Forests in many areas of California are just waiting for a spark

The Energy Release Component is at or above record levels in some areas of the state

Energy Release Component wildfire fire central sierra California
The Energy Release Component (or flammability) of the vegetation in the Central Sierra area is the highest recorded for this time of the year. (Click to enlarge)

The forests and brush lands of many areas of California are ready to burn. The effects of precipitation received in the winter and spring have been negated by relentless warm, dry, and occasionally very windy weather. The recent Kincade and Maria Fires were examples of wildfire potential during strong winds.

The Energy Release Component (ERC) is a measure of the heat produced within the flaming front of a vegetation fire and is largely influenced by the moisture in the live and dead fuels. In other words, it reflects the flammability of the vegetation. The weather in the last few months in California has resulted in many areas having record or nearly record high ERCs in recent days, including the Southern Mountains, Bay Marine, Central Coast, South Coast, Central Sierra, and Santa Cruz Mountains.

The data in these ERC charts shows the most current levels being above the 97th percentile for any date and close to or above the maximum ever recorded on November 5. (Charts for more areas in California)

Energy Release Component fire wildfire California mountains southern
The Energy Release Component (or flammability) of the vegetation in the Southern California Mountains is the highest ever recorded for this time of the year.

One thing that is striking about this information is the ERC in the Central Sierra, an area where the wildfire danger usually drops quickly after September. The conditions we are seeing now are similar to or perhaps more extreme than in 2017 and 2018 before the Camp, Woolsey, Thomas, and North Bay Fires that combined destroyed over 29,000 structures in October, November, and December.

This is not normal. The fire seasons are longer than they were a couple of decades ago.

The fuel is ready now. The only things lacking are very strong winds and an ignition source.

 Santa Ana wind events per month
The mean number of Santa Ana wind events per month. The dark bars refer to NCEP–DOE reanalysis and the clear bars refer to the CFS climate run. (Charles Jones, Leila M.V. Carvalho, and Francis M. Fujioka in Monthly Weather Review, December 2010)

There are no forecasts for very strong winds within the seven days in California, but wind is difficult to forecast and can sneak up on you. There is a possibility for an off-shore flow around November 15.

The three months with historically the most Santa Ana wind events are November, December, and January. The forecast for California in November is for higher than average temperatures and precipitation that is at or below average.

outlook probability precipitation temperature
One-month outlook for probability of precipitation and temperature, made Oct. 31, 2019, valid in November, 2019.

It rained in Southern California ahead of Santa Ana wind event

(Originally published at 9:10 a.m. PDT October 13, 2018)

Significant amounts of rain accompanied by copious amounts of lightning fell in Southern California Friday night ahead of a predicted moderate Santa Ana wind event that is expected to begin Sunday afternoon and intensify on Monday and Tuesday.

Many areas from Los Angeles to San Diego received over half an inch and there is a chance it could continue on Saturday. Beneficial rains fell in most areas, but there was too much in some of the desert areas where flooding was reported in the Coachella Valley and Imperial County. Some of the highest totals included 1.54″ at Ocotillo Wells and 1.10″ at Indio.

Accumulated precipitation
Accumulated precipitation during the 24 hours ending at 7 a.m. PDT October 13, 2018. Click to enlarge.

Firefighting agencies have been preparing for the strong, dry Santa Ana winds by prepositioning air tankers in Southern California. They were heavily used Friday to quickly knock down the North Park Fire north of San Bernardino before it could burn more than 50 acres.

wind forecast southern california october 15
The forecast for wind gusts in Southern California at 11 a.m. PDT Monday October 15, 2018.

Sunday afternoon the strong winds will surface in the mountains, foothills, inland valleys, and Orange County, and will begin to dry the fuels Monday. Winds in these areas will range from 20 to 40 mph with gusts in the wind prone areas up to 60 mph. The rest of the week should be dry and breezy.

Weather forecast for Riverside, California
Forecast for wind, wind gusts, and relative humidity, Riverside, California. NWS.

Santa Ana winds increasing in southern California

The weather station at Chilao recorded a gust of 58 mph at 10:53 a.m. PDT on Sunday.

red flag conditions

At 11:11 a.m. PDT 17 weather stations in southern California met the criteria for Red Flag Conditions. Five of them at that time had recorded gusts  of 40 and above, with Chilao having sustained winds out of the northeast at 30 mph with a gust of 58. The extreme fire weather conditions are predicted to continue on Monday, but with less severe winds.

The map below is a screen grab from an animated wind map (which is mesmerizing to watch).

wind map

Scientists find that stratospheric intrusions can increase the effects of Santa Ana winds on wildfires

This important research about a little known weather phenomenon that affects wildfires was conducted by government employees working for the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado at Boulder. However, to get a copy of this taxpayer-funded research, you will have to pay $38 to a private organization, John Wiley & Sons, Inc., a corporation that for the year that ended April 30, 2015 had $1.8 billion in revenue and a net income of $176 million. In that year, 64 percent of their revenue came from journal subscriptions.

