How Santa Ana Winds Work
The Santa Ana's get their start in the Great Basin, the vast expanse of desert that covers much of Nevada, Utah and southern Idaho. High pressure over the Great Basin forces cool, dry desert air toward the southwest. There, the winds plunge down through the mountains of Southern California, toward areas of comparatively lower pressure. As they whistle through canyons and valleys of the mountains that separate the desert from the coastal strip between San Diego and Santa Barbara, the air is compressed and heated as it descends, sometimes dramatically. The winds also pick up speed as they travel toward the coast.
"Think of a whole bunch of air getting shot down through a funnel," said Bonnie Bartling, a meteorological technician with the National Weather Service in Oxnard.
Coastal Southern California is normally bathed in cool, moist air blowing ashore from the Pacific Ocean, creating its moderate climate.
Santa Ana's reverse that flow. As they blow through the region, the winds -- which can feel like the blast of heat from an oven -- dry out vegetation and sap the air of humidity, creating the potential for destructive fires.
If a fire does break out in the dry chaparral that carpets many undeveloped areas of Southern California, the gusting Santa Ana's only further fan the flames.
The Santa Ana winds typically blow between September and February. In October and November 1993, the winds exacerbated unrelated fires that charred thousands of acres, killed three and destroyed 1,000 buildings in Malibu, Altadena and Laguna Beach.
One benefit of the Santa Ana's is that the winds push out to sea and disperse smog from the Los Angles region.The winds were named by settlers in the area of Santa Ana, a city 40 miles southeast of Los Angeles.
Dry, hot and windy weather increases the likelihood of a major wildfire. High windspeeds, in particular, can transform a small, easily controlled fire into a catastrophic event.These conditions:
- make ignition easier
- help fuels burn more rapidly
- increase fire intensity
Fuel is required for any fire to burn. In a wildfire, fuels are usually living vegetation (trees, shrubs, brush, grass) and dead plant materials (dead trees, dried grass, fallen branches, etc.) Homes, when in the path of wildfire, can become fuel. The quantity, size, moisture content, arrangement and other fuel characteristics influence the ease of ignition, rate of fire spread, length of flames and other fire behavior.
Of the topographic features, the steepness of slope is among the most influent' on fire behavior. The steeper
the slope, the faster a fire will spread. Other important factors are:
- "aspect"– south and southwest slopes usually have more fires
- "chimneys"– steep, narrow drainage
Federal and state regulations have been established to protect rare and endangered plants and animals that live in wildfire country. Whenever there is any doubt about clearing or thinning native brush, the US Fish and Wildlife Service and State Fish and Game Department should be consulted.
As people move into wildfire country, the human-built environment become important in predicting loss of life and property. Following are examples of increased risk to people living with the threat of wildfire.
- Combustible construction, especially roofs
- Narrow roads, limited access
- Lack of fire-smart landscaping
- Inadequate water supply
- Poorly planned subdivisions