How Santa Ana winds fuel LA wildfires
Forest fires are deadly and destructive It breaks up the Los Angeles areaand strong winds literally fan the flames.
As of Wednesday afternoon, four fast-moving blazes have killed two people, injured scores more and destroyed more than 1,000 structures, threatening another 28,000 and forcing at least 70,000 to evacuate.
Here’s how winds make wildfires more dangerous and harder to fight.
What are these winds and why are they so strong?
Santa Ana winds are strong winds that blow from dry land to the coast, usually for a few days to a week during the colder months.
The National Weather Service says Santa Ana’s wind gusts could reach 129 km/h in some areas around LA by Wednesday, and 160 km/h in the mountains and foothills.
LA County fire crews said Wednesday that winds will reach 95 mph by Thursday.
These winds come from the dry desert regions of Nevada, Utah, Idaho, and southeastern Oregon and become drier as they sweep over the mountains.
Meteorologist Peter Mullinax, a meteorologist with the weather service’s office in College Park, called the area “extremely critical fire weather conditions” due to the combination of strong wind gusts and extremely low humidity in the highest area.
The Mountain Fire, which started earlier this week in California’s Ventura County, has spread to more than 80 square kilometers and prompted the evacuation of about 10,000 people.
How does wind affect fire spread?
The faster the wind blows, the faster the fire spreads. Rule of thumb used by wildland firefighters Fires spread 10 percent faster than the wind speed. For example, a wind speed of 25 km/h will cause a fire to spread at a speed of 2.5 km/h.
There are several reasons for this.
- Wind helps provide air and oxygen to the fire.
- It also straightens and bends flames toward dead wood and other fuel ahead. This can cause spot fires by preheating and blowing sparks and embers into new, dry fuel sources.
- The National Weather Service reports that wind direction largely determines the direction in which a fire will spread.
- Wind also dries vegetation, turning it into more flammable fuel.
Lyndon Pronto, chief fire expert at the European Fire Institute, says the Santa Ana winds’ ability to dry vegetation to the lowest humidity levels of the year is one of their “really dangerous effects.”
“The fuel itself becomes extremely accessible to fire and can ignite and carry flames very quickly,” he told Reuters.
This combines increased fire risk and worse fire conditions caused by climate change.
Sylvia Dee, an associate professor and climate scientist at Rice University in Houston, said that climate change has created warmer and drier conditions in the region as a whole, “which creates a kind of tinderbox.”
How does it affect firefighting efforts?
As of mid-Wednesday, 1,400 firefighters were on the ground, but aerial efforts were hampered by weather too windy for firefighting planes to fly, the Associated Press reported.
Winds can cause turbulence, especially in mountainous areas, or even damage aircraft if they are too strong.
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