Researchers study factors that affect long-distance spotting of wildfires

The results could lead to more accurate models for spotting and fire behavior

map spot fires wildfire Australia
New South Wales Rural Fire Service line scan showing three separate source fires (three largest polygons). Most actively burning fire is yellow, orange is still hot after main fire front has passed, brown is extinguished, green is unburnt vegetation, blue is part of the smoke plume. Red dotted lines indicate spot fire (small polygons) distances measured for analysis. Red arrow indicates spread direction. (from the research)

Data collected in an Australian study could lead to the development of more accurate predictive models for wildfire behavior and spotting, especially for extreme wildfires.

Burning embers driven ahead of a wildfire can dramatically increase the rate of spread and the danger faced by firefighters and the public. Under moderate burning conditions a small number of spot fires might be suppressed if enough firefighting resources are available, but on large plume-dominated fires pushed by strong winds spot fires far from the  main fire can burn together making suppression at the head of the fire impossible. In many cases ember showers have been the primary ignition source for the destruction of structures in the wildland urban interface.

During the 2009 Black Saturday bushfires in eucalpyt-dominated forests in Australia the maximum spot fire distances were 30 to 35 km (18 to 22 miles) and during the 1965 wildfires in eastern Victoria were 29 km (18 miles). Spot fires in North America have been documented at distances of up to 19 km (12 miles).

A research paper on spotting distance in Victoria and New South Wales was published earlier this week by the International Journal of Wildland Fire, written by Michael A. Storey, Owen F. Price, Jason J. Sharples, and Ross A. Bradstock, titled “Drivers of long-distance spotting during wildfires in south-eastern Australia.”

The researchers took advantage of the increasing use of airborne mapping technologies on wildfires in Australia, including infrared and multispectral line scanning, to analyze data from 338 observations. (See map above.) They used ArcGIS to manually draw polygons and determine the size of the actively burning areas of the fire, which they called “source fire area”, and measured the distance to spot fires and the size of each. They also collected fuels, weather, and topography information.

Below is an excerpt from the research:

Maximum spot fire distances ranged from 5.0 m to 13.9 km (mean, 0.9 km; 95th percentile, 3.9 km). The mean number of spot fires per source fire (irrespective of distance) was 13. The distribution of maximum distance values appeared exponential, with a high proportion of shorter distances (Fig. 4a). Very long-distance spotting was rare; only 11 source fires had a maximum spotting distance >5 km.

maximum spot fire distances
Frequency distribution histograms of (a) maximum spot fire distance values from each source fire and (b) number of long-distance spot fire (>500 m) values from each source fire. (from the research)

Eleven of the fires had spotting distances more than 5 km (3.1 miles). The longest distance measured to a spot fire was 13.9 km (8.6 miles).

The analysis of 338 wildfire line scan observations found the size of the active area of the source fire to be the strongest predictor of long-distance spotting. Important secondary effects were fuel, weather, and topography.


Wind speed was important to both Maximum-distance and long-distance Spot-number. Upper-level wind speed had weaker but still significant effects in the models. Wind at different levels can influence many aspects of wildfire behaviour, including plume development, plume turbulence and tilt, fire intensity, vorticity development, firebrand transport and ignition likelihood in receiver fuels.

A steep slope somewhere within the source fire (i.e. source fire max. slope) increased the maximum spot fire distance and the probability of spot fire occurrence >500 m. TRI [Terrain Ruggedness Index] performed similarly but was highly correlated with slope (>0.9), so was not included in the same models. An area of relatively high wind exposure (e.g. exposed ridge) also increased maximum spotting distance. Slope and wind exposure may be important through interactions with wind, changing wind speed, increasing turbulence and potentially enhancing pyroconvection, leading to enhanced firebrand generation and transport.

[W]e did not find a commonly used measure of bark spotting potential to be a significant predictor. Our results suggest that to accurately predict long-distance spotting, models must incorporate a measure of source fire area. Gathering data on spotting and plume development at wildfires over a range of intensities (including measuring intensity and frequent line scans) and improving fuel maps should be prioritised to allow for the development of reliable predictive spotting models.

The fibrous or stringy bark on some eucalyptus species is particularly suited aerodynamically for being lofted in a convection column and traveling for long distances while still burning, and is one of the primary ignition sources for long range spotting in Australia. The bark on North American trees is different, but the methods used by the Australian researchers could be used to collect similar spot fire occurrence data in the United States and Canada which could lead to improved spotting and fire behavior models.

