[dramatic music plays]
>>Gary England: You’re looking at a very large EF4 tornado that occurred east of Oklahoma
City – May 19, 2013. See the clear air on both sides? Huge funnel in there. Strong rotation
from near the ground right on up to the top of the thunderstorm. Now this one occurred
in southwest Oklahoma City and Moore, Oklahoma on May 20, 2013. Kind of looks like the other
one, doesn’t it? Okay, let’s see the sky or the light on both sides of it, huge funnel.
And keep in mind, the tornado isn’t just that funnel, it’s this whole area around.
All this air is flowing in, and it’s going up, once again, to the top of the thunderstorm
in most cases. Now look at this one. This is the El Reno tornado of May 31, 2013. This one was west of Oklahoma
City. Now this was a monster storm; as you look at this, there are multiple tornadoes
inside that funnel. Some of them were about the same size of two football fields end to end,
and there were smaller ones that were moving with a forward speed up to 175 miles
per hour. Now the maximum wind in this monster tornado was around (or very close to) 300 miles
per hour. But once again, it looks kind of like the other ones. It’s just a little
bit bigger and a little bit stronger – all three of them very similar. Let’s look at
this surface map here. This goes with the first tornado you looked – just east of
Oklahoma City. The Shawnee EF4, Carney EF3, and we look at Oklahoma there in the middle
and we see that little line coming, that low pressure area. See that low pressure area
just northwest of Oklahoma City? You can see the dry line coming south out of the low pressure
area on down into Texas. And it gets extremely hot along that dry line, and sometimes it’ll
cause thunderstorms to go up. And you see in Texas and into Oklahoma dew points, you
see those green numbers, 70 and 68 and then a 66 in Oklahoma. This 70 dew point’s a
moisture available rushing into Oklahoma, temperatures 90s. Right along the dry
line, 100 plus. So that’s the first storm we looked at. Let’s look at the next one.
Well the surface map looks pretty much the same, doesn’t it? Still has a dry line,
that dry line – little bubbles with a clear area inside – go from central Oklahoma, about
Oklahoma City back southwest to about Wichita Falls. Along it got really, really hot, really,
really unstable, and we looked through Texas, we see dew points, the green numbers: 71 and a 75 down
south, 71 Corpus Christi. And look there in Oklahoma City – or in Oklahoma. We see a 72. Warm, moist, unstable
air flowing northward. Here’s a surface map for 1:00 PM on May 31, 2013, the El Reno
EF5 west of Oklahoma City. Monster tornado formed, monster supercell. And it’s not
really drawn on there, but there is a dry line. You see that number in western Oklahoma,
042? There’s a dry line right through that. And the dry line gets a little more well formed
during the day, moves up into central Oklahoma. So it’s the same basic map: little stationary
front, cool front northwest, dry line in the area, warm, not hot, unstable air coming
up from the south. And that stratus streaming by, if you could just see it on that map,
it would represent energy – convectively available potential energy. So there it is:
convectively available potential energy, CAPE. You have to have that. Now sometimes in the
summertime, you might get a number of 5,000. That stands for 5,000 joules per kilogram,
which is an energy statement – energy notation. And sometimes in the summer you’ll
get that 5,000 and it’s just hot and humid. And you can’t get any cooling; it’s thick
and sticky. But if you have those conditions along with a dry line and all that moisture coming
up, the jet stream coming up – all the ingredients you need to create severe thunderstorms and
tornadoes, you will have them. But it’s interesting, around 5,000, 4 to 5,000
here in the central strip of the state. And here’s the one convectively available potential
energy for the Moore tornado, May 20, 2013. Looks about the same, doesn’t it? No CAPE – no
energy available in western Oklahoma, but in central sections on to the east, lots
of moisture, lots of energy. These storms require lots of energy. Here’s the third
one that was to the west of Oklahoma City, Canadian county. Hey, what are we doing? Showing
you the same picture? It looks just like it, doesn’t it? That's 5,000 joules per kilogram
of energy in central Oklahoma. They all kind of look alike. Now we’re going to imagine
that you’re facing the screen, and in your right hand you have a thermometer, and it
is red. And in your left hand you have a, a piece of equipment that’s green, and it
will show you the dew point. Dew point can measure the moisture in the atmosphere.
Are we okay with that? Your right hand’s red, your left hand is green, and we’re
going to elevate you up toward 4,000 feet – that’s that first horizontal line coming
up. And you see those lines tilt a little bit to the left; that means the temperature’s cooling
a little bit, dew point's decreasing a little bit. Then it reaches about 4,000 feet and wow, your right
hand goes to the right and bam! Your left hand goes to the left. And that means on the
left, the green, that's very dry air coming in. And on the right, that means that it is warmer.
This is the cap; this is the lid everyone talks about. If you can break the
cap, you can break the lid. Well this is what we call a shotgun, a loaded, a loaded gun sounding.
Because all that energy, all that CAPE is below that little area where the red went
right and the green went left. So all that CAPE is below that, and once you can bust that
cap, all that energy starts up and there’s no way you can stop it. If you have the proper
wind directional shear, wind speed shear, and some other factors, you’ll have tornadoes.
This is the Moore, May 20, 2013 tornado. EF5 and the, the trace looks about the same. In
your right hand is the temperature; in your left hand is the dew point indicator. They
go up, they go up and then bam! Temperature takes off. The right’s getting very warm up
here to the left on the green, and it's getting drier. That’s the cap, that’s the lid. Once again,
this is a loaded gun sounding. Once you break it, you can’t stop it, and the storm will
explode. So you have to have something to cause that air to go up, to break that cap,
break through there. And that happens for a number of reasons. It could be a low pressure
area, it could be the dry line, could be just temperatures, could be conversions, could be jet stream.
Lots of things can cause it. And this is the day of the monster tornado: Canadian county,
Oklahoma, May 31, 2013. Same thing – red hand’s got the thermometer, left hand’s
got the green dew point reading. And they go up a little higher, a little above 4,000
feet and they squirt off right and left. That’s your cap; they all three
look alike. You take a picture and they look alike. You take a look at the surface conditions; they look alike. You
look at the available potential energy; they look alike. You look at the sounding; they
look alike.