Was Air Canada’s Severe Turbulence Encounter Actually an Undular Bore?

If you’ve been reading the blog for awhile, you might have noticed that I’m kind of a weather wonk as well as an airline dork. So I was really interested to see that a recent Air Canada flight that hit turbulence may have encountered an undular bore. What the heck is that?

You may have heard about this flight. An Air Canada A319 was going from Victoria to Toronto when something happened and the plane had to make an emergency landing in Calgary. At least 10 people were injured, but not much other information has been released, except that there was a computer problem.

I read a post in the Turbulence Forecast blog today pointing to an article saying that it could have been a rare atmospheric (aka undular) bore that caused turbulence severe enough that it impacted the computers (or more likely just knocked out the autopilot).

I had visions of a giant tidal wave in the sky crashing down on the plane, but admittedly, I had no idea what an atmospheric bore was at all. Turns out I wasn’t quite right. A little research brought me to this fascinating blog post from ABC 33/40 in Birmingham, Alabama of all places. Now, I’m a huge fan of true weather wonks. I regularly read Tom Skilling’s blog for WGN in Chicago, and I used to really like watching Sean McLaughlin when he worked for channel 12 in Phoenix. After reading this post by Tim Coleman in Alabama, I think I’ve found another weather geek to follow.

Tim explains the undular bore phenomenon very well. Basically, when a warm air mass comes into contact with a cool, stable air mass (or vice versa?), they can create waves in the air similar to what you’d see when you drop a pebble into a body of water, only these waves move at 10 to 50 mph. The tops of those waves will have winds going one way while the bottoms may be going another way. On October 3, 2007, a webcam caught an amazing view of one of these undular bores. Check it out.

Watch the trees at the very beginning. As the waves roll by, the winds quickly shift direction. That’s just cool. But this post makes it sound like this isn’t the rarest event. It actually happens quite often, though you often can’t see it because there are no clouds to show it. That’s a stark contrast to the original article saying it’s an extremely rare event. Maybe it’s only rare at such high altitude. I’m just not sure. Pretty cool stuff though, huh?

I’m just glad I didn’t have fly through it. Then again, it’s nice to know that flying through such violent air only resulted in some minor injuries and the plane landed safely.

Update 2/13/09: It appears that the video has been pulled down from YouTube. Watch the undular bore in action at NASA.