Tropical Storm Rachel pushes towards California and Arizona with rare strength
Abnormally warm seas are sustaining the cyclone as it threatens coastal flooding in San Diego and flash floods across Arizona.
Tropical Storm Rachel is bearing down on Southern California and the American South-west, threatening coastal communities with severe sea surges and spreading heavy rain and high winds deep into Arizona.
The system could make landfall in northern Baja California or San Diego County as early as Saturday night, according to the National Hurricane Center. Tropical storms in the eastern Pacific usually unravel quickly when they hit cooler northern waters, but Rachel is drawing power from an intense marine heatwave and strong El Niño conditions that have left ocean waters 10 to 13 degrees Fahrenheit warmer than average.
Forecasters at the National Weather Service in San Diego have issued a tropical storm watch covering most of San Diego County, including Chula Vista, Carlsbad and Oceanside. It is only the second time such an alert has been called in California's modern record.
What is happening on the California coast
Coastal flooding is already spreading through beach towns before the storm's centre arrives. In Long Beach, city officials ordered mandatory evacuations along Seaside Walk between 64th and 66th Place. Streets in downtown Laguna Beach and Newport Beach were submerged on Friday morning as high tides collided with storm swells.
Tide gauges have measured water running well above standard charts: 17 inches higher than predicted in San Diego and La Jolla, 16 inches in Santa Monica and 14 inches in San Francisco. A coastal flood advisory covering Ventura, Los Angeles, Orange and San Diego counties remains in place until Tuesday afternoon.
Only two storms in modern recorded history have retained tropical-storm strength inside California: the 1939 Long Beach tropical storm, known as El Cordonazo, which caused dozens of deaths, and Hurricane Nora in 1997 along the Arizona border.
Rain in Southern California will be heaviest inland. While metropolitan Los Angeles expects between a quarter of an inch and an inch, the weather service warned of a 40 per cent chance of flash flooding across San Diego County, the Inland Empire, Palm Springs and the Mojave Desert. The San Diego River near Fashion Valley may reach minor flood stage.
What to expect in Arizona
As Rachel's outer moisture pushes east, Arizona faces several days of severe weather. Flood watches cover much of northwestern Arizona and sections of the Mogollon Rim from Saturday morning through Sunday evening, with forecasters warning that dry desert washes, swimming holes and recent wildfire burn scars could turn dangerous rapidly.
The Phoenix metropolitan area is forecast to receive half an inch to an inch of rain between Saturday and Tuesday. State-wide wind advisories take effect on Sunday, with sustained winds forecast to reach 35 mph and gusts touching 50 mph.
The storm will also break the regional heat, dropping daytime highs in the Valley into the 80s on Sunday and into the 70s by the middle of next week.
Key numbers
| What | Figure | Source |
|---|---|---|
| Sea surface temperature anomaly | 10 to 13 degrees Fahrenheit higher than normal | National Hurricane Center and climate scientists |
| Observed high tide anomaly in San Diego | 17 inches above predicted levels | National Oceanic and Atmospheric Administration tide gauges |
| Expected wind gusts in Arizona | 40 to 50 mph | National Weather Service |
| Rainfall forecast for Phoenix area | 0.5 to 1 inch | National Weather Service |
In this story
| Name | Role in the story |
|---|---|
| Arizona | State facing flood watches, high winds, and heavy rain from storm moisture |
| Tropical Storm Rachel | Tropical cyclone tracking towards Southern California and Arizona |
