Palm trees bend in the wind as powerful winds forced Southern California Edison to shut off the power to the area on Thanksgiving day Nov. 24, 2022 in San Jacinto, California.
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Gina Ferazzi
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Los Angeles Times via Getty Images
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Topline:
Between Tuesday and Wednesday this week, the National Weather Service has issued a "particularly dangerous situation" warning for L.A. and Ventura counties — otherwise known as a PDS. So what is it?
Why it matters: A PDS warning was issued for last week's historical wind storm behind the Palisades and Eaton fires.
The backstory: The "PDS" label was already in use by National Weather Service to describe other weather hazards. The tag was adopted for fire weather starting in 2020.
Read on... to find out more about what a PDS is.
The National Weather Service uses a number of shorthands to warn the public of adverse fire weather conditions.
For example, we've been hearing a lot about red flag warnings — a combination of heat, winds and low humidity that could lead to bad fires.
What is a "particularly dangerous situation" alert?
Areas expected to be most impacted by dangerous winds starting on Tuesday.
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National Weather Service
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Think of it as the Olympic gold of fire weather warnings, says National Weather Service meteorologist Ryan Kittell.
Kittell said the "PDS" label was already in use by the National Weather Service to describe other weather hazards.
In October 2020, the weather service started adopting it for fire conditions. Two months later, the second one was issued.
In 2020, "when we saw just an extreme red flag events — damaging winds, extremely low humidities," Kittell said. "We just felt the need to try to message that this is a red flag warning for sure, but the upper echelon, upper tier of what could happen."
In other words, says fellow NWS meteorologist Rose Schoenfeld, "this tagline is one of the loudest ways that we can shout."
What are the criteria?
The weather service issues this super duper rare fire weather alert under these weather conditions:
Single digit relative humidity
Sustained winds of 35 mph or greater and/or gusts 60 mph or greater
Very dry vegetation — live fuel moistures less than 60%; dead fuel moisture less than 7%
Conditions that could lead to a high risk of:
Extreme fire behavior and very rapid growth
Many downed trees
Power outages and Public Safety Power Shutoffs
How often is it issued?
They are rare, but the PDS red flag warning has already been issued three other times in as many months — an indication of the kind of extreme weathers Southern California has faced of late.
Specifically, the nearly 20,000-acre Mountain Fire in Ventura County in November and the Franklin Fire in Malibu in December.
And of course, it was issued last week for the historic Santa Ana windstorm behind the Palisades and Eaton fires that are still currently burning across Los Angeles County.
The weather service says the PDS for peak winds this week, however, won't be as severe.
"This is not going to be as strong as last week's historical windstorm," Schoenfeld said.
Do you have a question about the wildfires or fire recovery?
Check out LAist.com/FireFAQs to see if your question has already been answered. If not, submit your questions here, and we’ll do our best to get you an answer.
