Significant Severe Events: June 14th-19th

[JC-CT]

Let's consider a halfway plausible scenario... An EF-3 hits town, does a bunch of EF-3 type damage... Then that tornado is followed shortly afterwards by an EF-4... Wouldn't the EF-3 damaged structures hit by a subsequent EF-4 show greater signs of damage than would be caused by a single EF-4? Or do they have a way of determining the damage caused by each specific tornado individually??

I don't think there is a predetermined method of analyzing that situation. It just doesn't happen very often.

Theoretically, the EF scale is still a measure of wind speed, but it is approximated by using damage metrics. Does context change the actual wind speed? No...but ask the NWS what the protocol is, cause I have no clue. It's a good question.

[andyhb]

Could be isolated EF 4 damage when the dust clears, but I haven't see anything indicating the +. Most pics I've seen look like EF 3-4, which means they COULD be EF 4, but you don't see that kind of debris and standing structure left in anything more than an EF 4...which one could only infer to mean EF 5. EF 5 typically = swept clean.

Just my opinion though and worth the price I've charged for it, I'm not looking for a fight.

 

Can we just wait until the surveys are done (and this does not just go for JC)?

[Ian]

Scott Peake is very good. Isn't he the one who got Hattiesburg (last yr)and Louisville (I think?) this year?

[Stebo]

I'd say it is safe to say we haven't seen enough pictures from there to get a true idea of the intensity of the tornado, any tossing of numbers at this point would be very preliminary.

[JC-CT]

Can we just wait until the surveys are done?

Yes. It won't tell us wind speed, but it will give us our EF rating. So, as I posted just a few minutes later, let's wait and find out.

[Stebo]

Scott Peake is very good. Isn't he the one who got Hattiesburg (last yr)and Louisville (I think?) this year?

I believe so, yes.

[David Reimer]

Tornadoes (and other intense weather) are big business. The increase in coverage over the last few years is huge.

 

I guarantee at least one chaser will will make at least $40,000 off video sales and video player advertising from today's tornadoes. A couple chasers will probably make enough today to put a downpayment on a new car. I mean you know all of this but still it goes to prove your statement. 

[David Reimer]

Scott Peake is very good. Isn't he the one who got Hattiesburg (last yr)and Louisville (I think?) this year?

 

Yup! He also got the Joplin footage. He reminds me more and more of Andy Gabrielson. 

[JC-CT]

OK I realize I may have instigated this issue here.

Let's send our thoughts for the critically injured in Pilger and for those who have lost.

[SluggerWx]

Storm SW of Sioux City actually showing a few tighter couplets - granted 6,000 ft in the air - but this is concerning.

[SluggerWx]

Couplet now 100kt plus SW of Sioux City - 5,800 feet.

[EricHaley]

I don't think there is a predetermined method of analyzing that situation. It just doesn't happen very often.

Theoretically, the EF scale is still a measure of wind speed, but it is approximated by using damage metrics. Does context change the actual wind speed? No...but ask the NWS what the protocol is, cause I have no clue. It's a good question.

Actually, this is kind of what I was looking for... That the damage is what determines the true scale, and that they err on the side of caution (actually one of the more powerful points).

I certainly wasn't trying to pin numbers on this, just curious about methodology (I'm a software engineer, so I love algorithms).

[Buckeye05]

Couplet now 100kt plus SW of Sioux City - 5,800 feet.

I'm at a loss as to where you are seeing this.

[Ensō]

Context is certainly a big consideration. A hypothetical home struck by an EF3 tornado and then struck shortly after by another EF3 may look like it was hit by an EF4 or EF5 afterward, and that would have to be considered in the rating process. The same as if a home was obviously impacted by a large missile. If a home is completely destroyed and swept away, the expected value may be 200 mph. But if surveyors find that it was impacted by a car or a mobile home frame or something, they may opt to go with a lower bound estimate of 175 or 180 or something instead on the premise that the missile strike weakened the structure and allowed the wind to do more damage than you'd otherwise expect.

 

Which is all to say that damage surveying can be ridiculously complex and it's hard to appropriately account for all factors. If homes were struck by two tornadoes and there was no way to tell exactly how the damage was caused, they'd probably opt for a lower estimate. It's very much an imperfect solution, but I don't know what else you could do in that case. That's a problem that doesn't happen very often at all, but it has cropped up a few times (several times on 4/11/65, in the Tanner area on 4/3/74, etc.)

