[dramatic music plays]
>>Gary England: Now, let’s take another look at the Piedmont computer simulation. Had
a big tornado that day, F5. They took the data from it, pumped it into a computer program
they’d written, and they came up really with – a lot of these are streamlines. What was
the wind doing? Horizontal tubes of vorticity being tilted into the vertical. Look at all
that motion in there. Isn’t it amazing that you can do that with mathematics? Horizontal
tubes tilted into the vertical, stretched, and the winds increase. Now let’s look at
a more simple presentation on this. What in the world do we have here? Well, we have a
very large thunderstorm. It’s a little bit narrow, and it’s rotating, and there’s
the updraft. And you see that tube? Well that’s caused by differing wind speeds and wind directions
in the lower levels. Let's say at 3,000 feet the wind is 30 miles an hour, and let’s say at 6,000
feet it’s 60 miles an hour. So you can just put a pencil down on the desk there and
roll it, because when the wind is stronger at the top than it is at the bottom of that
tube, it will rotate. So it kind of floats along through the atmosphere, it gets close
to the thunderstorm, gets caught in the updraft and goes up, and that can become part
of a tornado. How does that work? Well, it’s kind of fascinating. Let me give you an example
here – ice skater. Ice skater spinning with her arms out, all right? Certain speed brings
the arms in, spins faster. This tube is tilted into the vertical, and as it goes up, it’s
stretched. And as you stretch it – and you can show all this mathematically – you stretch
it, the diameter becomes less. And so what does it try to do? It tries to conserve its
speed. So the speed increases. And sometimes you’ll just have a total rotating thunderstorm
that comes to the ground; sometimes you’ll have many of these horizontal rotating tubes
or vorticity, you call it, come into the storm, get tilted into the vertical, get
stretched, and become a part of a thunderstorm.
Like I said, this is an absolutely fascinating world. Visually, the first indication of a
tornado to come may be a wall cloud. A wall cloud is a lowering, usually in a rain-free
area. And for it to be dangerous, it must be rotating. Now sometimes it’s really difficult
to tell if they’re rotating when you’re observing them. You know, it may produce no tornadoes.
It may produce a small tornado. It may produce more than one medium-sized tornado. It may
produce a large one. It might produce a multi, multi-vortex, or just a huge tornado. Most of them spin
counterclockwise, but sometimes they spin the other way. So keep that in mind. There’s
a lot of ifs, and, and buts in meteorology.
Let’s check out some wall clouds now. Look at these – look at these images. And it’s
lowering in a rain-free area. Now sometimes, I have got to tell you, they do come in the
rain, all righty? There’s another one: rain free area, lightning off to the left, it’s
lowering. What’s happening if you’re standing there, that wind is coming from past
your back – into your back, flowing into that storm, into that wall cloud. Remember
that little tube we had going up? That’s what’s happening. Air is flowing into it.
Another one a little closer, very close to the ground. The more moisture in the atmosphere,
the closer the wall cloud will be to the ground. And normally you could look at a wall cloud
like this and you could be about 95 percent accurate if you say there’s going to be
a tornado.
Now this is the monster, the monster storm: May 31, 2013, Canadian county. That’s the base of
the thunderstorm. It's over you, then there’s this Titanic-sized wall cloud that’s rotating
in the distance. The winds inside the storm around that updraft we were talking about
are rotating violently at this point. And here’s a, here's a night shot for you. This could
be a wall cloud; it could be just an updraft region. Because that air starts up, it cools,
it condenses and it forms a cloud. So it may just be updraft, might be a wall cloud. Observing
a lot of times at night, you can make mistakes along those lines. Now this – you see a
big corkscrew thunderstorm covering the right-hand half of the page. And the left, you see what
appears to be this huge area of air and clouds moving into it, and that’s exactly what’s
happening. The entire thunderstorm is rotating, and that huge area there is a large area of moisture
and clouds and high-speed winds. A feeder band moving into the storm. Now there’s one
– this particular day is up near Cherokee, Oklahoma. The entire storm is rotating; it’s
rotating above your head. And there’s one funnel getting ready to come down. By the way, a funnel
is a tornado not touching the ground. When a funnel touches the ground, it becomes a
tornado. There’s other ones hanging down that finally produced some tornadoes that day.
And here’s one, pretty obvious if you’re out there – and really if you’re
out there and taking this picture, you’re in the wrong position. Big lowering, big rotation.
Keep in mind the rotation is just not with the tornado and the wall cloud – it extends
all the way up to the thunderstorm. And if it’s really large like that Canadian County
tornado, it can put down tornadoes in different locations. Tornadoes sometimes come from wall
clouds. Sometimes they don’t. Sometimes wall clouds produce no tornadoes, but let’s
look at a few tornadoes that we’ve had that come from generally wall clouds.
