The Tubbs and Atlas (as well as several other small fires) fires began on October 8th.  The death toll climbed  to 44 today. It is likely to continue rising, as several people are unaccounted for.  The fire completely destroyed thousands of homes.

Fire Weather

We do not know exactly how the fire started. However, weather conditions certainly made things a lot worse.  First of all, relative humidity averaged 10%-20% below normal for this time of year.  These anomalies have been present since late September, most likely caused by the abnormally strong North Pacific High.  High pressure systems promote subsidence (sinking air), which helps dry out the atmosphere. Subsequently, the bone dry conditions result in easier combustion of twigs, plants and trees.

humidity, fire, wildfire,

The other, and possibly more dangerous weather factor resulting from the North Pacific High was strong winds.  The sea level pressure gradient (difference in pressure) determines the strength of the wind.  Sustained winds measured 20-30 mph with higher gusts. Winds spread embers to unburnt areas and also ventilate the flames, providing more oxygen to for combustion.

high pressure, fire, anabatic, wind

Upwind from the fires are the both the Mendocino and Sierra Nevada Mountain ranges.  As a result, winds from the northeast ride down the southwest slopes these ranges, increasing fire potential.  Gravity helps increase the wind speed and the fact the air is sinking leads to lower humidities.

Winds have died down and the fires are becoming more contained. Luckily, rain is in the forecast, too. A cold front will com through overnight on Thursday.  The latest GFS forecasts 0.1″-0.15″ of rain.  After this brief respite, a ridge will build back in early next week.

The bottom line is the problems could continue.  Hot temperatures next week could aggravate an already serious situation -Jim Roemer

rainfall, california


BBC covered the horrendous destruction caused by the these wildfires:

Finally, if you would like to help to those affected by these fires, you can donate to the Red Cross


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