Double whammy of weather systems could heighten bushfire risk

An El Nino could combine with a positive Indian Ocean Dipole later this year to create challenging conditions for bushfire risk across parts of Australia.

The latest update from the Bureau of Meteorology says while conditions in the tropical Pacific are currently neutral, “there are signs an El Nino may form during winter”, putting the likelihood at 50%.

All but one of the international climate models used by the Bureau indicate El Nino thresholds will be met or exceeded by July, with all models meeting El Nino thresholds by August.

El Nino typically suppresses rainfall in eastern Australia during winter and spring, potentially leading to heightened bushfire risk.

The Indian Ocean Dipole (IOD) is neutral but all models suggest that a positive IOD event may develop.

“A positive IOD can supress winter and spring rainfall over much of Australia, potentially exacerbating the drying effect of El Nino,” the bureau says.

The combination of the two weather systems can spell disaster, but nothing is guaranteed.

“As a result of decreased rainfall and increased maximum temperatures, the frequency of high fire danger ratings and risk of a significant fire danger season in southeast Australia are significantly higher following an El Nino year, particularly when combined with a positive IOD event,” the Bureau website says.

“Some El Nino years have been followed by very severe summer fires, including Ash Wednesday (16 February 1983) and the 2002–03 and 2006–07 seasons.

“However, not all major fires follow El Nino years. The spring bushfires in the Blue Mountains during October 2013 occurred during a neutral ENSO year, while Black Saturday (7 February 2009) in fact followed a weak La Nina (but notably, a positive IOD).”

The US-based National Oceanic and Atmospheric Administration puts the chances of an El Nino this year at 80%, and estimates there’s a 40% chance it will be a strong event.