SANTA ANA WINDS

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SANTA ANA WINDS

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SANTA ANA WINDS

• LOCATION
• DESCRIPTION
• DEVELOPMENT
• SPEED
• TEMPERATURE
• DURATION
• CONSEQUENCES

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LOCATION

• The Santa Ana Winds occur below the passes and
  canyons of the coastal ranges of Southern
  California and in the Los Angeles Basin.
• The winds blow with exceptional speed in the
  Santa Ana canyon the canyon from which it
  derives its name.

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SANTA ANA MOUNTAINS
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DESCRIPTION

• The Santa Ana winds are hot and dry, and they
  blow from east to west instead of the normal west
  to east.
• Bring beautiful clear skies, and the presence of
  smog is limited.

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DURATION

• Winds commonly occur between October and February
  with December having the highest frequency of
  events.
• Summer events are rare.

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DEVELOPMENT

• The winds develop when a high pressure system
  builds over the Rocky Mountains (Nevada, Utah).
  At the same time there exists a low pressure
  system over Southern California.
• The regions to the west of a high-pressure center
  have southerly winds bringing in relatively warm
  air.

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DEVELOPMENT

• High pressure systems usually form where the air
  converges aloft. As the air converges in the
  upper-levels of the atmosphere, it forms an area
  of higher pressure and is forced to sink.
• Winds blow from high pressure to low pressure.

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DEVELOPMENT

• Clockwise circulation around the center of this
  high pressure area forces air downslope from the
  high plateau.
• The air warms and is compressed as it descends
  toward the California coast at the rate of 5
  degrees Fahrenheit per 1000 feet due to adiabatic
  warming.

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SPEED

• The winds are usually gusty and can change
  direction quickly.
• Wind speeds are enhanced as the flow channels
  through the mountain passes.
• Wind speeds are typically north to east at 40 mph
  through and below passes, and canyons with gusts
  to 57 mph. Gusts can be greater than 115 mph in
  favored areas.

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SANTA ANA WIND LOG

• 10/17/99 - First Santa Ana wind event of the
  season. Wind speeds of 38 MPH.
• 11/22/99 - Winds reached 45 MPH.
• 12/19/99 - December has the highest frequency of
  events. Winds speeds of 48 MPH.
• 1/5/00 - Winds gusted to 50 MPH and remained
  strong all night. End of Santa Ana wind season.

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TEMPERATURE

• The sinking air can warm by 54 degrees Fahrenheit
  or more and attain temperatures in excess of 104
  degrees Fahrenheit near the coast.
• Santa Ana Winds are not warm because they pass
  over hot desert surfaces, it is compression that
  causes their high temperature.

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CONSEQUENCES

• Power outages.
• The most notable consequence of Santa Ana Winds
  is fires, especially wildfires.
• Although Santa Ana Winds do not usually initiate
  a fire, the spreading caused by the winds
  prevents it from being controlled and amplifies
  the damage.

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CALIFORNIA FIRES

• Also, the winds are dry to begin with. Since no
  moisture is added, the relative humidity drops,
  often into the single digits. The extremely low
  humidity helps dry out vegetation, making it a
  better fuel for fires.

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DAMAGES

• In 1996 Santa Ana winds whipped up fires in
  Malibu and Carlsbad.
• The fires destroyed 140 homes, forced thousands
  to evacuate, and scorched more than 20,000 acres
  of brush land.