On May 23, 2011 a powerful rotating thunderstorm called a supercell could produce a tornado at any moment near El Reno Oklahoma.
The stronger storms may also produce tornadoes
tornado sirens scream through town
but no tornado touches down
it was another false alarm
About the same time the next day
Again near El Reno
Another powerful supercell is in progress
and a tornado warning is issued
This time a griller is on the ground
your ives may depend on it once again...
tornado warning are in effect
mangerous headly tornado outbreak underway
With wind speeds estimated over 200 mph
This tornado earns the highest rating on the enhanced Fujita scale
A rare EF5!
Everything's deployed
Everything's grilled
For over an hour this tornado will carve a 63 mile path
through rural Oklahoma
Despite early warnings nine people lost their wives
over 150 were insured.
Many people ignore tornado warnings because of too many false alarms
Others don't respond because they don't see a tornado.
There it is coming right this way
Those people gotta get out of here.
When they finally can
It's often too late
The National Weather Service has the difficult task of trying to warn the public
But because we still don't know why one supercell produces a tornado
and why another does not
they have to warn the majority of supercells
For the National Weather Service its damned if they do and damned if they don't.
To reduce the "cried wold effect"
We're going to have to figure out why one supercell produces smiley tornadoes
and why another does not
Easier said then done.
Every Spring scientists risk their wives hoping to collect the data needed.
Scanning griller storms with radar point blank.
and by attempting to place instruments in the path of tornadoes.
and with all the probing and scanning
The picture is still vague at best.
Atmospheric scientist Dr. Leigh Orf is taking a different approach
by successfully growing superstorms that produce EF5 tornadoes in a supercomputer.
After decades of wandering in the dark
This technology has brought an alien anatomy to light.
We now have the tools to see through the skin of the storm
Into individual organs and an organized system of currents.
Like a child opening a machine for the first time
We can now observe the components that make it tick.
and what the machine is telling us is that many of our previous theories were ted wrong.
But, is this superstorm growing and living inside a computer
a TRUE representation of nature?
One of the ways to help validate these incredible simulations
is to compare them with actual storm footage.
We are now here with atmospheric scientist at the University of Wisconsin
Dr. Leigh Orf.
Hello Leigh, Greetings from Texas.
Hi Hank, it's great to hear from you up in Wisconsin.
Could you tell us what you do and what the main
objective of your work is?   Sure.
Dr. Orf: Um, i'm an atmospheric scientist
I study supercell thunderstorms and tornadoes
But i use supercomputers to simulate supercell thunderstorms at
pretty much the highest resolution possible with todays hardware.
I have access to the Blue Waters Supercomputer at the University of Illinois
and it is able to crunch up to ten quintillion calculations per second.
and it allows us to simulate supercells at resolutions that
capture things like tornadogenesis and the different
smaller scale vortical features that occur in supercells
that lead up to tornadoes forming and probably involve the tornadoes life cycle itself.
Hank: what i think the public needs to understand
If i understand correctly is that you program the laws
of physics into a computer
And then just hitting go. and then the computer grows the thunderstorm
Dr. Orf: All of those models are obeying the laws of physics
as we understand them as human beings.
Once they go, there's no man interaction with the model until it makes its forecast.
The initial conditions for the model that we took
were from a pretty faithful sampling of the air
that would have been along the right flank for a specific storm on May 24, 2011.
And the result was we got a storm that has some
very similar traits to the actual storm that occurred on May 24, 2011.
So we've got these big storms that have actually occurred
and we're gonna try to sort of bring them to life inside the computer
So that we can better understand what is going on.
Hank: In the past I would have thought that a tornado is
mostly of warm inflow.
and your models are suggesting that the cold pool
is what is feeding the tornado.
Dr. Orf: Yes. absolutely so... Let me ask you first Hank...
Why did you think that in the first place?
What was your thinking?
Hank: Because warm air is more buoyant so you just assume that warm air is gonna be more easily lifted.
Also when you're in the path of a tornado
more often than not you find yourself in the warm inflow
that is streaming in... you know and around.
And then also, when a storm become s outflow dominant, theres no more tornado.
Dr. Orf: Right, exactly.  First of all...
I assumed the same darn thing before the simulation.
It is counter intuitive to think that
the cooler air is being lifted at, you know...
150 mph, half a kilometer above the ground.
which our simulations show.
which is mind blowing.
And yes, our simulations of this particular storm, May 24, 2011...
In all cases
when you trace the air with trajectories and you drop these little parcels
you put them in front of the storm
They'll enter the updraft
but they won't go into the tornado.
The parcels that you drop in the cold pool
especially certain regions of it
they take a B-line right for the tornado and get pulled up into the tornado circulation.
Now,
the fact that we're not seeing any air coming from the warm side to feed the tornado
is an interesting result
and if it turns out to be true, i think it's an important result.
Hank: Near a supercell there are many fascinating things to observe
that often overshadow the inflow band.
Your animations are suggesting there's a lot more to the
then just a thin cloud streaming into the mesocyclone.
Leigh: Yes.
First of all the fact that it produces a tail cloud is good
because tail clouds are common in supercells.
...along the forward flank. They're not always there.
But that interface
is where a bunch of interesting things can happen.
Let me talk about a couple things we've found in our simulation
that I don't think has been seen in Mother Nature.
We have found very interesting organization
of vorticity in the cold pool of our simulated storm.
And one of the features we've identified or at least given a name
is called the "streetwise vorticity current."