While some government and university employees may be able to access this and other research papers, they can only do it because their employer pays tens or hundreds of thousands of dollars in subscription fees to these private companies. The employees can seamlessly read the papers, and don’t always realize that non-employees can’t.

Gowers Weblog has an exhaustive article about this issue in which he lists the exorbitant subscription fees paid by some universities in the United States.

He noted, for example, that the state universities in Arizona pay a total of $2.7 million to just one of these private outfits, Elsevier.

The authors of the paper are Andrew O. Langford (U. of Colo.), R. B. Pierce (NOAA), and P. J. Schultz (NOAA).

The University of Colorado and NOAA have graciously allowed this brief summary of the publicly-funded research to be released — to the public:


Southern Californians and writers love to blame the hot, dry Santa Ana winds for tense, ugly moods, and the winds have long been associated with destructive wildfires. Now, NOAA researchers have found that on occasion, the winds have an accomplice with respect to fires, at least: Natural atmospheric events known as stratospheric intrusions, which bring extremely dry air from the upper atmosphere down to the surface, adding to the fire danger effects of the Santa Anas, and exacerbating some air pollution episodes.

Springs Fire
Satellite image of the smoke on 2 May 2013, the first day of the Springs Fire northwest of Los Angeles. The photo was taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra satellite.

The findings suggest that forecast models with the capacity to predict stratospheric intrusions may provide valuable lead time for agencies to issue air quality alerts and fire weather warnings, or to reallocate fire fighting resources before these extreme events occur.

“The atmosphere could give us an early warning for some wildfires,” said Andrew Langford, a research chemist at NOAA’s Earth System Research Laboratory in Boulder, Colorado, and lead author of the study. Researchers at NOAA’s National Environmental Satellite, Data, and Information Service (NESDIS) and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder coauthored the work, which was accepted for publication this week in the American Geophysical Union journal Geophysical Research Letters.

The authors took a detailed look at the May 2013 “Springs Fire” that burned 25,000 acres about 50 miles northwest of Los Angeles. The researchers used a NOAA forecast model that incorporates satellite observations of ozone, wind data, and other atmospheric information to detect the occurrence of the intrusions.

The analysis showed that in the early hours before the Springs Fire, a tongue of air characteristic of the stratosphere—extremely dry and very high in ozone from the stratosphere’s ozone layer—reached to the surface in southern California and extended as far south as Baja California.

The researchers found that ground-based monitoring stations near the fire’s origin also confirmed the telltale signs of the intrusion right before the fire broke out: A large drop in relative humidity and a rise in ozone. As the day went on, a combination of factors accelerated the fire: Low humidity, persistent high winds, dry condition of the grasses and other vegetation, clear skies and bright sunlight, and very warm surface temperatures. A few days later, cloudy skies, a drop in temperature, a shift in winds, and widespread rainfall helped extinguish the fire.

The stratospheric intrusion also had another downside during the Springs Fire: it added ozone from the upper atmosphere to the urban and fire-related pollution produced in the lower atmosphere. On the second and third days of the fire, this helped to push levels of ozone—which can harm people’s lungs and damage crops—over the federal ozone limit at 24 monitoring sites across southern California. Monitors as far away as Las Vegas also saw a spike in ozone on the third day of the fire. The observed exceedances of the ozone standard were unusual for the region for that time period, suggesting that the stratospheric intrusions were a contributing factor.

“Stratospheric intrusions are double trouble for Southern California,” said Langford. “We knew that the intrusions can add to surface ozone pollution. Now we know that they also can contribute to the fire danger, particularly during La Niña years when deep intrusions are more frequent, as recently shown by our NOAA colleagues at the Geophysical Fluid Dynamics Laboratory. The good news is that with models and observations, we can get an early warning from the atmosphere in some cases.”

The authors note that stratospheric intrusions have previously been implicated in the explosive development of wildland fires in New Jersey and Michigan, but have not previously been connected to fires in southern California or to the Santa Ana winds. The frequent occurrence of stratospheric intrusions above the west coast during the fall, winter, and spring suggests that similar circumstances may have played a role in other major southern California fires, including the series of destructive fires that burned more than 800,000 acres in October of 2003, and burned nearly a million acres in October of 2007, say the authors.


(UPDATE July 12, 2015: We contacted one of the authors, Andrew Langford, and he sent us a copy of the paper, which has not been copyedited and typeset yet.)

Information about unrestricted online access (Open Access) to research funded by taxpayers.

Thanks and a tip of the hat go out to Barbara.

