Wildfires can burn thousands of acres, devastate communities, and sometimes even claim lives. Janice Coen at the National Center for Atmospheric Research is studying how weather and fire interact in order to develop a wildfire prediction system to forecast fire behavior. "When Nature Strikes" is produced by NBC Learn in partnership with the National Science Foundation and The Weather Channel. For a classroom activity related to this video, please click the Links section below.
When Nature Strikes -- Wildfires
MARSHALL SHEPHERD reporting:
With just one lightning strike, a wildfire can ignite and burn thousands of acres of land, sometimes devastating communities, and even claiming lives. Janice Coen, a project scientist with the National Center for Atmospheric Research and funded by the National Science Foundation, is working on a problem that could save hundreds of lives - how to predict wildfire behavior.
On June 30, 2013, a wildfire that had been smoldering for days in Yarnell, Arizona, began to spread. An elite group of firefighters, known as the Granite Mountain Hotshots, were battling the blaze when something caused the fire to make an unexpected turn toward their position.
GRANITE MOUNTAIN HOTSHOT: Our escape route has been cut off. We are preparing a deployment site.
SHEPHERD: In the end, 19 of the veteran firefighters were killed, making the Yarnell Hill wildfire one of the deadliest in American history. So what caused the wildfire's behavior to change? Scientists are pointing to weather, in this case, strong gusts of wind.
JANICE COEN (National Center for Atmospheric Research): The 40-mile-per-hour gusts were likely, but there was no specific warning when or where or what that might do to the fire behavior.
SHEPHERD: Janice Coen has been studying wildfires for over 20 years and has developed cutting edge computer models to simulate how weather and fire interact.
COEN: Weather is the most rapidly changing of the factors influencing fire and it's the wildcard in any fire event.
SHEPHERD: Changes in weather, including humidity, air temperature, and most importantly wind, have a major effect on a fire's behavior. Wind adds more oxygen to the blaze, pushes the flames toward additional fuel, such as shrubs, trees, and pine needles, and can change the direction the fire is spreading. Weather ultimately directs where a fire goes, as well as influences how fast it consumes fuel and it often begins with one lightning bolt.
COEN: Weather in the form of lightning is a source of a lot of fires so weather and fire are intricately connected.
SHEPHERD: According to the National Interagency Fire Center, there were over 63,000 wildland fires in the United States in 2014 that burned over 3.5 million acres of land. While most wildfires are initiated by humans, an average of 10,600 wildfires are caused naturally by lightning each year, the majority of which are reported in the southwest. When lightning strikes and the resulting fire starts to consume fuel, particles and gases are released into the atmosphere, making the air warmer.
COEN: As that air rises, it pulls air in behind it to replace what's moved upwards. So in that way, the fire creates updrafts over itself that changes the winds and its environment. This, in turn, shapes the fire behavior.
SHEPHERD: This can trigger a vicious cycle as the fire burns, creating clouds, precipitation, and strong wind. Coen has developed computer model simulations of various wildfires, including the Yarnell Hill fire, to understand more about the weather changes over time and how that's connected to the fire's behavior. This allows her to look at important transitions, such as when a gust of wind came through at Yarnell Hill.
COEN: So you're looking at near surface wind vectors. These arrows are pointing downwind and the longer they are, the faster the winds are traveling. There's a ton of moisture coming from the northeast over several mountain ranges, and as this rain falls into the boundary layer, it evaporates and makes the air cool and it spreads out at the ground. So what that does is creates this line of strong winds, and when it passes over the fire, it suddenly changes the direction the fire is spreading and makes it become more intense.
SHEPHERD: The physical effects of fires can be seen for years, from scorched Earth to soil erosion. The United States spends billions of dollars each year suppressing wildfires, but the economic problems go far beyond what meets the eye.
COEN: Fires also spread into impacts on businesses, as when it's smoky, nobody wants to come here for tourism. There's an impact on infrastructure as a lot of the power supplies have to be rebuilt after a fire, and economists have estimated the cost of them can be from two to 50 times what it costs to put the fires out.
SHEPHERD: To forecast wildfire behavior, Coen is leading a team to develop a fire prediction system that incorporates weather data, computer models, and high-resolution satellite imagery to warn first-responders between 12 and 18 hours in advance.
COEN: From the time you can first detect the fire until there's no longer enough heat to be detected by the satellite, we can have a forecast of the fire for the next day or so, which is really quite good and we couldn't do that before.
SHEPHERD: As technology improves, research from scientists like Coen could change the way we fight wildfires and save the lives of those on the frontlines.
SAN FRANCISCO, California — A carelessly discarded cigarette, a downed power line, a car's backfire or a chainsaw's pull. Just about anything could have started any one of the wildfires now tearing through Northern California, authorities said.
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