In stark contrast to last summer, when devastating bushfires raged, Australia will likely be cooler and have more rain and flooding this year.
The Bureau of Meteorology has issued an alert saying there’s a 70 per cent chance of La Nina developing this summer, bringing cooler temperatures, increased rainfall and more chance of widespread flooding.
The increased rainfall associated with La Nina usually means above-average winter and spring rainfall for Australia, particularly across the east and north, raising the risk of flooding in some parts with wetter soils bringing milder daytime temperatures.
“We can also see an earlier start to the tropical cyclone season,” a BOM spokeswoman said.
The six wettest winter-spring periods on record for eastern Australia occurred during La Nina years.
In the Murray-Darling Basin, winter/spring rainfall averaged over all 18 La Nina events since 1900 was 22 per cent higher than the long-term average, with the severe floods of 1955, 1988, 1998 and 2010 all associated with La Nina.
Unlike El Nino years, the impacts of La Nina often continued into the warm months, the BOM said.
In eastern Australia, the average December-March rainfall during La Nina years is 20 per cent higher than the long-term average, with eight of the 10 wettest such periods occurring during La Nina years.
The east coast, which tends to be less affected by La Nina during the winter months, can experience severe flooding during La Nina summers.
Of the 18 La Nina events since 1900, 12 resulted in floods, with the east coast experiencing twice as many severe floods during La Nina years than El Nino years.
Some areas of northern Australia typically experience flooding during La Nina because of an increase in tropical cyclone numbers.
The wettest years on record for Australia occurred during the strong 2010-2012 and 1974 La Nina events with the 2010-12 La Nina event bringing widespread flooding across Australia.