The Grand Canyon fire exploded in size, catching officials off guard. Why?
When a lightning strike ignited a wildfire on the Grand Canyon's North Rim, fire officials allowed it to burn for several days as they set up containment lines and urged the public that it was not a threat.
But then a dangerous shift in the weather occurred, turning the seemingly low-risk fire into a fast-moving blaze that jumped containment lines and torched dozens of buildings in the park over the weekend, including a historic lodge.
What fueled the explosive growth of the Dragon Bravo Fire was a mix of gusty winds, dry air and above-normal heat – weather conditions experts described as atypical for this time of year, when monsoonal moisture typically tamps down wildfire risk across Arizona.
“It was a break in the monsoon pattern,” Robert Rickey, a science and operations officer with the National Weather Service, told The Arizona Republic, part of the Paste BN Network. “Rather than having daily afternoon showers, we had a period of several days without that. Instead, we had extremely dry, warm conditions.”
Since its rapid expansion over the weekend, the wildfire has torched over 14 square miles of land, making it one of the largest wildfires to break out in a national park since 2021. No one has been injured as the North Rim and nearby communities were evacuated late last week because of a separate fire. Officials also shut down the North Rim – which receives only 10% of all park visitors – for the rest of the year.
In recent days, members of the state's congressional delegation and Arizona Gov. Katie Hobbs criticized the National Park Service's decision to initially treat the fire as a controlled burn – a practice that's regularly employed to reduce wildfire risks and promote healthy plant growth.
The park service has said the wildfire was "expertly handled," blaming "historic" winds for the blaze's explosive growth and highlighting the evacuation of hundreds of residents, tourists and park employees.
How the weather fueled the Grand Canyon wildfire
After the fire started on July 4, the National Park Service decided to manage the blaze as a controlled burn to benefit the land. But by July 10, the threat of expansion set in as a dry trough of low pressure passed over northern Arizona, pushing out monsoon moisture and bringing in drier air and gusty winds.
Relative humidity dropped into the single digits. The winds shifted, blowing 20 mph from the west and northwest, fanning the flames and driving them across the North Rim. Temperatures climbed to the upper 80s and low 90s, about 10 degrees above average for this time of year.
On Friday, July 11, the fire expanded by more than eight times its size. The rapid growth continued Saturday night as peak winds around 40 mph pushed the flames to buildings and a row of cabins that firefighters had sought to protect.
The combination of weather conditions is unusual during the region's monsoon season, which officially runs from June 15 to Sept. 30, as heavy moisture and thunderstorms drive up humidity levels and limit the risk of wildfires.
"During the monsoon season, we usually have high pressure sitting in place so we’re not often dealing with strong west or northwest wind events," Rickey said. "This pattern just happened to line up in a way that really fueled the fire.”
Should fire officials have attacked the blaze sooner?
The "contain/confine" strategy that the National Park Service employed in the initial days of the wildfire is not uncommon, especially in national forests, said Susan Prichard, a research scientist specializing in wildfire ecology and management at the University of Washington.
Prichard said such a decision is reached through extensive calculation, with authorities employing risk models and simulations to analyze the potential fire spread. If it's considered low-risk, fire managers will let a wildfire burn so it can chip away at fire fuels and limit the danger of future blazes.
On the Grand Canyon's North Rim, the method worked for several days until gusty winds combined with low humidity and high temperatures to set the stage for extreme fire growth.
"I feel bad for the managers here, because unfortunately the winds were not as predictable as we wish and they got an outlier event," Prichard said. She added that research supports the use of "let-it-burn" practices but said the damaging wildfire and its handling should be investigated.
"Fire is a blunt tool so everything is risky," she said. "But when there's an outcome that's so far from what was expected, we need to learn from it."
As fire rages on, pressure mounts over federal wildfire response
The Dragon Bravo Fire has continued to grow in recent days but fire officials are hopeful that thunderstorms this week will help tamp down the flames.
Officials said over 350 emergency responders were working in shifts with hand crews and bulldozers, setting up containment lines as they seek to "hold the fire to as small a perimeter as possible" and protect other buildings on the North Rim. As of Wednesday, July 16, the fire remained at 0% containment.
Meanwhile, both sides of the political aisle have demanded an investigation into the National Park Service's response to the fire.
Democratic Sens. Mark Kelly and Ruben Gallego in a joint letter to Interior Secretary Doug Burgum requested a probe of why the blaze was initially treated as a controlled burn. And Republican Reps. Eli Crane and Paul Gosar pledged support for an investigation into the agency's wildfire response. Their demands came after the state governor called on the federal government to look into the matter.
"The destruction of the Grand Canyon Lodge was a tragedy and Arizonans deserve answers," Hobbs said.
Contributing: Perry Vandell and Caitlin McGlade, Arizona Republic