Scientists say climate change increased risk of extreme bushfires in Australia

The researchers found the climate models consistently underestimated the observed increase in temperatures in southeast Australia

bushfire in Victoria Australia
Photo of a fire in Victoria, Australia, by Forest Fire Management Victoria Forest Fire Operations Officer Dion Hooper. It was taken in January, 2020 on Wombargo Track looking towards Cobberas (north of Buchan in East Gippsland).

A group of scientists published a study that shows global warming led to warm and dry weather that created conditions favorable to large bushfires in Australia.

From the BBC:

…Global warming boosted the risk of the hot, dry weather that’s likely to cause bushfires by at least 30%, they say.

But the study suggests the figure is likely to be much greater. It says that if global temperatures rise by 2C, as seems likely, such conditions would occur at least four times more often. The analysis has been carried out by the World Weather Attribution consortium.

Co-author Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute in De Bilt, The Netherlands, told the BBC even the study’s very conservative estimates were troubling.

“Last year the fire prevention system in Australia, which is extremely well prepared for bushfires, was straining. It was at the limits of what it could handle, with volunteers working for weeks on end,” said Prof van Oldenborgh.

“As the world warms, these events will become more likely and more common. And it’s not something that we are ready for.”

During the 2019-2020 fire season in Australia, record-breaking temperatures and months of severe drought fueled a series of massive bushfires across the country. At least 33 people were killed and more than 11 million hectares (110,000 sq km or 27.2 million acres) of bush, forest and parks across Australia burned.

Although it makes sense that human-induced global warming is likely to have led to more bushfires, assigning a figure to that increased risk is complex. That is because other factors not directly related to climate change may also play a significant role. These include increased water use making the land drier, urban heating effects or unknown local factors.

Nevertheless, Prof Jan van Oldenborgh and 17 fellow climate scientists from six countries gave it their best shot. “It was by far the most complex study we have undertaken,” he told the BBC.

The researchers found the climate models consistently underestimated the observed increase in temperatures in southeast Australia and so could not pinpoint a figure for the increased risk from climate change. They were, however, able to tease out a minimum risk.

“We show that climate change definitely increases the risk of the extreme weather that makes the catastrophic bush fires (that south-east Australia has experienced) in the past few months more likely by at least 30%.

“But we think it could be much more. We don’t know how much more. It could be a lot more.”

Prof van Oldenborgh is among those attempting to find out if the current climate computer models really are underestimating the influence of global warming – and if they are, working out how to correct them.

Three commissioners appointed to lead royal commission on Australia’s bushfires

The findings will be due by the end of August, 2020

satellite photo smoke from bush fires New South Wales
The Suomi Joint Polar Satellite System captured this photo of smoke from bush fires in New South Wales, Australia, November 8, 2019. The red areas represent heat.

The Governor-General of Australia has appointed three commissioners to lead a royal commission to look into the bushfires that so far during the 2019-2020 fire season have devastated to an unprecedented extent large areas of Queensland, New South Wales, and Victoria.

From ABC Australia:

Two more commissioners, former Federal Court judge Annabelle Bennett and leading environmental lawyer Andrew Macintosh, will join former Australian Defence Force (ADF) chief Mark Binskin.

The trio are due to deliver their findings to the Federal Government by the end of August.

More than 30 people died across the country during the disaster, and thousands of homes were destroyed.

The ABC revealed earlier this month that hazard reduction would form a key part of the inquiry, after Prime Minister Scott Morrison demanded an investigation into whether controlled burns and land clearing operations had been hampered across the country.

Climate change, and specifically its effect of creating longer, hotter and drier fire seasons, will also be considered by the royal commission.

In January when a royal commission was being proposed, the United Firefighters Union of Australia said there had already been numerous bushfire-related inquiries over the past two decades. One more commission would likely come up with the same issues, they said.

The union believed there should be instead, an audit all of the existing recommendations that haven’t been implemented. They said Royal Commissions are expensive, can take hundreds of days, force witnesses to relive the trauma, and the commission has no binding power to implement recommendations.

A royal commission evaluated the Australian bushfires that occurred in February, 2009. Public hearings began on April 20, 2009, with the Commission hearing from 434 witnesses over 155 hearing days before concluding on May 27, 2010.

