April 2010 Red Flag warning policy change: officials hope new policy will save money, lives

New: Sustained winds of at least 25 mph or frequent gusts of 35 mph, combined with 15 percent or lower humidity over at least 6  hours.

Expectation: About half as many red-flag warnings, given similar weather.

The frequency of red-flag warnings signaling an elevated wildfire threat has too often become white noise. Today, the Weather Service is changing the rules, which could yield more meaningful alerts


Old criteria: Many red-flag alerts were issued when the relative-humidity level in a region was projected to dip to 10 percent or lower for 10 hours or more.

Warnings issued: 96 in 2007; 137 in 2008; 36 in 2009, a calm fire year

New criteria: Sustained winds of at least 25 mph or frequent gusts of 35 mph, combined with 15 percent or lower humidity over at least six hours.

Expectation: About half as many red-flag warnings, given similar weather.
Firefighters try to get a handle on a wildfire between Ramona and Santa Ysabel.

The region’s most visible alert system for extreme fire danger is undergoing a major revision that should lead to far fewer warnings — and a more accurate portrayal of the risk.

Starting today, the National Weather Service will change its criteria for issuing red-flag warnings by putting more emphasis on high winds and less on low humidity levels alone.

The shift probably will save taxpayer money and, equally important, fire officials said, lower the chances of residents tuning out.

“Crying wolf isn’t a good policy. It makes the red-flag warning kind of superfluous,” said Bruce Risher, who works for the U.S. Forest Service and helps coordinate firefighting resources at the Geographic Area Coordination Center in Riverside. “By having less, it makes it more valuable.”

For many people in a county ravaged by massive wildfires in 2003 and 2007, “red flags” conjure images of infernos racing from the foothills toward the sea.

The warnings, initially designed for fire managers, are put out when forecasters anticipate conditions ripe for explosive fire growth. When the weather service took over the warning system in 2003, the information became readily available to the public, including the news media, through the agency’s Web site.

That vastly increased the ability of red-flag warnings to ignite widespread concern or even alarm.

Some firefighters believe the threshold established in 2003 for the warnings was too low, making the advisories too common and often unwarranted.

“It seemed (they) were becoming more regular. I felt that to the public, it really didn’t represent the high fire danger that should be associated with a red-flag warning,” said Carlton Joseph, deputy fire chief for the Cleveland National Forest.

Firefighting agencies and public utilities have attached varying amounts of significance to the warnings. Several do their own analyses of the fire risk and set their own criteria for allotting resources.

Others beef up staffing and move engines based largely on the weather service’s warnings. That has led to some personnel and equipment being shifted needlessly, fire chiefs said.

“We find ourselves spending the taxpayers’ money to satisfy the public perception that we are doing the right thing,” Joseph said.

Thirty-six red-flag warnings were issued last year for the region, which spans San Diego County, Orange County and parts of San Bernardino and Riverside counties. But 2009 was a time of calm fire weather.

The weather service put out 137 warnings in 2008 and 96 the year before.

Forecasters at the National Weather Service and representatives of various fire agencies reviewed the major fires and warnings since 2003. They found that under the old system, many alerts were issued solely because meteorologists expected prolonged periods of extremely low humidity.

If the relative-humidity level in a region was projected to dip to 10 percent or lower for 10 hours or more, the red flag was raised. But in almost all of those cases, major fires did not develop unless there were strong winds, too.

The new standards call for sustained winds of at least 25 mph or frequent gusts of 35 mph, combined with 15 percent or lower humidity over at least six hours. They should result in about half as many red-flag warnings being issued, given similar weather patterns.

And the warnings will probably expire after fewer days, said weather service forecaster Steve Vanderburg. Previously, many warnings during the fall stayed in effect for several days after Santa Ana winds died down but humidity levels remained low.

The public tends to become numb to warnings when there’s no immediate effect on their lives and people don’t foresee any future impact, said psychologist Jerry Gold, director of Scripps Behavioral Health Services. Warnings can impart a sense of control, but if nothing comes of them, people are more likely to disregard the next one.

