From the Cliff Mass Weather Blog
Cliff Mass
My group and scientists from the University of Albany are now studying the meteorology of the LA wildfires earlier this month and have significant early results. At the American Meteorological Society meeting last week, I attended many wildfire meteorology sessions and talked to several colleagues who have actively studied such events. The LA fires were a topic of considerable discussion.
We have a good idea of what happened: an extreme/unusual Santa Ana event associated with severe downslope winds. In this blog, I will show you some early simulations and explain why this event occurred.
I will also describe why climate change did not play a significant role.
As I will explain below, this is not only a Santa Ana event, but an unusual one, with extreme winds descending to lower elevations. Some lower-elevation stations, such as Burbank, experienced their strongest wind gusts on record. Model simulations suggest the development of what is known as a high-amplitude mountain wave leading to a downslope windstorm event.
Santa Ana 101
Santa Ana’s are associated with strong northeasterly (from the north to east) winds over southern California. These strong winds are accompanied by very low relative humidity and are very favorable for southern CA wildfires.
The typical large-scale weather pattern associated with Santa Anas includes a large high-pressure area over the Great Basin, with the strongest events also having a low center to the southwest (see below). Such a pattern results in strong northeasterly winds approaching the mountains of southern CA.
The observed sea level pressure pattern at 4 PM January 7 (below) showed many of these elements, with the low to the south being particularly strong (warm colors indicate above-normal pressure, cool colors show below-normal pressures).
This pattern produced extreme, perhaps precedented. northeasterly winds approaching the region in the lower atmosphere. To illustrate, the color shading in the map below shows wind differences from normal at 925 hPa (about 2500 ft above sea level) at 10 PM Tuesday (January 7) evening. The light gray indicates very unusual winds (more than six standard deviations from normal). The wind direction and speed at some points are also shown.
This was not your normal Santa Ana.
To understand what happened, UW Research Scientist David Ovens, a member of my research group, ran a very high-resolution forecast/simulation of the event using the WRF model, with a grid spacing of 1.3 km (this is very high resolution).
Let me show you a surface wind gust forecast (32 hours into the prediction) for 12 AM on Wednesday, January 8. The areas of the Palisade and Eaton fires (the two biggest ones) are shown by red outlines.
Extreme winds (with gusts exceeding 70 knots, 81 mph) were forecast over and downwind of the San Gabriel Mountains. HUGE threat. Lesser, but still strong winds (50-60 mph gusts) are noted in the Palisades area extending to the west and south.
To understand what is going on, it is useful to plot vertical cross-sections through the fire areas to show the 3-D atmospheric structure. Below is a cross-section (at 8 PM Tuesday) through the Eaton fire; a section that crosses the San Gabriel Mountains. The shading shows sustained winds in knots, the x-axis is the horizontal distance and the y-axis is height in pressure (700 is about 10,000 ft)
Wow. Very strong acceleration of the air as it descends the southern slopes of the San Gabriels, with the strongest winds near Altadena, where the fire went crazy. This was a very powerful downslope windstorm with a highly amplified mountain wave pattern.
Another cross section, this time going through the Palisades fire at 10 AM on Wed. January 8, is shown below. Very strong winds to the lee (south) of both the interior mountains and Santa Monica mountains to the south (left side of the figure).
These and earlier simulations by the UW WRF model and NOAA/NWS models (such as the HRRR, High Resolution Rapid Refresh) consistently forecast the extreme downslope winds DAYS in advance
It was also clear that there were unusually large amounts of dried “fuels” ready to burn. The fuel load was particularly high after TWO unusually wet winters (2022-2023, 2023-2024). A dry start of winter ensured massive amounts of fuels were ready to burn.
This was clearly a situation of extraordinary extreme wildfire danger. That is why I blogged a strong warning the day before. Why the National Weather Service did the same. LA officials should have know a severe threat was in place.
All that was needed was an ignition source. For the deadly and large Eaton Fire near Pasadena, it appears that a problematic electrical transmission tower was the origin of the fire.
For the Palisades inferno, it is either some smoldering embers from a New Year’s Eve fireworks blaze or the failure of some aged powerlines found north of Skull Rock. Perhaps, arson is another possibility. Several fire experts I talked to at the AMS wildfire meeting thought the powerlines were the most probable cause, but a definitive evaluation is not yet available.
