The Santa Ana Wildfire Threat Index is forecasting that the worst of the winds is over. However, several additional rounds of moderate Santa Ana winds will occur through the middle of next week, with continued significant challenges on existing fires and potential for new fires. Extreme fuel dryness is also present over the region.
Wind forecast animation
As the ongoing fires continue to impact the Los Angeles area, Spire Global’s Weather Risk Communications Forecasters team has analyzed key weather data and put together high-resolution forecast images highlighting critical factors such as wind gusts (see below) and soil conditions — conditions that are drier than normal for this time of year. The animation shows a few areas with winds getting in the 40 mph range.
End of the wind?
Over the period from 1950 to 2020, there were 3,219 Santa Ana wind days, and fires ignited on 12% of those days. Over this same period, there were 22,704 non-wind event days, and 12% of those days had ignitions. The number of Santa Ana wind days will decrease but continue through February. A marginal Santa Ana wind event is expected Tuesday.
Intense mountain waves
There is no threat of the mountain waves of intense wind impacting the area in the next few days. On Tuesday, Jan. 7, the wind event originated in the Nevada and Utah regions of the Great Basin, where high pressure produced winds that are flowing into Southern California.
The recent fires in Los Angeles County were made worse by a phenomenon called mountain waves. Mountain waves are oscillations in airflow that can happen when the wind blows across a mountain or hill. If a mountain wave occurs and a fire is present, the fire may become unexpectedly severe as the strong downslope wind fans the flames. A few areas in Los Angeles County had gusts over 100 mph, making fire suppression efforts in the air and on land extremely limited.
A red flag alert is usually issued when a combination of high winds, low humidity and high temperatures is expected.
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Sources: Santa Ana Wildfire Threat Index, California Fire Science Consortium, Spire.com, Cal Fire, FEMA, NOAA, California Fire Science Consortium,