Southern California may experience fires into December

During October, above normal fire activity is expected throughout California. Map courtesy of the National Interagency Fire Center, Boise, Idaho

Summer 2019 has been a very light fire season, thus far. Both the U.S. Forest Service’s National Interagency Fire Center (NIFC) in Boise, Idaho and Cal Fire’s Predictive Services unit at its Southern Operations Center expect a return to a normal fire season in September and October.
They are also forecasting that the threat of wildfires in Southern California will likely prevail into December.
In its August wildfire outlook, Predictive Services staff wrote, “We have high confidence of an above normal large fire potential this fall into early winter … It might be well into December before Southern California sees potential fall to normal levels.”
The very wet winter accompanied by a cool spring elevated live fuel moisture levels, which lowered the threat of fires and lowered the rate of spread during the spring when one fire did ignite. These fuel moisture levels remained higher than average for August.
However, the lack of monsoonal moisture in August and warming temperatures are rapidly lowering live fuel moisture levels. It has been about two to four weeks behind the normal calendar average. However, the time lag is closing quickly, according to both agencies.
Both NIFC and the Predictive Services unit expect more “offshore” wind events this year than in 2018. This means more Santa Ana winds, but they should be less frequent than they were in 2017, according to the Cal Fire Outlook.
These winds are most likely to occur before any meaningful rain, according to both outlooks.
The National Weather Service (NWS) expects neutral El Niño conditions from fall to early spring 2020. Nevertheless, the NWS says the probability of an El Niño next winter is twice the chance of a La Niña. Cal Fire suggested that a wet winter may occur later than usual.

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