Updated 12/31/2021 9:56
Winds as high as 110 miles per hour pushed a grass fire far faster than a car can drive, jumping the length of a football field in seconds yesterday in the Front Range towns of Superior and Louisville. Up to 600 homes have been destroyed, but as of this writing, no fatalities have been reported.https://coloradosun.com/2021/12/30/boulder-grass-fire-evacuations/
Here’s a map of the destruction:
What drove the winds to such extreme speeds?
It’s strange to think about, but air masses don’t want to mix — the bigger the temperature difference, the less they want to mix. Yesterday and today a strong cold front is moving down from Canada, pushing warm air in front of it. This set us up for a warm, dry chinook wind. https://amylawscigeek.com/2021/02/22/chinooks-blow/
Chinooks have a number of strange behaviors. They blow extremely fast. They tend to hit the same areas hard – – several weeks ago tractor-trailer rigs blew over along the same stretch of highway as where the fires started yesterday. And, as I mentioned in my blog from earlier this year, chinooks can bounce. 9News, one of the local TV news stations, got some great video of the wind bouncing. https://twitter.com/i/status/1476639063981580289
Notice that you can see the smoke hugging the ground in the right of the frame. It actually stays close to the ground for a long time. That’s because the high winds are holding it down. Think about that for a moment — heat, including fire and smoke want to rise. In the video, they are held firmly in place by the high winds.
In the video, the fire hugs the ground as winds push down on it. In the center left of the frame, the fire and smoke are suddenly allowed to rise, and form a pillar of smoke. This is normal fire behavior. This is why you put your fire alarms on the ceiling.
And then … on the far left of the frame, the smoke is pushed back down. That’s the wind bouncing.
We’ve had chinooks before — they are a normal part of winter along the Front Range. But this year, the very dry fall dried out the grasses. The chinook brought warm, dry very high winds. Officials think the fire started when power lines blew over and ignited the grass.
As the fire leapt along people had literally minutes to get out. It will be incredible if, after all the homes that were burned, there were no fatalities.
Chinooks are already a feature of the Mountain West. Global climate change will make the West warmer and drier. These sorts of events will be more common in the future.