Hurricane Hilary is building around Baja right now, but forecasts show it could head straight towards us here in Southern California in the coming days.
Its exact path is still up for debate, but it’s looking pretty likely that it’s going to drop heavy rain and cause substantial flooding in California, particularly out in the desert, where up to 6 inches is possible.
It’s not often that we find ourselves talking – and worrying – about hurricanes here in Los Angeles, which got us wondering: Just how rare are these types of storm systems here?
“So far this season has played out as expected,” said Jamie Rhome, deputy director of the National Hurricane Center.
To learn more, we reached out to a handful of experts to help fill us in.
Where’s the hurricane coming from?
It’s spinning up off the southwest coast of Mexico, a very common area for tropical storms to form between May and November. Usually they head west, out into the Pacific Ocean. Sometimes they head up into the Baja peninsula and on rare occasions head all of the way to the southwestern U.S.
As one expert pointed out, we’re already at the letter ‘H,’ for this hurricane season — tropical storms are named alphabetically as they occur throughout the year — so these storm systems can’t be all that rare. Bet you may have missed news about "Greg."
How often does this happen in SoCal?
“It’s not typical, but not unorthodox,” said Rhome.
These large, sprawling tropical cyclones can have considerable impacts hundreds of miles away from their centers. Just last year, Hurricane Kay dropped over 5 inches of rain, damaged homes and caused flooding and debris flows.
“Generally speaking, Southern California receives more of the glancing blow from these systems,” Rhome said.
However, Hilary’s forecasted track — with its center smashing into Southern California — is a bit unusual. We haven’t had a tropical storm make landfall locally since 1939 in Long Beach, according to the National Weather Service in Oxnard.
What’s the difference between a tropical storm and a hurricane?
Wind speeds.
Both are tropical cyclones. Here’s how NOAA defines the differences:
- Tropical depression – wind speed less than 39 mph
- Tropical storm – wind speed between 39 mph and 73 mph
- Hurricane – wind speed between 74 mph and 110 mph
- Major hurricane – wind speed greater than 110 mph
Will it be a hurricane by the time it reaches California?
The circulation will get weaker as it reaches cooler waters to the north. It’ll also lose energy as it moves over land and is likely to be downgraded.
Interestingly enough, our mountainous terrain will also take a toll as it disrupts the storm’s wind fields, according to Paul Iñiguez, meteorologist with the Center for Western Weather and Water Extremes at the Scripps Institution for Oceanography.
“They’re large speed bumps in the air basically,” he said. “That’s another reason why it’s hard for these systems to maintain themselves if they go further north.”
The rain from Hilary could also be amplified by another weather system sitting off the coast of California. Forecasters are predicting as much as 6 inches of rain in some areas.
Will Hilary still present a hazard even if it’s downgraded to a tropical storm?
Yes, just because wind speeds will have slowed, it doesn’t mean that this storm’s not a risk. There are flood watches in effect across the region from Saturday to Monday.
Here's the latest rainfall totals and flash flood risk for Hurricane #Hilary. The current track has the center making landfall near San Diego Monday at 6 am, as a tropical storm. Shifts in the track to the east or west could increase impacts for our region. #LArain #CAwx pic.twitter.com/8Q8AWVORU0
— NWS Los Angeles (@NWSLosAngeles) August 17, 2023
“I think the rain’s going to be the biggest deal that will wind up happening,” said Iñiguez.
“People tend to be very focused on the wind, and the winds with tropical systems can have hazardous impacts. But the flash flooding and heavy rain that comes with tropical systems tends to cause more widespread damage and deaths than the winds actually do.”
We generally don’t see this much rainfall during this time of year. Debris flows and flash floods will be possible, especially in burn areas.
Hazardous marine conditions are also a concern.
Could the storm track still change?
Yes. As of this writing we’re still four days out. It’s not clear exactly where the center of the system will go, but even a change of 50 miles or so can have sizable impacts on local weather.
Is this storm related to El Niño?
Generally speaking, the eastern Pacific is a bit more active than the Atlantic during El Niño years in part due to warmer-than-normal waters and weaker trade winds.
So far, this season has been quite active.
How much is climate change playing a role?
“Previous work has shown that there is a link between climate change and an intensification of hurricanes,” said Janine Baijnath-Rodino, director of meteorology at the Atmospheric and Oceanic Sciences Department at UCLA.
“For hurricanes to form, three main ingredients are needed, including warm surface temperatures, thunderstorms or tropical disturbance already in place, and small differences in wind speed and direction. Some of these key ingredients can be exacerbated with climate change.”
All that said, it’s difficult to attribute any single weather event to climate change, especially as it’s happening.
