SHORTER WET SEASONS ARE EXPANDING CALIFORNIA’S FIRE SEASON
May 2, 2021 –The Washington Post is reporting that California’s wildfire season is expanding as the wet season is compressed. In a story by Matthew Cappucci, the Post examined 60 years of rainfall datat for more than half a dozen California locations, from Mount Shasta in the north to San Diego in the South. The report concludes that while California’s west season isn’t necessarily drier than in the past, rain coming later in the autumm/winter and stopping earlier in the spring/summer is extending the fire seasons. Sample results showed Mount Shasta’s dry season 22 days longer, Fresno slighter longer wet season with later onset and San Diego fire season five days longer, wet season arriving later. The practical import is that California is drier during months when we typically see high wind events, which can drive wildfires dramatically.
The Post results line up with a study published in Geophysical Research Letters February 2021 edition (Vol. 48, Issue 4 28 Feb 2021), where an abstract states:
Californian hydroclimate is strongly seasonal and prone to severe water shortages. Recent changes in climate trends have induced shifts in seasonality, thus exacerbating droughts, wildfires, and adverse water shortage effects on the environment and economy. Previous studies have examined the timing of the seasonal cycle shifts mainly as temperature driven earlier onset of the spring season. In this paper, we address quantitative changes in the onset, amounts, and termination of the precipitation season over the past 6 decades, as well as the large‐scale atmospheric circulation underpinning the seasonal cycle changes. We discover that the onset of the rainy season has been progressively delayed since the 1960s, and as a result the precipitation season has become shorter and sharper in California. The progressively later onset of the rainy season is shown to be related to the summer circulation pattern extending into autumn across the North Pacific, in particular, a delay in the strengthening of the Aleutian Low and later southward displacement of the North Pacific westerlies.
ANOTHER BAD FIRE YEAR EXPECTED
April 30, 2021 – Experts are expecting another bad fire year in the Western United States, with California singled out for particular concern. Continuing drought conditions have created an unusually dry year, raising wildfire risks. Weather models suggest the West will be dry at least through June with above-normal temperatures expected.
Last year, California saw six of the largest wildfires ever recorded. The largest was the August Complex Fire, which spanned across five counties. Nearly 4.4 million acres burned in California in 2020, doubling the previous record set in 2018.
With things so dry, it’s important to be extra careful in fire areas, since studies have shown that more than 80% of wildfires in the US are started by humans. Wildfires started by humans make up 97% of all wildfires that threaten homes.