Why in news?

Wildfires in Los Angeles, California, have killed 10 people, forced over 130,000 evacuations, and destroyed homes, including those of celebrities like Paris Hilton and Billy Crystal.

Major fires, such as the Palisades, Eaton, Sunset, Hurst, and Lidia fires, continue to burn, affecting areas like Hollywood Hills.

The Oscars nominations announcement has been delayed due to the fires. Although wildfires are common in California, the intensity and speed of these winter wildfires are unusual.

What’s in today’s article?

• California Wildfires 2025
• Possible Cause of California Wildfires
• What are Santa Ana Winds?

California Wildfires 2025

• Origin and Timeline
  • The first fire started on January 7 in the Pacific Palisades neighbourhood of Los Angeles.
  • It is the worst firestorm in recent memory, occurring unusually in January, traditionally the coldest winter month.
• Unusual Timing and Drought Conditions
  • Wildfires typically occur between June and October, but the current blaze defies this pattern.
  • Southern California has been facing drought conditions, with only 40.9% of the state drought-free as of December 31, 2024, compared to 96.65% the previous year.

Possible Cause of California Wildfires

• The exact trigger remains unknown, but power cables blowing in the wind are a likely cause.
• Three Key Factors Behind the Conflagration
  • Wet Weather Followed by Extreme Dryness
    • Unusually wet winters in 2022 and 2023 led to dense vegetation growth in the Los Angeles region.
    • The winter of 2024-25 has been exceptionally dry, turning the vegetation into dry kindling.
    • NASA Report: Since October, Southern California has had negligible rainfall, with Los Angeles recording its driest start to a water year since 1944.
  • Santa Ana Winds
    • Common in the region but unusually strong this year. These winds:
      • Blow westward from high-pressure systems in the Great Basin.
      • Lose humidity, gain heat, and increase in speed as they descend over mountains.
      • Result: Fast, dry, and warm winds that rapidly spread flames over dry vegetation, power cables, and flammable wooden structures.
  • Impact of Climate Change
  • Climate change has intensified extreme weather events, including wildfires.
• Key Observations:
  • Rising global temperatures, warmer springs, and early snow melts have extended and intensified dry seasons, increasing vegetation moisture stress.

What are Santa Ana Winds?

• About
  • These are strong, dry, and warm winds that blow from the inland deserts of Southern California toward the coast.
  • These winds are most common in the fall and winter months but can occur any time of the year.
  • They are known for their ability to quickly spread wildfires due to their dry and powerful nature.
• Causes of Santa Ana Winds
  • 
  • High-Pressure Systems in the Great Basin
    • Santa Ana winds are caused by high-pressure systems that develop over the Great Basin, a desert region that spans parts of Nevada, Utah, and California.
    • These high-pressure systems create a clockwise circulation of air, pushing winds toward lower-pressure areas along the California coast.
  • Descending Air
    • As the winds move westward, they descend from higher elevations (like the Sierra Nevada and Santa Ana Mountains) toward lower elevations near the coast.
    • During this descent: The air compresses, heats up, and loses humidity.
• Narrow Passages and Speed Increase
• The winds are funnelled through mountain passes and canyons, which increase their speed significantly.
• Gusts can reach over 100 mph (160 km/h) in some areas.
• Characteristics of Santa Ana Winds
  • Warm and Dry: The air warms as it descends, making the winds hot and dry.
  • Strong Gusts: The winds can reach extreme speeds, causing power outages and property damage.
  • Fuel for Wildfires: The dryness and speed help spread flames rapidly by drying out vegetation.