Minutes to Escape: How One California Wildfire Damaged So Much So Quickly

The wildfire that raced toward Santa Rosa, Calif., late Sunday night, arrived so quickly that the city’s sleeping residents had minutes to escape. At least 1,800 structures were reduced to ash, making the fire one of the most destructive in the state’s history.

The inferno, officially called the Tubbs fire, started around 9:43 p.m. on Sunday near Calistoga, a small town in Napa County known for its wineries and mud baths.

The fire moved quickly, traveling about 12 miles in a little over three hours.

By 1 a.m. Monday, the fire had reached Santa Rosa, a city of about 175,000 people in Sonoma County.

Christine Sims, a resident of Coffey Park, a neighborhood where several hundred homes were burned to the ground, said she could tell the fire was headed their way based on the wind.

“When we opened up the front door, the wind was blowing so fiercely, and there was so much smoke,” Ms. Sims said.

She fled at about 2 a.m. When she looked back, the neighborhood was glowing orange.

The winds that drove the fire from north of Calistoga to Santa Rosa are common in Northern California in October. At about 4:30 a.m. on Monday, these so-called Diablo winds reached a peak speed of more than 60 miles per hour, according to the National Weather Service.

The map below shows the wind conditions around this peak time.

Winds in excess of 50 miles per hour will cause flames to “sheet across the ground,” said Janet Upton, a deputy director of the California Department of Forestry and Fire Protection. “It was literally parallel to the ground, racing across, almost like water rushing across the ground.”

Many of the homes that were incinerated were inside what are called wildland-urban interfaces — areas where homes and businesses are close to or intermingled with otherwise undeveloped wildlands.

Development in wildland-urban interfaces increases frequency of fires and contributes to the ferocity of a fire, said Volker Radeloff, a forest and wildlife ecology professor at the University of Wisconsin-Madison.

“When you have more people in an area, the chances that something will go wrong and a fire will start is higher,” Dr. Radeloff said.

“It’s not only that the fires ignite the houses,” he continued, “but then the houses kind of fuel the fire.”

High-velocity winds in combination with this fire’s proximity to an urbanized area made it especially dangerous, said Jan Null, a meteorologist and adjunct professor at San Jose University.

A six-year drought was declared over in most of California in April, but dry vegetation still litters the state.

Record amounts of rain fell at the end of 2016 and in the beginning of 2017, which triggered new plant growth. Since then, there has been extreme heat and little rainfall, causing much of the new vegetation to become tinder dry by the fall.

Conditions were further exacerbated when the relative humidity reached single digits in recent days. Anything below 22 percent relative humidity means that there is a likelihood that something could ignite, said Ms. Upton of the California Department of Forestry and Fire Protection.

The dry conditions made it easy for the fire to spread as winds blew flaming embers onto withered trees, grass and brush.

“The fire had plenty of food to consume,” Ms. Upton said.