Hot, dry and breezy conditions are expected this week along the Pacific Coast where Los Angeles is expected to see triple digit temperatures Monday and Tuesday.
The common weather phenomenon that brings these conditions to parts of California is referred to as the Santa Ana Winds. These winds can be responsible for the highest annual temperatures in some locations, occurring in fall rather than in the summer. Santa Ana winds are a down-slope winds originating from high-pressure air masses over the Great Basin and upper Mojave Desert flowing toward the lower elevations of the California coast.
The National Weather Service defines Santa Ana winds as “Strong down-slope winds that blow through the mountain passes in southern California. These winds, which can easily exceed 40 miles per hour, are warm and dry and can severely exacerbate brush or forest fires, especially under drought conditions.”
Within the Santa Ana’s, air descends from higher elevation in the Great Basis to lower lower elevations along the coast, it is heated adiabatically, warming about 5 °F for each 1,000 feet it descends. As the air is warmed adiabatically, its capacity to hold moisture increases and the relative humidity values drop. These hot, dry winds are also funneled through mountain passes where the Venturi effect increases wind speeds dramatically.
The combination of wind, heat, and dryness accompanying the Santa Ana winds can create critical fire weather conditions in the area. The Santa Ana’s are known for fanning the flames of wildfires and are sometimes referred to as “Devil Winds”.
Meteorologist Mike Morrison