Heavy showers and thunderstorms have flared up across parched bush fire zones in southeastern Australia, and in some cases these storms are delivering the most rain these areas have seen in months. Due to a shift away from hot, dry conditions across southeastern Australia and toward more typical summer thunderstorm activity, storms have formed during the past two days from Victoria northward into Queensland.
The forecast calls for more rains through the weekend, particularly across eastern New South Wales and Queensland. However, the hit or miss nature of the thunderstorms means that some fire zones could miss out on the wet weather entirely.
Some spots picked up more than 2 inches of rain on Wednesday into Thursday, while other areas saw just a few raindrops as thunderstorms rumbled past.
The storms have brought with them severe weather including large hail, damaging winds as well as dust storms given the drought conditions. They could also cause landslides and debris floes to form in recently burned areas.
According to the Australian Bureau of Meteorology, widespread rainfall amounts of between 0.4 to 1 inch has fallen across a large area from Melbourne northeast to Gladstone, Queensland. Localized amounts of 2 inches or more was associated with some slow-moving thunderstorms, including in the Melbourne metropolitan area and areas just north of Brisbaareas just north of Brisbane. Large hail and frequent cloud-to-ground lightning have also been occurring with these storms.
The rain is courtesy of a trough of low pressure that has set up across inland parts of eastern Australia, drawing warm, humid air to the north-northwest, and leading to daily rounds of showers and thunderstorms. This feature is not expected to dissipate during the next few days, raising the prospect that some places could receive several inches of rain.
Notably, the heaviest rains are largely bypassing parts of hard-hit Victoria and South Australia, which could make those areas more vulnerable to additional bush fires if more dangerous fire weather conditions occur during the rest of the summer season.
The reaction from firefighters and meteorologists alike is one of relief and glee at finally seeing meaningful rains, despite the fact that the wet weather won’t be sufficient to end the drought, which in some areas has lasted for more than 3 years, nor will it put an end to the bush fire crisis. Last year, for example, was Australia’s hottest and driest on record, and in December, the country smashed its record for the hottest day in recorded history.
However, for the fire zones that see heavy downpours, the weather pattern could allow firefighters to get the upper hand on blazes that have been difficult to impossible to control, since the rains may help limit the fires’ spread.
More than 2,000 firefighters are still deployed across Australia, including some from the U.S., New Zealand and other countries. More than 80 bush fires are still burning in New South Wales alone, despite the rain.
Computer model projections show the potential for another several inches of rain in northeastern New South Wales and southeastern parts of Queensland in particular, with lesser but still beneficial amounts occurring in New South Wales, including the Sydney region. If Sydney receives up to 2 inches of rain on Thursday, it would be the most rain to fall there since mid-September.
Heavy rain can cause flash flooding in areas downstream from fire zones, due to enhanced runoff from unstable tree cover and soils in post-fire ecosystems. In addition, the rains could harm animals that survived the flames, only to be swept up in flooding.
There are larger factors at play that favor wetter, comparatively cooler weather in Australia during the months to come. These include an atmospheric overturning circulation in the Indian Ocean, known as the Indian Ocean Dipole, which had favored sinking and drying air over southeastern Australia through the first part of the summer.
The other is the circulation high above Antarctica, in the thin layer of air known as the stratosphere. A sudden warming event there prior to the summer reversed the circulation of the Antarctic polar vortex. This too increased the odds of hotter and drier weather in southeastern Australia.
Combine those two patterns with long-term climate change, and the country faced a potent combination for an unprecedented bush fire crisis.