“I think people are overloaded with information — more specifically, warnings on products, food labels, public safety, the weather,” Gold said.

Besides the psychological effects, the new policy will have a few practical consequences for residents.

In some cases, the absence of red-flag warnings will mean that campfires that would have been banned will be permitted, and some U.S. Forest Service areas that might have been closed could remain open.

The emphasis on both strong winds and low humidity is actually a return to similar standards followed before 2003. Other areas of the state have different red-flag criteria, based on topography, vegetation, weather patterns and other factors.

Next year, fire agencies and the weather service will re-evaluate the warning system again, said Risher of the Forest Service.

“I think in the past, we’ve overreacted,” he said. “I think we’ve come to an agreement for all the parties that is much more realistic. But we’re not going to have this cast in bronze so we can’t change it again.”

It is often said that the air is heated and dried as it passes through the Mojave and Sonoran deserts, but according to meteorologists this is a popular misconception. The Santa Ana winds usually form during autumn and early spring when the surface air in the elevated regions of the Great Basin and Mojave Desert (the "high desert") becomes cool or even cold, although they may form at virtually any time of year. The air heats up due to adiabatic heating during its descent. While the air has already been dried by orographic lift before reaching the Great Basin as well as by subsidence from the upper atmosphere, the relative humidity of the air is further decreased as it descends from the high desert toward the coast, often falling below 10 percent.

The air from the high desert is initially relatively dense owing to its coolness and aridity, and thus tends to channel down the valleys and canyons in gusts which can attain hurricane force at times. As it descends, the air not only becomes drier, but also warms adiabatically by compression. The southern California coastal region gets some of its hottest weather of the year during autumn while Santa Ana winds are blowing. During Santa Ana conditions it is typically hotter along the coast than in the deserts.

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QuikSCAT image showing the speed of the Santa Ana winds (m/s).Note that while the Santa Ana Winds are an adiabatic wind, they are not a Föhn wind. A Föhn wind results from precipitation on the windward side of a mountain range which releases latent heat into the atmosphere which is then warmer on the leeward side (e.g. the Chinook or the original Föhn). The Santa Ana winds do not originate in precipitation, but in the bone-dry high deserts.

The combination of wind, heat, and dryness accompanying the Santa Ana winds turns the chaparral into explosive fuel feeding the infamous wildfires for which the region is known. Wildfires fanned by Santa Ana winds burned 721,791 acres (2,921 km²) in two weeks during October 2003.[1] These same winds have contributed to the fires that have burned some 426,000 acres (1,720 km2) as of late October 2007.

Although the winds often have a destructive nature, they have some positive benefits as well. They cause cold water to rise from below the surface layer of the ocean, bringing with it many nutrients that ultimately benefit local fisheries. As the winds blow over the ocean, sea surface temperatures drop about 4°C (7°F), indicating the upwelling. Chlorophyll concentrations in the surface water go from negligible, in the absence of winds, to very active at more than 1.5 milligrams per cubic meter in the presence of the winds.

Santa Ana fog
A Santa Ana fog is derivative phenomenon in which a ground fog settles in Southern California during the end of a Santa Ana wind episode. When Santa Ana conditions prevail, with winds in the lower two to three kilometers (1.25-1.8 miles) of the atmosphere from the north through east, the lower atmosphere continues to be dry. When the Santa Ana winds cease, the cool and moist marine layer forms rapidly. The air in the marine layer becomes very moist and fog occurs. 

A related phenomenon occurs when the Santa Ana condition is present but weak, allowing hot dry air to accumulate in the inland valleys that may not push all the way to sea level. Under these conditions auto commuters can drive from the San Fernando Valley where conditions are sunny and warm, over the low Santa Monica Mountains, to plunge into the cool cloudy air, low clouds, and fog characteristic of the marine air mass. This and the "Santa Ana fog" above constitute examples of an air inversion.

Cold Santa Anas
While characteristically hot and dry, the Santa Anas can also blow cold and dry, and in fact can bring some of Southern California's coldest weather.[citation needed] High cloudiness, most commonly cirrus and altostratus, but also lenticular clouds may be observed, and on rare occasions these usually dry southwest-flowing winds can bring rain.

