A Storm Born in Warm Waters Sets Its Course for a Coast That Rarely Knows Such Visitors

There is a particular strangeness to the weather when the calendar and the elements disagree—when October arrives not with the crispness of autumn but with the humidity of the tropics, when a storm born in warm Pacific waters sets its course toward a coastline that has not known such a visitor in nearly a century. San Diego County is preparing for precisely such a moment.

The National Weather Service issued a tropical storm watch for San Diego County on Friday morning, only the second time in recorded history such an alert has been issued for the region . The first came in 2023 for Tropical Storm Hilary, which had weakened to a post-tropical low before reaching California . This time, forecasters say Tropical Storm Rachel could maintain its tropical characteristics as it approaches the U.S.-Mexico border, making landfall potentially as the first tropical storm to strike California since September 25, 1939 .

The storm was located approximately 840 miles south-southwest of San Mateo Point on Friday morning, carrying maximum sustained winds of 50 mph and moving northeast at 5 mph . Forecasters expect it to make landfall near Tijuana or just south late Saturday night before racing northward, its moisture plume spreading across Southern California and into the desert Southwest .

The timing of Rachel's arrival is significant because it follows an early-season trough that has ended a record-breaking autumn heatwave. That pattern shift—from unseasonable heat to tropical moisture—has created conditions where the atmosphere is primed for heavy rainfall. The Weather Prediction Center now forecasts 1 to 3 inches of precipitation over coastal Southern California by early Tuesday, with the heaviest rain expected Sunday . The National Weather Service's most likely scenario brings 0.25 to 1 inch to San Diego's coast, valleys, and deserts, with 1 to 2 inches in the mountains. A higher-end scenario could bring 1 to 2 inches to lower elevations and 2 to 4 inches to the mountains .

But rain may not be the primary concern. Coastal flooding is expected to be the most significant impact, according to meteorologist Miguel Miller. "We've got water that's already high and then we're going to have periods of high tides each morning and evening and then on top of that we have high surf," he said. "We have all these things stacking up on each other" . The combination of tropical storm swell—5 to 7 feet with local sets to 9 feet—alongside seasonal high tides near 7 feet and elevated sea levels from El Niño conditions has created what forecasters describe as high confidence in impactful coastal flooding .

Wind represents another hazard. Sustained winds of 39 mph or greater are expected on the southeastern side of the storm, with stronger gusts possible in higher terrain and the Mojave Desert . The weather service warned of potential damage to porches, awnings, carports, and unanchored mobile homes, as well as large tree limbs broken off and a few trees snapped or uprooted, particularly in coastal and valley locations that do not typically experience strong winds .

The storm's reach will extend well beyond San Diego. Orange and Los Angeles counties are expected to see periods of rain, dangerous surf, and beach erosion . Inland areas including the San Bernardino Mountains, Palm Springs, Las Vegas, and Phoenix face a slight risk of flash flooding . The Mojave Desert and Inland Empire could see more significant precipitation than coastal areas .

For a region more accustomed to drought than deluge, the weekend ahead represents a rare convergence of tropical energy and temperate latitude. The storm will weaken and lose its tropical characteristics after landfall, but its moisture will continue moving inland through Monday . Residents are advised to monitor forecasts, avoid the ocean if rip current warnings are issued, and prepare for possible power outages and travel disruptions .

AI Image Disclaimer: The visuals in this article were produced using artificial intelligence and are intended solely for illustrative purposes.

Sources: Center for Western Weather and Water Extremes, Los Angeles Times, The Weather Network