What is clear is that LA did not shut off the power to the region even AFTER the fire was initiated and that only limited fire-fighting resources were in place before the fires began. Not good.
Bottom Line: A very skillfully predicted Santa Ana event with record-breaking winds hit LA earlier this month. Two wet winters resulted in unusually high levels of dried fuels. Human ignitions initiated the fires.
Influence of Global Warming
There are several media outlets and climate activists that are suggesting that LA fires were the result of global warming or significantly enhanced by human-caused warming.
These claims are contrary to the best science, which indicates minimal impacts of human-caused warming.
Such claims undermine the importance of key societal failures, from not shutting off power and fire-hardening homes to not having sufficient fire-fighting capabilities or adequate warnings and evacuation protocols.
Key reasons why global warming is not an important factor include:
1. There is no evidence that global warming increases Santa Ana winds. In fact, there are strong physical reasons (with supporting scientific literature) that global warming WEAKENS Santa Ana winds.
2. The available fuels were unusually abundant because the two previous years have been much wetter than normal. There is no evidence this is caused by global warming. And there is no long-term trend for wetter winters, which would be evident if this was a climate issue.
3. The immediately prior months were drier than normal. This is not predicted by global warming projections and there is no historical trend to drier early winters which would occur if climate was a cause (see plot below of Los Angeles precipitation for Oct. 1-January 6 ).
3. There are some outrageous claims that the LA fires are the result of increasing “weather whiplash” due to climate change. This “whiplash” theory is unsupported by observations, such as the plot shown above.
I am particularly troubled by the media pushing weather/climate theories that are untrue. A prime example is the unsupported claim that the Lahaina fire was associated with the passage of a hurricane to the south. This was proven to be false.
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There are some live feed cameras from this UCSD program https://alertcalifornia.org/ that reportedly captured the start of the Palisades fire. A clip is included in the video below. I’m not sure this is correct. Lots of questions.
Put simply, strong wind descending rapidly = very hot = very dry conditions = very high fire danger. CO2 plays no part.
Just out of curiosity, are CO2 fire extinguishers sill legal California?
Also, has anyone though of dropping a large (several tons) liquid CO2 container on the flames with an explosive attached to ensure the tank ruptures?
Blasphemy!
Interesting thinking
But water – a known fire extinguisher with a fire retardant added is easier
Carbon dioxide can only exist in solid or gas phase at normal pressure. A CO2 fire extinguisher works by both displacing air (separating Oxygen from fuel) and cooling the fuel at the same time. It works well on small fires, but water works far better on large fires and over greater distances.
When I looked the temperatures in Los Angeles were in the 60s F, not warm at all.
For winter ?
Los Angeles temperatures only seem a couple of degrees warmer than Sydney, and much of a muchness with Brisbane.
Yes, for LA it has been cooler than normal. Coldest Santa Ana I have experienced.
Very nice Cliff.
“Weather whiplash”
I wonder how long this new term will last?
All the others have overstayed their welcome.
The AP strikes again. Not only do they need multiple people to write a single story, they have to invent new and scarier adjectives that have nothing to do with the event to describe it.
The Democratic Peoples Republic of California does not do brush or forest management as a matter of ideology. Green Blob members like the Sierra Club and The Center For Biological Diversity block all brush clearing and controlled burns, with the complicity of the local politicians.
Chaparral will burn, the only question is when.
Near Palisades, Los Angeles started a project to clear firebreaks and replace a lot of wooden power poles dating back to the 1930’s to 1950’s, to be replaced with steel poles.
An “endangered” plant, Braunton’s milkvetch, was in the area. California Coastal Commission fined the Los Angeles Department of Water and Power (LADWP) $1.9 million and forced the removal of the firebreaks along with reverting other alterations intended to prevent initiation and spread of fires.
Yup. They don’t want any kind of forest and brush and dead material “management” of any kind, because they insist humans don’t interfere with what is “natural.”
To which my response is “You know what else is “natural? FIRE.”
Either you remove the ‘fuel,’ or it WILL burn. Just a matter of time.
“To which my response is “You know what else is “natural? FIRE.””
The environmentalists have absolutely no idea about “burning”. Cultural burning in Australia are “cool” burns. Prairie burning in the Central US Plains are “cool” burnings. Both serve to *enhance* the environment. But the environmentalists want “no burning” at all. So they get instead NATURAL burning, which usually turn out to be hot burns – destroying everything in its path.
