The world’s oceans are absorbing most of the heat emitted globally. During La Nina years,the ocean absorbs more heat. There are three phases of the ENSO pattern,as conditions seesaw between El Nino and La Nina and the neutral stage in between.
While La Nina causes warmer than average sea temperatures off Australia’s coast which drive storms,it cools downocean temperatures in the northern hemisphere which creates drier onshore weather.
Australia’s wet weather will linger throughout late winter and spring after a negative Indian Ocean Dipole (IOD) was declared earlier this month. If a La Nina does occur,it would be the first time on record that we have seen three consecutive La Nina events coinciding with back-to-back negative IOD events.
When the Indian Ocean is cooler than average on the western side,and warmer than average on the eastern side,it causes more moisture-laden air to flow to Australia and fuels the north-west cloud bands that develop over north-western Australia,extending to the south-east of the continent.
It also brings a high chance of above-average rainfall over large areas of Australia in late winter and spring.
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This is the second negative IOD in a row,with the same weather pattern occurring last year. This is only the second time a negative IOD has occurred back-to-back since reliable records began in 1960.
University of Melbourne climate scientist Andrew King said there were not enough long-term records to be able to say if climate change was a factor in a possible third La Nina event. But he said climate projections show these types of events could become more intense or frequent as climate change worsens.
“Climate change is having big effects in terms of heatwaves and things like that,but in terms of rainfall variability and La Nina and El Nino,it is harder to see the climate change element at the moment,” he said. “We need to see these things that occur every few years and we need to have long-term record observations to build a pattern and we don’t have that yet.”
NSW SES Commissioner Carlene York said water systems and saturated soils would exacerbate flooding risks. She urged people to prepare emergency evacuation kits now.
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The possibility of a third La Nina event is the last thing many flood-affected residents across Australia will want to hear. It comes as those in NSW wait for the government to release the much anticipated independent flood inquiry which will recommend apartial merger of the State Emergency Service and NSW Rural Fire Service.
The partial merger would see the RFS and SES combine their back-of-house functions,although each agency will retain its core purpose of responding to floods or bushfires. The report will also recommend that any flood operations be managed from RFS headquarters rather than the SES’ Wollongong base.
The independent report will recommend thatResilience NSW boss Shane Fitzsimmons be dumped and the disaster management and response agency dramatically scaled down. It will also suggest a new deputy police commissioner be appointed to emergency and disaster management.
The report is likely to be released in the coming days.
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