[Buckeye05]

Also here's Reeds video from today FWIW. I think something must be wrong with him right now because he apparently managed to stay calm  . Scene at 5:50 looks like something out of a disaster movie.

 

[David Reimer]

The trees are stripped there, EF-4 damage.

 

God what is it with everyone trying to assign damage ratings based on photos posted on the forum? Can we not just wait for the official survey on Tuesday? I guarantee the emergency workers pulling survivors out of structures tonight don't care what the tornado is rated. We know it was a strong to violent tornado. We know it is a probable EF3+ tornado. Beyond that it doesn't matter right now whether it was an EF3, EF4, or EF5. What happened to these severe weather threats in the central forum? I remember a day not too long ago where we kept speculation in a separate thread. 

[SluggerWx]

Those are straight line winds.

 

Good call on the winds - here's the scan I was looking at when I made the OP. 

Here's the BR from the scan I was referring to:

And, here's the velocity scan:

To me, the cell looked like it had a potential hook - with a velocity couplet.

Obviously, that wasn't the case. 

[andyhb]

To me, the cell looked like it had a potential hook - with a velocity couplet.

Obviously, that wasn't the case. 

 

That's actually an interesting look, but I think having smoothing on is taking away some of the details. There also appears to be some errors in that velocity scan. 

[EricHaley]

Context is certainly a big consideration. A hypothetical home struck by an EF3 tornado and then struck shortly after by another EF3 may look like it was hit by an EF4 or EF5 afterward, and that would have to be considered in the rating process. The same as if a home was obviously impacted by a large missile. If a home is completely destroyed and swept away, the expected value may be 200 mph. But if surveyors find that it was impacted by a car or a mobile home frame or something, they may opt to go with a lower bound estimate of 175 or 180 or something instead on the premise that the missile strike weakened the structure and allowed the wind to do more damage than you'd otherwise expect.

Which is all to say that damage surveying can be ridiculously complex and it's hard to appropriately account for all factors. If homes were struck by two tornadoes and there was no way to tell exactly how the damage was caused, they'd probably opt for a lower estimate. It's very much an imperfect solution, but I don't know what else you could do in that case. That's a problem that doesn't happen very often at all, but it has cropped up a few times (several times on 4/11/65, in the Tanner area on 4/3/74, etc.)

Exactly the kind of answer I was looking for. Thank you so much!!

[SluggerWx]

Wanted to post these here from earlier today.

Concurrent GRLevel2 scan with supporting video feed from Ben McMillan's team
Velocity (21:30 UTC)

Video


 

[andyhb]

 

I'm still in awe of this absolutely ridiculous 19z sounding from OAX. Rarely do you ever see low level winds that strong this time of year, that early in the day and especially in a relatively uncapped environment. On top of that you have a 75 degree dewpoint leading to incredibly low surface based LCL heights and an extremely robust CAPE profile.

 

In addition, you have mid level lapse rates of nearly 9 C/km (you rarely see anything that close to dry adiabatic in an environment that is not cap bust prone) and effective shear of 60 kts + effective SRH over 500 m²/s². This then all leading to the ridiculous composite indices including the normally very conservative fixed layer STP putting out a 12.5. You can also see how the effective STP is actually off the box and whisker plot scale in the bottom right.

 

Obviously this type of environment feeding that supercell all by itself was gonna lead to bedlam, and that's exactly what happened.

[Thunder Road]

Does anyone know if there was still a TOG in Dakota County?

[bdgwx]

Here are a few screenshots. Sorry if any of these frames are reposts...just picking out a few interesting ones right now.

 

The two tornadoes are about 2.75 miles apart at 21:15. It looks like they both have their own RFD structures.

 

 

There is an interesting NROT pattern 21:32.

 

 

And finally the TDS is about 4 miles wide at 21:37.

 

[Jayhawkers]

I'm still in awe of this absolutely ridiculous 19z sounding from OAX. Rarely do you ever see low level winds that strong this time of year, that early in the day and especially in a relatively uncapped environment. On top of that you have a 75 degree dewpoint leading to incredibly low surface based LCL heights and an extremely robust CAPE profile.

In addition, you have mid level lapse rates of nearly 9 C/km (you rarely see anything that close to dry adiabatic in an environment that is not cap bust prone) and effective shear of 60 kts + effective SRH over 500 m²/s². This then all leading to the ridiculous composite indices including the normally very conservative fixed layer STP putting out a 12.5. You can also see how the effective STP is actually off the box and whisker plot scale in the bottom right.

