A PDS is a National Weather Service shorthand that stands for Particularly Dangerous Situation. Learn how and why it is used.
It has been nearly two months since the devastating fires in Eaton and Palisades destroyed neighborhoods in Altadena and the Pacific Palisades.
Strong winds and dry terrain worsened these fires, creating ideal conditions for a natural disaster. Prior to the fires, the National Weather Service (NWS) Los Angeles office forecasted strong red flag conditions more than a week before the firestorm on Jan. 7.
“Over a week before, we were seeing signals in the weather patterns and observations indicating the possibility of a highly volatile fire weather event,” said NWS Los Angeles Chief Meteorologist Ariel Cohen.
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Their confidence in the forecast increased day by day as the weather event approached. Cohen stated that they alerted emergency officials early regarding the forecast to help prepare cities and municipalities.
A few days before the event, the NWS issued a PDS (Particularly Dangerous Situation) alert, which is the highest alert level for fire weather events.
Cohen explained that PDS events represent environments capable of fostering explosive growth in any fires that break out. These conditions are characterized by damaging wind gusts, relative humidity below 10%, and dry fuels, creating a recipe for fires to grow rapidly and spread long distances due to embers igniting new fires.
Since November of last year, federal meteorologists have forecasted five PDS events, each resulting in a wildfire: the Mountain Fire on Nov. 6; the Franklin Fire on Dec. 9; and the Palisades and Eaton fires on Jan. 7.
“A PDS is a tool from the NWS to help draw extra attention in comparison to our regular Red Flag Warnings. It’s an urging to pay even closer attention to the forecast over the next couple days,” said NBC4 meteorologist David Biggar.
A PDS is not a guarantee of fires. There are other factors to consider including our Southern California’s microclimates and topography.
Forecasting and guiding viewers during the firestorm was an unprecedented event for our NBC4 meteorologists.
“To be honest, this setup was something I had never seen before in my 10 years at NBCLA, and was an unfortunate perfect mix of conditions (damaging gusts, and extremely dry fuels). Had this happened during the same time last year, we likely would have had something similar to 2011 with hundreds of trees coming down, but possibly no significant fire activity due to the amount of rain we had received,” said Biggar.
Some people are concerned that fires or Santa Ana wind events may become more common during the winter season following the recent fires last month.
“Santa Ana winds typically occur between September and May, but they are typically strongest during the fall months,” said NBC4 meteorologist Stephanie Olmo.
The past two Januarys experienced more rainfall than this year. In January 2023, there were 6.66 inches of rain, while January 2024 had only 1.98 inches. This year, January concluded with less than an inch of rainfall.
“However, in recent years, because of climate shifts, warmer, drier conditions have extended fire risk beyond the traditional fall fire season, making wildfire threat a year-round concern.”
NBC4 provided continuous wall-to-wall coverage during this firestorm.
“During a flareup of the Palisades Fire, I was watching where the fire was burning (as seen live by our chopper) in order to telestrate on our maps where we were looking and potential conditions and concerns for nearby communities," said Biggar. “I knew viewers were relying on us for real-time updates. At that point you’re just focusing on providing the most accurate information as the situation unfolded.”
For all the meteorologists involved, the top priority was public safety, ensuring that people had the information they needed to stay safe
