Scientists simulate Lahaina Fire to improve prediction of wildland-urban fires

Scientists have successfully applied a pair of advanced computer models to simulate last year’s wildfires that devastated Lahaina, Hawaii. This development could lay the groundwork for more detailed predictions of wildfires moving through towns and cities, ultimately helping firefighting efforts and safe evacuations, as well as the design of wildfire-resistant communities. do

The study, led by the US National Science Foundation’s National Center for Atmospheric Research (NSF NCAR), brought together a cross-disciplinary team of climatologists with structural and atmospheric engineers.

Their combined skills enabled them to simulate how strong winds fanned brush fires and sent flames in different directions through neighborhoods and commercial districts, igniting and destroying multiple structures amid chaotic evacuations. gave the study I was published. Natural Hazards and Earth System Sciences,.

Although scientists have worked for years to improve fire forecasts in forests and grasslands, they have recently turned to the more difficult challenge of predicting them. How the fire will behave once it encounters populated areas. Such incidents have become more frequent in the past decade, often with tragic results.

“It’s a complex situation when fires move from remote areas to a town, but this research shows that we will have the ability in the near future to know the location and time of a fire within minutes. will be able to predict fire outbreaks,” said NSF NCAR scientist Timothy Juliano, lead author of the new study.

“Our approach can serve as a basis for further understanding. Extreme weather conditions can influence fire behavior in a variety of built environments and ultimately better protect vulnerable communities.”

Juliano witnessed the need for better forecasting firsthand when he had to evacuate his home in Louisville, Colorado during the 2021 Marshall Fire that destroyed more than 1,000 structures.

The research team included experts from the University of Buffalo, the University of Nevada-Reno, and the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder.

Rapidly spreading wildfires in recent years have devastated communities as far away as Superior and Louisville, Colorado. Talent and Phoenix, Oregon; Paradise, California; and Gatlinburg and Pigeon Forge, Tennessee. The Lahaina fire of August 8–9, 2023 was particularly tragic, killing 100 people and destroying more than 2,200 structures. It was the deadliest American fire in more than a century.

In each of these cases, flames spread from vegetated areas into subdivisions and strip malls during high wind events, requiring massive firefighting efforts and extensive damage within 12 hours of ignition. Scientists are working to better understand such events, which requires painstaking analysis of local environmental conditions to determine how fires can ignite in forests or grasslands. And then, the city ignites one structure after another.

To get a detailed picture of the Lahaina fire, the research team combined two computer models with different capabilities.

One, the NSF NCAR-based Weather Research and Forecasting (WRF) model, was used to simulate the downslope winds that erupted on the day of the fire, producing 80 mph gusts. The high-resolution model can show turbulent airflow around Lahaina and a “hydraulic jump” — a phenomenon in which downwind winds suddenly rise when they collide with winds flowing in the other direction, causing Chaos and powerful movements of air begin.

Wind fields from the WRF simulation were fed into another model, the Streamlined Wildland-Urban Interface Fire Tracing (SWUIFT). The model can simulate the spread of flames in a developed area, capturing the ways that intense heat and shooting embers can ignite structures.

Duplicate images were captured. strong winds On the morning of August 8, east of Lahaina, the Pu’u flows down the slopes of Koku’i. These winds encountered a reverse flow, creating a hydraulic jump that would gradually move offshore.

By mid-afternoon, the strongest winds were blowing just east of downtown Lahaina, where the fire is believed to have started in dry grass. In the early evening, the hydraulic jump began moving eastward back toward Lahaina and then partially ascended the slopes of Pu’u Kukui. It enveloped the city in particularly treacherous wind fields, known as turbulent rotors, in which moderate winds reverse from west to east in contrast to the earlier strong east-to-west flow during ignition. They go and flow.

Changes in wind direction proved fatal. The simulation shows that the initial fire spread around 3:30-4:30 p.m., moving in a narrow downwind path from vegetation to structures and reaching historic areas along the seashore.

The fire front then slowly expanded and, beginning around 7:30 p.m., shifting winds fanned the flames in all directions, reaching structures on the south side of Lahaina as well as north. continued to spread.

“The later, and rather sudden, shift of winds to the coast (west) and extreme variability was particularly insidious as it allowed the fire to spread in all directions, and thus, from the initial east-west run. The fugitives had no. safe haven but the sea,” the paper said. “In other words, this was not a simple situation of getting out of the way of the fire.”

Tracking with witness reports, videos

The results of simulations are usually well-tracked with witness reports and recorded videos for fire spread.

The authors noted that, in addition to unusually strong and turbulent wind fields, several factors influenced the death toll. They said more research is needed on the role of building construction types, evacuation plans and orders, blocked exits, and demographics (many of the fire victims were elderly).

Still, even in such a complex situation, Juliano and his co-authors conclude that advanced computer modeling can make a difference when a community is threatened by a fast-moving fire.

Their research suggests that it should be possible to develop new technologies to aid in firefighting and evacuation that can run computer simulations faster than real time. Such technologies can also help guide planning to reduce fire risk long before a fire occurs.

“I was surprised at how well the simulation came out,” Juliano said. “This study shows the potential for an active development.Fire A decision support system that could revolutionize fire response in the built environment and empower a future in which society coexists with wildfires.”