Australian cyclone risk increases under La Niña

The Bureau of Meteorology has declared that La Niña has developed in the Pacific Ocean. 

During La Niña, there are typically more tropical cyclones in the Australia region, with twice as many making landfall than during El Niño years on average. This means an increased likelihood of major damage and flooding related to strong winds, high seas and heavy rains from tropical cyclones.

La Niña typically brings above-average spring rainfall, particularly across eastern, central and northern regions. It can also mean cooler days, more tropical cyclones, and an earlier onset of the first rains of the wet season across the north.

The last La Niña event occurred from 2010-2012 and resulted in one of Australia’s wettest two-year periods on record. Widespread flooding occurred in many parts of Australia associated with the record rainfalls.

Tropical cyclone activity in the 2010-2011 season was near normal. However, five of the tropical cyclones during 2010-11 were in the severe category, which is above average, including Tropical Cyclone Yasi, which caused widespread damage to far north Queensland.

The impacts of La Niña can vary significantly between events. It is likely this year will not see the same intensity as the 2010-11 La Niña event, noted BOM, but is still likely to be of moderate strength.

David Gow, QBE’s head of Major Loss Property Claims said the BOM report is extremely helpful for those engaged in the insurance, risk and mitigation industry.

“The Brisbane floods were heartbreaking,” he commented in a recent blog post. “l remember those images of the boats being pushed down the Brisbane River and the houses being completely submerged. It was the busiest time I’ve ever experienced in insurance.”

Severe tropical cyclones also hit Queensland during the last event, including Cyclone Yasi in January 2011 which was deemed the most powerful cyclone since 1918, which was also a La Niña year.

”The impact and frequency of these weather events aren’t predictable,” said Gow. “You can’t rely on what’s happened in the past. A single major weather event every 100 years is no longer a given. Thanks to climate change, weather is becoming more extreme and unpredictable. The latest bushfires are an example.”

It’s no longer safe to make decisions on the basis that an extraordinary event is unlikely to happen, he added.