Deadly and destructive wildfires are ravaging the Los Angeles area and powerful winds are literally fanning the flames.
By Wednesday afternoon, four fast-moving fires had killed two people, injured numerous people and destroyed more than 1,000 structures, while threatening 28,000 others and forcing at least 70,000 people to evacuate.
Here’s how winds make wildfires more dangerous and harder to fight.
What types of winds are these and why are they so strong?
Santa Ana winds are strong winds that blow from dry inland areas toward the coast, usually during the cooler months, for a few days to a week.
The National Weather Service says Santa Ana winds exceeded 80 mph in some areas around Los Angeles early Wednesday and could exceed 100 mph in the mountains and foothills.
Wind gusts of up to 95 km/h are expected through Thursday, Los Angeles County firefighters announced Wednesday.
These winds originate from the dry desert regions of Nevada, Utah, Idaho, and southeastern Oregon, and become even drier as they flow down the mountains.
Peter Mullinax, a meteorologist at the Weather Service office in College Park, Md., called what the region is experiencing “extremely critical fire weather conditions” due to a combination of strong wind gusts over the most higher and extremely low humidity.
The mountain fire, which broke out earlier this week in California’s Ventura County, has grown to more than 50 square miles and prompted evacuation orders for some 10,000 people.
How does wind affect the spread of a wildfire?
The stronger the winds, the faster the fire spreads. The basic rule used by forest firefighters This is because fires spread at a speed 10% faster than that of the wind. For example, a wind of 25 km/h would allow a fire to spread at a speed of 2.5 km/h.
There are several reasons for this.
- The wind helps supply the fire with air and oxygen.
- It also flattens and bends the flames toward dead wood and other fuels in front of them. This can preheat and blow sparks and embers into these new dry fuel sources, causing spot fires.
- Wind direction is what primarily determines the direction a fire spreads, according to the National Weather Service.
- Wind also dries out vegetation, turning it into more combustible fuel.
Lindon Pronto, senior fire management expert at the European Fire Institute, said the Santa Ana winds’ ability to dry vegetation down to its lowest humidity of the year is one of their “really dangerous effects”.
“The fuel itself becomes extremely available for the fire and can pick up and carry the fire very quickly,” he told Reuters.
This compounds the increased fire risk and worsening fire conditions already caused by climate change.
Sylvia Dee, an assistant professor and climate scientist at Rice University in Houston, said climate change has created overall hotter and drier conditions in the region, “and that creates a kind of tinderbox.”
How does this affect firefighting efforts?
As of midday Wednesday, 1,400 firefighters had been deployed on the ground, but aerial efforts were hampered by the fact that it was too windy for firefighting planes to fly, the Associated Press reported.
Winds can generate turbulence, particularly in mountainous terrain, and even damage aircraft if they are too intense.
