Tornado or not?

[rdale]

Gotcha - thought you were photogrammatically analyzing the raindrops ;> I think anything will be cleared up once we see the damage pics.

 

[Tony Lyza]

Gotcha - thought you were photogrammatically analyzing the raindrops ;> I think anything will be cleared up once we see the damage pics.
[/b]

Sorry guys, I really don't have damage pics. It's all cleaned up, and I ran off to chase another cell in IL soon after our storm passed over. Geez, I gotta stop being an airhead and do what need be done. About 2 miles away, the same storm ripped the roof off of a pizza place, but I haven't driven past that area to get pictures. Also, the same storm produced 75 MPH winds a few miles SW of me in Crete, IL. I am confident in my wind estimate and the fact that the wall cloud (confirmed to be one by Tom Skilling) was rotating (weakly, as I have mentioned before).

 

[Tony Lyza]

Hey Tony,

We always get really excited when something is "happening in our own backyard" (I myself am guilty of this on many occasions) so some tend to turn into a reporter, trying to inflate the story for the best scoop (lol also occasionally guilty ). Weather weenies like outdoing each other's stories methinks, so the reporting is probably an offshoot of that. So what I have learned to do is to first take a step back and refresh my brain and then look for only what I am SURE I am seeing. In this case it appears to be a wall cloud or gust front (stills don't show rotation so I can't say either way) and your estimated wind gust speed. Then I look for anything suspicious to make sure I'm not missing anything. However, unless you're reasonably confident in your observation its better not to call it in IMO and watch it to become more certain. I mean a rotating wall cloud is a rotating wall cloud and if you see an obvious one you should call it in, but if you just see a suspicious lowering from a distance...that can be in the grey area that I am talking about. A false tornado report would mean an extra trip out and more work for the NWS folk. IMO I don't see a tornado in there at all so I would have called in the wind gust estimate and perhaps made a note to tell them that i saw a cloud formation that looks suspicious but I cannot tell if its a rotating wall cloud yet (or something thereabouts).

Never heard anyone ask me for a second verification on my report before...that was strange. I wouldn't beat yourself up too much about it. Just roll with the punches and remember that we all get excited in the heat of the moment!
[/b]

Hi Alex!

1) I never called it in as a tornado in my report. I knew it was at least a wall cloud because it was in the updraft of this odd storm. I observed it for about a minute, noted weak rotation, confirmed it on Doppler radar, and called it in as a "rotating wall cloud."

2) Having been through what was confirmed to be 90+ MPH winds in a terrible supercell on 7/17/03, I am very confident in my estimation of ~75 MPH. It also fits reasonably well with a 75 MPH report to the southwest of me, and two 70 MPH reports of me, all with the same storm.

3) They never "asked" for a second report. They just never created an LSR for my 60-70 MPH report or my 75 MPH report (which was made about 5 minutes after the 60-70 MPH report as the storm grew worse). This happened this year also when we got ~60 MPH winds from a collapsing cell that had no warning on it on 5/17. This time, though, my mom (as I stated, another trained spotter), called just in order to get a gosh darn LSR on the darn storm. My only reasoning for this error on LOT's part is that I live on the border between a town that was listed in the warning and one that was not (I officially live in the town that was NOT in the warning). I gave my position as the SW edge of my town. Maybe they thought that since I don't live in one of the towns in the warning that it was a false report? I just don't know. Then again, I called to report 8" of standing water in the south suburbs on a storm chase that I went on (the aforementioned one) and an LSR was never written on that. Maybe they just ignore me because I'm a teenager; then again, they sure as heck took my 60 MPH report on 3/12. I just don't know with LOT anymore.

 

[rdale]

"I knew it was at least a wall cloud because it was in the updraft of this odd storm."

Finding it near the updraft does NOT mean it is a wall cloud.

"confirmed it on Doppler radar"

The radar image you posted does NOT show rotation, and it certainly wouldn't be picking up rotation in a wall cloud.

I would not take Tom Skilling's "confirmation" of the above pic being a wall cloud as a real confirmation. There are PLENTY of chasers with MUCH MORE experience than Tom who already explained to you why that can't be done with a simple still photo.

What type of damage was done? At the least that awning should be a long way away from your neighbor's house and his yard furniture should be downstream too.