With respect to the Eaton fire, I find it very odd that the first started at the bases of the pylons supporting the transmission lines. The insulators supported far enough on the cross arms to make conductor contacting a grounded structure or a conductor of a different phase unlikely. SCE stated that no line transients were recorded until an hour after the fire started.
My experience from spending most of my life in southern California is that the worst fire seasons happen after a very wet year. An example was early 1969 was known for excessive rainfall in areas and fall 1970 saw a number of major fires. The Laguna fire of that year was the largest in San Diego County prior to the 2003 Cedar fire. I do remember a cold Santa Ana taking place in early 1971, though the winds weren’t as strong as happened.
No argument on the accuracy of the short term high resolution forecasts, though the various fire agencies could have done more about pre-positioning equipment where the strongest winds were forecast to happen.
Those sort of fires cant be fought by fire-trucks and firemen. Its a type of firestorm with a huge fire front moving quickly and its too dangerous to control on the ground . The only method is the ariel water drops
They aren’t terribly effective, either. Their main benefit is in quickly extinguishing spot fires in hard to reach locations.
The most effective method is to starve them of fuel with wide burn-backs from fire breaks well ahead of the main fire, and fighting spot fires which jump the containment. Both of those would be quite difficult in the terrain.
The only saving grace of the Santa Ana winds may be that they are less prone to the wind direction changes we get in Australia.
An even more effective way of fighting fires is trimming brush and clearing dead vegetation along with careful use of controlled fires when the vegetation is relatively moist and winds are calm. The clearings from small scale fires are known to greatly slow down the spread of major fires.
Big herds of goats would manage all that growth
Definitely.
An ounce of prevention is worth a pound of cure.
It took 44 minutes for the first truck to arrive in the Palisades, So far no explanation.
I see that Cliff did not mention again the GRL paper he cited in his last post, saying that it said that global warming would diminish Santa Ana winds. Well, it did, but mainly in fall and spring. But it also had a very clear prophecy of the current situation, which it said would be made more likely:
“In light of these projections, the largest wildfire in SoCal history (Thomas Fire) occurring in December 2017 and fanned by back‐to‐back SAW events is likely a harbinger of wildfire seasonality we would expect to experience more often in the future. In December, back to back SAWs are most probable providing opportunities for wildfires to burn longer and bigger. In the future, the probability of back‐to‐back events will diminish somewhat, but will still remain much stronger in December than it ever was in October or even November. The higher year‐to‐year precipitation volatility (Polade et al., 2014) translates into higher probability of extremely wet winters followed by extremely dry winters (Swain et al., 2018) and additionally suggests a boost to the availability of dry fuels, bolstering the later peak in future wildfire activity, that is, nudging the extremes of future later fires to be more intense and, therefore, more extensive. “
They say that recently the peak fire season was October/November, because the SA winds were rising, and it was still warm enough. In Dec/Jan the winds were stronger, but the weather was too cold. But with AGW, it is much more likely that winter winds will come with November temperatures. That is a worse combination; the winds are stronger than November even if slightly reduced from past winter strength.
The temperature of a Santa Ana event doesn’t matter if the vegetation has been given months to dry out. Once a fire starts in those conditions, it doesn’t matter if the temp is 15C or 40C. Coastal southern California hasn’t seen much rain since last spring, so long time residents were getting a bit nervous, especially after a couple of wet years.
There may be something as to timing of the Santa Ana’s, 50 to 60 years ago the Santa Ana’s seemed to strike shortly after the start of the school year.
If temperature doesn’t matter, then the fires would have been common and bad in winter, when the winds are strongest.
Like the Thomas fire in 2017, the Loop fire in 1966, the Inaja fire in 1956, the Woolsey fire in 2018?
At a first pass, it appears that northern California fires occur in summer or early autumn, and souther California fires occur in late autumn or winter.
Fires need fuel, oxygen, and an ignition source. It takes years for fuel levels to build up after a big fire.
The spread of the recent/current southern California fires appear to be have more to do with fuel buildup, a dry spell, and high winds. Temperature is much less a factor, or we wouldn’t be able to light fires in the fireplace in the middle of winter to keep ourselves warm.
Jim Steele’s recent article covered it well.
