The 20th Anniversary of the Jarrell Tornado

[Austin Dawg]

So, the parent supercell that eventually produced the Jarrell tornado formed right along a boundary, likely driven by a series of gravity waves that were coming in from a collapsing thunderstorm complex well to the northeast. This combination of factors, along with absolutely ridiculous instability, caused the supercell to sort of propagate along the boundary in the direction of the gravity waves (roughly southwest) rather than moving as you'd expect. It's a very odd and fluky series of events, but you see it happen occasionally under similar conditions, especially in central Texas.

You can see this play out pretty clearly in the visible imagery. Here I've marked the cold front (blue line), dryline (yellow line) and propagating gravity waves (orange lines). The supercell explodes basically as soon as the gravity waves begin to intersect the boundary, and then the whole thing just sort of "unzips." I included a bit more detail in my blog post if you're interested.

I live just south west of Jarrell and it is not uncommon for our stronger storms to move in odd directions. Some of the worst storms I’ve experienced came out of the northeast or northwest and moved south as part of a front or isolated MCS. I may be wrong but it seems like I remember that this tornado confirmed a theory of some kind about the overall system type being able to create a tornado.

 

[Austin Dawg]

I find it telling that both the Jarrell tornado and the Smithville tornado of 4/27, at opposite ends of the forward speed spectrum, are both described as producing some of the most extreme damage ever surveyed (the edge going to Jarrell for being essentially unsurviveable above ground). I think both were exceptionally violent and it's likely they would have produced similar, if not quite as extreme, damage had they been moving at closer to "average" speed.

I only recently came across this video of the Jarrell tornado, and the violence of the rotation even in its narrow early stages was truly astounding. You'd swear the video has to be sped up, but it isn't.

Yes, though it does not get as much press the Smithville tornado had a short path of extensive damage. My brother lived there and his house is the one in the ground zero photos on the western edge with only a wall standing. Across the street there was nothing. I can’t confirm it but I was told that there were fire hydrants damaged. I do know it threw and moved tombstones.

 

[SGFmoTwister]

An article questioning the F5 rating of the Jarrell tornado.
https://archive.org/details/fujitatornadoint1426phan/mode/2up