And following the normally dry summer months, vegetation-which was especially luxuriant following last winter’s good rains-was primed to burn.

Los Angeles and San Diego have received only a tiny amount of rain since October 1. However, the beginning of the rainy season this year has been an absolute bust in southern California. Isn’t it the rainy season? What was burning?Ĭalifornia’s rainy season does in fact begin in October, and it normally manages to stave off huge wildfires during Santa Ana months. The winds helped the burgeoning fires grow thousands of acres in size in the matter of a few hours, forcing the quick evacuation of residents. During the beginning of December, the strongest Santa Ana wind event of the season took place as hot Santa Ana winds were clocked at 70 to 80 mph in the mountains surrounding Los Angeles. As the elevation drops, the pressure rises, compressing, warming, and drying the winds even further. Funneled into natural channels as they tumble down the mountains, the winds gather speed. Those high pressure systems help move air down the coastal mountains of southern California. The Santa Ana winds that have spurred the fires to new extremes peak in intensity during early the winter months as cold air settles into the high elevations of the basin and range terrain to the east. Similar to the recipe list that led to the massive Tubbs fire in October, a “perfect” combination of ingredients came together: extremely dry conditions, plenty of dry vegetation ready to ignite in an instant, and Santa Ana winds roaring down off the coastal mountains. The atmospheric set-up was perfect for creating strong Santa Ana winds over southern California, which fanned the flames of multiple wildfires. NOAA map based on data from NCEP/NCAR Reanalysis data. During the period, a broad high pressure circulation (clockwise rotation of the winds) was present over western North America and an anomalous low pressure circulation (counter clockwise rotation of the winds) was located over the eastern United States. The Skirball fire formed less than 5 miles from UCLA, which had to cancel classes on December 6.ĭifference from normal winds at the 300mb atmospheric level for December 5 - 9, 2017.

Smaller but still destructive, the Skirball, Rye and Creek Fires have burned through areas north of Los Angeles in the San Fernando Valley, as well. It still has a long way to go to reach number one, though, as the Tubbs fire in northern California-which we wrote about here-burned over 5,600 structures just two months ago in October. The Thomas fire now ranks as the eigth most destructive fire on record after burning over 970 structures to the ground. NOAA image based on data from the ESA.Īnd when large fires burn this close to a sprawling metropolitan city like Los Angeles, destruction is inevitable. Ongoing fires can be seen along the edge of the burn scar in the northern part of the figure. This false color image shows the large burn scar left by the raging Thomas Fire near Ventura, California, north of Los Angeles. Image taken by the European Space Agencies (ESA) satellite, Sentinel 2 on December 8, 2017.

Fires in california 2017 map