Popular experience
In the Los Angeles Basin, the winds are often credited with the extremely high visibility experienced in the area during the winter, in contrast to the hazy, smoggy summers.

The adverse pulmonary health impacts have been understood by local doctors for decades; the winds pick up and transmit grit, dust, pollens, mold spores and other irritants and allergens for considerable distances. Gastrointestinal effects such as hypermotility and psychological effects such as anxiety and irritability can be produced by these winds.[5]. These effects are thought to be produced by increased levels of serotonin in the body . It has been hypothesized that the positively charged CO2 ion, produced by these winds prevents the naturally occurring breakdown of serotonin in the body, giving rise to the increased levels. These serotonergic effects have been reported to be successfully reduced with ambient anionization.

Residents regularly notice a build-up of dust in their homes and grit on their properties during these periods, which are frequent during the winter.

Similar winds
To the north, in the Santa Barbara area, the Santa Ana winds are weaker and are usually held at bay by topography: the local mountains offer no prominent outlets, in the form of passes or river valleys, from the elevated inland source areas. However, a variant of the Santa Ana wind, known locally as Sundowner winds, often invade the area. These are downslope winds which occur when a high pressure area lies due north of Santa Barbara, and occur most frequently in the late spring to early summer, and are strongest at sunset, or "sundown," hence their name. Since high pressure areas usually migrate east, changing the pressure gradient in southern California to the northeast, it is common for "sundowner" wind events to precede Santa Ana events by a day or two.

Winds blowing off the elevated glaciated plateaus of Greenland and Antarctica experience the most extreme form of katabatic wind, of which the Santa Ana is a type, for the most part. The winds start at a high elevation and flow outward and downslope, attaining hurricane gusts in valleys, along the shore, and even out to sea. Like the Santa Ana, these winds also heat up by compression and lose humidity, but since they start out so extraordinarily cold and dry and blow over snow and ice all the way to the sea, the perceived difference is negligible.

Historical impact
The winds are also associated with some of the area's largest and deadliest wildfires, including the state's largest fire on record, the Cedar Fire, as well as the Laguna Fire, Old Fire, Esperanza Fire, Santiago Canyon Fire of 1889 and the Witch Fire.

In October 2007 the winds fueled major wild fires and house burnings in Escondido, Malibu, Rainbow, San Marcos, Carlsbad, Rancho Bernardo, Poway, and in the major cities of San Bernardino, San Diego and Los Angeles. The Santa Ana winds were also a factor in the November 2008 California wildfires.

Etymology

Wind patterns in the western United States result in the Santa Anas. According to the Los Angeles Almanac: "The original spelling of the name of the winds is unclear, not to mention the origin. The name "Santa Ana Winds" is said to be traced to Spanish California, when the winds were called devil winds due to their heat. Santa Ana winds may get their name from the Santa Ana Mountains in Orange County, the Santa Ana River or Santa Ana Canyon, along which the winds are particularly strong. The original form may have been Satanás winds, from the Spanish vientos de Satán ("winds of Satan"). Sanatanas is a rarer form of Satanás and is a translation of a native name in an unspecified language.

Dr. George Fischbeck was a widely viewed newscaster in Southern California in the 1970s and 1980s who incorrectly called the winds the "Santana winds", noting that they were not confined to Orange County (where Santa Ana is located), but occurred throughout Southern California. He delighted in the symbolism of the devil's breath playing havoc with Southern California.

A recent popular guide book Los Angeles A to Z (by Leonard & Dale Pitt), credits the Santa Ana Canyon in Orange County as the origin of the name Santa Ana Winds. This might be supported by early accounts which attributed the Santa Ana River bed running through the canyon as the source of the winds. However, since the phenomenon occurs throughout Southern California and not just Orange County, this explanation is likely only a recent one.

One account places the origin of the term Santa Ana winds with an Associated Press correspondent stationed in Santa Ana who mistakenly began using Santa Ana winds instead of Santana winds in a 1901 dispatch.

