In the hours before fierce Santa Ana winds swept through the canyons of Los Angeles, setting homes ablaze and claiming lives, we felt the Diablo winds here.
But they only created waves in mud puddles. They moved the heavy leaves of the drenched trees. They warmed our yards and sent fresh breezes through the air, frivolously scented with the scent of early manzanita and daffodil blossoms.
“The same weather system that produces Santa Ana winds also produces Diablo winds, often 12 to 24 hours earlier,” said atmospheric scientist Neil Lareau of the University of Nevada, Reno. We will proceed to see stronger northeasterly winds across the Bay Area in the approaching days.
But there’s one crucial difference: It rained here, but not in Los Angeles. That set the stage for the deadly inferno in Southern California. As of Friday, the fires in Los Angeles County had killed at the least 11 people, destroyed at the least 9,000 buildings and compelled greater than 100,000 people to evacuate.
The Diablo and Santa Ana winds, officially classified as Foehn winds, are an ancient meteorological phenomenon.
Just as water tends to hunt its own level, air also desires to equalize its pressure and flow from areas of high pressure to areas of low pressure, said Jan Null of Golden Gate Weather Services.
“Everything is trying to achieve balance,” he said.
The winds originate within the deserts of the northern Great Basin, where high pressure builds up. This strong high pressure system occurs more often within the cooler seasons.
Then they race west toward low pressure systems along the California coast. Called “inside sliders,” they fall down the edges of the Sierra, gaining speed as they go.
They then go through mountain passes akin to Soledad Pass, Cajon Pass and San Gorgonio Pass in Southern California, where the so-called Venturi effect accelerates their speed. They also contribute to large offshore waves on the coast and potentially dangerous conditions.
Winds gusted between 50 and 70 mph at lower elevations Wednesday evening, peaking at 80 to 100 mph within the Santa Monica Mountains – the equivalent of a powerful Category 1 hurricane.
According to Lareau, the recent winds were so strong that they reached and descended the San Gabriel Mountains, quite than simply blowing through passes.
“The winds are at the upper end of the spectrum for Santa Ana winds, but are not unprecedented or beyond our expectations,” Lareau said.
An identical phenomenon might be observed in other mountainous areas around the globe. In the Rocky Mountains we speak of the Chinook wind; within the Alps it is known as favogn; within the Andes it is known as Puelche.
As the air sinks and condenses right into a low-pressure trough, it warms.
While much of the country is affected by cold, snow and ice, temperatures reached a balmy 73 degrees in San Jose on Friday. It was 68 degrees in Oakland. Even San Francisco felt comfortable at 59 degrees.
But because the temperature increases, the relative humidity decreases. Fuels with 20% moisture can catch fire; Light fuels with 2% moisture can burn like gasoline.
They contributed to a few of the most devastating wildfires lately, akin to the 2017 Tubbs Fire, which destroyed parts of Santa Rosa, and the 2018 Camp Fire, which destroyed the town of Paradise.
The exact trajectory and strength of the winds may vary. They are influenced by the strength and placement of the Great Basin High and the strength and placement of the low pressure system to the southwest.
In the Bay Area, the present often changes because it meets the Coast Range, which might guide wind over ridges and canyons.
This pattern occurs most frequently in the autumn when the polar jet stream moves seasonally south.
(In spring and summer all the pieces turns around. The air flows eastwards from the ocean towards the inland valleys, creating afternoon breezes and thick fog.)
While the Diablo and Santa Ana winds are strongest in the autumn, their frequency and intensity proceed throughout the “cold season.” A study by Carrie Bowers of San Jose State University found that the common monthly variety of Diablo wind events is higher in January than in November and about 80% as frequent as the height month of October.
In the autumn, they keep us on high alert. The nerves are nervous. A faint smell of smoke causes discomfort.
But in January the threat is less noticeable because the landscape is normally wet. For example, San Francisco International Airport received 107% of a yr's average annual precipitation.
There has been little rain in Southern California, leaving many of the region extremely dry.
The conditions that worsened the wildfire, rising temperatures and dry fuels, are all symptoms of the planet overheating.
On Friday, climate researchers reported that the Earth's average temperature rose greater than 1.5 degrees Celsius above pre-industrial levels for the primary time in 2024. The data reported by the World Meteorological Organization represents only one yr, but adds to mounting evidence that the world is moving into dangerous territory, perhaps faster than previously thought.
“When the conditions come together for these really strong events,” akin to extreme and adjoining high and low pressure systems, “we can get very strong winds in places like Pasadena, which are often more sheltered.”
“But the real problem,” he added, “is the state of the fuels. “Due to the extreme lack of rain in Southern California, it is critically dry.”
Originally published:
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