This is probably like a lot of tornadoes in the plains and elsewhere: not very big, not
on the ground too long, and they don’t do too much. Here’s another one. Now by the
way, if that funnel cloud – looks like a funnel cloud – is two-thirds of the way
to the ground, it’s probably on the ground. You just can’t see it. So what you do,
you look for the dirt and the debris and the dust, all that being kicked up by it.
Here's a – this is just classic. See the wall cloud up above? From it comes a tornado. Now sometimes,
you know, they go through stages. They start little babies, and they grow up, they get
really big and mean sometimes. This one is pretty well formed, fairly strong, that tornado
being generated part—in part by the wall cloud. Aerial shot we’ll just show you – we
have, you know, you, you get trapped and say well, tornadoes look this way and do this way.
These were two tornadoes side by side.
Now here’s a tornado in western Oklahoma, as I recall, that was an F4. And you notice
if you’re facing this tornado, it in fact is moving from your left to your right. But
it’s a – there’s no rain or hail. So what happens as a thunderstorm approaches
that has severe weather – possibly a tornado – the wind blows, it rains, it hails, and
many, many times, it stops raining and it stops hailing. Here’s a big one. There’s
no precipitation close to this storm. This thing was at least 200 miles per hour, most
likely stronger down near Chickasha, Oklahoma. Huge, huge tornado: May 3, '99.
Huge wall cloud – entire thunderstorm was rotating. And this comes in from May 20, 2013
in the Moore area. And you see kind of the clear area back to the left there, and I’ll
just tell you what that’s caused by. That’s caused by what we call the rear flank downdraft.
It just comes down the backside of the storm, wraps around the storm, and actually we think
helps increase the intensity of the tornado. But major tornado, very large, and as I said
huge wall cloud – the entire thunderstorm rotating. This is what we call the monster tornado.
This was in Canadian county. It ended up being 2.6 miles across, and you want to talk about
the thunderstorm rotating, it was absolutely horrendous what was going on with this storm.
Extreme wind speeds and capable of extreme damage, extreme winds, all the things that come with
a monster tornado – and you notice, it’s not raining, it’s not hailing right at this location.
How does hail stay in the air? Look at this picture. It's a huge piece of hail! They’re usually
smaller than that. But how does it stay up there? Updraft, vertical wind sometimes over
100 miles per hour keeps that hail in the air. And when it gets heavy enough to fall
out, that’s exactly what happens. Now let’s take a look at this graphic and it will show
updraft wind speed versus hail size, when it’s going to fall out, so really fascinating
there. But what happens with hail – let’s say a little raindrop gets thrown up through
that thunderstorm. It goes way up there. It goes into that area, it’s below freezing,
and it, and it freezes. But around that area, as I mentioned, there is what we call supercooled
water. It’s below freezing, and – but it’s not solid. It’s liquid, and it collects
on that little piece of ice. It goes on up and then it comes back down and overcomes
the updraft. And it gets throws again, and the storm is thrown up and down and up and
down. And every time it moves through that zone of supercool water – that water that's
that is below freezing – ice just collects on it. Finally, it becomes heavy enough to
overcome the updraft. Pretty simple stuff, really. [laughs] It took a lot of people to figure
that out, all righty. Let’s take a look at a vertical schematic of a full blown supercell.
You have the air flowing in there on the lower right kind of coming in. It’s being pulled
into the mesocyclone. The mesocyclone is just a low pressure inside this thunderstorm
as it rotates and goes up. Also helps to produce the wall cloud; sometimes the tornado comes
from that. But the air, the moist air from the Gulf of Mexico is coming in. On the right you have
the – what we call a forward flank downdraft. Because you’ll be watching that storm, and
suddenly you'll be hit with air – strong winds from the west and other directions,
too. But that flows out, there’s your rotating mesocyclone – goes all the way to the top
of the storm. It's really strong, like say it’s warmer, warmer than
the surrounding air, and it’s the overshooting top. It’s the bubble we looked at on that
satellite photograph earlier. So that bubbles up through there. And there's your, where it says upper-level winds.
That is generally 40 to 60,000 feet above that. And that’s that anvil made out of
ice crystals, and we have mid-level winds coming in from the west. Sometimes they’ll
wrap in the mesocyclone – help intensify. Other times they’ll come down the back side of
the thunderstorm as a rear flank downdraft and, and almost tip your car over. This is just
an excellent, excellent presentation on a, what’s called a cross-section of a supercell thunderstorm.