The Bureau of Meteorology (BOM) today upgraded its La Nina outlook, declaring the flood-inducing weather pattern is now underway, potentially bringing more rainfall than usual this summer and above average numbers of tropical cyclones over the next few months.

The BOM declaration comes after the bureau last month moved its La Nina dial to “alert” mode.

This is the second straight year that Australia will experience a La Nina.

La Nina years have historically been more costly for the insurance industry due to more extreme rainfall and elevated cyclone formation risk. Insurers on average have paid $3.025 billion each year the La Nina weather pattern was in effect, triple the long-term average and six times higher than El Niño losses.

Head of Operational Climate Services Andrew Watkins says La Nina typically leads to wetter-than-normal periods for eastern, northern and central parts of Australia.

This year the risk of flooding has increased given the deluge of heavy rainfall that has occurred in recent weeks.

“The issue at the moment is that we already have quite wet soils, quite full rivers and quite high catchments ... so any further rainfall raises the risk of widespread flooding, particularly in south-eastern Australia,” Dr Watkins said at a press conference.

“[But] the good news about La Nina is it tends to reduce the bushfire risk at least in terms of those big wild bushfires that we saw a few years ago.”

He says while this current La Nina will be weaker than last year, it is still capable of bringing heavy rainfall. BOM expects this La Nina to persist until at least the end of January.

“With the wet landscape that we have, we are at risk of more widespread flooding over the summer,” Dr Watkins said.

In relation to cyclones, he says La Nina means there is a 65% chance of above-average numbers of events this cyclone season, which runs until April.

Dr Watkins says the last significant La Nina event was in 2010 to 2012.

“This strong event saw large impacts across Australia, including Australia’s wettest two-year periods on record, and widespread flooding,” he said