The jet stream has been sharply contorted

Once low-pressure areas riding along the jet stream land in Colorado, high-pressure zones build in quickly to their north and west over northern Nevada and Utah, a region known as the Great Basin. The difference in pressure over this relatively short distance starts generating these winds.

The winds are then drawn westward toward California, where air pressure readings are lower (air flows from high to low pressure), and often, they gain speed passing through channels in the high terrain. Illustrating how powerful this weather phenomenon can be, wind gusts well above hurricane force were recorded over the weekend in the North Bay, near the Kincade Fire.

Over the past week or so, the jet stream has been sharply contorted, with a massive ridge of high pressure parked over the Gulf of Alaska and a sharp and deep trough to the east, which is ideally situated to drop low-pressure systems into Colorado, along with trailing zones of high pressure toward the Great Basin.

Here’s how a Weather Service forecaster in Los Angeles described the upcoming situation: “All three elements of a strong Santa Ana (Offshore flow, Upper level support, Cold air advection) are in place. Additionally most of these elements are also very strong and all of this will add up to be high end dangerous event. If everything comes together as forecast there will be 60 mph to 70 mph gusts not only in the mountains but in some of the valleys as well.”

The ongoing wildfires follow the devastating 2017 and 2018 California fire seasons, which featured the worst blazes in state history in terms of size, destruction and death toll. The Camp Fire, for example, which started Nov. 8, 2018, killed 88 people and destroyed much of the town of Paradise in a few hours.

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