A slow moving upper level low pressure system moved onshore during the previous day. This system was enhanced by subtropical moisture, which helped increase the threat of heavy rainfall during the day.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS HNX wrote it up.
A slow moving upper level low pressure system moved onshore during the previous day. This system was enhanced by subtropical moisture, which helped increase the threat of heavy rainfall during the day. Afternoon thunderstorm activity was anticipated due to heating and orographic lift.
The Los Angeles radar (KVTX), 74 km away, was scanning. The volume nearest the first event began at 20:59 UTC.
4 flash flood. Local standard time, as filed.
Public reported flash flooding on state road 33 near Maricopa. This lead to the roadway closing.
California Highway Patrol reported mud and debris flowing across Interstate 5 around the Tejon Pass on the Grapevine. This report was also followed by numerous reports on social media and TV media.
Numerous social media and later TV media reported mudslide along Highway 58. The area had experienced some heavy rainfall through out the afternoon. Then a heavy convective shower developed near a burnt area from years prior. This allowed a large debris flow to develop and move into the Tehachapi area. This area is a known alluvial basin that can develop quick flowing flash floods, but the amount of mud and debris with this event was on the order of four to six feet deep. This trapped multiple vehicles and closed the roadway for multiple days. One individual was reported later to have been swept away during the event, with no recovery made to date.
Public reported flooding at the State Road 99 and State Road 198 interchange. This area was closed due to the flooding that occurred. This area was under construction during time of this event with bare soils on the side of the roadway. Crews were able to get the road open quickly once storm drains were opened.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2015Every state in 2015This day in weather historyWarnings in California, October 2015
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 605776, 605777, 605781, 605784.