Obviously this type of environment feeding that supercell all by itself was gonna lead to bedlam, and that's exactly what happened.

very good analysis. if more convection had been able to fire anywhere close to E Nebraska today, it would've been a pretty memorable day (as if it wasn't already given the dual-wedges. And devastation in Pilger) Am pretty interested as to why that supercell lost a lot of it's intensity as it crossed the NE/IA border, it's not like it crossed a boundary and moved into a far inferior environment or something like that. I've kinda noticed a bit of a trend with supercells like this one--that put down a significant long-lived tornado-- after the main tornado dissipates, the storm disappates as well within an hour or two, and fails to produce anymore noteworthy tornadoes. Esp across the plains. (Moore '99/'13, wichita '12, SE NEB a few weeks ago, And several other examples) correct me if I'm wrong, but it just seems to happen a lot, and yes there are numerous other instances where this did not happen and it continues to put down sig tor's for an extended amount of time afterward. But it certainly seems to happen at least semi-frequently.

[1900hurricane]

very good analysis. if more convection had been able to fire anywhere close to E Nebraska today, it would've been a pretty memorable day (as if it wasn't already given the dual-wedges. And devastation in Pilger) Am pretty interested as to why that supercell lost a lot of it's intensity as it crossed the NE/IA border, it's not like it crossed a boundary and moved into a far inferior environment or something like that. I've kinda noticed a bit of a trend with supercells like this one--that put down a significant long-lived tornado-- after the main tornado dissipates, the storm disappates as well within an hour or two, and fails to produce anymore noteworthy tornadoes. Esp across the plains. (Moore '99/'13, wichita '12, SE NEB a few weeks ago, And several other examples) correct me if I'm wrong, but it just seems to happen a lot, and yes there are numerous other instances where this did not happen and it continues to put down sig tor's for an extended amount of time afterward. But it certainly seems to happen at least semi-frequently.

 

I couldn't tell you if it was the sole reason or not, but there was a cell merger that occurred between the multi-mesocyclonic monster and another developing cell right about as it abruptly weakened. The remaining rotation took a turn left (north) and into the rain at that point and the cell was never the same after that. My early guess is that at least played some sort of role, but then again, just a correlation instead of concrete causation.

[andyhb]

very good analysis. if more convection had been able to fire anywhere close to E Nebraska today, it would've been a pretty memorable day (as if it wasn't already given the dual-wedges. And devastation in Pilger) Am pretty interested as to why that supercell lost a lot of it's intensity as it crossed the NE/IA border, it's not like it crossed a boundary and moved into a far inferior environment or something like that.

 

I thought it might have crossed into rain cooled air and/or subsidence from the previous convection, but I'd have to look at analysis from earlier (and also the s/w trough was passed it by that time meaning weaker deep layer shear). The storm merger might have also had an effect and it appeared that the storm was cut off from inflow as it approached the Sioux City area. The storm almost took on a NW flow type look as it was dying out.

[Thunder Road]

I did end up chasing today, but it was completely ill-conceived.

 

In retrospect, it should have been obvious as early as 18z that the atmosphere was going to recover behind the morning convection in eastern NE, but I had already gone on two long days chases recently, 6/3 and 6/14, that both ended up being busts, so I was hesitant to miss more work time and spend more gas money.

 

When I saw the special OAX sounding, and then immediately after the PDS, I jumped in the car and flew south.  I made it to Sioux City as rain started, checked the radar and realized I was too late to make it down US 77 (and then cut west, which was my initial plan), so I made a futile attempt to intercept a few of the supercells embedded within the complex near Storm Lake, but there was nothing impressive that far west by the time I got there, and nothing that could have even been seen anyway.

 

A crushing defeat, but I admit responsibility.  I should have left earlier.

[EricHaley]

Oh you know people are going to say it's the river that stopped it... Which was of course proven wrong when a tornado jumped the river, hit a power plant at Port Neal, and past Sloan, not far from my home at the time (I was a child then).

[andyhb]

Oh you know people are going to say it's the river that stopped it... Which was of course proven wrong when a tornado jumped the river, hit Port Neal, and not far from my home at the time (I was a child then).

 

Those people will shut up quick when the river becomes the Burnett's Mound of Sioux City.

[Ensō]

It's amazing what superstitious things otherwise sane and reasonable people will buy into. There are so many areas that have those same sort of legends. Woodward residents used to believe the bowl-shaped hills ringing the city protected them from tornadoes, too.. until the 1947 tornado tore directly over the hill and demolished the west side of the city.