The Bureau of Meteorology has issued an alert saying there's a 70 per cent chance of La Niña developing in Australia this year, bringing cooler temperatures, more rain and an increased chance of widespread flooding.
The increased rainfall and cloudiness associated with La Niña 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 Niña years.
In the Murray-Darling Basin, winter/spring rainfall averaged over all 18 La Niña 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 Niña.
Unlike El Niño years, the impacts of La Niña often continued into the warm months, the BOM said.
In eastern Australia, the average December-March rainfall during La Niña years is 20 per cent higher than the long-term average, with eight of the ten wettest such periods occurring during La Niña years.
Stranded vehicles are seen from above as floodwater engulfs the intersection of Stuart Drive and the Bruce Highway in Townsville, Monday, 4 February, 2019. Source: AAP
The east coast, which tends to be less affected by La Niña during the winter months, can experience severe flooding during La Niña summers.
Of the 18 La Niña events since 1900, 12 resulted in floods, with the east coast experiencing twice as many severe floods during La Niña years than El Niño years.
Some areas of northern Australia typically experience flooding during La Niña because of an increase in tropical cyclone numbers.
The wettest years on record for Australia occurred during the strong 2010-2012 and 1974 La Niña events with the 2010-12 La Niña event bringing widespread flooding across Australia.
