Hurricane Hilary is expected to complete its march toward Southern California today, and while it is a relatively mild hurricane by east coast standards, experts warn that it could nonetheless be extremely deadly due to features of California’s geography that could cause “devastating” flooding due to an expected 10 inches of rainfall.
Rain has already fallen in dangerous amounts across the southwest in advance of Hilary’s landfall, as much of the region has been under flash flood warnings throughout most of the weekend. As Hilary makes landfall, the National Hurricane Center warned Saturday that the situation would get works, leading to likely “catastrophic and life threatening-flooding… over Baja California and the Southwestern U.S. through Monday.”
The bulk of the rainfall is expected to come in two waves: one Sunday morning, and the second Sunday afternoon into Sunday night. The second wave is expected to bring the most intense rainfall as well as damaging winds. Expert’s estimate that rainfall rates during the second wave could reach 1 to 3 inches per hour.
Due to the combination of mountain runoff and desert terrain without adequate drainage basins, the conditions are expected to create not only catastrophic flooding but also potentially deadly mudslides and landslides. Disruptions to travel routes, including widespread road closures, are also expected. These closures will likely cause complications for any rescue and relief efforts that may need to be undertaken. Additionally, the risk of flooding aftershocks is not likely to abate for several days.
According to the Washington Post, a National Weather Service spokesperson said, “By day three [post storm], whatever falls will flow. We’re talking several inches of rain completely flowing into Death Valley, which is incredibly vulnerable to flash flooding.”
Officials are urging the public to prepare for the eventuality of widespread and prolonged disruption of travel routes, including having necessary devices fully charged, and having multiple ways to receive emergency information including battery powered radios.