Only One Tropical Storm Has Ever Hit Southern California. Could Rachel Be Next?

While Hurricane Isaias is understandably grabbing all of the weather headlines this week, the western U.S. will be dealing with its own tropical weather impact. Here is a look at how what is left of the former Hurricane Rachel will impact the Desert Southwest beginning this weekend.

Rachel's Remnants Taking Aim at the Southwestern U.S. with Heavy Rain

The good news is that the heat wave is about to break across the Pacific Southwest. The bad news is that drenching rainfall and windy conditions will accompany the cooler temperatures.

Tropical Storm Rachel is currently churning over the Eastern Pacific, moving to the west-northwest at a slow crawl of 3 mph. Rachel is forecast to approach the West Coast later this weekend, potentially surviving as a tropical storm or depression when it moves into California.

California is not typically subject to tropical weather landfalls. The last tropical storm to come ashore intact in the Golden State was back in 1939. However, several major storms have come close to making landfall over the years. For instance, 2023's Hilary was downgraded to a post-tropical cyclone just before the center of the storm reached land. The heavy rain associated with Hilary triggered significant flooding and other impacts that lasted for days, proving that a feature can still wreak havoc after it is downgraded.

Although Rachel was less intense than Hilary at its peak, it is still forecast to usher in heavy rain and gusty conditions as it moves farther inland across the southwestern corner of the U.S. The expected interaction with a dip in the jet stream will amplify Rachel's impacts, giving it life as it tracks through the Desert Southwest and beyond.

Unlike Hilary, which was distinguished by its narrow rain path, Rachel's impacts could be more widespread. Forecasters are warning that those with outdoor plans will want to be aware of the likelihood of heavy rain falling at a rate of 1 to 3 inches per hour at times. Rain of this magnitude will inevitably raise the threat of flash flooding.

Flash Flooding, Mudslides, and Large Swells Likely 

A separate non-tropical storm will spread moisture before Rachel's arrival in the Southwest, priming the ground for flooding when the tropical moisture arrives. The silver lining is that the combination of Rachel and the secondary storm will break the stubborn heat dome that has been anchored over much of the West for more than a week.

Beachgoers in Southern California are being put on alert for incoming large swells and breakers throughout the weekend. Be sure to pay heed to all posted warnings if your plans call for time on the coast.

Los Angeles and San Diego will dodge the heaviest rain bands, but will still be soggy at times. Widespread rainfall totals of 1 to 2 inches are in the forecast for a zone from Baja California, Mexico, to the north into central Utah. Totals of 2 to 4 inches are likely near the center of the storm, while localized amounts of 4 to 8 inches could cause concerns in a concentrated zone of southwestern Utah and northwestern Arizona.

The threat of flash flooding and mudslides will be the highest in recent burn scar locations and through the canyons and arroyos that dot the landscape of the southwestern U.S. Cities that could see urban flooding include Phoenix, Flagstaff, Palm Springs, and Las Vegas.

The colder air associated with this weather pattern will also support the development of snow at the high and intermediate elevations of the interior West.

While the surge of tropical moisture will put a wrinkle in outdoor plans in the coming days, the rain is much needed for the drought-stricken Colorado River Basin. Water levels dropped to historic low levels this summer in the Colorado River, Lake Powell, and Lake Mead.

Elsewhere in the Eastern Pacific, Tropical Storm Simon is forecast to become a major hurricane by Saturday. The latest forecast models from the National Hurricane Center (NHC) signal that the system will make landfall in southwestern Mexico this weekend. The moisture coming along with Simon could creep as far as New Mexico and the Great Plains by early next week.

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