How wet is this year’s rainy season?

Sonoma faced powerful atmospheric rivers last year. Data from the National Weather Service show the 2024 water year is progressing at a more gradual pace.|

Winter rains have been an oracle of sorts for Sonoma Valley, creating the conditions for the next fire season, the next grape harvest or the next drought.

Now at the midway point of California’s rainy season, when the state receives approximately 80% of its annual rainfall, according to U.S. Climate Data, the predictions for the next year are growing clearer.

“We're running about anywhere from 90% to 110% of average currently,” National Weather Service meteorologist Roger Gass said. “We're kind of in back-to-back years of having at or above-average rainfall. And that definitely will help out the local growers.”

The Index-Tribune mapped the past five years of National Weather Service data between Oct. 1 and Jan. 31 to provide context for how 2024’s water year is shaping up for the agriculture industry, fire districts and Sonoma County’s reservoirs.

The beginning of the time period reviewed by the Index-Tribune shows depressed levels of rainfall as Sonoma County and huge swathes of California faced intense drought between 2019 and 2022.

But California had one of its wettest years on record in 2023. A series of atmospheric rivers flooded coastal and low-lying areas of Sonoma County and ended a 3-year long drought across the state of California. Combined with a colder than average winter, last year in one of the largest snow packs on record in the Sierra Nevada mountain range.

This winter, California is facing an El Niño weather system bringing warm, wet air near the equator above the Pacific Ocean toward the West Coast. The World Meteorological Organization expects El Niño conditions to last through April 2024, which will increase the likelihood of precipitation and warmer-than-average temperatures.

“We are anticipating additional storm systems to move through the region, at least within the next month,” Gass said. “And that's going to only add to those totals and increase them to higher levels.”

Gass said these winter conditions will promote grass and foliage growth throughout the winter. This could benefit grape farmers during the growing season and indicates drought will remain at bay for the near future.

But the threat of fire remains unclear until future weather conditions crystallize in late summer and early fall when dried grass becomes fuel for fires, Gass said. Past El Niño winters have been followed by historic wildfires that feed off the increased access to fuel.

If the summer is especially dry and windy, Gass said, the climate could produce conditions for increased fire risk.

Early atmospheric projections by the National Weather Systems show the El Nino weather system will be replaced in late summer and early fall by the La Niña system, which brings dry and cool conditions.

“We are projected to go into more of a neutral and then the La Niña pattern as we head into the fall months, and so that does raise a little bit more of concern,” Gass said. “The weather patterns that set up in the fall are more directly correlated to how bad the fire season is.”

Chase Hunter covers the Sonoma city government, crime, agriculture, housing and homelessness. Contact the reporter at chase.hunter@sonomanews.com.

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