With California currently experiencing wildfires, and a large amount of California under an “elevated” risk for fire weather, it is important to understand some of the key factors that help fuel these fires. One of the most notorious factors is the Santa Ana winds. These winds are different from wind patterns that occur in other places of North America.
The Santa Ana winds are also known as katabatic winds (which are found in places like Greenland) meaning that they originate from higher elevations and flow downhill to lower elevations bringing the air with them. Specifically, Santa Ana winds originate from high pressure systems over the Great Basin, which spans from eastern California to New Mexico, and as north as Wyoming and Idaho. The Great Basin has a very dry climate, which helps fuel these winds.
For Santa Ana winds to form, a high pressure system over the Great Basin is needed. High pressure systems are clockwise anticyclonic winds with wind flow spreading out from the center. A basic diagram is included below to help you understand the flow of motion.
(Image from weather.gov)
These winds will then flow towards lower pressure, which is usually located off the California coast. The cool, dry air will flow outwards and eventually downwards towards California. When these air masses descend, through compression, the air warms. For every 1,000 ft that the air descends, the air warms by approximately 5-degree F. This makes for the winds that are now flowing towards parts of California to be very hot and very dry. These air masses that are descending and warming rapidly lead to a very hot and dry air mass that is then pushed over regions of Southern California. During the time of the year that Santa Ana winds occur, Southern California is experiencing some of the hottest temperatures that they see all year round. This air mass makes the air even hotter and drier.
When thinking of fire, there are certain “ingredients” needed to help sustain a fire. You need a fuel source, heat, and oxygen. The fuel source in California wildfires is the vegetation on the ground, such as, brush, shrubs, and trees. Since there is no way to stop the oxygen input into a wildfire, the next variable ingredient is the heat input. These Santa Ana winds are bringing along a very hot and dry air mass to the region, which helps fuel the fire even more. They add more heat to the fires, and the winds push the fires into different regions and communities.
When you add the Santa Ana winds to the California wildfires, the wildfires will become a greater threat. Thankfully, the U.S. Forest Service and firefighters are there to help mitigate the risks of these fires. Also, it is important to listen to the U.S. Forest Service and the National Weather Service to understand if your community is at risk and precautions to take. If your area isn’t at risk of wildfires, there are many different ways that you can help support people who are affected. The American Red Cross is a life-saving organization that helps many people who are affected by these wildfires.
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Credits: Weather.gov and UAlbany
©2019 Weather Forecaster Allison Finch