Devil winds stoke hellish con­di­tions

Low hu­mid­ity con­trib­utes to blaze con­sum­ing wine coun­try

USA TODAY International Edition - - FRONT PAGE - Doyle Rice @us­ato­day­weather USA TO­DAY

A bru­tal com­bi­na­tion of fe­ro­cious winds and near-record low hu­mid­ity fu­eled the deadly wild­fires that are scorch­ing North­ern Cal­i­for­nia’s wine coun­try and leav­ing a breath- tak­ing trail of de­struc­tion.

Fierce north­east “Di­ablo” winds that cir­cu­lated around a ridge of high pres­sure over the Great Basin blew through the re­gion late Sun­day, said Brian Me­jia, a Na­tional Weather Ser­vice me­te­o­rol­o­gist in Mon­terey, Calif.

The winds al­lowed the run­away fires to jump fire lines and dec­i­mate en­tire neigh­bor­hoods, seem­ingly com­ing out of nowhere and caus­ing res­i­dents to run for their lives in the mid­dle of the night — the worst pos­si­ble time for such an emer­gency.

The toll on Tues­day was stag­ger­ing and could get worse from the more than a dozen blazes, of­fi­cials warned: 15 peo­ple killed, more than 100 in­jured, more than 2,000 busi­nesses and homes

This is a “clas­sic wild­land fire pat­tern in Cal­i­for­nia.”

Jan Null, Golden Gate Weather Ser­vices

de­stroyed.

Through much of the sum­mer, winds blow into Cal­i­for­nia from the ocean. But winds can switch in late Septem­ber or early Oc­to­ber to north­east­erly from the bone-dry deserts of Ne­vada or Utah. This is a “clas­sic wild­land fire pat­tern in Cal­i­for­nia, af­ter five months of dry weather plus high pres­sure over the Great Basin, creat­ing warm, dry winds,” said me­te­o­rol­o­gist Jan Null of Golden Gate Weather Ser­vices.

In ad­di­tion, as the winds howl down from the moun­tains to­ward coastal ar­eas, they are com­pressed and be­come warmer. Then, as winds squeeze through canyons and val­leys, they speed up, fur­ther fan­ning the flames.

Me­jia said sus­tained winds were at least 40 mph in some spots; one gust reg­is­tered as high as 79 mph in north­ern Sonoma County.

Ear­lier Sun­day, the weather ser­vice had is­sued a “red flag” warn­ing for the area, mean­ing con­di­tions were ripe for the spread of wild­fires.

Ex­tremely low hu­mid­ity — in the sin­gle dig­its, which is un­usual for the area — also was a fac­tor, Me­jia said. Low hu­mid­ity helps dry out vege­ta­tion, which makes it bet­ter fuel for fires.

A record wet win­ter of 2016-17 also al­lowed plenty of trees and brush to grow this spring, which be­came po­tent wild­fire fuel.

The weather was sim­i­lar to the con­di­tions that led to the most de­struc­tive fires in Cal­i­for­nia his­tory: the Oc­to­ber 1991 firestorm that struck the Oak­land and Berke­ley hills. The blaze killed 25 peo­ple and de­stroyed 2,900 struc­tures.

Oc­to­ber is al­ways a dif­fi­cult time in Cal­i­for­nia for wild­fires, but this year the wild­fire erup­tions seem ex­treme even to the most sea­soned Cal­i­for­nian.

The fires that roared across North­ern Cal­i­for­nia prob­a­bly were not started by light­ning, ac­cord­ing to the weather ser­vice, which did not de­tect any strikes late Sun­day or early Mon­day. That means the spark for the blazes prob­a­bly was man-made, whether ac­ci­den­tal or de­lib­er­ate.

That isn’t sur­pris­ing: About 84% of wild­fires in the United States are started by peo­ple, ac­cord­ing to a comprehensive study this year that was pub­lished in the Pro­ceed­ings of the Na­tional Academy of Sciences.

Of­fi­cially, the cause of the fires re­mained un­der in­ves­ti­ga­tion, said Barry Bier­mann, deputy in­ci­dent com­man­der for the Cal­i­for­nia De­part­ment of Forestry and Fire Pro­tec­tion. But he wouldn’t say the rash of fires seemed sus­pi­cious.

“The wind were ex­tremely er­ratic,” he said. “Dur­ing those con­di­tions of high winds, it doesn’t take much to start a fire.”

JEFF CHIU, AP

Mary Caughey finds her wed­ding ring as res­i­dents sift through de­bris Tues­day in Ken­wood, Calif.

JOSH EDELSON, AFP/GETTY IM­AGES

Flames over­take a struc­ture as nearby homes burn Mon­day in the Napa wine re­gion in Cal­i­for­nia. Wind-driven fires whipped through the re­gion.

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