Southern California Spring wildfire risk isn't looking good
Thursday, March 1, 2018, 13:11 - Wildfires could be on the rise across California this spring.
The dry Fall and Winter weather pattern and above-normal temperatures have created the perfect breeding grounds for wildfires in many parts of the state, especially in Southern California where conditions are especially dry.
Every year around February, it is common to see wildfire potential in the southern third of the U.S. increase, and this year will be no exception. Coastal and mountain areas of Southern California, as well as the foothills and mountains surrounding the central San Joaquin Valley, are on the list of places likely to experience above normal wildland fires between March and May.
So far this winter, the only significant rain event in Southern California occurred in early January, when intense rain showers caused the deadly landslides that affected the coastal mountains of Santa Barbara county. Since then, not a drop in sight.
April-May Wildfire Potential
Fire potential to grow in Southern California as Spring moves along
This winter, precipitation has been more abundant in the north and in some sections of central California, a situation that is likely to keep large fire potential low. Further south, it's a whole different story, with the southern Sierra Nevada's experiencing well below average snowfall. The risk of above average wildfires has been growing week after week, as fire fuel in some areas has grown above critical levels.
Image courtesy of U.S. Drought Monitor. Drought conditions as of February 20, 2018.
When the feared warm, sunny days with gusty winds return to the region in such a dry environment, the likelihood of fires igniting and spreading rapidly is high. It's hard to forecast way in advance when critical Santa Ana wind conditions will develop, but we do know from The Weather Network's seasonal forecast, that a drier and warmer than average Spring is on the way across much of the southern half of the state (see below).
2018 Spring Temperature Outlook from The Weather Network.
2018 Spring Precipitation Outlook from The Weather Network.
The rainy season in California slowly tapers off between March and May, but the atmospheric dynamics should still be favorable for wet weather episodes to reach the northern half of the state. The rest of California will progressively see fuels dry from south to north, with areas below 5,000 feet capable of supporting large fires especially during dry warm Santa Ana wind days.
Drought Seasonal Tendency Map.
Drought forecasts published by the Climate Prediction Center are in agreement with the Spring Weather forecast elaborated by The Weather Network. Most of the Southwest U.S. will see drought persist under warmer drier weather, and some areas of central and southern California are likely to even see drought develop and intensify during the next three months.
Image courtesy of NOAA. Santa Ana winds
Aside from the drought, the number of times Southern California experiences Santa Ana winds will also be crucial for wildfire episodes to develop. After a very active December, the number of January Santa Ana wind days was closer to normal, with 9 days in the Los Angeles county area, and 8 in San Diego county.
Santa Ana wind occurrence from Scripps Institution of Oceanography
Forecasts based on Pacific SSTs (Sea Surface Temperatures) anomalies such as those seen now with La Niña, indicate that a high pressure ridge pattern favorable for Santa Winds to develop will continue to dominate during the Spring months. Then, with a decaying La Niña after Spring, we should expect the situation to return to normal. Moreover, it is important to note that the period of Santa Ana wind peak activity has already passed, and during the coming months offshore wind days in Southern California should be less common.