Tornado in the forest - what to look for when doing a damagae survey?

[Patrick Boomer]

It seems that on July 30, a tornado touched down in the Alberta foothills west of Sundre, turning a 2x.5 mile swath of pine trees into a tangled mess.
I was wondering if anyone with experience in tornado damage surveys would have any tips on what exactly to look for if a person wanted to try and figure out the damage scale.
I'm not sure if anyone else will every go look at it, so I thought I'd take some time out there and try to get a good grasp on what happened, if this really is tornado damage from 2 weeks ago.

I've looked around and read a few papers on identifying convergence/divergence lines etc, but there isn't a lot of info on pure forest damage out there. I did find one good paper but I need to go back to school before I can read the whole thing.

There are two photos in this post on my blog, sent in from a fellow who spends a lot of time out there, he states two foot diameter trees have been snapped off like twigs.
http://blog.boomerphoto.com/2010/08/12/more-on-the-july-30-tornado-west-of-sundre/

Thanks
PB

 

[John Vandehei]

Well it's hard to tell without being there, but by looking at the right picture in the center row, the trees appear to be knocked down in a general right to left orientation. That would suggest a violent downburst, not a tornado. We had a very violent downburst here in Michigan about ten years ago and the downed trees were laid down in a similar pattern. If any more pictures are available, it could be helpful

 

[Skip Talbot]

What a beautiful looking storm.

I'm not at all qualified to judge tornado damage, but John brings up a good point that it might be downdraft/downburst damage. Even though the damage was quite close to where the tornado was, and I'm sure the tornado did its own damage if observers noted trees lofted into the air, the size of the tornado (or the cone funnel in the photos) does not lead me to believe it would have a half mile wide damage path. I think it more likely that it was the rear flanking downdraft wrapping around the tornado that might have caused that.

The pine forests that we have in Wisconsin by my family's cabin are highly susceptible to wind damage. It seems they catch more wind, the roots are shallower, and the soil is loose and sandy so they tip pretty easily. I could see how a large swath of them would go down in a severe downburst.

For actually rating tornado damage caused to trees you can check out the degrees of damage for trees in the Enhanced Fujita Scale:
http://en.wikipedia.org/wiki/Enhanced_Fujita_Scale#Damage_Indicators_and_Degrees_of_Damage

 

[Chris Koetters]

So if a tree is hit by a tornado in the forest, and no one is around to see it, does it make a sound?

Sorry I thought for sure someone would have posted that one. lol. Couldn't resist...

 

[Jason Boggs]

It was near a nudist colony! Now that's funny. Wouldn't have been able to tell how strong it was from the amount of clothes it removed!

 

[Tim Shriver]

Most of the knocked down trees are all in the same direction
but this could be just the way the images were shot.

There is debarking of trees in some spots and what sort of appears
to be a circulation pattern on the left side of the image (image on the right side of webpage) but it could just be a land feature.

From the images it is hard to tell as the damage area seems very
isolated and contained.

Looks like pine so it is a soft wood(TS) also. Bends easier
than hardwood (TH).

I see no man made structures with damage. So can not use that
damage indicator leaving us with only the TS indicator.

Would have to see if it had downdraft markings or pattern.
Central point with damage radiating outward.

Straight line would push them down in the same direction.

Swirling and twisting patterns would indicate possible tornado.

Not seeing trees fully uprooted and displaced. Some but not
much in the way of tree debarking. Most shallow root systems,
trees looked more pushed over then yanked out and tossed.

Damage Indicator DI-28 (TS)
Degree of Damage DOD - 4/UB 118-128

EF2. Significant Tornado.

Tim

 

[Patrick Boomer]

The tornado touchdown turned out to be far from the nudie camp, there was a bit of confusion in initial spotter reports that never got ironed out before it hit the papers.

We wound up going out for a look at the damage, it was a pretty impressive sight for us stubble jumpers up here.

http://blog.boomerphoto.com/2010/08/16/august-15-damage-survey-of-july-30-tornado-path/

I reported what we saw to Environment Canada, who were not very interested, estimating an F2 at most from looking at the photos.

 

[Clarence Bennett]

Very simple...look at the direction of the root balls or the trees that have been snapped off. The picture in this link is a very good example of a tornado that touched down in Middle TN in 2006. Notice the direction of the trunks in relation to the rootball.

http://www.srh.noaa.gov/images/ohx/surveys/images/WEB/cheatham1.JPG

 

[Scott Weberpal]

You can see in this picture that many thin pines were snapped, but the buildings near the trees were almost untouched. This occurred near Eagle, WI this year - the tornado was rated EF2, but that rating was based on residential damage later in the life of the tornado.

 

[Tim Shriver]

I think the use of the TS or TH damage indicators is a recent addition.
I always thought that EF scale was from damage to only man made structures.

But with the TS (Tree Softwood) and TH (Tree Hardwood) added for trees adds a needed element.

But with trees there are many items that can affect the rating.
Wet Soil?
Dry Soil?
Sickness/health of tree
Location
Root depth

Most of the time determining if is a tornado or not is not real hard.
Rating it can be a little odd to do as you get a mix of damage indicators
and degrees of damage.


Tim

 

[Kara Jones]

The tornado touchdown turned out to be far from the nudie camp, there was a bit of confusion in initial spotter reports that never got ironed out before it hit the papers.

We wound up going out for a look at the damage, it was a pretty impressive sight for us stubble jumpers up here.

http://blog.boomerphoto.com/2010/08/16/august-15-damage-survey-of-july-30-tornado-path/

I reported what we saw to Environment Canada, who were not very interested, estimating an F2 at most from looking at the photos.

Hello neighbour!
Wasn't that a beautiful storm!? I was so happy I decided to take a quick drive west of town to see what it would do. I got to the top of Rice's Coulee just in time to set up my camera before the funnel came down.
Here are some of the pictures I got. Sorry about the quality, I can't wait to get a dslr. Although all the smoke from the BC forest fires wasn't helping either.

This is the cell that was just south of the Sundre one. I assume it is the one that produced the unconfirmed tornado by Water Valley. The timing was about right if I remember.

Sorry for picture overload. I hope it is ok that I posted them
Kara

 

[Patrick Boomer]

Those are great shots Kara, especially considering you were 30 miles away from it!
Thanks for sharing those I hadn't seen them before.
I talked to a fellow from the forestry company that handles the area, he said there was a company person very close to the touchdown and witnessed it.
Hoping to make contact, would love to hear that story!

I also learned that this patch of forest dates back to the early 1890's, the last big fire in the area was 1888-1889, so it tore through fully mature timber.
They are going to try to get in there and clean it up soon, before the wood dries out too much.

 

[Kara Jones]

Thank you Patrick. That is the first time I have posted them anywhere.
I sure hope you are able to get in contact with that person, it would be amazing to hear their story! I wish you luck and can't wait to read it on your blog if you do.
That is amazing how old the timber was, a little sad as well. Do you know if any of the wild horses were affected by it? I know you had spoke with that one gentleman that was part of the society, but I can't remember if he ever told you if they were.