How Cold Fronts, Thunderstorms, Foehn Winds, and Fire Whirls Impact Fire | Wildfire Insider Ep. 18

Описание: We don't usually have cold fronts during fire season, but if you do combine a cold front and a wildfire, it can have very interesting impacts on fire behavior and the direction of spread.
Winds as the cold front moves through are going to be strongest just before the front due to the temperature/pressure gradient.
You'll also have southerly winds as the front is moving in, and westerly to northwesterly winds after it passes.
This can lead to a rapid change in the direction your fire is moving.

Thunderstorms can impact wildfires in a number of ways.
Lightning strikes can be the source of fire ignitions.
Gusty indraft and downdraft winds can lead to rapid fire spread and erratic direction of spread.
Rainfall can potentially reduce fire danger if enough moisture finds its way into your fuels.

While I may not be pronouncing foehn winds correctly, they can have major impacts on wildfire in California, and especially this time of the year.
In Southern California we call these Santa Anas, in Santa Barbara we call them Sundowners, and in Northern California, we call them Diablo winds.
What happens is you have air rush downslope, in most cases offshore in California, and as the air sinks down the side of the mountain, it warms up and dries out, leading to hot, dry, windy conditions that can promote extreme fire behavior.

Fire whirls typically happen during unstable atmospheric conditions, where you get rising air due to either surface heating or heat from the fire, and then this forms a vortex as the air rises.
In some cases, these fire whirls can grow quite large and have tornado-strength winds that can pick up burning branches and start new spot fires as well as lead to extreme fire behavior.

Fire in California’s Ecosystems,
Ch. 3 Fire Weather Principles (pg. 33-34)

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