08/15/07 DISC: IN/OH

[Robert Dewey]

Given that link posted by Justin, yesterday would have qualified as a MDT risk for much of northern IN through central OH. That's a relatively small area, but not so small that a MDT couldn't be issued. But, that's hindsight.

My thought, personally, was a high-end SLGT with 5-10% TOR and 30% wind. SPC had no TOR risk out, which was unusual given the parameters involved (0-1km SRH around 300m2/s2, MLCAPE over 2000j/kg, creating EHI's over 10)... throw in the MCV moving through, and I would have been very hesitant to go with a 0% TOR risk on the 0100Z outlook.

 

[Tony Lyza]

Thanks - they had a lot of bad timings on reports (one came from a 'ship' near I-69 ;> ) so it was probably more a communication breakdown than anything else. Still interesting that no tornado came from the massive supercell!

WGN-TV is reporting an unconfirmed report of a touchdown near Kouts in southern Porter County, and there are images of high-tension truss towers being brought down right around where the mesocyclone crossed IN Rt. 8 last night. I'm probably going to go see if I can take a look, but I sincerely hope LOT is going to go survey that damage. The expected value for bringing down truss towers on the EF-scale is 141 MPH.

 

[rdale]

I sincerely hope LOT is going to go survey that damage.

I'm willing to put a good deal of money down - care to guess what I think they'll do ;> ?

 

[Adam Lucio]

They did have a 2% torn out for the whole day, it shifted around a bit but at the time of the event it was over northern IN and IL I believe.

 

[Tony Lyza]

I'm willing to put a good deal of money down - care to guess what I think they'll do ;> ?

They've been pretty good about doing surveys, so I'm thinking they'll probably go out.

 

[Tony Lyza]

They did have a 2% torn out for the whole day, it shifted around a bit but at the time of the event it was over northern IN and IL I believe.

There was no 2% tornado region on the 01z outlook. But that's old hat. There was plenty of warning, and a tornado watch was issued promptly when it became clear that a serious threat existed.

 

[Adam Lucio]

WGN-TV is reporting an unconfirmed report of a touchdown near Kouts in southern Porter County, and there are images of high-tension truss towers being brought down right around where the mesocyclone crossed IN Rt. 8 last night. I'm probably going to go see if I can take a look, but I sincerely hope LOT is going to go survey that damage. The expected value for bringing down truss towers on the EF-scale is 141 MPH.

141? That would make it a significant tornado

Does LOT investigate Porter county? I thought they only took care of Lake in Indiana.

 

[Tony Lyza]

141? That would make it a significant tornado

Does LOT investigate Porter county? I thought they only took care of Lake in Indiana.

LOT's counties are as follows:

In Illinois:
Winnebago
Boone
McHenry
Lake
Ogle
Lee
De Kalb
Kane
Du Page
Cook
La Salle
Kendall
Grundy
Will
Livingston
Ford
Kankakee
Iroquois

In Indiana:
Lake
Porter
Newton
Jasper
Benton

 

[Robert Dewey]

I am not good with predictions or weather models but I felt we just never got the right conditions in place for storms. Once the heating left for the day I was ready to call it a bust for severe weather.

Actually, instability was forecast to increase after sunset. The RUC showed this quite well, and the mesoanalysis showed instability advecting in as lapse rates increased... so the earlier precipitation probably wasn't as big of an instability-kill as one would think.

I'm just curious as to why the TOR threat was so low... with such a high shear / instability combination, and a decent trigger moving through... you would think that at least a 2% probability would be warranted.

 

[rdale]

IWX says two EF1 tornadoes hit near Argos, embedded within a microburst.

 

[John Farley]

Damage survey from LOT here:

http://kamala.cod.edu/il/latest.nous43.KLOT.html

Straight-line winds, mostly associated with RFD, peak winds 100-120 mph.

 

[rdale]

The survey makes no mention of power trusses being down - was that in a different area?

 

[Tony Lyza]

The survey makes no mention of power trusses being down - was that in a different area?

No, that was about 1.5mi east of Kouts.

I went on a personal ground survey of that area where the trusses were downed. I came to a slightly different conclusion than LOT, but it's really just splitting hairs at this point.

http://blog.tornadotony.com/weather/porter-county-damage-survey/

Cliffnotes from our survey:

Obviously, the most striking damage was the set of downed high tension towers. Before the storm, there were two sets of high-tension towers running in tandem right next to each other. There was a 4.5mi long stretch where both sets ran north to south, with the lines continuing NW at the N end and SW at the S end. The entire north-south "block," if you will, of the west set of towers was downed. The east set was undamaged. There was only one area where intense crop damage occurred in tandem with a tower (it also happened to be the most severely mangled tower). This lead us to believe that tower had some deficiency that made it fail, and it somehow sent a force (perhaps some sort of wave?) down the rest of the "block" of N-S running lines, causing all the towers in that "block" to collapse, with the orientation of the NW-SE and NE-SW towers perhaps making them less susceptible to this force.

Interestingly enough, that path of crop damage that coincided with that most mangled tower was part of a rather long track of particularly intense damage, with included an apparently convergent path of EF1 hardwood tree damage (trees snapped at the bottom of the trunks) in a subdivision. It was a very distinct path about 100y wide and probably a good 6-7mi long, and would have coincided well with the tornado-warned circulation.

 

[rdale]

Good survey! Sometimes I find that even more intriguing than the chase, at least the "detective" part. And agree that in fast-moving storms it's impossible to determine low-end tornado due to the speed.

 

[Tony Lyza]

Good survey! Sometimes I find that even more intriguing than the chase, at least the "detective" part. And agree that in fast-moving storms it's impossible to determine low-end tornado due to the speed.

Thank you. I couldn't have done it without the help of the other two guys I chase with, who also first came up with the "first failed, then the rest failed" idea when we were trying to figure out why EF2 damage was surrounded by corn that was in near-perfect shape.

As for the low-end tornado damage, even Grazulis has mentioned it being a problem in storm surveys of fast-moving cells. Though I left the caveat in my survey that the path may have been mostly strong RFD leading into the convergent damage mentioned, I really lean more toward the whole thing being a borderline EF1/EF2 tornadic damage path, from about 600 S where it crossed the power lines to 900N-ish (the corn damage on 900N was substantially weaker than at 600N, 700N, or Hwy. 8). I really have a hard time envisioning a microburst that uniform and with such a well-defined path.

And I don't really mean to bash LOT by doing this survey or voicing a different conclusion. I think they did a good job considering the extremely large area of fairly strong damage (from Gary all the way to NE Jasper County as the cell left the CWA) that had to be surveyed in one day. I just happen to disagree on this small section of the damage and wanted to get a look and opinion for myself since this was significant damage.