MEZIESBLOG

There’s a difference between the cause of a wildfire – that is, what sparked it – and what fuels it, which is the conditions that allow it to spread.

The causes of all three blazes in California are still being investigated, with some 85% of US forest fires are caused by humans, whether deliberately or negligently, according to the US Forest Service.

But officials already have a good idea about what is fuelling the fires to make some of them so intense, so quickly.

They have been whipped in the so-called Santa Ana winds: extreme, dry winds that are common in LA in colder winter months, which have already topped 60mph this week.

This “atmospheric blow-dryer” effect, as a UCLA scientist put it, and low humidity are causing “extreme wildfire risks”, the California Department of Forestry and Fire Protection said.

These northeasterly winds blow in from the interior of southern California towards the coast, picking up speed as they squeeze through mountain ranges that border the urban area around the coast.

They blow in the opposite direction to the normal onshore flow that carries moist air from the Pacific ocean into the region.

The lack of humidity in the air parches vegetation, making it more prone to burning once a fire has started.

Last summer was particularly hot in Southern California, followed by an unusually dry wet season.

California governor Gavin Newsom said this time of year “traditionally has not been fire season” but it has now become “year-round in the state of California”, apparently alluding to the role of climate change.

Scientists will need time to assess the role of global warming in these specific fires.

But broadly we know that the hot, dry weather that parches land, thereby creating the fuel for wildfires, is increasing in the US due to climate change – that’s according to scientists at World Weather Attribution.

Malibu residents told to prepare to evacuate

Officials in the affluent Malibu area have told residents to be prepared to evacuate. 

“The city of Malibu urges all residents not currently under evacuation orders to be prepared to evacuate,” the city government said. 

“If you require additional time to evacuate, or if you have pets or livestock, consider making preparations to leave now.”

Six evacuation shelters are in operation, three of which can take people with animals.

Winds up to 60mph fuelling fires will last until tomorrow

The warm winds that are helping wildfires to spread across parts of Los Angeles aren’t expected to die down soon.

In an update this morning, the LA County Fire Department said wind gusts of up to 60mph could continue into tomorrow.

It added that “extreme fire behaviour” was continuing to challenge firefighting efforts.