Explaining Santa Ana Winds

22 Dec 2020, 1:01 pm

Santa Ana winds are one of Southern California’s most recognized weather features, especially from the fall to the spring. This week, they will elevate fire danger from San Luis Obispo County to Los Angeles from Wednesday through Thursday.

“It’s one of the most impactful patterns we can have in Southern California,” said Mark Jackson, Meteorologist in Charge at the National Weather Service in Los Angeles, CA. “Everybody hears about the wildfires in Southern California and the driving force behind that are these Santa Ana winds.”

These are northeasterly, offshore winds that descend in elevation and can sometimes reach hurricane-force strength.

“When you get the very hot, the very dry conditions combined with very strong winds, we can have some Santa Anas that have winds gusting over 100 mph,” Jackson said.

These winds originate from high pressure over the Great Basin with low pressure off the coast. Winds flow from high pressure to low pressure, and the stronger the gradient (or pressure difference between the two), the stronger those winds can be. As the winds get closer to sea level, they speed up, dry out, and heat the air.

“It can actually warm on a rate of almost 30 degrees Fahrenheit per mile!” Jackson said.

Critical FIRE WEATHER likely again Wed-Thu this week due to gusty offshore winds. Use caution during this time!! RH will be VERY LOW at 3-10% and fuels still extremely dry. NOTE – critical fire weather areas include interior San Luis County! #SoCal #CAwx pic.twitter.com/D16lJ49Wlz

— NWS Los Angeles (@NWSLosAngeles) December 21, 2020

The combination of hot, dry and windy contributes to a number of changes to the weather including record setting temperatures and, most notably, dangerous fire weather conditions.

“I would say that our strongest Santa Anas are probably in the early morning hours so just before sunrise and just after sunrise,” Jackson said. “When you have a better chance at getting very hot temperatures, that can naturally bring that relative humidity even lower in the afternoon.”

Thousands still evacuating as California wildfires grow out of control. This has been the longest and strongest Santa Ana wind event so far this season. #fires #CAwx pic.twitter.com/8FVvhd3Pee

— WeatherNation (@WeatherNation) December 6, 2017

Santa Anas last around the clock and sometimes days in a row, with little to no relief. Fortunately, forecasters are able to spot this pattern up to 6 to 7 days in advance.

“We may not have the exact time of when that may peak between a certain 6 or 12 hour period, but we can provide the fire agencies information with the idea that say a week from now things are setting up that we could have a pretty strong Santa Ana,” Jackson said.

About the author

Meredith Garofalo

Meredith is a Certified Broadcast Meteorologist as designated by the American Meteorological Society. She was born and raised in Cleveland but has worked from coast to coast covering almost every type of weather. Meredith is a weather, space, and STEM journalist and has been live out in the field during destructive tropical storms on the Gulf Coast of Florida, raging wildfires in Southern Cali... Load Morefornia, and covered the wreckage from tornadoes in the Great Plains. In 2009, she reported on the damaging hail storm during the Sturgis Motorcycle Rally and in 2017, the historic California winter storms that produced record rain totals and devastating flash flooding. Prior to joining WeatherNation, Meredith worked at KEYT/KKFX in Santa Barbara, CA, KOTA-TV in Rapid City, SD, WWSB-TV in Sarasota, FL, and began her career as an intern at WGN-TV in Chicago. She was Santa Barbara's "Favorite Weathercaster of the Year" in 2016 and the Community Partner of the Year in 2017 for her volunteer work with Make-A-Wish Tri-Counties and awarded with the 2018 Valparaiso University Alumni Association First Decade Achievement Award. Meredith is the current chair of the American Meteorological Society's Station Scientist Committee, which focuses on raising greater awareness & outreach when it comes to science education for viewers. She's also an accomplished journalist, producing weather and science stories including rocket launches at Vandenberg Air Force Base and the new GOES-16 satellite and it's impacts on weather forecasting. Meredith was personally invited by NASA's Johnson Space Center to interview astronauts on the International Space Station and was the only meteorologist in the nation to do an exclusive report accompanying the GOES-West satellite from Colorado to Florida, reporting on and covering it's launch in 2018. Meredith's also worked on features that took her paragliding along the coast, white water rafting in Northern California, learning to surf in the Pacific Ocean, and how to be an aerial photographer while flying a single engine plane! Say hi on Facebook, Twitter, & LinkedIn!