King tides have swamped parts of both U.S. coasts this week, sending seawater across streets and into homes and businesses in beach communities in California, Florida and the Carolinas. Forecasters said some areas could see flooding into the weekend.
The tides began with the full moon earlier this week. King tides result from the gravitational pull and alignment of the Earth, moon and sun. They can happen several times a year and last for several days. Forecasters said on Wednesday that additional factors have made this week's events worse.
In Florida, strong high pressure to the north combined with low pressure over the Caribbean to increase swells, said Chris Fisher, a National Weather Service meteorologist in Miami. On the California coast, the ongoing super El Niño has warmed the ocean and increased the volume of seawater. Roger Gass, a meteorologist with the weather service's Bay Area forecast office in Monterey, pointed to another contributor: Kelvin waves, a series of pulses of warm water that raise the sea level.
In Southern California, Huntington Beach residents put sandbags outside their homes on Wednesday in an effort to keep floodwaters out. Some people got around the streets on paddleboards and surfboards. Stretches of the Pacific Coast Highway were closed, and tides were expected to approach record levels in Orange and San Diego counties.
Farther north in the state, the weather service expected minor flooding through Saturday in low-lying areas along shorelines and tidal waterways during peak high tides. Gass said coastal flooding generally occurs within an hour and a half before and after high tide. In Northern California, the high tides are peaking 1.9 feet (about a half-meter) above normal.
Most of Florida's Atlantic coast was under flood warnings through early Friday. Street flooding was also reported in South Carolina coastal cities, including Charleston and Myrtle Beach, and rip currents were possible as far north as North Carolina's Outer Banks.
"It's been a rough beach week," Fisher said. "We've had a high risk of rip currents and some high surf out there. The beach conditions are going to continue to be rough through the weekend. It's been a good week to stay out of the water and stay away from the beaches."
In Fort Lauderdale, Florida, reaching the multiple waterfront venues of what is billed as the world's largest in-water boat show was difficult, requiring drivers to pass through flooded streets beside marinas, hotels and convention centers.
Virginia Key, a barrier island in Miami, recorded its highest king tide and its third-highest water level since records began three decades ago, Fisher said. "The only times we've seen higher was during hurricanes," he said. "It's historical from a king tide perspective."
