Santa Ana wind
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Santa Ana winds are warm, dry winds that characteristically appear in Southern California weather during autumn and early winter.
Santa Anas are a type of foehn wind, the result of air pressure buildup in the high-altitude Great Basin between the Sierra Nevada and the Rocky Mountains. This air mass spills out of the Great Basin and is pulled by gravity into the surrounding lowlands. The air circulates clockwise around the high pressure area bringing winds from the east and northeast to Southern California (the reverse of the westerly winds characteristic of the latitude). 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 actually form during autumn and early spring when the desert is relatively cold. The air heats up due to wet and dry adiabatic heating while being compressed during its descent. It is further dried as it passes over the Transverse and Peninsular Ranges. The air is then forced down the mountain slopes out towards the Pacific coast; the air mass is further heated by compression as it drops in altitude before reaching the Los Angeles Basin and western San Diego County at typical speeds of 35 knots. The southern California coastal region gets 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 and the humidity plummets to less than 15%.
As the Santa Ana winds are channeled through the mountain passes they can approach hurricane force. The combination of wind, heat, and dryness turns the chaparral into explosive fuel for the infamous wildfires the region is known for. Wildfires fanned by Santa Ana winds burned 721,791 acres (2,921 km²) in two weeks during October 2003.
Santa Ana winds may get their name from the Santa Ana Mountains that lie in Orange County or the Santa Ana Canyon through which the winds are noted for their high speed. Many Southern Californians believe that the traditional name is Santanas, meaning devil winds in an undetermined language. That name was occasionally used in early reports, but modern scholars have not agreed on the etymology of the word. It is rarely spelled that way today, though the pronunciation is still heard.
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. The hottest temperature ever recorded in North America outside Death Valley, 133°F (56°C), was recorded on June 17, 1859 off the coast of Santa Barbara during a Sundowner wind.
Further north, in the San Francisco Bay area similar downslope winds are called Diablo winds and in the northern plains such winds off the Rocky Mountains are called Chinook winds.
There is also a band named The Santa Ana Winds Youth Band.
See also
External links
- University of California, Los Angeles, Meteorology Dept.: Santa Ana Winds (http://www.atmos.ucla.edu/~fovell/ASother/mm5/SantaAna/winds.html)
- What are the Santana or Santa Ana Winds? (http://www.losangelesalmanac.com/topics/Weather/we23.htm)eo:Vento de Santa Ana