|The Santa Ana winds are strong, extremely
dry offshore winds that characteristically sweep through in Southern
California and northern Baja California in late fall into winter. They can
range from hot to cold, depending on the prevailing temperatures in the
source regions, the Great Basin and upper Mojave Desert. However, the
winds are remembered most for the hot dry weather (often the hottest of
the year) that they bring in the fall.
Santa Ana winds are a type of drainage wind, an offshore wind that results
from the buildup of air pressure in the high-altitude Great Basin between
the Sierra Nevada and the Rocky Mountains. When upper level winds are
favorable, this high altitude air mass spills out of the Great Basin and
is propelled gravitationally towards the southern California coastline,
generally as a northeasterly wind.
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. 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. 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.
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.. 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
Residents regularly notice a build-up of dust in their homes and grit on
their properties during these periods, which are frequent during the
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.
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
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
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"