 

[nickgrillo]

In all honesty, I don't see anything that resembles a wall cloud in neither of the those stills... I see a high-based (possibley slightly elevated in terms of inflow) storm -- with a very outflow-ish looking lowering. I was chasing that afternoon in northcentral and northeast IA, and all of the storms that I witnessed were charactorized by excessive outflow given the incredibley weak deep-layer shear and considerable dewpoint depressions. I'm not saying that a storm cannot organize slightly in these conditions -- especially in cases of local-scale effects that may increase rotation in deep convection (e.g. increased low-level vorticity along an OFB).

Remember that shelf clouds can exhibit excessive turbulance that may resemble rotation. I'm not saying this is the absolute case, but from your photos above -- I see nothing but a high-based, outflow-ish looking storm (and that is not a wall cloud). I am not surprised by the severe wind gusts, since the atmosphere favored decent downburst potential (e.g. dry adiabatic low-level lapse rates) on the 29th -- but nothing more than "pulse" cells (which is pretty much all there was).

 

[rdale]

Nothing like 3 days of CAPE to 3000-ish all WASTED on lack of winds! Next time we see those numbers around here will be...???...

 

[Tony Lyza]

"I knew it was at least a wall cloud because it was in the updraft of this odd storm."

Finding it near the updraft does NOT mean it is a wall cloud.

"confirmed it on Doppler radar"

The radar image you posted does NOT show rotation, and it certainly wouldn't be picking up rotation in a wall cloud.

I would not take Tom Skilling's "confirmation" of the above pic being a wall cloud as a real confirmation. There are PLENTY of chasers with MUCH MORE experience than Tom who already explained to you why that can't be done with a simple still photo.

What type of damage was done? At the least that awning should be a long way away from your neighbor's house and his yard furniture should be downstream too.
[/b]

The awning became wedged in a corner of their house, and tons of lawn furniture, ornaments, pool toys, you name it, was strewn around the neighborhood.

I nearly find it funny that the same folks here that claim they cannot determine anything from a single photo are so quickly dismissing me even though I am the only one who actually viewed the whole storm. I observed it, and, though I'm not an "experienced" storm chaser, I have been trained to know what I'm seeing. I watched the storm agonizingly approach, I watched its every move, its evolution. There was decent inflow into the wall cloud, and the real "fun" activity (the severe wind) started AFTER the feature passed. Was it an impressive wall cloud? Hell no. Was there strong rotation? Definitely not the case. However, I've been trained to know what I see, and I KNOW WHAT I SAW.

And Nick, we have something in this area called the lake breeze that was acting to organize and intensify the storms in this area all day that day. It even helped them to congeal into a couple MCSs. The same type of situation developed a normal "pulse" storm on 7/17/03 into a massive HP supercell with 90+ MPH winds and tennis-ball-sized hail (under slightly more favorable wind profiles, of course). What was going on in NE IA was not of the severity of the situation in this area.

 

[rdale]

"I nearly find it funny that the same folks here that claim they cannot determine anything from a single photo are so quickly dismissing me even though I am the only one who actually viewed the whole storm."

Those are two completely separate issues... 1) You CANNOT determine anything from a single photo.

2) You aren't being dismissed - we're just curious to see the damage and how you rated it 75mph winds.

The questions came when you thought that it was a tornado, and when you matched it up with the radar. 1) There was no tornado, 2) What you showed on radar was not rotation.

 

[nickgrillo]

Alright, I went ahead and downloaded some WSR-88D data from KLOT during that selected period... The storm was obviously just a pulse storm, and exhibited linear structure on radar. You have to remind yourself that the day had ~10kts deep-layer shear at the very most, and extreme instability (for most of the region) -- and even in most cases when a lake breeze boundary is involved with this type of background environment -- you'll still get multicellular/pulse deep convection (which would be capable of damaging downbursts, and large hail given the extreme CAPE associated with the parcels ingested). I'm looking at the scan at the time of the 75mph report over Schererville (IN) and the only thing I could even see in the velocity scan (in every tilt) would be just a tad of horizontal shear along the thunderstorms gust front between Highland and Gary.

The thunderstorm weakened rapidly as it pushed northeast towards Lake MI towards 2140 UTC, as it moved away from the instability on land (which was augmented by the excessive insolation/diabatic heating and considerable low-level moisture). It was your typical multicellular/linear-type structure that you'd see on days like this. According to the KLOT SVR issued for Lake Co, another spotter reported a 75mph gust further west in Will Co.

