If you’re driving a car, it’s pretty easy to know if there's a bumpy road ahead.
Because you can see the road, and it’s bumpy, and sometimes there’s a sign that says “hey,
the road’s bumpy.”
But what if you’re flying a plane?
It’s not like there’s anywhere to plant a sign, and rough air moves around.
So how do pilots, dispatchers, and air traffic controllers forecast turbulence?
And how do they know when to— Uhhhh, attention HAI viewers, this is your
captain speaking.
I’m getting reports of light infotainment up ahead, so I’m gonna turn on the “fasten
seatbelt sign” and ask that you remain seated for the duration of the video.
Turbulence is what happens when funky air currents push on the wings or body of a plane
and make it pitch, roll, or yaw.
The FAA categorizes it with four intensity levels: light, moderate, severe, and extreme.
At cruising levels, there’s light turbulence in about three percent of the atmosphere,
moderate in about one percent, and severe in a few tenths of a percent.
So it’s not super common, but it still sucks.
From 2009 to 2021, 30 airline passengers and 116 crew members were seriously injured during
turbulence, which airlines have to report.
They do not have to report the minor injuries and indignities wrought by turbulence, such
as, uh, I dunno, spilling your little cup of apple juice on your lap and then having
the person next to you point and laugh and say “hahaha, lap-ple juice,” just as a
hypothetical and not something that happened to this video’s writer.
Oh also, turbulence has been estimated to cost airlines up to $500 million a year in
damage, delays, and injuries, so: bad.
There are basically four types of turbulence: wake, mechanical, thermal, and clear-air.
And even though they’re all atmospheric bumpies, they’re caused by different stuff,
so you need different forecasting methods to avoid each.
The first is wake turbulence, which mostly affects planes coming in for a landing.
Much like a boat in water, a plane in the air leaves a wake behind it, only instead
of swirly water waves, it’s swirly air waves, and if you try to water-ski in it, you’ll
die.
The bigger the plane, the bigger the wake.
It’s easy to predict: see a plane?
The wake turbulence is behind it.
Avoiding it is pretty easy too, since an adjustment of about 50 feet, or just over 15 meters,
is enough to get out of the way.
Also, the FAA has separation rules that ensure safe distances between planes, sort of like
a restraining order—if it were keeping a plane away from turbulence instead of keeping
me away from the Wendover guy’s house.
Next up: mechanical turbulence, which is turbulence caused by stuff.
Buildings, mountains, buildings on mountains…
all these things obstruct and redirect the wind, creating eddies in the troposphere that
shake aircraft like a Polaroid picture.
One type of mechanical turbulence is called “mountain wave:” If you’ve got decently
fast wind moving perpendicular towards a mountain range, it’ll bounce over the top and kick
up rotors of air way higher than the mountains themselves, sometimes all the way into the
jet stream.
Sometimes, this kind of turbulence is actually visible thanks to rotor clouds in the eddies
and lenticular clouds over the tops of the mountains, but ideally, you know about it
before you see it.
Long before a flight takes off, atmosphere nerds model where there’s most likely going
to be mountain wave and other types of turbulence.
NOAA, for example, uses an algorithm called GTG that accounts for everything from wind
speed to different structures’ eddy dissipation rates to forecast where turbulence might be.
Pilots and dispatchers review these models and use them to pick the safest, smoothest
flight path ahead of time—hopefully avoiding the turbulence entirely, or at least going
through as little as possible.
Those same mapping and charting tools also help them forecast our third type of turbulence:
thermal.
Thermal turbulence is the drama queen.
She’s what happens when warm air meets cool air in the atmosphere, often—though not
exclusively—in the context of a thunderstorm.
Here, we’re talking about big vertical columns of air yanking planes up and down, hail, foreboding
cumulus clouds… stuff you don’t wanna fly through.
On top of all the forecasting tools used to create the flight path before takeoff, pilots
also have some tools to spot thermal turbulence while airborne.
Besides the sometimes-obvious visual cues, they also get real-time weather information
from a radar display in the cockpit.
If it’s showing precipitation, you can bet there’ll be turbulence, and they’ll try
to fly around or over it.
If that’s not possible because going around would burn too much fuel or the turbulence
goes up too high, they’ll aim to go through the lightest part.
This last type is the strong-and-silent one: clear-air turbulence.
It’s the most unpredictable of the bunch, and 75% of the time, it’s in literal clear
air—meaning it’s totally invisible.
Clear-air turbulence, or CAT, as I like to call it, is caused by wind shear, which is
what happens when wind meets other wind moving at a super different speed or direction.
This often happens around curves in the jet stream, and creates patches of turbulence
anywhere from two to ten-thousand feet deep, or about six hundred to three-thousand meters.
Area-wise, they can be in the range of about Rhode Island to Chad—though usually closer
to Rhode Island, and your best tool to spot ‘em is PIREPS: reports from other pilots.
Those can be pretty straightforward: Pilot A tells air traffic control that they just
went through a CAT patch, air traffic control tells Pilot B to navigate around said CAT
patch, buying Pilot B about 20 minutes of adjustment time.
There are also automated versions of this process that collect turbulence data from
all the planes in the air at once and create a sort of crowdsourced turbulence map.
So that’s how the people who plan the flights and fly the planes deal with turbulence.
But what about you, the anxious passenger?
Well, you can learn how to read graphical AIRMETs from NOAA or visit the turbulence
forecast before you fly… or you can just trust the trained professionals operating
your flight and the suite of tools they use to forecast and avoid rough skies.
But whatever you do, pop a lid on that apple juice.
Hey, you know what’s even rockier and more nausea-inducing than turbulence?
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