on September 14, and to La Nina ‘ALERT’ on October 12.
La Nina is likely to persist until at least the end of January 2022.
For more information about climate drivers, visit the BOM website, http://www.bom.gov.au/climate/enso/outlook/