The GRL paper addressed the Thomas fire, in particular,thus:
“The largest wildfire in SoCal’s recorded history, the Thomas Fire, was recently fanned by SAWs and raged through most of December 2017 into January 2018, until the first significant rains of the water year occurred, causing debris flows from the steep scorched landscape (Boyle, 2018; Oakley et al., 2018). Beyond the duration and magnitude of this fire, its most unusual feature was its December timing. Following a bone dry fall and early winter, the vegetation was desiccated in December 2017, allowing successive SAWs to fan the Thomas Fire. Although SAW activity peaks in December (Guzman-Morales et al., 2016), the vegetation is typically no longer as flammable by then as several rain storms would have normally occurred by that late into the wet season (Westerling et al., 2004). However, while enhancing extreme precipitation, climate change is projected to decrease the frequency of precipitation events in California (Polade et al., 2014, 2017), particularly in SoCal and especially in the shoulder seasons of fall and spring (Pierce et al., 2013). This is expected to result increasingly more often in dry flammable fuels persisting into the peak of the SAW season, therefore lengthening the wildfire season toward winter (Syphard et al., 2018). This reasoning is predicated on the assumption of no significant change in future SAW activity. In this work, we examine the validity of this assumption.”
The Loop fire was very early November. The Inaja and Woolsey fires were also in November.
As has been pointed by others, another complicating factor has been the long time to get a permit to clear brush or do a controlled burn. This largely due to overzealous enforcement of the Endangered Species Act. An example of that was one person was dinged for clearing weeds out of an empty lot in Ramona, which is part of normal fire protection.The irony is that the brush clearing and controlled burning are necessary to prevent the total destruction of the habitat.
The timing of the Thomas fire has more to do with strong Santa Ana’s not occurring in the September/October time frame. The root cause was the accumulation of brush.
It’s nice to see you agree it is rainfall rather than temperature.
They do matter, but rain, (a winter only event in Calif) or the lack of, is far more important. Lack of Rain plus wind, plus lack of preparations, and prevention, plus more people, and more crazy people.
And the variability of rain fall from season to season has not changed. It has always been that way in Calif. Ask Jim Steele. There has been no global increase in extreme weather from year to year, or drought to heavy rain in Calif, until PERHAPS this year with a sudden and unexplained ocean warming, followed by a sudden and unexplained ocean cooling. (Definitely not CO2 caused!)
California is certainly having a very dry year this year so far. Even Cresent City, There is zero reason to think CO2 is causing it any more then it caused the two droughts in Calif in the last 1200 years that lasted about a century each, one of which killed most of the oak trees.
After 50 years of doom predictions, the earth MAYBE having an unusual number of rare events on a global basis which should be expected to happen every so often. It is not just Hunga Tunga, putting 17 percent extra w/v in the stratosphere, but numerous other signs of increased geo thermal activity, and potential overturning of some ocean layers. (Something caused the record warming and cooling of the oceans, and it was NOT CO2.)
Outdoor human activity, a large factor in wildfires, bottoms out in the winter. Why do you never consider analyzing things on a holistic basis instead of just tying everything to temperature?
That’s all he’s
trainedpaid to do.So why would reduced human activity cause wildfires in winter?
“So why would reduced human activity cause wildfires in winter?”
It helps explain why fires go down in the winter. That doesn’t mean they disappear.
you: “If temperature doesn’t matter, then the fires would have been common and bad in winter, when the winds are strongest.”
Winds don’t ignite anything, they only spread it after ignition.
Less ignition –> fewer fires
You *really* have a problem doing holistic analysis, don’t you?
The GRL paper starts out:
“The wildfire season in coastal Southern California (SoCal: bounded by Southern California’s Coast Ranges from the Transverse Ranges to the north to the Peninsular Ranges to the south) displays a unique seasonality. While the rest of western North America is mainly susceptible to wildfires during summer, SoCal’s fire season peaks, historically, in the fall (Kolden & Abatzoglou, 2018). This timing results from a climatic coincidence of two seasonal factors: the long dry summer defining this Mediterranean climate regime and the dry gusty downslope winds, whose season starts in the fall when vegetation is at its seasonal driest. The Santa Ana winds (SAWs; Guzman-Morales et al., 2016; Hughes & Hall, 2010; Raphael, 2003), rooted in cold air masses over the elevated Great Basin, are notorious for fanning California’s largest wildfires.”
The fall is not peak human activity season.
“The fall is not peak human activity season.”