Those hot dry winds that come down through the mountain passes and curl your hair and make your nerves jump and your skin itch. On nights like that every booze party ends in a fight. Meek little wives feel the edge of the carving knife and study their husbands' necks. Anything can happen. ” 
—Raymond Chandler, "Red Wind"

“Los Angeles weather is the weather of catastrophe, of apocalypse, and, just as the reliably long and bitter winters of New England determine the way life is lived there, so the violence and the unpredictability of the Santa Ana affect the entire quality of life in Los Angeles, accentuate its impermanence, its unreliability. The wind shows us how close to the edge we are. ” 
—Joan Didion, "Los Angeles Notebook"

“The township itself was twenty miles (32 km) west of the Santa Ana Mountains, where the infamous winds came from. Time to time they blew in, dry, warm, steady, and they sent the whole of LA crazy. Reacher had seen their effects a couple of times. Once he had been in town after liaising with the jarheads at Camp Pendleton. Once he had been on a weekend pass from Fort Irwin. He had seen minor barroom brawls end up as first-degree homicides. He had seen burnt toast end up in wife-beating and prison and divorce. He had seen a guy get bludgeoned to the ground for walking too slow on the sidewalk.” 
—Lee Child, "Bad Luck and Trouble"

“Beakman and Trenchard could smell the fire—it was still a mile away, but a sick desert wind carried the promise of Hell.” 
—Robert Crais, "Chasing Darkness"

Inspection of weather maps associated with
large autumn and winter fires reveals that the
majority occurred during Santa Ana events.
Composites of 700 hPa heights—that is, the
average height of a 700 hPa atmospheric pressure—
for each forest for the ignition dates of
large fires exceeding 400 hectares from September
to January (1970–2000) indicate a consistent
pattern of anomalous atmospheric circulation
in the mid-troposphere.  The top panel in Figure 2
is the composite for 29 large fires reported
during this period in the Cleveland National
Forest near San Diego.  This pattern is characteristic of Santa Ana conditions, with an
anomalously deep Aleutian low and a high pressure system centered over the northwest.
The anti-cyclonic flow around the high-pressure
feature brings dry air from the interior
basins toward the southern California coast.
Fire ignitions peaked on 25 October for the
October 2003 Santa Ana-driven wildfires; four
large fires started that subsequently burned
nearly 200,000 hectares, including the largest
fire in California history—the Cedar fire in
Cleveland National Forest (CNF) that burned
over 113,000 hectares. Like 97% of large autumn
and winter wildfires in southern California’s
four national forests since 1970, these ignitions
were of human origin. The 700-hPa height
map for 25 October (Figure 2,middle panel)
shows a pattern similar to that of the large fire
composites. Observed wind speeds during the
fire period were typically 25–40 km/hr,with
gusts of around 65 km/hr.  While these winds
were not exceptional for a Santa Ana event,
they were, in combination with homogenous
dry fuel conditions, effective in promoting rapid
fire spread. One of the fires—the Cedar fire
near San Diego—grew from 200 to 12,500
hectares in 4 hours.  The combination of warm
temperatures and wind, even though moderate
in speed, reduced relative humidity to around
10% during most afternoons during the fires.
Humidity recovery overnight was also limited,
increasing to only 20–30%.The extended period
of low relative humidity was partially responsible
for the extreme fire behavior observed
during the events.
 

