The first storm of the season swept through West Marin last week, unleashing fierce winds and three days of unrelenting rain. The deluge was tied to a powerful weather system churning over the northeastern Pacific Ocean just offshore of Oregon and Washington. According to meteorologists from the National Weather Service, the system set a record for the lowest barometric pressure reading ever recorded in that area of the ocean—plunging to 942 millibars, rivaling the intensity of a historic storm in the same region in October 2021. Barometric pressure, a key indicator of a storm’s strength, fell so dramatically that the system qualified as a bombogenesis, or what is popularly known as a “bomb cyclone.” The term is used for storms that undergo rapid intensification, with their pressure plummeting at least 24 millibars within 24 hours, explained Nat Johnson, a meteorologist with the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Lab. The storm’s dramatic intensification was further energized by the presence of an atmospheric river, a concentrated plume of water vapor that transports heat and moisture from the tropics toward the poles. Bomb cyclones are more likely when an atmospheric river is already present, Mr. Johnson said. The 2021 storm also had an atmospheric river attached to it, which brought extreme winds, power outages and flooding to West Marin. This time, however, areas north of Marin bore the brunt of the storm, sparing our coastline from the worst impacts, said Dylan Flynn, a meteorologist with the National Weather Service in the Bay Area. Even so, more than a month’s worth of precipitation fell in just three days; the storm brought down trees and power lines and caused minor flooding of roads, the Inverness Store, and the Olema Campground and Post Office. (Power remained on for most residents.) In just three days, the storm produced between 20 and 30 percent of the region’s typical annual rainfall, Mr. Flynn said. Point Reyes Station recorded a staggering 12.45 inches of rain from Wednesday through Friday—more than four times the typical November average of 2.9 inches, according to the National Weather Service. Mr. Flynn characterized it as a once-in-a-century storm. By Friday evening, the axis of heavy rain had shifted southward, and by Saturday, the skies had cleared to reveal vivid rainbows and cotton-like clouds drifting across a cerulean sky. A smaller system brought showers to the area on Monday and Tuesday. Seasonal forecasts initially predicted this winter’s storms would favor the Northwest, a hallmark of La Niña conditions, in which cooler-than-average equatorial sea-surface temperatures push the jet stream northward, leading to wetter weather in the Northwest and drier weather in the Southern United States. But for now, the “Pacific remains in a neutral phase, with no particular push from the tropical Pacific one way or the other,” Mr. Johnson said. While La Niña could still emerge in the next couple months, “it’s currently neither La Niña nor El Niño, making weather patterns less predictable,” he said.