We weren’t discussing “fall”. We were discussing WINTER. Nice job of moving the goalpost!
Your quote does *NOT* address the issue of ignition of the fires. Again, wind is not an ignition source. It can only spread fires that have been ignited.
I’ll repeat – you totally fail at holistic analysis.
A large portion of fires are associated with outdoor human activity. That activity bottoms out during the winter. Why does climate science never consider anything on a holistic basis by considering *all* factors instead of just temperature?
A historic village in Japan is protected from fire by a bunch of automated water gun turrets. https://superinnovators.com/2024/01/automatic-giant-sprinkler-system-protects-thatched-japanese-village/
Why couldn’t neighborhoods in fire prone areas have a grid of elevated sprinklers on standpipes to all turn on when a fire is approaching? The mist in the air and wetting the buildings and ground ought to cool and put out flying embers. Wouldn’t need the fancy moving turrets if enough water could be sprayed out fine enough to literally put everything in a fog.
But California would need to build all the mountain reservoirs they were supposed to starting some years ago, but didn’t. They’d also need to build desalination plants with on site Small Modular Reactors to clean ocean water to fill those reservoirs.
With technology currently available it should be possible to plant a large grid of direct monitoring stations to measure temperature, humidity, fire sensors, wind speed and direction. Connect them all in a mesh network that ‘bucket brigades’ the data forward for collection. With small solar panels, each unit would be self sufficient and easily moved, taken in for maintenance, or replaced. Putting the grid up and over the mountains would provide high resolution, realtime information on conditions so that the instant Santa Ana winds start, emergency agencies could be notified to get ready.
Quite a number of houses have been saved over the years by homeowners using a gas powered pump to spray water from a swimming pool onto their house.
There are the usual seasonal weather patterns that develop every year – fall Santa Ana winds in southern California are one example, “nor’easters” in the wintertime north Atlantic seaboard is another, and summertime hurricanes hitting the Gulf (of America?).
Then there are the unusual circumstances that tend to either moderate or amplify these events, and they often have to do with low pressure systems and high pressure systems that just happen to be operating at the same time in relatively close proximity to each other. You get a double dose of winds to the north side of low pressure areas adjacent to the south side of high pressure areas that clearly amplifies the resulting windstorm. The fact that the air is very dry coming off the deserts of the southwest also amplifies the effects of the storm, as well as the topography of mountain winds and mountain waves that operate in the LA basin.
It’s called “weather” and it’s random, and does not occur frequently but it is always a risk.
In the Pacific southwest the consecutive wet winters certainly produced a bumper crop of wildfire fuels.
Dr. Mass is “particularly troubled by the media pushing weather/climate theories that are untrue.” I do not disagree but I am more disgusted by the scientists that are pushing these theories that they know are untrue.
At the risk of being repetitive, I think the main question begging answers is if these people demand that climate change causes this, why have they neglected to prepare for the doom they predict?
No matter what the cause is, prudent governance, indeed the only reason for government at all, would be to assemble the infrastructure to prevent and respond to such an eventuality. I suggest that solving problems is not the desire of progressive politics, only to capitalize on and even create the problems to begin with. Hardly a novel idea, I know, but it amazes me that people continue to be so gullible to the corrupt opportunists they continue to empower.
We have strong Chinook winds during the winter season in many places in the mountain west. The unusually strong Chinook winds that pushed the Marshall fire in Colorado in December 2021 was very much the same conditions that Dr. Mass describes here, except the winds blew from the southwest — a sort of point inversion image. We get these winds commonly.
Weather conditions of any sort are a random event, and even if the distribution describing the probability of such events is stationary, the longer the time interval considered, the more the process explores the extreme values of said probability distribution. It’s nature. Evaluate plans in anticipation of extreme events.
In climate science nothing exists except the “average”. They don’t understand that if the probability of something is greater than zero then it *can* happen. That includes extreme events.
The great Chicago fire, Peshtigo, WI, Lahaina, HI, Paradise, CA – all of the largest and most deadly and costly fires in US history have been extreme wind events. When there is a high fuel density, be it trees, grass, brush or buildings with combustible exteriors and roofs, all that’s required to start a conflagration is a spark and wind. I looked at the Google Earth view of Palisades (pre fire of course) and the housing density is obvious. Dozens of houses side by side with almost no space between them. The LAFD had no chance once the fires reached these neighborhoods.