Enhanced wildfire danger in southern California Thursday through Sunday

Southern California forecast
Southern California forecast, Thursday through Sunday. NWS Los Angeles.

The National Weather Service is predicting a mild Santa Ana, or offshore, wind for southern California Thursday through Sunday. The wind will not be strong, but the relative humidity in some areas will be in the single digits along with temperatures around 100, at least in the Riverside area.

The new Santa Ana Threat Index that was rolled out September 17 only lists some “Marginal” to “Moderate” Santa Ana conditions on Thursday and Friday. That could change, of course.

Explanation of Santa Ana or offshore winds.
Explanation of Santa Ana or offshore winds. NWS San Diego.

U.S. Forest Service launches new tool for fire preparedness

Santa Ana header

RIVERSIDE, September 17, 2014 — The USDA Forest Service, in collaboration with San Diego Gas & Electric (SDG&E) and UCLA, today unveiled a new web-based tool to classify the fire threat potential of a weather phenomenon unique to Southern California — the powerful, hot, dry Santa Ana winds that can turn a spark into an inferno.

The Santa Ana Wildfire Threat Index, which includes four classification levels from “Marginal” to “Extreme,” will be used to help fire agencies, other first-responders and the public determine the appropriate actions to take based on the likelihood of a catastrophic wildfire fueled by high winds.

“Given the current state of fuel conditions, we have the potential to see devastating fires this fall should significant Santa Ana winds occur,” said Forest Service Meteorologist Tom Rolinski. “This tool will directly benefit fire agencies by allowing us to better anticipate what kinds of resources may be needed, as well as where and when we could face the greatest challenges.”

Since the 2007 wildfires in San Diego County, SDG&E has been a partner in enhancing local fire preparedness and has taken major steps to strengthen its overhead electrical system – changing out wooden power poles for steel – to make the grid more wind- and fire-resistant. The utility also hired in-house meteorologists and installed 150 weather stations across its service area to gather real-time information about the impact of weather on utility equipment – all to improve situational awareness during emergencies.

SDG&E’s Dave Geier, vice president of electric transmission and system engineering, considered other ways to leverage this significant amount of weather data and to share it broadly.

“I asked my team to come up with something similar to the categories to rate hurricanes that could be used to classify Santa Ana wind events based on their potential to spread a major fire, which would help us in making operational decisions to protect our system and our customers,” said Geier. “The goal was to develop a uniform and recognizable system that also could be used to alert fire agencies and communities in time to prepare and take appropriate action.”

As luck would have it, Rolinski already had been working on a similar concept and was eager to share ideas and information. Initially, SDG&E’s meteorologists compiled hourly weather data for the last 30 years in Southern California — information that was used as a basis for the models that eventually led to the four-level wildfire threat index. The utility reached out to regional fire agencies, including the Forest Service and CAL FIRE, along with universities in Southern California, to partner in the development of the index. SDG&E also provided funding for state-of-the-art computing hardware and software to help turn the raw data into a manageable tool.

The actual “number crunching” was done by a team from UCLA, led by Dr. Robert Fovell, Ph.D., chair of the university’s Department of Atmospheric and Oceanic Sciences, who applauded SDG&E’s weather network for “its unprecedented station density and uniformity.”

“We not only have a new, deeper understanding of how the San Diego-area terrain influences weather, especially wind, which is crucial to SDG&E’s operations, but we also have been able to make improvements in weather modeling that will benefit forecasters worldwide,” said Dr. Fovell.

The threat index includes four levels of increasingly severe fire potential:

Santa Ana legend

The National Weather Service (NWS) is the agency that issues a Red Flag Warning when weather conditions indicate the development of a strong Santa Ana. Forecasters look at fuel moisture, humidity levels, temperature and topography, as well as wind speed, to determine whether to declare a Red Flag Warning, which typically means high fire danger with increased probability of a quickly spreading vegetation fire in the area within 24 hours.

“This index will help forecasters to quantify a Red Flag Warning and the public to better understand the risk,” said Roger Pierce, director of the NWS in San Diego. “We believe this new tool will support and complement our forecasts and provide even more information to help the public to be better prepared.”

The Santa Ana Wildfire Threat Index is intended to be used by fire agencies, emergency responders, the media and the public. The Forest Service “owns” the tool and is the agency responsible for determining and issuing the alerts, which can be found on the agency’s website at:

“Each of the levels includes recommended ‘calls to action’ that escalate as the chance of a catastrophic fire becomes more likely,” said Rolinski.

Recommended actions for the public include closely monitoring fire conditions, making sure cell phones are charged and vehicle gas tanks are full, as well as reviewing emergency evacuation plans at work and at home and registering phones to receive reverse-911 warnings for the latest information about an emergency.