The fire season is still alive and well in southern California and it’s being fueled by a local wind that is foreign to anyone who doesn’t live there. The localized winds are known as “downslope” winds which move down the slopes of the Santa Ana mountains, from the hot deserts.
Here’s the set-up. High pressure sitting across the desert and an ‘offshore’ flow are created. Instead of an ‘onshore’ flow where a cool sea breeze comes from the ocean, the offshore flow brings hot air in over the mountains. As the hot air is transported down the slopes of the mountains it travels over a lot of uneven terrains. These uneven terrains create lower to high pressure and increase the speed at which the air travels from the slopes to the valleys. So, when the wind arrives from the desert it is gusty and hot. It’s also dry which can fuel a wildfire. It’s the worst of both worlds. The wind in itself fuels the fire, but the hot and dry wind adds fuel to the fire and spreads it much more quickly.