Fire danger remains high in parts of Los Angeles that have been ablaze for days, but there is hope that better weather over the weekend will give firefighters battling the flames some much-needed relief.
After calmer weather on Tuesday helped firefighters snuff out fires, a rare warning of a “Particularly Dangerous Situation” was issued for Wednesday in an area near the two fires that killed at least 25 people and destroyed thousands of homes. A red flag warning was issued by the National Weather Service from Central Coast to the border with Mexico from 3 a.m. to 3 p.m.
Forecasts suggest that conditions for firefighting will improve later in the week.
What conditions are best for firefighting?
Just like wind and drought were major factors in why the fires spread so quickly, calmer wind speeds, more humidity, lower temperatures and more wind or rain can all help extinguish fires.
The level of humidity affects moisture in soil, trees and other organic matter. When potential fuels are more moist, then fire danger is reduced because they’re less combustible. Forecasters look out for relative humidity — or how much water vapor the air is holding. Fire warnings are issued when relative humidity is 15% or lower, combined with higher wind speeds.
Calmer or no winds also contribute to better conditions. Strong winds give oxygen to flames and can dry out vegetation, making it more combustible. While fires will continue even with no wind, they don’t spread as easily, making it easier for firefighters to put them out or for firefighting planes to get in the air to attack from above.
Rain or snow can also help put out fires, but often not completely, as that moisture can evaporate quickly.
When will LA get relief?
The Santa Ana winds will continue Wednesday before tapering off in the evening. “We do have a little bit of wind over the Palisades fire, but it’s not as strong as it was,” said Mike Wofford, a meteorologist with the National Weather Service.
On Thursday the normal sea breeze will return, bringing much-needed moisture from the Pacific Ocean to the region and boosting humidity, which should aid firefighting. That onshore flow will continue through the weekend.
Wofford said rain isn’t expected anytime soon. While rain can help, heavier rain could trigger mudslides in affected areas.
Another Santa Ana event is expected early next week. “We’re not super certain on the strength of it, but at this point it doesn’t look to be too bad,” said Wofford. The current forecast is for winds gusting to around 40 miles per hour or less, which are not considered particularly strong.
Even after these fires have ended, scientists say climate change means more frequent and intense wildfires in the future, with drought-like conditions in the western United States more likely.
What firefighters do when they start to gain on a fire
Fire agencies update their progress against a blaze by saying how much of it is contained. That happens when crews have made a fire line around some part of it, such as a dirt trail dug by shovels or bulldozers that stops flames from reaching more grass or trees, according to the U.S. Forest Service. For example, a fire is 25% contained when a fire line has been made around a quarter of its perimeter.
A fire is controlled when it is 100% contained, flames and smoldering and smoking fuels have been extinguished, and unburnt fuels from approximately 300 feet inside the fire line perimeter are removed. A fire is considered extinguished when no hot spots and smoke are detected within the lines for at least 48 hours.
Crews stay on the scene for days and even weeks cleaning up an area that has burned. They cut down teetering trees, remove brush and other possible fuel that could reignite, clear roads, and generally make the scene as safe as possible.
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