In Philadelphia, winds from the northeast are the bearers of rain, snow, and ice. In California, are the bearers of yet more wildfire dangers.

Around here, high pressure, or cloud-suppressing heavier air, usually is associated with benign weather. In California, it can be a tormentor.

The winds that have fanned the wildfires north of Los Angeles and in central California, and forced mass evacuations are forecast to intensify Saturday night, with gusts up to 80 mph.

The National Weather Service Office in the San Francisco on Saturday warned of “a potentially historic, long duration, extremely critical offshore wind event” Saturday night through early Monday.

The computer model output “reveals a scary situation developing over northern California,” according to Cliff Mass, a University of Washington researcher and specialist in the western climate.

And fire dangers are likely to persist for the next three weeks, said Alex Sosnowski, senior meteorologist at AccuWeather Inc., the fire risk is likely to persist for the next three weeks.

“They’ve got to get some rain,” he said. But no significant rain is on the radar through mid-November.

Even by California standards, this has been a bone-dry month. At the Santa Rosa airport, north of San Francisco, for example, a mere 0.02 inches of rain has been measured since Oct. 1; the normal is 1.25.

Los Angeles isn’t exactly a rain forest in October, but the current monthly total stands at 0.00. Relative humidities on Friday at the Camarillo airport, northwest of L.A., which recorded a record high temperature of 99 degrees on Thursday, were in the single digits.

And dryness has been a growing trend nationally in the last three months, according to the U.S. Drought Monitor, a government-academic partnership.

In July, it classified less than 10% of the country as “abnormally dry.” That figure has since grown closer to 40%, one of the biggest three-month jumps in records that date to 2000.

“It’s amazing how things can turn around that quickly,” said Sosnowski, senior meteorologist at AccuWeather Inc.

Despite all the recent rains that likely will bump Philadelphia’s monthly total well above near normal, the region experienced a bone-dry September and remained in the Drought Monitor’s “abnormally dry” and “moderate drought” zones in the most-recent update.

The dry zone has nosed into eastern California, and although it hasn’t yet reached the West Coast, dryness is a fire collaborator.

The big player is high pressure building from the Pacific to the Great Basin.

Working in tandem with a storm over the Rockies, it is forecast to help generate powerful “El Diablo” winds, with the National Weather Service in San Francisco calling for gusts up to 80 mph in the hills.

The government’s Storm Prediction Center has placed parts of the region in the “critical” and “extreme” fire-danger zones.

Parts of California are in the government's "critical" and "extreme" fire-danger zones.
Parts of California are in the government's "critical" and "extreme" fire-danger zones.

Some of those winds are forecast to howl out of the northeast Saturday night and Sunday. Around here, those would be blowing off the Atlantic Ocean; in California, that would be land. Thus the “red flag” warnings.

Fortunately, so far the fires haven’t been as destructive as those in recent years, but they are a seasonal hazard in California, and the “Santa Ana” winds to the south were forecast to weaken after dark Friday.

The fires are a seasonal hazard, and climate change affecting temperatures and precipitation patterns wouldn’t be the only contributors to their severity, says Mass.

Besides climate change, the human imprints are unmistakable, he said. They include “mismanagement” of wild areas, and the introduction of “invasive and often highly flammable” non-native species, such as eucalyptus.

They also include the obvious: increasing population and increasing vulnerability.