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12 FOUR SEASONS BREEZE | JULY 2021 As we get into the heat of the summer, the next fire season begins to ramp up. Given the very dry winter, the ever-increasing temperatures from climate change, and a host of other factors, many experts are warning of an aggressive fire season this year. Before getting into the details, let's first examine the typical fire season from a weather perspective. In Southern California, the fire season has typically been defined primarily as the months between July and November, with the September and October time frame as the most critical months. This is due to several important meteorological factors: (1) the primary Santa Ana wind season which produces high winds and very low humidity; and (2) the hot and dry months of the year which dry out vegetation creating ample fuel supply for fires. (For insight into the cause of Santa Ana winds, please refer to the weather article in last September's Breeze.) This past rain year, Beaumont received only about 35 percent of normal rainfall, and this figure is fairly accurate in describing precipitation across all of the region. This has caused earlier drying of vegetation leading to enhanced fire potential. However, one ameliorating factor is that the low rainfall has diminished the amount of vegetative growth that normally occurs in a typical rain year. Whether or not this is significant enough to offset the early season vegetative drying is subject to debate. For the upcoming season, if we get some early season major storms, that could put a significant damper on the fire potential. But if conditions remain dry into October and November and beyond, then an active fire season would be expected. Looking at the potential for wet versus dry, the computer model forecasts of sea surface temperatures issued by the National Climate Prediction Center provide a hint of what is to come. This past year, we had a very strong La Niña condition which promotes a drier than normal rain season. Current model projections show a greater than 50 percent chance of a weaker La Niña for the coming rain season, which, again, would promote drier than normal conditions, but not as severe as the past season. There would be more likelihood of some storms, but still not as many as a normal rain year. According to California State University (CSU) researchers, climate change is also exacerbating the potential for prolonged drought conditions. Furthermore, drier conditions are symptomatic of the type of weather conditions conducive to more frequent Santa Ana winds, and therefore, the fire season can be extended into the winter months, as has occurred this year. The bottom line for this upcoming fire season is to be prepared and follow the guidance issued by the Ad Hoc Power Outage Committee. "Understanding the Weather" – A Series by Mel Zeldin, Retired Meteorologist Fire Weather & the Upcoming Fire Season Bracing for fire season

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