 

[Jeff Snyder]

While I agree with most of you, let's try to be as considerate as possible. We were not there; Tony was the only one on here who actually saw everything. Yes, the photo doesn't show much, but that doesn't necessarily mean nothing was there before or after this photo. Photos can never show rotation, given that a photo is taken at an instant at time, while rotation requires a change in position with time... Yes, we can't see rotation, but what does that mean? In addition, the WSR-88D, given it's resolution, can only very very very rarely capture the actual tornado. Most of the time, rotation on radar is not an identiification of the actual tornado (and yes, I know we all know that). My point being is that there have been tornadoes in a lot stranger-looking storms. So, while radar doesn't show much in terms of velocity, that doesn't necessarily mean that a tornado was not there. It's not bad to question a photo (for clarification or interpretation reasons), but let's just all try to be as considerate as we can (not saying we aren't -- just a reminder).

 

[rdale]

It might sound like we're ganging up - but seriously we're not. Thanks to emotion-less means of communication ;>

 

[Tony Lyza]

Alright, I went ahead and downloaded some WSR-88D data from KLOT during that selected period... The storm was obviously just a pulse storm, and exhibited linear structure on radar. You have to remind yourself that the day had ~10kts deep-layer shear at the very most, and extreme instability (for most of the region) -- and even in most cases when a lake breeze boundary is involved with this type of background environment -- you'll still get multicellular/pulse deep convection (which would be capable of damaging downbursts, and large hail given the extreme CAPE associated with the parcels ingested). I'm looking at the scan at the time of the 75mph report over Schererville (IN) and the only thing I could even see in the velocity scan (in every tilt) would be just a tad of horizontal shear along the thunderstorms gust front between Highland and Gary.

The thunderstorm weakened rapidly as it pushed northeast towards Lake MI towards 2140 UTC, as it moved away from the instability on land (which was augmented by the excessive insolation/diabatic heating and considerable low-level moisture). It was your typical multicellular/linear-type structure that you'd see on days like this. According to the KLOT SVR issued for Lake Co, another spotter reported a 75mph gust further west in Will Co.
[/b]

Hey Nick!

Could you please post or PM me a couple radar grabs? I don't have an advanced radar system (yet), and even though I am extremely confident of what I saw, a little more research never hurt anything.

 

[beau_gjerdingen]

I volunteer at the WFO in Minneapolis, MN and work many of the severe events... And for what its worth, that forecaster was likely doing his job in not filing the LSR. We have been instructed to only file wind LSRs with specific (Meaning 10" Diamater Branches...Siding ripped off home etc) damage. Wind speed is only to be put into an LSR when the winds have been measured with an anemometer.

Humans are simply terrible at estimating wind speed, myself included. We almost always waaaay overestimate the wind even when we try our best to be conservative with our estimates.

 

[Tony Lyza]

I volunteer at the WFO in Minneapolis, MN and work many of the severe events... And for what its worth, that forecaster was likely doing his job in not filing the LSR. We have been instructed to only file wind LSRs with specific (Meaning 10" Diamater Branches...Siding ripped off home etc) damage. Wind speed is only to be put into an LSR when the winds have been measured with an anemometer.

Humans are simply terrible at estimating wind speed, myself included. We almost always waaaay overestimate the wind even when we try our best to be conservative with our estimates.
[/b]

Thank you for that valuable information, Beau! Unfortunately, my problems with LOT did not stop with this storm. As I mentioned in a previous post, my chase team and I embarked on a very short chase after this bad storm. We went to the south suburbs of Chicago, where we observed several areas where the roadways were covered with up to 8" of water. I called in the report, making sure to identify myself as a storm spotter. I gave my observation, the town, even the actual streets where the flooding was taking place. Still, an LSR was never written on that report. So, I understand what you are saying, but that still doesn't lessen my feelings toward LOT in this incident.

I just thought of something else. LOT took my report of estimated 60 MPH winds with a squall line on 3/12, so I know that they do take estimated wind speeds.

 

[Robert Dewey]

DTX takes estimated wind speeds...

Even with an anemometer, it's still usually an approx. estimation at best. You might be witnessing winds of 75MPH destroy a large tree across the street, but your anemometer (with you standing behind the car) might be reporting 45-55MPH. I think using a combination of visual and instrumental readings would be best.