SoCal and Hillary: Not the apocalypse but a handful of places are going to get hammered

Eastern journalists have a tendency to get overwrought when it comes to Western weather, so let's all calm down and keep things in perspective.

Hillary is a fast moving tropical storm -- here in LA we're looking at a little over twenty-four hours of rainfall -- and the ground isn't saturated from earlier precipitation which bodes well for us evading catastrophic flooding. We have plenty of experience dealing with storms this bad or worse. With a few exceptions like Palm Springs, what's remarkable here is not the magnitude and the potential for damage, but the type and timing. We do get major storms out here, inevitably with flash floods, just almost never in August.

We have spent many years saying that the damage from atmospheric rivers is similar to hurricanes. Now we are getting a tropical storm in SoCal that is predicted to give us the sort of rain and wind that we see in a bad winter atmospheric river.

— Dr. Lucy Jones (@DrLucyJones) August 19, 2023

 That said, a few areas are going to see extraordinary, perhaps unprecedented amounts of water.

As alluded to from the Excessive Rainfall graphic, very heavy rainfall looks to target the mountains and deserts Saturday through Monday. Isolated areas in the mountains could receive 10+ inches of rainfall! #CAwx #Hilary pic.twitter.com/ZHOahei0tB

— NWS San Diego (@NWSSanDiego) August 18, 2023

Needless to say, infrastructure is virtually never designed to handle years worth of rain in a single day.

Some (if not many) CA inland empire and desert flood control systems will be undersized to contain runoff from Hilary. Extreme rainfall estimates used in civil design are smaller in Riverside and Palm Springs compared to Los Angeles. @NWSSanDiego @Weather_West @UCIrvine pic.twitter.com/hTOChU8fgL

— Brett Sanders (@UCIFloodLab) August 19, 2023

We're not talking about the kind of widespread devastation you see after a hurricane in the Southeast, but we may have some bad spots.

When people who aren't familiar with  the region try to write about LA and Southern California, they almost always fail to grasp the scale, the range, and the complexity of the place. Just in terms of Los Angeles terrain, we have valleys, mountains, beaches, high deserts and low deserts all of which can be different in terms of temperature, cloudiness, fogginess, and precipitation. It's not unusual to call someone else in LA and ask "how's the weather over there?"

Right now, the answer's not bad. We'll let you know if anything changes.