Maybe it wasn’t the hurricane that blew up the Maui wildfires

Scientists have introduced a new theory for the cause of the Maui fires in August, and the theory casts doubt on previous assumptions that linked the wildfires to nearby Hurricane Dora. Weather models show the fires were actually blown by the same meteorological phenomenon that’s often behind California’s worst wildfires — a downslope windstorm (see Rattlesnake).

Nearly four months after the Lahaina Fire that devastated Maui — leaving 100 people dead and 6,000 still homeless — scientists have clarified a new theory; according to a report by the Daily Mail, video footage documenting the fire revealed a wind-driven firestorm, but the power outages during the firestorm left scientists uncertain about which factors had caused the fire behavior.

Atmospheric researchers have now simulated the weather and fire trends in western Maui. In Lahaina, the main cause of the fires was a strong high-pressure system north of Hawai’i that intensified the easterly tradewinds, and when those winds ran up against the slopes in West Maui, the speed increased as the winds blew downhill. When they hit Lahaina they’d reached hurricane strength.

Simulations by the University of Nevada-Reno and the State University of New York at Buffalo showed that sustained winds in Lahaina on August 8 were nearly 80 mph with gusts exceeding 90 mph. Studies by the University of Hawaii and the University of Washington simulated similar wind speeds.

Cliff Mass, an atmospheric sciences professor at the University of Washington who simulated the Maui windstorm, said the combination of fuels, strong winds, and ignition sources is a common set-up for destructive wildfires.

“There’s a real story for Californians here because what happened in Maui, what happened in the Marshall Fire, what happened at Paradise … they’re all the same thing,” Mass told the San Francisco Chronicle.

The Chronicle reported that videos from Lahaina showed a wind-driven fire, but that because weather stations in the area had lost power during the fire, researchers could not be certain about exactly which factors had  combined to create the firestorm. Many had initially attributed the disaster to Hurricane Dora near the island.

Below is a  forecast vertical cross-section of the situation on the island at about 11 a.m. Hawaii time. Cliff Mass explains that winds are shown by the color shading and arrows.  “The solid lines are potential temperature. An extraordinarily high amplitude wave had formed, with air descending the western side of  the Maui Mountains, accelerating as it plummeted toward Lahaina. At low elevations, the flow abruptly ascended, in a feature often termed a hydraulic jump.”
Cliff Mass illustration -- Maui Mountains
Cliff Mass illustration — Maui Mountains

He said the Lahaina situation involved a wet winter, followed by a dry summer, causing grasses to grow exceptionally in the spring to create a  dense fuel load, ready to burn.

Nearly 6,200 people still struggle to find housing while residents and their beloved Maui town of Lahaina works to rebuild.

~ Thanks and a tip of the hardhat to Jim.