A windstorm experts called “life-threatening” and “destructive” prompted warnings across Southern California Tuesday and highlighted in the forecast was a meteorological phenomenon known as “breaking mountain waves” that could wreak havoc on Southern California.
The NWS predicts 100 mile per hour winds to bombard the tops of the San Gabriel Mountains Tuesday afternoon, which can cause standing mountain waves. This occurs when strong winds hit a mountain range perpendicularly, causing air to repeatedly rise over the mountains and then swing back down, similar to ocean waves, meteorologists said.
“If you’re standing on a mountain and you look forward, the wind goes in a vertical circle, like a wheel,” NWS meteorologist Kristan Lund said. “It causes really gusty and erratic winds.”
When “there is enough moisture in the air, standing mountain waves can be seen by lenticular clouds, which are smooth and nearly stationary formations”, according to the NWS forecast.
Similar to how ocean waves crash when they become too big, standing mountain waves can break, pushing high air speed down the mountain. This is likely to cause damaging winds between 80 and 100 miles per hour into the foothills. Lund said winds of that speed could cause significant damage, such as knocking large trees down, which has already been reported in Pasadena. There is also a possibility of damage to structures, power lines and difficulties for drivers in maintaining control over their vehicles, Lund said.
“It’s not necessarily rare in terms of wind speed, it’s more rare of how expansive it is,” Lund said. “We’re seeing it in areas that might not necessarily see winds in a typical Santa Ana.”
The greatest concern is for the following areas: Highways 118/210 corridors, San Gabriel, Santa Susana, Santa Monica Mountains and foothills, San Gabriel and San Fernando Valleys, Pasadena, Burbank, Hollywood, Beverly Hills, Simi Valley, Sylmar, Porter Ranch, Altadena, La Crescenta and Malibu.
The strongest winds are expected to continue through Wednesday afternoon. Residents across Southern California, especially those in areas flagged with an extreme risk, should stay indoors and away from windows and prepare for potential power outages.