Firestorm devastating portions of Napa Valley, CA.

Sunday Night, major fires erupted in California’s Napa Valley under strong easterly winds and low relative humidity. This resulted in a conflagration engulfing communities and homes in flames and forcing thousands to make quick escapes in the early morning hours. One of the worse hit communities is Santa Rosa, where much of the city has been destroyed by fire. Over 1500 homes and businesses are believed to have been burned down in the Napa Valley region. The flames continue to grow at this time with over 75,000 acres burned.

Photos via the San Francisco Chronicle.

The fires are occurring in a region which is currently not in drought conditions hydrologically (as of last Thursday). However, after an unusually wet winter, an unusually hot, dry season followed. This allowed fuels, which grew in abundance following the wet season to dry out, leading to the massive fires in CA in this summer going into the Fall. Much of Western North America has been suffering significant fires in 2017 (year-to-date acreage burned in the US, as of Friday, was 3rd to 2012 and 2015). Intensifying wildfire seasons (on regional/continental scales) and increasing frequency of large fluctuations in extremes between very wet and very dry periods are predicted signals of climate change from global warming as well.

january-to-march-2017-us-total-precipitation-percentiles-map
Much above average to record precipitation in Northern California in January-March 2017.
august-2017-us-total-precipitation-percentiles-map
Much below average to record minimum precipitation (including NO measurable rain) in Northern California in August 2017. June-August 2017 saw much below average precipitation.
august-2017-us-average-temperature-percentiles-map
Much above average and record warmth across the West Coast during August 2017. San Francisco Bay Area saw record highs over 100 degrees at the start of September.

So far the fires have killed 10 people (as of 10 pm PDT Monday Night), while more than 110 have been injured, some severely from burns, most from smoke inhalation. It’s being reported Monday Night that 100 missing persons reports have been called in to the Sonoma County, CA office.

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Region where fires are in progress in the San Rosa and Napa region far north of San Francisco and west of Sacramento.

Although relative humidity conditions will improve somewhat tomorrow, no rainfall is forecast for this region of Northern California for the next 7 days to dampen the fire situation. Winds Tuesday will likely gust over 20 mph and may be locally stronger near the fire, continuing the self-sustaining burn.

us_model-en-087-0_modusarpd_2017101004_2_1900_219
11 pm PDT Monday Analysis by the High-Resolution Rapid Refresh (HRRR) showing the low dew point temperatures near and east of Santa Rosa. This area delineates a region of low relative humidity, allowing fires to burn and spread with little moisture on fuels to slow their extent.

 

For further updates see this updating page by the San Francisco Chronicle.

–Meteorologist Nick Humphrey

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Author: Meteorologist Nick Humphrey

Meteorologist and geoscientist in Lincoln, NE. Seattle, WA native. Love weather, storm chasing/photography and planetary science.

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