Thread by @reveal

Our @esagara has been covering catastrophic wildfires for years. Here’s his take on what we’re seeing in Northern California. 1/

1st, quick background: Four wind-driven fires are ravaging Northern California, consuming thousands of acres in Napa and Sonoma counties. 2/

As of this afternoon nearly 60K acres have been charred. About 1,500 homes have been lost. 10 people have died. 3/

It’s not unusual to have wildfires this time of year. Fire season is now year round here. But these spread quickly with little warning. 4/

(By the way, imagery and data in these tweets are from Cal FIRE, Google and the Silvis Lab at the University of Wisconsin Madison.) 5/

Why is a fire in these areas so dangerous? Several reasons. 6/

Wide swaths of Napa/Sonoma are rated as having moderate to very-high fire severity - where the chances of destructive fire is highest. 7/

The four fires all began in areas rated at moderate or very-high fire severity. 8/

Another risk factor is that much of the area is in what’s called the Wildland-Urban Interface, or WUI. 9/ apps.revealnews.org/wui/

The shaded areas on this map show WUI zones in the area: where buildings are intermixed with forest. 10/

Nationwide, about 8.5 million homes have been built in these areas since 1990. Not only are there more homes at risk of burning… 11/

..But more people living in these areas means a greater chance for fire. Humans cause as much as 90 percent of wildfires. 12/

Another exacerbating factor: The fires are burning in areas that have not seen fire for decades. 13/

The vast majority of North American forests are supposed to burn every few years ... 14/

A century of land use policies stopped forests from burning like they're naturally supposed to. revealnews.org/article/when-s… 15/

The #Tubbs and #Nuns fire started in areas that last burned in 1964. 16/

The #Atlas fire began in an area that hasn't seen fire since 1981. CAL FIRE has no recorded fire history where the #Patrick fire began. 17/

These fires are nowhere near contained, and there’s a lot we don’t know about their extent, where they began and what has been lost. 18/

You can read more of @esagara’s wildfire coverage on our site revealnews.org/topic/americas…

Or listen to our podcast. revealnews.org/episodes/ameri…

And holler at @esagara if you have questions.