Truth about Turbulence

Turbulence comes in several varieties since it is caused by different things.  The  vast majority of the time the severity of turbulence is not reported clearly.

My Dad, C.V. explained it like this: If you are really good at it you can usually drink coffee in light turbulence. Not always, but usually. If the ride isn’t smooth but it is still easy to drink coffee just report it as almost smooth. Unless you go to work for Delta …. then just complain all the time.

It is impossible to drink coffee in moderate turbulence. You can try but you’ll end up wearing some of it.

In severe turbulence you forget that you even had coffee.

Severe, or worse than severe, will hurt people that are even wearing seat belts and can damage the airplane. The coffee doesn’t enter into it. This almost never happens.

There are other descriptions, codes, number systems, etc, but these work pretty well. Different airlines have different methods of warning their pilots about rough air that has been reported or forecast. None of these is perfect since many of the things that cause rough air are invisible, and there isn’t always somebody if front of us to report what is out there.

Low Altitude Bumps: This is caused by uneven heating of the Earth’s surface by the sun’s energy. Thermal currents which are pretty much just wind blowing up or down instead of sideways jostle the airplane up and down as it goes along.  This uncomfortable nonsense usually stops at the altitude where the cloud bases are.

Strong surface winds interacting with the ground also make it rough down low.

These types of rough air are predictable. If it is hot or windy and you are going to land or take off it is going to be rough. This is rarely worse than light to moderate and isn’t dangerous. Prolonged flight when it is rough like this will probably start a barfing contest. These are great fun.

Even experienced fliers often think this is what we are talking about when we ask everyone to stay seated. Not true.

The reason we want you to wear a seat belt is to keep you from breaking your neck if you hit the ceiling at sixty miles an hour. This sort of turbulence almost never happens but when it does bad things happen. The airplane will be just fine, there is no need to worry about it coming apart or anything interesting like that. It is the contents of the airplane we are concerned with.

I know a lot of our valued passengers are anxious about flying in any kind of weather, good  or bad. The majority of the time when the passengers are all having a freak fit the guys in the front still have their feet up looking outside.

When there is information available to the pilots we can usually tell what is coming. Often it is more of an art than a science so buckle up while I explain the weird part.

A very long time ago toward the end of World War II airplanes started to get lost. Very lost. As in “we ended up 800 miles from the destination” lost. The Japanese already knew about it but this is how we discovered the high altitude winds called the Jet Stream.

The Jet Stream is a relatively small “river” of fast moving air that circles the globe at high altitude from West to East in the northern hemisphere. In winter months the Jet Stream can be found relatively low and farther south than in summer. This is why you can always expect a strong tailwind from Los Angeles to New York in the winter.

The jet stream can be as much as 200 knots. Imagine a garden hose of high velocity water. Imagine putting the garden hose in a big fish tank. Imagine you are a fish. This is how the jet stream creates “clear air” turbulence.

We know that the Jet Stream is near the Tropopause. This is the boundary between the unstable low altitude Troposphere where most of the weather resides and the relatively stable Stratosphere where the air is thin, cold, and usually smooth. We can watch the outside air temperature and find the Tropopause. Sometimes it makes sense to stay in it if the tailwind is good enough.

Another type of high altitude turbulence is the “Mountain Wave”. This is caused by a dramatic interaction between strong surface wind and mountains.  It doesn’t seem like mountains would be big enough to make a difference but they do when the wind is really strong. A two mile high mountain can easily create turbulence that causes problems ten miles high. This is common when crossing the Rocky Mountains  or the Sierra Nevada.

Now you know as much as most pilots remember about rough air.

What should you do if you are up and around and the air gets rough?

If possible hook your feet under that railing beneath a seat, and put your hands up to hold against an overhead bin. Try to keep your knees and elbows bent slightly instead of locked stiff.  If you are standing in a galley area (you aren’t welcome there), (even if you are tolerated), try to hang on but beware of the galley doors flying open and creating sharp corners.

Please keep your seat belt loosely fastened while you are seated ……….. this is why.


4 Responses to “Truth about Turbulence”

  1. why does it get bumpy when you go through the clouds? And while we’re at it, we live in a coastal city and we always seem to fly home along the coastline. Is this just to give the guys up front a better view or is there some advantage, as it doesn’t seem to be the most direct route…

  2. luckyjet1 Says:

    Some clouds are formed because of the same vertical currents that cause the bumps. Uneven heating of the ground cause shafts of air to be heated more than the surrounding air. These areas of warmer air become relatively light and create a vertical air current.

    The clouds are there because as the air rises it cools off. When the air cools down to a temperature where it cannot hold all of the moisture it contains condensation will happen.

    So, the altitude below where the cloud bases are will have vertical updrafts and bumps.

    The puffy Cumulus clouds start at the “dewpoint” or condensation altitude and can hold quite a kick.

    Condensation is the opposite of evaporation. Evaporation is a cooling process, condensation is a warming process.

    When conditions of moisture are just right the condensation will add just enough heat to a column of air to kick off vertical development. This instability is the beginning of a storm but doesn’t show up well on radar since it doesn’t reflect energy very well.

    As for why the route takes you off the coast it is quite probably a short cut even if it is farther. Either coast tends to have a concentration of traffic from one direction since that is where most other places are. By routing traffic out over the water it gets airplanes out of the way of departing traffic and makes everything flow better.

    Unless there are thunderstorms off the coast, then all the traffic has to go the same direction and things are slowed down considerably. And we like the view too.

  3. This is really cool info.

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