Atmospheric rivers are narrow and long streams in the atmosphere that carry substantial water vapor from the tropics to other regions. They resemble rivers in the sky. When they make landfall, they can release an enormous amount of water vapor in the form of intense rain or snow.

An atmospheric river, with high winds and heavy precipitation, drenched California on Monday and Tuesday, March 13-14. Some 30 million people were placed under flood alerts as the storm moved from north to south. Over 300,000 residents were left without electricity in the San Francisco Bay Area counties of San Mateo, Santa Clara, Alameda, Contra Costa, Solano and Marin. 

Further down the coast there were significant power outages in Monterey County. The Central California Coast, from Monterey down to Santa Barbara, was hit with unexpected amounts of rain, as was the Sacramento region to the east, together with the Central Valley cities of Fresno and Bakersfield. So far, the economic cost estimate for the San Francisco Bay Area exceeds $46 million.

In Los Angeles County, the Office of Emergency Management warned of potential mudslides in areas that had been previously devastated by wildfires.

This latest storm, the eleventh since December 2022, came on the heels of a previous set of storms that had saturated the soil and dropped large amounts of snow in the mountain areas. The combination of heavy rain, floods, mudslides and intense snowfall have killed 18 people so far this year. 

The damage estimate from the series of storms now stands at $31-34 billion, including homes and vehicles damaged or lost due to the extreme weather.

Monterey County is among the hardest hit by the latest wave of atmospheric storm systems. A previous storm last week had flooded over the Pajaro River Levee.

According to the Los Angeles Times, officials had known that the levee could fail, isolating the town of Pajaro, home to many migrant farmworker households, but they had chosen not to do anything, having determined that it was not worth the cost. “[T]hey believed it did not make sense to protect the low-income area, interviews and records show,” the Times noted.

Even before this series of intense storms, agricultural workers in California’s Central Valley and coastal areas had been hard hit by a three-year drought, which has damaged crops, caused wildfires and resulted in the destruction of towns and homes, heat strokes and the forced migration of farmworkers to other regions.

Adding to and compounding all that damage, the rain, snow, wind storms and floods are wrecking agricultural fields, as well as irrigation and farm equipment, causing even more misery. Not only are farmworkers’ jobs affected, their vehicles and homes have been damaged as well. 

A Los Angeles Times article published on January 21 interviewed Michael Méndez, a professor of environmental planning and policy at UC Irvine, who described the state of affairs in the fields. “We have compounding and cascading disasters from extreme storms, flooding, wildfires, heat waves and drought that are all impacting farmworkers. … This is just a part of the larger history of disproportionate impacts that this population is experiencing.”

According to Méndez, state and local authorities ignore the needs of farmworkers, many of whom are low-income undocumented immigrants, ineligible for unemployment benefits and health insurance.

Officials “have not provided enough resources, disaster planning, preparedness, translation services for these communities before a disaster happens,” he said. So, when disasters do strike, “the experiences are amplified because resources are often not targeted, or they’re withheld from these communities.”

In Southern California, Santa Barbara County issued evacuation alerts and orders for Monday and Tuesday, warning residents that those who did not evacuate may be left stranded for several days. A similar alert was issued to residents of Santa Cruz County. In all, over 70,000 people have received evacuation alerts.

California’s Democratic Governor Gavin Newsom requested emergency federal aid last week for 15 counties. Coastal residents have been advised to store up to two weeks of food and essential supplies in preparation for this and other upcoming storm systems.

Last week, mountain communities were hit by massive snowfalls. The current storm system is expected to bring even more. High elevations along the Oregon border to the north were expected to see at least a foot of snow, between one and six inches for lower elevations, both north and south. The Sierra Nevada Mountains could see more than a foot of snow.

Scientific studies from as far back as 2017 have warned that, while average rainfall numbers and the succession of dry and wet years would not necessarily change, as the result of human-driven climate change, so-called “mega storms,” with 30 or more days of continuous storms and floods, will become the norm. As the air warms, it can hold more moisture, which, also because of climate change, will fall more as rain than as snow, creating the danger of mega floods.

A January 2023 report by Yale Climate Connections discussed the very near-collapse of the Oroville Dam in Northern California that prompted the evacuation of 170,000 people and listed 15 other dams that are in danger of mega-flooding, including the Whittier Narrows Dam in Pico Rivera (Los Angeles County), which if it were to collapse would flood highly populated areas of southeast Los Angeles County and the city of Long Beach.

The economic costs of such mega storms would be in the $1 trillion range, with hundreds of casualties.