The NFDRS Energy Release Component (ERC)
is an indicator of heat energy at the head of
the flaming front calculated in units of J/m2.
ERC is also an index of longer-term drought
conditions, and thus provides a general state
of fuel dryness.  All NFDRS stations in the region
observed numerous daily record ERC values
leading up to and during the main fire period
(17–30 October).  Many of these extremely high
values were also near or exceeded all-time
October monthly records.
Antecedent Climate
Large fires in autumn and winter in coastal
southern California chaparral appear to be
linked to antecedent climate as well as to
concurrent meteorology. Precipitation tends to
be above normal in the winter or early spring
prior to the fire season (Figure 3, top panel),
suggesting that large fall and winter fires are
preconditioned two or more seasons in advance.
Wet winters enhance the growth of grasses
and other fine fuels.  The 2003 fire season differed
somewhat from the composite in that
the positive precipitation anomalies in late
winter and spring followed an extended 5-year
drought.  However, this precipitation and subsequent
cooler temperatures were sufficient
to promote the growth of fine fuels during the
winter and spring, increasing the continuity
and load of fine fuels across the region
[Predictive Services, 2003].
Temperatures during years with large autumn
and winter fires do not follow a distinct pattern.
In composite, monthly mean temperatures are
slightly warmer than average in the preceding
winter and spring and during the autumn period
when large fires occur, but they contain a
great deal of variability across large fire events.
The year 2003 saw a very warm winter followed
by a cool spring and then a very warm summer
and autumn (Figure 3).Temperatures during
the first week of the fires were record-setting
and averaged 10–20°C above normal. This pattern
probably accentuated the growth and curing
cycle for the grasses and other annual
vegetation that burned over much of the area.
Fire Management
Wildfires can become large and costly when
antecedent climate and meteorology facilitate
their rapid spread. They are also more likely to
escape early control under dangerous conditions
when there are multiple ignitions that
overwhelm locally available suppression
resources, and when ignition locations are not
easily accessible. Although Santa Ana winds
are intensified locally in settings such as
mountain passes and canyons, they are driven
by regional and larger-scale atmospheric patterns.
Consequently, they usually occur over a broad
footprint so that the same dangerous conditions
are likely to affect the entire 400-km coastal
mountain reach of southern California.
This synchrony of risks in inaccessible terrain
over a large region poses a serious challenge
for wildfire management. Judging from
U.S.National Forest Service fire records, the
probability of multiple large fires occurring
similar to those in 2003 is historically high. In
southern California, from 1970 through 2003,
whenever one or more large fires (greater than
400 hectares) burned in a national forest in
September through January, there was a nearly
one in four chance that one or more of the
other three forests would also experience a
large fire starting within the same 9-day period.
Early control is crucial when conditions
favor rapid spread. Not only does the rapid
growth of the fire perimeter greatly complicate
containment, but the heat of a large fire dries
neighboring fuels and generates its own winds,
facilitating both the spread of the fire and
extreme fire behavior that increases the risk to
fire fighters and the public.  The 2003 southern
California fires behaved unlike any reported
before [Mission-Centered Solutions, 2003].The
extreme nature and severity of the fire behavior
surprised firefighting crews and subsequently
caused them to realize that traditional suppression
attack tactics were ineffective. Fire whirls were
dramatic, as much as 800 m wide, crossing
burned areas into unburned areas and causing
spot ignitions ahead of the fire by as
much as 1200 m.  Pilots reported burning debris
as high as 450 m above ground. Fire and heat
from burning structures and ornamental vegetation
were as much of a problem as any of
the natural fuels.
Many forested areas that burned in October
2003 probably burned much more completely
than they would have in the absence of successful
fire suppression over the past century.
Dense vegetation fostered the rapid spread of
high-intensity fires in the forest canopy.  Widespread
die-offs of this vegetation may help to
reduce the risk of canopy fires in the future. In
recent years, large portions of southern California
have experienced substantial
vegetation mortality resulting from drought,
insects, and disease [Predictive Services,
2003].After the fine canopy fuels (needles,
leaves, twigs, etc.) fall to the ground, the standing
dead trees may be less prone to spreading
fires in the canopy (Craig Allen, pers.comm.).
About 80% of the area burned in the October
2003 southern California fire siege, however,
was in chaparral or grassland. Whereas healthy
forests in southern California can sustain a
low-intensity fire regime with regular surface
fires in the absence of fire suppression, chaparral
always experiences canopy fires that
consume much of the vegetation. Not only
does chaparral regenerate quickly, but a relatively
small proportion of the areas with homes
proximate to wildland vegetation actually
burned—only about 5% of southern California’s
wildland-urban interface in total (S. Stewart,
pers.comm.).  Consequently, the risk of large
regional-scale fires remains high.

California Hot Shot crews org.