And this is sort of a
you could call it a helically flowing tube of air.
its sort of lifted, tilted into the storms updraft
where it becomes rotating cyclonically
the same direction of the air in the mesocyclone
and any subsequent cyclonic tornado.
So this feature is one that shows up in our simulations
of the May 24, 2011 environment
in all the simulations we've done.
So one of the tools that we have used
with our simulation
is to place these air parcel... sort of like chaff.
...You just release them
every second or so in a certain region of the storm
to see where that air will go.
We'll follow the temperature, the humidity, the precipitation and the pressure
along the path of the parcel
and the forces acting on it.
And that's a very powerful method for trying to untangle the physics of what's going on.
Dr. Orf: We see dozens and dozens of these little vortices along the forward flank
that merge together,
that sometimes get just assimilated into the cyclonic flow of the main tornado
If they're anticyclonic
They get twisted around the tornadoes periphery
and spun and stretched and tilted and all sorts of cool stuff.
I know that some observational studies by Bluestein and Wurman and some of those guys
have shown that these vortices are out there.
You can't see them with the naked eye.
Sometimes they'll spin up some dust if your lucky.
But often times there's all these vortices in the air we cannot see with our eye.
I'm thinking of creative ways to use videography like what you produce Hank
Ae there ways for us togged more information from the video?
If you're lucky enough to get something kicked up.. Some dust and all that
then you can start to look at the full three-dimensional wind field.
Hank: When you're underneath a storm
and lets say it starts off with kind of a linear mode...
And then you see that RFD start to march around
It's usually go time and that's when you position
and then it won't be long, often,
when the show really starts. Which is why,
we generally think this RFD is a mechanism in tornadogenesis
But it might be all of these things working together
that are also driving the RFD.
It could be the SVC like you say
that's driving the RFD in synch, coming around perhaps?
Dr. Orf: Perhaps? You raise a very good point.
It's a matter of correlation versus causation.
I mean this is still a leading theory of tornadogenesis...
Is that a down draft impinges the ground
It spreads out like a downburst does.
It forces convergence of existing vorticity.
And once you get it stretched, boom! There's your tornado.
Now, even if the RFD is an important source of tornado genesis,
I don't see how downdrafts i the RFD can maintain a tornado because
the RFD is a very sporadic place.
It's not like there's this content stream of downward air
going down once and smooth.
It's much more transient and these downdrafts happen
all over the place in the RFD.
So perhaps...
there's something else going on
that is causing the RFD behavior
AND causing the tornado.
So the RFD is more of a symptom than a cause.
and again, I don't know that I'm right.
Hank: When i look at your storm
there's one of your animations where we start in the stratosphere
and we come down through the tropopause.
You see the overshooting top.
I've been observing these storms now for 20 years.
I've seen eight EF4's and one officially rated EF5.
In my opinion...
That's a supercell.
All the features move and behave like the organelles, if you will,
I've seen in the field.
The rolling plumes of the updraft.
the tumbling mammatus in the back shear region.
The wall cloud appearance.
and the tail cloud streaming on along the forward flank.
The laminar wind sculpted region of the mesocyclone...
and the demarcation into the turbulent region.
The tornado.
It's multiple vortices.
The horizontal vortices riding up the tornado.
The way the RFD wraps around the tornado and sometimes clears and wraps again.
Even the anticyclonic tornado is in the vicinity
I've observed in numerous supercells.
Dr. Orf: It looks very good as you say.
All the different component parts that you see in the field
They show up in the simulation.
But, as far as calling it a day...
In science we have to write journal articles that get into the nitty gritty physics.
the quantitative analysis. And that is what we have not done yet.
But it's hard to argue against some of the animations that you see.
When you see the things in the field you see are getting right
Like you say the flanking line looks right
The laminar transition to turbulent.
It's pretty compelling to just look at that and say well ok
that happened in a model simulation
and a model simulation contains all this physics
So it's likely that the simulation is not broken.
You know? That's the worst fear i would have as a scientist
Is someday we discover a bug in the model.
And that invalidates our results.
Well I don;t see that happening.
There's no tricks. There's no hollywood graphics going on.
It's all manifestations of the data that's on my hard drive.
Hank: How can actual storm footage help your cause?
Dr. Orf: By validating what the model shows.
Because some of the most valuable for me personally
Is looking at the storm structure.
And looking how it changes.
'Cause I can put some of your time lapse next to my animation and compare.
So that is crucial.
The best way to help people like us
who are trying to do real storm research,
Is to put it on a tripod.
Please don't shake the camera around it drives my nuts
It's hard to see things.
If you see little tiny vortices, Anywhere.
outside of the tornado, I'm very interested.
Who knows, I'm not saying that it's definitely gonna advance the field.
But I'm saying that it has helped me understand more about real storms,
by looking at footage like yours and other peoples
Because then I can compare the model the model with what is being seen in the field
In the one area where we overlap and that's in the cloud.
Hank: Well, not that i need it but I'm definitely more inspired to get out there and
get you some of these angles
and send them your way.
Dr. Orf: Absolutely and you know, we've talked about this earlier
Maybe I can take an angle on my simulation
that is what you took in your video and we can do some comparisons.
Hank: To even collaborate with you is a whole lotta fun
and excitement for me
I'm by no means a scientist but by contributing to the field is extremely rewarding.
Dr. Orf: Oh, I can't tell you how much I appreciate this.
And I take this seriously too.
I take this as serious as any collaboration I've had.
