Hawaii went from lush to bone dry in just a few weeks — a key factor in a dangerous mix of conditions that appear to have combined to make the wildfires blazing a path of destruction in the state particularly damaging.
Experts say climate change is increasing the likelihood of these flash droughts as well as other extreme weather events like what’s playing out on the island of Maui, where dozens of people have been killed and a historic tourist town has been devastated.
“It’s leading to these unpredictable or unforeseen combinations that we’re seeing right now and that are fueling this extreme fire weather,” said Kelsey Copes-Gerbitz, a postdoctoral researcher at the University of British Columbia’s faculty of forestry. “What these … catastrophic wildfire disasters are revealing is that nowhere is immune to the issue.”
Here’s a look at what’s behind the Maui fires:
FLASH DROUGHTS: Flash droughts are so dry and hot that the air literally sucks moisture out of the ground and plants in a vicious cycle of hotter-and-drier that often leads to wildfires. And Hawaii’s situation is a textbook case, two scientists told The Associated Press.
As of May 23, none of Maui was unusually dry; by the following week, it was more than half abnormally dry. By June 13, it was two-thirds either abnormally dry or in moderate drought. And this week, about 83 percent of the island is either abnormally dry or in moderate or severe drought, according to the U.S. drought monitor.
Maui experienced a two-category increase in drought severity in just three weeks from May to June, with that rapid intensification fitting the definition of a flash drought, said Jason Otkin, an atmospheric scientist at the University of Wisconsin Madison.
INVASIVE GRASSES: Elizabeth Pickett is the co-executive director of the Hawaii Wildfire Management Organization, a nonprofit that works with communities across Hawaii on wildfire prevention and mitigation. She said there used to be massive tracts of land occupied by irrigated pineapples and sugar cane, and as those businesses declined, the lands were taken over by invasive, fire-prone grass species.
“The problem is at such a large scale, 26 percent of our state is now invaded by these grasses,” she said Thursday. “The landscape that has been invaded is steep, rocky and challenging to access. It’s a really hard landscape. You can’t just go with a lawn mower.”
When these grasses burn, they burn into the native forests, and then the forests are replaced by more grass, Pickett said.
WHAT’S FANNING THE FLAMES? Major differences in air pressure drove unusually strong trade winds that fanned the destructive flames, according to meteorologists.
Trade winds are a normal feature of Hawaii’s climate. They’re caused when air moves from the high-pressure system pressure north of Hawaii — known as the North Pacific High — to the area of low pressure at the equator, to the south of the state.
But Hurricane Dora, which passed south of the islands this week, is exacerbating the low-pressure system and increasing the difference in air pressure to create “unusually strong trade winds,” said Genki Kino, a meteorologist with the National Weather Service office in Honolulu.
Hawaii’s state climatologist, Pao-Shin Chu, said he was caught off guard by the impact Dora had from roughly 500 miles away.
“Hurricane Dora is very far away from Hawaii, but you still have this fire occurrence here. So this is something we didn’t expect to see,” he said.
