The Bureau of Meteorology (BoM) officially declared on Sept. 19 that the El Niño weather event and a positive Indian Ocean Dipole (IOD) are underway, indicating warmer and drier conditions most likely to occur for two-thirds of Australia during this Spring and Summer, raising bushfire dangers.
“Over spring, their combined impact can increase the chance of below average rainfall over much of the continent and higher temperatures across the southern two-thirds of the country,” Mr. Braganza said.
The Bureau’s three-month forecast implies a warm and dry condition for some time, and an established EI Niño and positive IOD reinforce the Bureau’s predictions.
“Based on history, it is now also more likely that warm and dry conditions will persist over eastern Australia until autumn,” said Mr. Braganza.
With extreme temperatures causing heatwaves and hotter days under EI Niño, fire danger has increased as a result. Further, a positive IOD further enhances the elevated fire risk for both Spring and Summer over southeast Australia.
The declaration for El Niño was made based on three of the four criteria that were met, including a sea surface temperature that is 0.8 degrees warmer than average; trade winds that are weaker than average in the western or central equatorial Pacific Ocean during any three of the last four months; and a three-month average Southern Oscillation Index of negative seven or lower.
Some of the Driest Years Likely Incoming
Based on BoM’s record, about two-thirds of Australia’s driest years happened during El Niño season, which takes place every three to five years, but the impacts may not be the same.“Around two-thirds of Australia’s driest years on record were during El Niño however, no two El Niño or IOD events or their impacts are the same,” Mr. Braganza said.
“El Niño is part of a natural climate cycle that affects global weather and occurs on average every three to five years.”
According to Senior Climatologist Catherine Ganter from the Bureau, the Indian Ocean Dipole alone can cause as much of an impact on Australia’s rainfall and temperature as that of El Niño.
“A positive IOD often results in below-average rainfall during spring for much of central and southern Australia and warmer than average maximum temperatures for the southern two-thirds of Australia,” she said.
“Similar to El Niño, the IOD describes a natural climate cycle brought about by sustained changes in the difference between sea surface temperatures in the tropical western and eastern Indian Ocean.”
When reliable records began for the IOD in 1960, there were 16 positive IODs and 15 El Niño years. In seven instances, positive IOD and El Niño events happened at the same time.
The U.S. and Japan as well as the World Meteorological Organization have already declared an El Niño weather event.