Witnesses included two expert panels and 100 “lay” witnesses drawn from bushfire-affected communities. Almost 1,700 written submissions were considered by the Commission, close to 1,000 exhibits tendered and 20,500 pages of written transcripts produced.

Meanwhile, New South Wales is conducting an “independent expert inquiry” into the 2019-2020 bushfire season. Dave Owens APM, former Deputy Commissioner of NSW Police, and Professor Mary O’Kane AC, Independent Planning Commission Chair and former NSW Chief Scientist and Engineer, are leading the six-month inquiry, which is reviewing the causes of, preparation for, and response to the 2019-20 bushfires.

The Inquiry welcomes submissions from bushfire-affected residents, emergency and support personnel, organizations and the general public.

Huge sign in Times Square thanks firefighters

Times Square billboard thanks firefighters

A large electronic billboard in New York’s Times Square featured a video message this week thanking the firefighters from the United States and Australia that worked on the bushfires in Australia.

Some firefighters return from Australia while others are deploying

Angeles National Forest crew returns after 30 days

Incident Management Teams arrive in Victoria, Australi
Incident Management Teams arrive in Victoria, Australia. Photo posted February 11, 2020 by Emergency Management Victoria.

Three more Incident Management Teams from the United States and Canada have deployed to Victoria, Australia. These teams will continue to support local crews in East Gippsland, positioned in the regional Incident Control Centres and out on the fire ground.

Incident Management Teams arrive in Victoria, Australi
Incident Management Teams arrive in Victoria, Australia. Photo posted February 11, 2020 by Emergency Management Victoria.

The 20-person hand crew that left January 7 from the Angeles National Forest (ANF) in Southern California to assist with the bushfires in Australia returned 30 days later on February 5.

20-person hand crew Angeles National Forest Australia
The 20-person hand crew from the Angeles National Forest returned from Australia February 5. USFS photo.

I admit, I am old-school about some issues related to firefighting. I could not help but notice a striking difference between the first photos of U.S. personnel en route down under, compared to the more recent groups. The early photos from December of the personnel from scattered locations around the Western U.S. looked like they could have been on their day off on the way to McDonalds. But beginning in January the photos began to show what was obviously professionals on the way to an important assignment. As they walked, wearing their uniforms, through the airport in Australia other travelers in the airport spontaneously applauded. Very different from the early groups wearing sneakers, jeans, and a wide variety of t-shirts in assorted colors.

I mentioned to Robert Garcia, the Fire Chief for the ANF, the difference in the appearance of the various groups of firefighters when they were traveling. He said:

We honestly believe that how we show up is a key part of professionalism and as such, their duty. Despite many changes, we are trying our best to hold to the professional core values of duty, respect, and integrity.

We insisted that they all depart and arrive in the FS uniform and although they are represented by all 5 ANF IHC crews, ANF Engine crews, prevention, and aviation, they all wore the USFS, Angeles NF Nomex and T-shirt.

Here is a link to more information about the crews from the U.S. working in Australia. The article includes a couple of videos.

Below are photos of the ANF firefighters in more casual attire as they were working in Victoria, but still wearing the ANF t-shirts.

20-person hand crew Angeles National Forest Australia
USFS firefighters from the Angeles NF pose with firefighters from Victoria, Australia. USFS photo.
20-person hand crew Angeles National Forest Australia
USFS firefighters from the Angeles NF in Victoria, Australia. USFS photo. USFS photo.

20-person hand crew Angeles National Forest Australia

20-person hand crew Angeles National Forest Australia
USFS firefighters from the Angeles NF pose with firefighters from Victoria, Australia. USFS photo.

Saving a Very Large tree

Huge tree in the Eucalyptus genus

firefighters save Messmate tree Victoria Australia
Firefighters work to save a Messmate in Victoria, Australia. Photo by Forest Fire Management Victoria.

Chris Hardman, Chief Fire Officer for Forest Fire Management Victoria, distributed these photos of firefighters working to save a very large tree in Australia. Here is what he wrote:

FFMVic Firefighters Henry Lohr and his team mates protected this really important community asset, an ancient Messmate near Bendoc. I hope the work they have done clearing around the base and pumping 600ltrs of foam into the root area saves this tree.

Messmate is a common name for a group of species of tree in the plant genus Eucalyptus.

firefighters save Messmate tree Victoria Australia
Firefighters work to save a Messmate in Victoria, Australia. Photo by Forest Fire Management Victoria.